HK1238000A1 - Ac/dc power conversion system and method of manufacture of same - Google Patents

Description

AC/DC power conversion system and method of manufacturing the same

Cross Reference to Related Applications

This application claims priority from united states provisional patent application No. 61/464,000, filed 24/2/2011, which is hereby incorporated by reference in its entirety, in accordance with 35u.s.c 119 (e).

Technical Field

The present disclosure relates generally to systems, methods, and products for converting Alternating Current (AC) to Direct Current (DC), such as AC/DC converters that include a transformer having primary and secondary windings and a rectifier.

Background

AC/DC converters are commonly used to convert an alternating current source into a direct current source. AC/DC converters, such as those used in avionics, typically include a transformer and a rectifier. In many applications, a transformer converts a first AC signal having a first voltage level to a second AC signal having a second voltage level, and a rectifier converts the second AC signal to a DC signal.

Transformers typically include at least two windings of electrically conductive material (e.g., wire). The windings are spaced sufficiently close together that current flowing through one winding will induce current to flow in the other winding when it is connected to a load. The winding through which the drive current passes is generally referred to as the primary winding, while the winding in which the current is induced is generally referred to as the secondary winding. The transformer may also include a core, such as a magnetic or iron core, extending between the windings.

Rectifiers typically comprise a plurality of diodes or thyristors configured to convert an AC signal to a DC signal. For example, a full bridge rectifier may be used to convert an AC signal to a DC signal. Additional devices may be used to provide power regulation, such as interphase transformers, balancing inductors, interphase reactors, filters, and the like.

In many applications, transformer size and/or weight are important factors in achieving a practical and/or commercially successful device. For example, power converters for use in avionics typically must be lightweight and may need to occupy a small volume. However, such applications typically require high performance, such as high current, low noise power conversion. Many applications may additionally or alternatively require a low cost power converter. The cost may depend on a number of factors including the type of material, the amount of material, and/or the complexity of manufacturing, among other factors.

Disclosure of Invention

In one embodiment, a power converter includes: a transformer having: three primary windings configured to receive respective phases of a three-phase Alternating Current (AC) input signal in a delta configuration; and three secondary windings, each secondary winding split into two parts, the parts of the secondary windings coupled together in a closed regular hexagon with each part of each secondary winding having at least two taps and the taps distributed at regular angles on the closed regular hexagon; a first rectification path coupled between a tap of the secondary winding and a positive output of the power converter and having an inductance; and a second rectification path coupled between a tap of the secondary winding and a negative output of the power converter and having an inductance different from an inductance of the first rectification path. In one embodiment, one of the secondary windings has a polarity opposite to the polarity of the other secondary windings. In an embodiment, one of the primary windings has opposite polarity to the other primary windings, and the secondary winding corresponding to the one primary winding has opposite polarity to the other secondary windings. In one embodiment, the one primary winding and the corresponding secondary have the same polarity. In an embodiment, each primary winding is split into two parts, and each secondary winding is sandwiched between the two parts of the corresponding primary winding. In an embodiment, the first rectification path comprises 12 rectifiers, each rectifier being coupled to a respective tap of the secondary winding by a respective coupling having a first inductance, and the second rectification path comprises 12 rectifiers, each rectifier being coupled to a respective tap of the secondary winding by a respective coupling having a second inductance different from the first inductance. In an embodiment, the coupling of the first rectifying path has a length different from the length of the coupling of the second rectifying path. In an embodiment, the couplings of the first rectification paths each comprise an inductor. In one embodiment, the first rectification path includes: a first plurality of rectifiers having cathodes coupled together; an inductor coupled between the cathodes and the positive outputs of the first plurality of rectifiers; a second plurality of rectifiers having cathodes coupled together; and an inductor coupled between the cathodes and the positive outputs of the second plurality of rectifiers. In an embodiment, the first rectifying path comprises leads having different lengths than corresponding leads of the second rectifying path. In an embodiment, the inductance of the first rectifying path is at least five times greater than the inductance of the second rectifying path. In an embodiment, the taps of the secondary windings are distributed at substantially the same central angle on a regular hexagon. In an embodiment, two taps on one portion of the secondary winding are on adjacent turns of the portion of the secondary winding. In an embodiment, the transformer comprises three substantially identical coils, each coil comprising one of the primary windings and a corresponding secondary winding. In one embodiment, the transformer includes a transformer core, and the coil is wound on the transformer core. In an embodiment, the coils are positioned beside each other in a row, and the central coil has a polarity different from the polarity of the other coils.

In an embodiment, a method includes: coupling together three primary windings of a transformer in a differential configuration to receive respective phases of a three-phase alternating current; coupling split parts of three secondary windings of a transformer together into a regular hexagonal configuration; providing a plurality of taps distributed at regular angles on the secondary winding, each split secondary winding portion having at least two taps; forming a first rectification path between the plurality of taps and the positive output, the first rectification path having an inductance; and forming a second rectification path between the plurality of taps and the negative output, the second rectification path having an inductance different from an inductance of the first rectification path. In an embodiment, the transformer comprises first, second and third coils, and the method comprises: the first, second and third coils are positioned together in a row with the second coil separating the first and third coils, the secondary winding of the second coil having a polarity different from the polarity of the secondary windings of the first and third coils. In an embodiment, the primary winding is split into first and second primary portions, and a portion of each secondary winding is sandwiched between the first and second primary portions of the respective primary winding. In an embodiment, the inductance of the first rectifying path is at least five times greater than the inductance of the second rectifying path.

In one embodiment, a power converter includes: means for converting a three-phase Alternating Current (AC) power signal to a multiphase AC power signal; first means for rectifying a multi-phase AC power signal; second means for rectifying the multi-phase AC power signal; first means for coupling, the means for converting to the first means for rectifying and the first means for rectifying to the first output of the power converter; and second means for coupling, the means for converting to couple to the second means for rectifying and the second means for rectifying to a second output of the power converter, wherein the first means for coupling has an inductance different from an inductance of the second means for coupling. In one embodiment, the means for converting comprises a transformer having: a primary comprising three primary windings configured to be coupled to respective phases of an AC power signal in a delta configuration; and a secondary comprising three secondary windings, each secondary winding corresponding to a respective primary winding and split into two parts, wherein the parts of the secondary windings are coupled together in a closed hexagon and each part of the secondary windings comprises at least two taps. In an embodiment, two of the secondary windings have opposite polarity to the other secondary windings. In one embodiment, one of the primary windings has an opposite polarity to the other primary windings, and the corresponding secondary winding has an opposite polarity to the other secondary windings. In an embodiment, the primary windings are each split into two parts, and the two parts of the corresponding secondary winding are sandwiched between the two parts of the corresponding primary winding. In an embodiment, the first means for coupling comprises an inductor coupled between the first means for rectifying and the means for converting. In an embodiment, the first means for coupling comprises an inductor coupled between the first means for rectifying and the first output of the power converter. In an embodiment, the means for converting is configured for converting a three-phase Alternating Current (AC) power signal to a twelve-phase AC power signal, and the power converter is configured for providing a twenty-four pulse direct current voltage. In an embodiment, the inductance of the first means for coupling is at least five times the inductance of the second means for coupling.

In one embodiment, a power converter includes: means for converting a three-phase Alternating Current (AC) power signal to a twelve-phase AC power signal; first means for rectifying a multi-phase AC power signal, coupled to the means for converting; and second means for rectifying the multi-phase AC power signal, coupled to the means for converting and the first means for rectifying the multi-phase AC power signal. In one embodiment, the means for converting comprises a transformer having: a primary comprising three primary windings configured to be coupled to respective phases of an AC power signal in a delta or differential configuration; and a secondary comprising three secondary windings, each secondary winding corresponding to a respective primary winding and split into two parts, wherein the parts of the secondary windings are coupled together in a closed hexagon and each part of the secondary windings comprises two taps. In an embodiment, one of the primary windings has an opposite polarity to the other primary windings, and the corresponding secondary winding has an opposite polarity to the other secondary windings. In one embodiment, the one primary winding and the corresponding secondary winding have the same polarity. In an embodiment, the primary windings are each split into two parts. In an embodiment, the two portions of each secondary winding are sandwiched between the two portions of the corresponding primary winding. In an embodiment, a first means for rectifying the multi-phase AC power signal is coupled between the means for converting and the output of the converter through a first rectification path, and a second means for rectifying is coupled between the means for converting and the output of the converter through a second rectification path, wherein the first rectification path has an inductance different from an inductance of the second rectification path. In an embodiment, the first rectification path includes an inductor coupled between the first means for rectifying the multi-phase AC power signal and the means for converting. In an embodiment, the first rectification path includes a plurality of inductors coupled between the first means for rectifying the multi-phase AC power signal and the means for converting. In an embodiment, the first rectification path includes an inductor coupled between the first means for rectifying the multi-phase AC power signal and an output of the power converter. In an embodiment, the first means for rectifying the multi-phase AC power signal includes first and second legs, and the first rectification path includes a first inductor coupled between the first leg and an output of the power converter and a second inductor coupled between the second leg and the output of the power converter. In an embodiment, the first rectifying path comprises leads having a length different from a length of corresponding leads of the second rectifying path. In an embodiment, the inductor comprises a wire length. In an embodiment, the inductance of the first inductive path is at least five times greater than the inductance of the second rectifying path. In one embodiment, the power converter does not employ an interphase transformer in the rectification path. In one embodiment, the power converter does not employ an input inductor between the AC power source and the means for converting.

In one embodiment, a power converter includes: a transformer having: three primary windings configured to receive respective phases of a three-phase Alternating Current (AC) input signal in a delta configuration; and three secondary windings, each secondary winding split into two parts, wherein the parts are coupled together in a closed regular hexagon, each part of each secondary has at least two taps, and the taps are distributed at substantially the same central angle on the regular hexagon; a first rectifier branch coupled between a tap of the secondary winding and a positive output of the power converter; and a second rectifier branch coupled between a tap of the secondary winding and a negative output of the power converter. In an embodiment, one of the primary windings has an opposite polarity to the other primary windings, and the secondary winding corresponding to the one primary winding has an opposite polarity to the other secondary windings. In one embodiment, the one primary winding and the corresponding secondary have the same polarity. In an embodiment, the primary winding is split into two parts. In one embodiment, each secondary winding is sandwiched between two portions of a corresponding primary winding. In an embodiment, the first rectifier branch has an inductance different from an inductance of the second rectifier branch. In an embodiment, the first rectifier branch comprises 12 rectifiers, each rectifier coupled to a respective tap of the secondary winding by a respective coupling having a first inductance; and the second rectifier branch comprises 12 rectifiers, each rectifier being coupled to a respective tap of the secondary winding by a respective coupling having a second inductance different from the first inductance. In an embodiment, the coupling of the first rectifier branch has a length different from the length of the coupling of the second rectifier branch. In an embodiment, the couplings of the first rectifier legs each comprise an inductor. In one embodiment, the first rectifier leg includes: a first plurality of rectifiers having cathodes coupled together; an inductor coupled between the cathodes and the positive outputs of the first plurality of rectifiers; a second plurality of rectifiers having cathodes coupled together; and an inductor coupled between the cathodes and the positive outputs of the second plurality of rectifiers. In an embodiment, the first rectifier leg includes leads having a length different from a length of corresponding leads of the second rectifier leg. In an embodiment, the inductance of the first rectifier branch is at least five times greater than the inductance of the second rectifier branch. In one embodiment, the power converter does not employ an interphase transformer between the secondary winding and the output of the power converter.

In one embodiment, a transformer includes: a primary comprising three primary windings configured to be coupled to respective phases of an AC power signal in a delta or differential configuration; a secondary comprising three secondary windings, each secondary winding corresponding to a respective primary winding and split into two parts, wherein the parts of the secondary windings are coupled together in a closed hexagon and each part of the secondary windings comprises two taps. In an embodiment, one of the primary windings has an opposite polarity to the other primary windings, and the corresponding secondary winding has an opposite polarity to the other secondary windings. In one embodiment, the one primary winding and the corresponding secondary have the same polarity. In an embodiment, the primary windings are each split into two parts. In an embodiment, the two portions of each secondary winding are sandwiched between the two portions of the corresponding primary winding. In one embodiment, the closed hexagon is a closed regular hexagon, and the taps are distributed at substantially the same central angle on the closed regular hexagon. In an embodiment, two taps on one portion of the secondary winding are on adjacent turns of the portion of the secondary winding. In an embodiment, the transformer comprises three identical coils, each coil comprising one of the primary windings and a corresponding secondary winding. In an embodiment, the transformer further comprises a transformer core, wherein the core is wound around the transformer core. In an embodiment, the coils are positioned beside each other in a row, and the central coil in the row has a polarity different from the polarity of the other coils. In an embodiment, the power converter comprises a transformer as described herein.

In an embodiment, a method includes: forming a first coil having a primary winding and a secondary winding split into first and second portions; forming a second coil having a primary winding and a secondary winding split into first and second portions; forming a third coil having a primary winding and a secondary winding split into first and second portions; coupling together the primary windings of the first, second and third coils in a differential configuration; and portions of the secondary windings are coupled together in a regular hexagonal configuration. In an embodiment, the method further comprises: the first, second and third coils are positioned together in the row while the second coil separates the first and third coils. In an embodiment, the method further comprises: a second coil is formed having a polarity different from the polarity of the first coil and the second coil. In an embodiment, the primary winding of the coil is split into first and second primary portions, and portions of the secondary winding are sandwiched between the primary portions of the respective windings. In an embodiment, the method further comprises: providing a plurality of taps at regular angles on the secondary winding; forming a first rectification path; forming a second rectification path; and coupling the tap to the first and second commutation paths. In one embodiment, the first rectification path has an inductance different from an inductance of the second rectification path. In an embodiment, the inductance of the first rectifying path is at least five times greater than the inductance of the second rectifying path.

Drawings

In the drawings, like reference numerals identify similar elements or acts unless context dictates otherwise. The dimensions and relative positioning of the elements in the figures are not necessarily to scale. For example, the shapes of various cells and angles may not be drawn to scale, and some of these cells may be enlarged and positioned to improve drawing readability. In addition, the particular shapes of the elements as drawn, are not intended to convey any information regarding the actual shape of the particular elements, and have been solely selected for ease of recognition in the drawings.

Fig. 1 is a schematic representation of a power converter.

FIG. 1A is a schematic representation of an aircraft power system.

Fig. 2 is a schematic representation of a power converter.

Fig. 3 is a schematic representation of a power converter.

Fig. 4 is a schematic representation of a power converter.

Fig. 5 is a schematic representation of an embodiment of a delta-hex power converter.

Fig. 6 is a schematic representation of an embodiment of a delta-hex power converter.

Fig. 7 is a schematic representation of an embodiment of a delta-hex power converter.

Fig. 8 is a schematic representation of an embodiment of a transformer.

FIG. 9 is a top view of an embodiment of a transformer.

Fig. 10 is a front view of an embodiment of a delta-hex power converter.

Fig. 11 is a first side view of the embodiment of the delta-hex power converter of fig. 10.

Fig. 12 is a second side view of the embodiment of the delta-hex power converter of fig. 10.

Fig. 13 is an isometric view of an embodiment of a delta-hex power converter.

Fig. 14 is a graphical representation of ripple in the DC output of an embodiment of a 6-pulse power converter.

Fig. 15 is a graphical representation of input current for an embodiment of a 6-pulse power converter.

Fig. 16 is a graphical representation of ripple in the DC output of an embodiment of a 12-pulse power converter.

Fig. 17 is a graphical representation of input current for an embodiment of a 12-pulse power converter.

Fig. 18 is a graphical representation of ripple in the DC output of an embodiment of a 24-pulse power converter.

Fig. 19 is a graphical representation of input current for an embodiment of a 24-pulse power converter.

Detailed Description

In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures associated with power converters, transformers, and machines using transformers useful in manufacturing power converters and transformers have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments.

Throughout the specification and claims which follow, unless the context requires otherwise, the word "comprise" and variations such as "comprises" and "comprising", will be understood in an inclusive sense.

Reference throughout the specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrase "one embodiment" or "an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and/or" unless the context indicates otherwise.

The headings and abstract of the disclosure provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

Fig. 1 is a schematic representation of building blocks of an example power converter 100 configured for converting a three-phase AC input to a DC output. Power converter 100 includes a three-phase to n-phase transformer 102 and an n-pulse rectifier 104.

The transformer 102 is configured to receive a three-phase input signal 106 and includes a three-phase primary 108 and an n-phase secondary 110. The transformer 102 is configured to provide an n-phase AC signal 112. The rectifier 104 includes a plurality of branches 114 that are coupled to respective outputs of the n-phase AC signal 112. As shown, each branch includes two diodes 116. Other rectifying devices, such as thyristors, etc., may be employed. The rectifier 104 produces a DC output 118.

Higher pulse rectification generally provides lower ripple on the DC output and lower AC input current distortion and therefore generally produces higher power quality for the power converter. In general, a 6-pulse converter topology may be considered acceptable for use in avionics with a rating of less than 35 VA. A 12-pulse converter topology is generally acceptable for a number of aerospace applications. The 24-pulse topology is typically used for higher power devices or when higher power quality is desired or specified.

Avionics applications may typically employ a transformer/rectifier unit, such as power converter 100 of fig. 1, to convert three-phase AC power, such as 115 volt AC power operating at a fixed frequency, such as 400Hz, 115 volt AC 360Hz to 800Hz variable frequency power, 230 volt AC 360Hz to 800Hz variable frequency power, and the like, to DC power, such as 28 volt DC power, and the like. The load presented to the power converter may typically be between 100 and 400 amps. Typical functions of a power converter for use in avionics may include supplying short term overloads to clear downstream faults, providing electrical isolation between the aircraft AC and DC power supplies, regulating power to provide acceptable power quality on the AC and DC sides of the power converter for proper operation of the aircraft power system and electrical loads, self-monitoring and reporting faults, and so forth. Power converters, such as the power converter of fig. 1, may be employed in other applications and configured to provide other functions. Transformer/rectifier power converters may employ topologies that use additional devices, such as interphase transformers, balanced inductors, interphase reactors, filters, and the like, in order to provide desired functionality, such as acceptable power quality.

FIG. 1A is a functional block diagram of an example aircraft power system 150. As shown, an aircraft engine or turbine 152 is configured to drive an electrical generator 154. Generator 154 is configured to provide an AC power signal to a power converter 156, such as power converter 100 shown in fig. 1. Typically, the power generated on board an aircraft is 115 volts AC power at 400Hz or variable frequency. Other voltage levels and frequencies may be used. The power converter 156 is coupled to the DC bus 158 and is configured to provide a DC power signal to the DC bus 158. One or more loads 160, such as flight devices including critical flight devices, may be coupled to the DC bus 158 and configured to draw power from the DC bus 158. Typically, flight equipment may operate using 28 volt DC power. Other output voltage levels may be employed.

Fig. 2 is an electrical schematic diagram of an example power converter 200 employing a transformer/rectifier topology. The power converter includes a transformer 210 having a primary 208 in a wye or star configuration, a first secondary 212 in a wye configuration, and a second secondary 214 in a delta or differential configuration. The power converter 200 may be used, for example, in aerospace applications. The power converter 200 includes an input 202 configured to receive a 3-phase AC power signal, such as a 115 volt AC signal. The inputs 202 are coupled to respective filter inductors 204 for each phase input, which are configured to attenuate EMI emissions generated by the rectifier stage 206.

The outputs of the filter inductors 204 are coupled to respective windings of a primary 208 of a transformer 210, the primary having three windings in a wye configuration. The first secondary 212 has three windings in a wye configuration and the second secondary 214 has three windings in a delta configuration.

The rectification stage 206 comprises a first full wave rectification bridge 216 coupled to the winding of the first secondary 212, a second full wave rectification bridge 218 coupled to the winding of the second secondary 214 and an interphase transformer IPT 222. The voltages in the secondary transformer windings are shifted 30 degrees with respect to each other, so the power converter has a power quality characteristic of 12-pulse rectification. As can be seen from fig. 2, three additional inductors and IPT transformers are used in order to meet the desired power quality. These additional components add size, weight, and cost to the power converter 200.

Fig. 3 is an electrical schematic diagram of a power converter 300 that employs a wye/delta-zigzag topology to achieve 24-pulse power quality characteristics. The power converter 300 may be used, for example, in aerospace applications. The power converter 300 includes an input stage 302, a transformer stage 304, and a rectification stage 306.

The input stage 302 includes three input inductors 308 configured to receive respective phases of a 3-phase AC power signal, for example, a 115 volt AC signal at 400Hz, or the like. The input inductor 308 is configured to attenuate EMI emissions generated by the rectification stage 306.

The transformer stage 304 includes two transformers 310, 312. Each transformer 310, 312 has a core 311, 313. First transformer 310 has a wye-zigzag configuration in which the primary coupled to input stage 302 is in a wye configuration, and first transformer 310 has two 3-phase secondary coupled to rectification stage 306 in a zigzag configuration. The second transformer 312 has a delta-zigzag configuration in which the primary coupled to the input stage 302 is in a delta configuration, and the second transformer 312 has two three-phase secondary coupled to the rectification stage 306 in a zigzag configuration.

The rectification stage 306 includes four full-wave rectification bridges 314 coupled to the windings of the respective secondary outputs of the first and second transformers 310, 312. The rectification stage 306 also includes an inter-phase assembly 320 including three inter-phase transformers IPT 322 as shown. The power converter 300 has a 24-pulse rectified power quality characteristic. As can be seen from fig. 3, three input inductors, an additional transformer in a transformer stage with two secondary levels in each transformer and three IPT transformers are employed in order to meet the desired power quality. These additional components add size, weight, and cost to the power converter 300.

Fig. 4 is an electrical schematic diagram of a power converter 400 having a delta-hex topology. Power converter 400 has a transformer 402 and a rectifier 404. The transformer 402 has a primary 406 with three windings coupled to an AC input signal, e.g., a three-phase 115 volt variable frequency signal, in a delta configuration and a secondary 408 with three split windings coupled together in a hex configuration. The winding of secondary 408 is coupled to full wave rectifier bridge 404. An example of a power converter employing a triangle-hexagon topology is described in U.S. patent No. 4,225,784 issued to Rosa.

Power converters in the delta-hex topology use fewer magnetic components than transformer/rectifier power converter topologies typically used in low voltage/high current applications where high quality power is desired or specified. Although attempts have been made to use the delta-hex power converter topology in applications where high power quality is desired or specified, in practice, the power quality produced by the delta-hex topology power converter is not good enough for use in low voltage/high current power converter applications. For example, the total harmonic distortion in a delta-hex power converter topology, such as the delta-hex power converter topology shown in fig. 4, may typically be 12% or more, which is too high for many high current/low voltage applications, such as many aerospace applications.

Fig. 5 is an electrical schematic diagram of an embodiment of a power converter 500 employing a delta-hex topology. The power converter 500 includes a transformer 502 and a rectifier stage 504. The transformer 502 includes a primary 506, a secondary 508, and a core 510.

The primary 506 has a first winding a, a second winding B, and a third winding C configured for coupling to a 3-phase AC input signal 512 in a delta configuration. Each winding A, B, C of the primary 506 has a respective first tap 1 and second tap 2. As shown, taps 1, 2 of winding A, B, C of primary 506 are at the ends of winding A, B, C. The reference numbers assigned to the taps or ends of the windings do not necessarily indicate the turn count at the tap or end. The primary winding A, B, C typically has more than one turn. For example, winding a of a primary winding, such as primary 506, may have 61 turns in one embodiment. Other numbers of turns may be employed. The polarity of each winding A, B, C of the primary 506 is indicated by an asterisk.

The secondary 508 includes first split secondary windings a coupled together at ends in a hexagonal configuration₁、A₂A second split secondary winding B₁、B₂And a third split secondary winding C₁、C₂. First split winding A of current sensing secondary 508 in first winding A of primary 506₁、A₂Of the primary 506, the current in the second winding B of the primary 506 induces the second split winding B of the secondary 508₁、B₂And a current in the third winding C of the primary 506 induces the third split winding C of the secondary 508₁、C₂Of the current in (1). Other currents, typically of lesser magnitude, may be included in other windings.

As shown, each split secondary winding has multiple turns, one half of a turn, two ends 3, 6 and a first portion of two taps 4, 5 (e.g., a₁) And a second part (e.g. A) having one half of a turn, two ends 7, 10 and two taps 8, 9₂) While taps 4, 5, 8, 9 are configured for coupling to the rectification stage 504. In one embodiment, a total of 8 turns may be employed with two turns between taps on the same portion of the secondary winding. Other numbers of turns may be employed and taps in embodiments with different numbers of turns may be at different turns of the winding. The polarity of each winding of secondary 508 is indicated by an asterisk.

The polarity of the second winding B of the secondary 508 is reversed relative to the polarity of the first winding a and the third winding C of the secondary 508. For example, the second split winding B of the secondary 508₁、B₂With respect to the first split winding a of the secondary 508₁、A₂And a third split winding C₁、C₂The polarity of (2) is reversed. Reversing polarity at least partially cancels out leakage fields from adjacent coils and by allowing shorter connections between adjacent coilsThis may further reduce leakage current, losses, parasitics, etc., to make it easier to manufacture.

In a delta-hex topology, such as that shown in fig. 4, the minimum actual number of turns between taps on the same portion of the secondary winding is 3 or higher in order to obtain a turns ratio closer to the ideal ratio and thus avoid power quality problems resulting from turns ratio deviations. In one embodiment, the split second winding B of the inverted secondary 508₁、B₂At least partially compensates for the larger turns ratio deviations and coil asymmetries and thus helps to achieve acceptable power quality even when the minimum number of turns between taps coupled to the rectifier stage 504 is reduced to, for example, two turns. Reducing the number of turns between the taps facilitates the use of transformers with windings having fewer turns and thus smaller, lighter and lower cost transformers and power converters.

The power converter 500 includes a first rectification path 530 and a second rectification path 532 between taps of the secondary winding of the transformer 502 and respective outputs of the power converter 500, with the first and second rectification paths 530, 532 having different inductances. This inductance difference provides an additional phase shift in the current. As shown, the rectifier stage 504 includes a first rectifier 514 and a second rectifier 516 configured to provide full-wave rectification to each secondary output. The first and second rectifiers 514, 516 may comprise diodes, thyristors, hysteretics, and the like. The taps are configured for coupling to the rectifier stage on two routes (e.g., taps 4, 5, 8, 9 of each of the secondary windings), one of the routes having a higher inductance, illustrated as inductance 520, than the other route. For example, an inductance difference of the order of 5 microhenries may be applied. Other inductance differences may be employed. In some embodiments, the desired inductance difference may be obtained by simply providing half of the secondary output with longer leads than the other half of the secondary output. The values of the inductance difference, such as inductance 520, may be selected such that the voltage/current in the output of the secondary 508 of transformer 502 is shifted approximately 15 degrees relative to each other, resulting in a 24-pulse rectified power characteristic without the use of an inter-phase transformer.

The desired inductance difference between the first and second rectification paths 530 and 532 may be achieved in other ways. For example, the desired inductance difference between the first and second rectification paths 530, 532 may be obtained by an inductor coupled between the node 540 and the positive output of the power converter 500, an inductor coupled between the node 540 and the first rectifier 514 and an inductor between the node 540 and the second rectifier 516 (see fig. 7), an inductor coupled between a tap of the secondary winding of the transformer 502 and the second rectifier 516, an inductor coupled between the node 542 and the negative output of the power converter 500, an inductor coupled between the node 532 and the first rectifier 514, and an inductor between the node 542 and the second rectifier 516, etc. As noted above, using a different length of lead wire than the inductor coil may be sufficient to obtain a desired inductance difference between the first and second rectification paths 530, 532.

In an embodiment, the transformer 502 includes three identical or substantially identical coils, each having a primary winding (e.g., primary winding a) and a split secondary winding (e.g., split secondary winding a)₁、A₂). Non-identical coils may be employed, although identical or substantially identical coils may generally provide higher power quality. The secondary winding may be physically split as well as logically split, which may facilitate access to the taps. In an embodiment, each portion of the split secondary winding may be the same. In an embodiment, the portions of the split secondary windings may be substantially identical. In an embodiment, the portions of the split secondary winding may have the same number of turns. In an embodiment, the portions of the split secondary winding may have similar, but different, numbers of turns. In an embodiment, the primary winding (e.g., primary winding a) may be physically split, which in some embodiments provides better power quality by, for example, reducing harmonic distortion at least in part at selected harmonics. For example, a physically split primary may have a split secondary winding sandwiched between portions of the split primary winding (see coil 810 of fig. 8). The split primary winding may have twoThe same portion, may have two substantially similar portions with similar, but different, turns, etc. In one embodiment, the coils may be substantially identical and one of the coils has a polarity opposite to the polarity of the other coils. The windings of the transformer 502 may, for example, comprise copper, anodized aluminum, combinations thereof, or the like.

The total harmonic distortion of an embodiment of the power converter 500 of fig. 5 is in the range of 3% to 5% for a 3-phase 115 volt AC input signal at 400Hz and a 28 volt DC output to a 125 amp load. The topology of the embodiment of fig. 5 is much simpler than the topologies of the power converters 200, 300 of fig. 2 and 3, and avoids the use of IPT transformers and filter inductors to achieve much lower harmonic distortion than a delta-hex power converter, such as the power converter 400 of fig. 4. Superior electrical properties can also be obtained in comparison with the manner of fig. 2 to 4. In an embodiment, voltage drops and power dissipation in the IPT transformer and input inductor can be avoided, power efficiency is improved, the rectifier diodes share current equally (which helps handle overload), EMI emissions are lower, and AC current distortion is at an acceptable level.

Fig. 6 is an electrical schematic diagram of an embodiment of a power converter 600 employing a delta-hex topology. Power converter 600 includes a transformer 602 and a rectifier stage 604. The transformer 602 includes a primary 610, a secondary 612, and a core 611.

The primary 610 has a first winding a, a second winding B, and a third winding C configured to be coupled to a 3-phase AC input signal 613 in a delta configuration. Each winding A, B, C of primary 610 has a respective first tap 1 and second tap 2. As shown, taps 1, 2 of winding A, B, C of primary 610 are at the ends of winding A, B, C. The reference numbers assigned to the taps or ends of the windings do not necessarily indicate the turn count at the tap or end. The primary winding A, B, C typically has more than one turn. For example, a primary winding, such as winding a of primary 610, may have 61 turns in one embodiment. The polarity of each winding A, B, C of the primary 610 is indicated by an asterisk.

The secondary 612 is included in a hexagonal configurationFirst split secondary windings A coupled together at ends₁、A₂A second split secondary winding B₁、B₂And a third split secondary winding C₁、C₂. First split winding A of current sensing secondary 612 in first winding A of primary 610₁、A₂Of the primary 610, the current in the second winding B of the primary 610 induces the second split winding B of the secondary 612₁、B₂And a current in the third winding C of the primary 610 induces the third split winding C of the secondary 612₁、C₂Of the current in (1). Other currents, typically of lesser magnitude, may be included in other windings.

As shown, each split secondary winding has multiple turns, one half of a turn, two ends 3, 6 and a first portion of two taps 4, 5 (e.g., a₁) And a second part (e.g. A) having one half of a turn, two ends 7, 10 and two taps 8, 9₂) And taps 4, 5, 8, 9 are configured for coupling to a rectification stage 604. In one embodiment, a total of 8 turns may be employed with two turns between taps on the same portion of the secondary winding. Other numbers of turns may be employed and taps in embodiments with different numbers of turns may be on different turns of the winding. The polarity of each winding of secondary 612 is indicated by an asterisk.

Second split winding B of secondary 612₁、B₂With respect to the first split winding a of the secondary 612₁、A₂And a third split winding C₁、C₂The polarity of (2) is reversed. As discussed above, in delta-hex designs, such as the one shown in fig. 4, the minimum actual number of turns between taps is 3 or higher in order to obtain a turns ratio closer to the ideal ratio and thus avoid the power quality issues created by the skew. In an embodiment, the second winding B of the primary 610 and the second split winding B of the secondary 612 are reversed₁、B₂At least partially compensates for the larger turns ratio deviations and coil asymmetries and thus helps to reduce even the minimum number of turns between taps coupled to rectifier stage 604 to, for example, twoAcceptable power quality is still obtained with turns. Reducing the number of turns between the taps facilitates the use of transformers with windings having fewer turns and thus smaller, lighter and lower cost transformers and power converters.

The rectification stage 604 includes a first rectifier branch 614 and a second rectifier branch 616. As shown, each rectifier branch 614, 616 includes six diodes 618 coupled in parallel with an optional hysteretic device 620. Other rectifier leg configurations may be employed. As shown, each hysteretic device includes a resistor coupled in series with a capacitor. The hysteretic device may, for example, comprise a 4 microfarad capacitor coupled in series with a 1 ohm resistor. Other flow retarders may be employed and may be omitted in some embodiments.

Respective anodes of the diodes 608 of the first rectifier branch 614 are coupled to the first split secondary winding a₁、A₂Taps 4, 9, a third split secondary winding C₁、C₂Taps 4, 9 and a second split secondary winding B₁、B₂Taps 5, 8. Respective cathodes of diodes 618 of second rectifier branch 616 are coupled to first split secondary winding a₁、A₂Taps 5, 8 of, and a third split secondary winding C₁、C₂Taps 5, 8 and a second split secondary winding B₁、B₂Taps 4, 9.

The cathodes of the first rectifier branch 614 are coupled together and to the positive output of the power converter 600, and the anodes of the second rectifier branch 616 are coupled together and to the negative output of the power converter 600. As shown, the power converter is configured to provide an approximately 28 volt DC output in response to a 115 volt AC input. As shown, the power converter 600 has an optional input filter 622, an optional output filter 624, and an optional current shunt 626 that may be used, for example, to monitor the performance and/or load conditions of the power converter 600. Other filter and shunt configurations may be employed.

In one embodiment, the transformer 602 includes three identical or basic transformersThe same coils, each coil having a primary winding (e.g., primary winding A) and a split secondary winding (e.g., split secondary winding A)₁、A₂). Non-identical coils may be employed, although identical or substantially identical coils may generally provide higher power quality. The secondary winding may be physically split as well as logically split, which may facilitate access to the taps. In an embodiment, each portion of the split secondary winding may be the same. In an embodiment, the portions of the split secondary windings may be substantially identical. In an embodiment, the portions of the split secondary winding may have the same number of turns. In an embodiment, the portions of the split secondary winding may have similar, but different, numbers of turns. In an embodiment, the primary winding (e.g., primary winding a) may be physically split, which in some embodiments provides better power quality by reducing harmonic distortion, e.g., reducing distortion at selected harmonics. In an embodiment, a physically split primary may have a split secondary winding sandwiched between portions of the split primary winding (see coil 810 of fig. 8). The split primary winding may have two identical portions, may have two substantially similar portions with similar turns, but different, etc. In one embodiment, the coils may be substantially identical and one of the coils has a polarity opposite to the polarity of the other coils. The windings of the transformer 602 may, for example, comprise copper, anodized aluminum, combinations thereof, or the like.

In simulations and tests applying a 3-phase 115 volt AC input signal to an embodiment of the power converter 600 of fig. 6, an approximately 28 volt DC output was obtained with total harmonic distortion in the range 7% to 7.5% and the input current waveform consistent with 12-pulse rectification. The topology of the embodiment of fig. 6 is much simpler than the topologies of the power converters 200, 300 of fig. 2 and 3, and avoids the use of IPT transformers and filter inductors to achieve much lower harmonic distortion than a delta-hex power converter, such as the power converter 400 of fig. 4. Superior electrical performance can also be obtained compared to the topologies shown in fig. 2-4. In an embodiment, voltage drops and power dissipation in the IPT transformer and input inductor can be avoided, power efficiency is improved, the rectifier diodes share current equally (which helps handle overload), EMI emissions are lower, and AC current distortion is at an acceptable level.

Fig. 7 is an electrical schematic diagram of an embodiment of a power converter 700 employing a delta-hex topology. Power converter 700 includes a transformer 702 and a rectifier stage 704. The transformer 702 includes a primary 710, a secondary 712, and a core 711.

The primary 710 has a first winding a, a second winding B, and a third winding C coupled to a 3-phase AC input signal 713 in a delta configuration. Each winding A, B, C of primary 710 has a respective first tap 1 and second tap 2. As shown, taps 1, 2 of winding A, B, C of primary 710 are at the ends of winding A, B, C. The reference numbers assigned to the taps or ends of the windings do not necessarily indicate the turn count at the tap or end. The primary winding A, B, C typically has more than one turn. For example, a primary winding, such as winding a of primary 710, may have 61 turns in one embodiment. The polarity of each winding A, B, C of the primary 710 is indicated by an asterisk.

The secondary 712 includes a first split secondary winding a coupled together at ends in a hexagonal configuration₁、A₂A second split secondary winding B₁、B₂And a third split secondary winding C₁、C₂. First split winding A of current sensing secondary 712 in first winding A of primary 710₁、A₂Of the primary 710, the current in the second winding B of the primary 710 induces the second split winding B of the secondary 712₁、B₂And a current in the third winding C of the primary 710 induces the third split winding C of the secondary 712₁、C₂Of the current in (1). Other currents, typically of lesser magnitude, may be included in the other windings (e.g., the current in the first winding a of the primary 710 may induce the second split winding B of the secondary 712₁、B₂But this current will generally be the current in the first winding a of the primary 710 at the first split winding a of the secondary 712₁、A₂A lesser magnitude of the current induced).

As shown in the figure, eachEach split secondary winding has a first part (e.g. A) with a plurality of turns, one half with turns, two ends 3, 6 and two taps 4, 5₁) And a second part (e.g. A) having one half of a turn, two ends 7, 10 and two taps 8, 9₂) While taps 4, 5, 8, 9 are configured for coupling to a rectification stage 704. In one embodiment, a total of 8 turns may be employed with two turns between taps on the same portion of the secondary winding. Other numbers of turns may be employed and taps in embodiments with different numbers of turns may be at different turns of the winding. The polarity of each winding of the secondary 712 is indicated by an asterisk.

Second split winding B of secondary 712₁、B₂With respect to the first split winding a of the secondary 712₁、A₂And a third split winding C₁、C₂The polarity of (2) is reversed. As discussed above, a delta-hex design, such as the one shown in fig. 4, has a minimum actual number of turns between taps of 3 or higher in order to obtain a turns ratio closer to the ideal ratio and thus avoid power quality issues resulting from skew. In an embodiment, the split second winding B of the inverted secondary 712₁、B₂At least partially compensates for the larger turns ratio deviation and coil asymmetry and thus helps to achieve acceptable power quality even when the minimum number of turns between taps coupled to rectifier stage 704 is reduced to two turns. Reducing the number of turns between the taps facilitates the use of transformers with windings having fewer turns and thus smaller, lighter and lower cost transformers and power converters. Some embodiments may reverse the polarity of primary winding B relative to primary windings a and C.

Rectification stage 704 includes a first set of rectifier legs 714A, 714B coupled to the positive output of power converter 700 and a second set of rectifier legs 716A, 716B coupled to the negative output of power converter 700. As shown, each rectifier leg 714A, 714B, 716A, 716B includes six diodes 718 coupled in parallel with an optional hysteretic device 720. Other rectifier leg configurations may be employed. As shown, each hysteretic device includes a resistor coupled in series with a capacitor. The hysteretic device may, for example, comprise a 4 microfarad capacitor coupled in series with a 1 ohm resistor. Other flow retarders may be employed and may be omitted in some embodiments.

Taps 4, 5, 8, 9 configured for coupling to each secondary winding of rectifier stage 704 are each coupled to a respective anode of diode 718 of first set of rectifier legs 714A, 714B and a respective cathode of diode 718 of second set of rectifier legs 716A, 716B.

The power converter 700 includes a first rectification path 730 and a second rectification path 732 between taps of the secondary winding of the transformer 702 and the output of the power converter 700, with the first and second rectification paths 730, 732 having different inductances. This inductance difference provides an additional phase shift in the current. As shown, a first rectification path 730 includes a coupling between the cathode of the diode 718 of the first set of rectifier legs 714A, 714B and the positive output of the power converter 700, and a second rectification path 732 includes a coupling between the anode of the diode 718 of the second set of rectifier legs 716A, 716B. As shown, the inductance difference between the first and second rectification paths 730, 732 is obtained by coupling inductors 734, 736 into a portion of the rectification path 730 that couples the diodes 718 of the first set of rectifier legs 714A, 714B to the positive output of the power converter 700. For example, an inductor having an inductance of approximately 5 microhenries may be employed. Other inductances may be employed and the desired inductance difference between the first and second rectification paths 730, 732 may be obtained in other ways. In some embodiments, the desired inductance difference may be obtained by simply configuring a portion of the rectification path 730 that couples the first set of rectifier legs 714A, 714B to the positive output of the power converter 700 to have a length that is longer or shorter than a portion of the rectification path 732 that couples the second set of rectifier legs 716A, 716B to the negative output of the power converter 700. For example, half of the secondary output may be configured with longer leads than the other half of the secondary output. The inductance difference may be selected such that the voltage/current in the output of the secondary 712 of the transformer 702 is shifted approximately 15 degrees relative to each other to produce a 24-pulse rectified power characteristic. Other examples of ways to obtain the desired inductance difference between the first and second rectification paths 730, 732 include placing an inductor between the node 740 and the positive output of the power converter 700, placing a pair of inductors between the node 742 and respective rectifier groups of the second set of rectifiers 716A, 716B, placing an inductor between a tap of the secondary winding of the transformer 702 and the first set of rectifiers 714A, 714B (see fig. 5), placing an inductor between the node 742 and the negative output of the power converter 700, and so forth. As noted above, using different lengths of wire instead of an inductor coil may be sufficient to obtain the desired inductance difference between the first and second rectification paths 730, 732.

In an embodiment, the transformer 702 includes three identical or substantially identical coils, each having a primary winding (e.g., primary winding a) and a split secondary winding (e.g., split secondary winding a)₁、A₂). Non-identical coils may be employed, although identical or substantially identical coils may generally provide higher power quality. The secondary winding may be physically split as well as logically split, which may facilitate access to the taps. In an embodiment, each portion of the split secondary winding may be the same. In an embodiment, the portions of the split secondary windings may be substantially identical. In an embodiment, the portions of the split secondary winding may have the same number of turns. In an embodiment, the portions of the split secondary winding may have similar, but different, numbers of turns. In an embodiment, the primary winding (e.g., primary winding a) may be physically split, which in some embodiments provides better power quality by, for example, reducing harmonic distortion at selected harmonics. For example, a physically split primary may have a split secondary winding sandwiched between portions of the split primary winding (see fig. 8). The split primary winding may have two identical portions, may have two substantially similar portions with similar turns, but different, etc. In one embodiment, the coils may be substantially identical and one of the coils has a secondary winding with a secondary winding that is identical to the secondary winding of the other coilThe opposite polarity. The windings of the transformer 702 may, for example, comprise copper, anodized aluminum, combinations thereof, or the like.

As shown, the power converter 700 is configured to provide an approximately 28 volt DC output in response to a 115 volt AC input. As shown, the power converter 700 has an optional input filter 722 and an optional output filter 724. Other filter configurations may be employed.

In simulations and tests applying a 3-phase 115 volt AC input signal to an embodiment of the power converter 700 of fig. 7, an approximately 28 volt DC output was obtained with total harmonic distortion in the range 3.3% to 4.2% and an input current waveform consistent with 24-pulse rectification. The topology of the embodiment of fig. 7 is much simpler than the topologies of the power converters 200, 300 of fig. 2 and 3, and avoids the use of IPT transformers and filter inductors to achieve much lower harmonic distortion than a delta-hex power converter, such as the power converter 400 of fig. 4. Superior electrical performance can also be obtained compared to the topologies of fig. 2-4. In an embodiment, voltage drops and power dissipation in the IPT transformer and input inductor can be avoided, power efficiency is improved, the rectifier diodes share current equally (which helps handle overload), EMI emissions are lower, and AC current distortion is at an acceptable level.

Fig. 8 is a schematic diagram of an embodiment of a transformer 800 suitable for use in embodiments of power converters such as those shown in fig. 5-7. Fig. 9 is a top view of an embodiment of the transformer 800 of fig. 8.

The transformer 800 includes three coils 810, 820, 830 wound on a core 802. The core 802 may, for example, take the form of a rod or bar of magnetizable or ferritic material, such as ferrite, samarium cobalt, or neodymium-iron-boron. Although not shown, the transformer 800 may include a case.

The first coil 810 includes a primary winding a split into an inner winding portion 812 and an outer winding portion 814. The inner winding portion 812 includes two taps 1, 2 located at the ends of the inner winding portion 812. The outer winding portion 814 includes two coils positioned at the ends of the outer winding portion 814Taps 11, 12. The primary winding a has a first polarity indicated by an asterisk. The total number of primary a turns may be selected to help achieve a desired turn ratio (see, e.g., table 1 below). The total number of turns of the primary winding a may be, for example, 181 turns, 121 turns, 61 turns, etc. The total number of turns of the inner winding portion 812 of the primary winding a may be, for example, 90, 91, 92, 60, 61, 62, 30, 31, or 32 turns, and the total number of turns of the outer portion 814 of the primary winding a may be, for example, 91, 90, 89, 61, 60, 59, 31, 30, or 29 turns. Other total numbers of turns and numbers of turns in the respective sections may be employed. The first coil 810 comprises a split secondary a with four ends 3, 6, 7, 10 and four taps 4, 5, 8, 9₁、A₂. Splitting Secondary A as shown₁、A₂Sandwiched between the first portion 812 and the second portion 814 of primary a. Secondary winding A₁、A₂Having a first polarity as indicated by the asterisk. Secondary winding A₁、A₂May for example be 22, 16 or 8 and each part a₁、A₂Typically having half of the total turns, e.g. 11, 8 or 4 turns. Other total numbers of turns and numbers of turns in the respective sections may be employed.

The second coil 820 includes a primary winding B split into an inner winding portion 822 and an outer winding portion 824. The inner winding portion 822 includes two taps 11, 12 located at the ends of the inner winding portion 822. The outer winding portion 824 comprises two taps 1, 2 located at the ends of the outer winding portion 824. The primary winding B has a second polarity indicated by an asterisk and different from the first polarity. The total number of primary B turns may be selected to help achieve a desired turn ratio (see, e.g., table 1 below). The total number of turns of the primary winding B may be, for example, 181 turns, 121 turns, 61 turns, etc. The total number of turns of the inner winding portion 822 of the primary winding B may be, for example, 90, 91, 92, 60, 61, 62, 30, 31, or 32 turns, and the total number of turns of the outer portion 824 of the primary winding B may be, for example, 91, 90, 89, 61, 60, 59, 31, 30, or 29 turns. Other total numbers of turns and numbers of turns in the respective sections may be employed. The second coil 820 comprises a split secondary B with four ends 3, 6, 7, 10 and four taps 4, 5, 8, 9₁、B₂. As shown in the figure, is disassembledSubclass B₁、B₂Sandwiched between the first portion 822 and the second portion 824 of the primary B. Secondary winding B₁、B₂Having a second polarity as indicated by the asterisk. Secondary winding B₁、B₂May for example be 22, 16 or 8 and each section B₁、B₂Typically having half of the total turns, e.g. 11, 8 or 4 turns. Other total numbers of turns and numbers of turns in the respective sections may be employed.

Third coil 830 includes a primary winding C split into an inner winding portion 832 and an outer winding portion 834. The inner winding portion 832 includes two taps 1, 2 located at the ends of the inner winding portion 832. The outer winding portion 834 comprises two taps 11, 12 positioned at the ends of the outer winding portion 834. The primary winding C has a first polarity indicated by an asterisk. The total number of primary C turns may be selected to help achieve a desired turn ratio (see, e.g., table 1 below). The total number of turns of the primary winding C may be, for example, 181 turns, 121 turns, 61 turns, etc. The total number of turns of the inner winding portion 832 of the primary winding C may be, for example, 90, 91, 92, 60, 61, 62, 30, 31, or 32 turns, and the total number of turns of the outer portion 834 of the primary winding C may be, for example, 91, 90, 89, 61, 60, 59, 31, 30, or 29 turns. Other total numbers of turns and numbers of turns in the respective sections may be employed. Third coil 830 comprises a split secondary C with four ends 3, 6, 7, 10 and four taps 4, 5, 8, 9₁、C₂. Splitting Secondary C as shown₁、C₂Sandwiched between the first 832 and second 834 portions of primary C. Secondary winding C₁、C₂Having a first polarity as indicated by the asterisk. Secondary winding C₁、C₂With a total number of turns of, for example, 22, 16 or 8 and each portion C₁、C₂Typically having half of the total turns, e.g. 11, 8 or 4 turns. Other total numbers of turns and numbers of turns in the respective sections may be employed.

The first coil 810, the second coil 820 and the third coil 830 are positioned beside each other in a row while the second coil 820 is positioned between the first coil 810 and the third coil 830.

In an embodiment, the first, second, and third coils 810, 820, 830 may be generally identical or substantially identical while the polarity of the second coil 820 is opposite to the polarity of the first and third coils 810, 830.

Fig. 9 is a top view of an embodiment of the transformer 800 of fig. 8 suitable for use, for example, in the embodiments of the power converters shown in fig. 5-7. The transformer includes a core 802 having three coils wound thereon, which are shown as first, second and third coils 810, 820, 830 of fig. 8. Fig. 9 illustrates coupling the secondary windings of the coils 810, 820, 830 to each other in one embodiment. Third tap 3 of third coil 830 is coupled to seventh tap 7 of first coil 810, sixth tap 6 of third coil 830 is coupled to seventh tap 7 of second coil 820, seventh tap 7 of third coil 830 is coupled to sixth tap 6 of second coil 820, tenth tap 10 of third coil 830 is coupled to sixth tap 6 of first coil 810, third tap 3 of first coil 810 is coupled to tenth tap 10 of second coil 820, and tenth tap 10 of first coil 810 is coupled to third tap 3 of second coil 820. A fourth tap 4, a fifth tap 5, an eighth tap 8, and a ninth tap 9 of the respective coils 810, 820, 830 may be used to couple to a rectifier stage (see, e.g., rectifier stage 704 of fig. 7).

Fig. 10-12 show front and side views of an embodiment of a power converter 1000 and illustrate an example layout of components of a transformer and rectifier suitable for use, for example, in an embodiment of the power converter 700 of fig. 7. As shown, the transformer employs the physical configuration of the embodiment of the transformer 800 of fig. 8 and 9, and the rectifier employs the electrical configuration of the rectifier 704 of the power converter 700 of fig. 7.

Fig. 13 is an isometric view of an embodiment of a power converter 1300. Power converter 1300 includes a transformer 1302 having a coil heat sink 1336 and a rectifier 1304 including a plurality of diodes 1318 coupled to the diode heat sink 1338. As shown, diode heat sink 1338 is electrically coupled to diode 1318 and is configured as a bus for the positive and negative DC outputs of power converter 1300. Although 12 diodes are shown, additional diodes may be employed in some embodiments. The power converter may, for example, employ a delta-hex topology, such as the topologies shown in fig. 5-7, and the like.

Fig. 14-19 graphically illustrate typical differences in power quality produced by power converters employing 6-pulse, 12-pulse, and 24-pulse conversion topologies.

Fig. 14 is a graphical representation of ripple in the DC output of an embodiment of a 6-pulse power converter. The DC ripple is shown to be about 14 percent of the output voltage. Fig. 15 is a graphical representation of input current for an embodiment of a 6-pulse power converter. The total harmonic distortion is shown to be approximately 28 to 32 percent.

Fig. 16 is a graphical representation of ripple in the DC output of an embodiment of a 12-pulse power converter. The DC ripple is shown to be about 3.4 percent of the output voltage. Fig. 17 is a graphical representation of input current for an embodiment of a 12-pulse power converter. The total harmonic distortion is shown to be approximately 9 to 14 percent.

Fig. 18 is a graphical representation of ripple in the DC output of an embodiment of a 24-pulse power converter. The DC ripple is shown to be about 0.9 percent. Fig. 19 is a graphical representation of input current for an embodiment of a 24-pulse power converter. The total harmonic distortion is shown to be approximately 3 to 5 percent.

Table 1 provides some examples of transformer winding turns, tap turn placement, and calculated results/center errors. Simulations of embodiments of the power converter in a delta-hex configuration, such as the embodiments shown in fig. 5-12, yield acceptable power quality for a center error as high as 7.5%. In practice, a coil having a total number of turns 181 or less in the primary winding may be utilized in power converters typically used in avionics applications. For topologies such as the one shown in fig. 4, the power quality is the boundary line when the number of turns is 181 and is generally too low when the number of turns is less than 181. In contrast, the power quality for the embodiments of the delta-hex topology shown in fig. 5-7 is generally good enough to be used in applications requiring high current, low voltage power supplies, such as avionics applications.

TABLE 1

The above description of illustrated embodiments, including what is described in the abstract of the specification, is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. While specific embodiments of, and examples for, the disclosure are described herein for illustrative purposes, various equivalent modifications can be made without departing from the spirit and scope of the disclosure, as those skilled in the relevant art will recognize. The teachings provided herein of the various embodiments can be applied to other transformers, rectifiers, and power converters, not necessarily the example transformers, rectifiers, and power converters generally described above. The teachings provided herein of the various embodiments can be applied to other circuits including other converter circuits and not necessarily the example converter circuits generally described above.

The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to employ systems, circuits and concepts of the various patents, applications and publications discussed herein to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims (16)

1. A power converter, comprising:

a transformer having:

three primary windings configured for connecting respective phases of a three-phase Alternating Current (AC) input signal in a delta configuration; and

three secondary windings, each secondary winding split into two parts, the parts of the secondary windings coupled together in a closed regular hexagon, each part of each secondary winding having at least two taps and the taps being distributed at regular angles on the closed regular hexagon;

a first rectification path coupled between a tap of the secondary winding and a positive output of the power converter, wherein a rectifier of the first rectification path is coupled to the positive output of the power converter by a coupling having a first inductance; and

a second commutation path coupled between a tap of the secondary winding and a negative output of the power converter, wherein a rectifier of the second commutation path is coupled to the negative output of the power converter by a coupling having a second inductance that is different from the first inductance of the first commutation path, wherein in operation, the difference in inductance causes the first and second commutation paths to convert the twelve-phase AC signal to twenty-four-pulse dc voltage; and

the first and second rectification paths are coupled to different taps of the secondary winding.

2. The power converter of claim 1 wherein the difference in inductance is selected such that the outputs of the secondary windings are shifted 15 degrees from each other.

3. The power converter of claim 1 wherein one of the secondary windings has a polarity opposite to a polarity of the other secondary windings.

4. The power converter of claim 3, wherein each primary winding is split into two portions, and each secondary winding is sandwiched between the two portions of the corresponding primary winding.

5. The power converter of claim 1, wherein each primary winding is split into two portions, and each secondary winding is sandwiched between the two portions of the corresponding primary winding.

6. The power converter of claim 1, wherein:

the first rectification path comprises 12 rectifiers; and

the second rectification path includes 12 rectifiers.

7. The power converter of claim 1, wherein the first rectification path includes leads having a length different from a length of corresponding leads of the second rectification path.

8. The power converter of claim 1, wherein the first inductance of the first rectification path is five times the second inductance of the second rectification path.

9. The power converter of claim 1, wherein the taps of the secondary winding are distributed on the regular hexagon, any two adjacent ones of the taps corresponding to a center angle, all of the center angles being the same.

10. The power converter of claim 1, wherein two taps on one portion of the secondary winding are on adjacent turns of the one portion of the secondary winding.

11. The power converter of claim 1 wherein the transformer comprises three identical coils, each coil comprising one of the primary windings and a corresponding secondary winding.

12. The power converter of claim 11 wherein the coils are disposed adjacent to each other in a row and a center coil has a polarity different from the polarity of the other coils.

13. A method of power conversion, comprising:

coupling together three primary windings of a transformer in a differential configuration to connect respective phases of a three-phase alternating current;

coupling split portions of three secondary windings of the transformer together in a regular hexagonal configuration;

providing a plurality of taps distributed at regular angles on the secondary winding, each split secondary winding section having at least two taps;

forming a first rectification path between the plurality of taps and the positive output, wherein a rectifier of the first rectification path is coupled to the positive output by a coupling having a first inductance; and

forming a second rectification path between the plurality of taps and the negative output, wherein the rectifier of the second rectification path is coupled to the negative output by a coupling having a second inductance, wherein in operation, the inductance is different such that the first and second rectification paths convert the twelve-phase AC power signal to a twenty-four pulse dc voltage; and

the first and second rectification paths are coupled to different taps of the secondary winding.

14. The method of claim 13, wherein the transformer comprises first, second, and third coils, and the method comprises:

the first, second and third coils are arranged together in a row while the second coil separates the first and third coils, the second coil having a polarity different from the polarity of the first coil and the third coil.

15. The method of claim 13, wherein the primary winding is split into first and second primary portions, and the split portion of each secondary winding is sandwiched between first and second primary portions of the respective primary winding.

16. The method of claim 13, wherein the difference in inductance is selected such that the outputs of the secondary windings are shifted 15 degrees from each other.