JP2009291035A - Synchronous electric motor driving system - Google Patents

Abstract

A synchronous motor driving system capable of suppressing an increase in the number of inverters that generate three-phase AC power is provided for a synchronous motor that operates by receiving a plurality of types of three-phase AC power.
A transformer is provided between an inverter and a synchronous motor. Then, using the three-phase AC power output from the inverter 7 as an input, the transformer 14 includes secondary coils 50, 51, and 52 inside the transformer so as to output a plurality of types of three-phase AC power that are out of phase. . The secondary coils 50 and 52 are staggered coils. The secondary coil 52 outputs three-phase AC power in which the phase of each phase of the three-phase AC power input to the primary coil is advanced by π / 9 radians, and the secondary coil 50 is the primary side The phase of each phase of the three-phase AC power input to the coil is output by three-phase AC power delayed by π / 9 radians.
[Selection] Figure 1

Description

  The present invention relates to a synchronous motor drive system including a synchronous motor and an inverter for driving the synchronous motor, and more particularly to a technique for supplying currents having different phases to a stator winding.

  The synchronous motor drive system includes a three-phase AC synchronous motor, an inverter circuit that converts DC power into AC power and supplies power to the synchronous motor, and a controller that controls the inverter circuit. Examples of the synchronous motor drive system include those for electric vehicles and hybrid vehicles. As the synchronous motor for traveling, a magnet type synchronous motor, so-called brushless DC motor, is employed.

In a synchronous motor having two sets of three-phase windings, a synchronous motor drive system configured by an inverter that gives a desired current phase difference to the two sets of three-phase windings is disclosed in Patent Document 1. .
In Patent Document 1, a rotor having 2P magnetic poles arranged at equal intervals and two sets of three-phase windings each having a phase difference of π / 6 or π / 3 radians in electrical angle are arranged on the circumference. Are used as a synchronous motor, and a plurality of currents having a phase difference of π / 6 or π / 3 radians in electrical angle (two in the case of Patent Document 1) are used. A technique for supplying by an inverter that outputs phase AC power is disclosed. By using a plurality of inverters, it is possible to generate three-phase AC power having more various phase differences.
JP 2000-41392 A

By the way, the inverter is equipped with six switching elements (power semiconductors) in order to supply three currents having different phases. Then, three different currents are supplied by switching control of the switching element.
The use of a plurality of inverters as in Patent Document 1 leads to an increase in switching elements, and the configuration of an inverter device that is a drive system for a synchronous motor becomes complicated. In addition, an increase in switching elements that are switched at high speed increases the possibility of failure of the switching elements, leading to a decrease in reliability of the entire system.

  Accordingly, the present invention has been made in view of the above problems, and a synchronous motor drive system that generates a plurality of three-phase AC powers that are out of phase and drives a synchronous motor while using a single inverter. The purpose is to provide.

In order to solve the above-described problems, the present invention provides an inverter that converts DC power into three-phase AC power and outputs the output, and the three-phase AC power output from the inverter is input to output a plurality of three-phase AC power. The phase of the AC power of a specific phase of one three-phase AC power to be output is different from the phase of the AC power of the specific phase in the other three-phase AC power to be output. A phase converter, and a synchronous motor that is rotated by a plurality of three-phase AC power output from the phase converter, and
It is characterized by having.

  With the configuration as described above, the phase conversion unit generates a plurality of three-phase AC powers to be supplied to the windings, so that the AC motors are supplied with AC powers whose phases are shifted from each other without providing a plurality of inverters. be able to. Since a plurality of inverters are not provided, the number of switching elements does not increase, and a decrease in system reliability due to the use of a large number of switching elements can be prevented.

Hereinafter, a synchronous motor drive system according to an embodiment of the present invention will be described with reference to the drawings.
<Embodiment 1>
FIG. 1 is a circuit diagram showing a configuration of a synchronous motor drive system.
As shown in FIG. 1, the synchronous motor drive system 100 includes an inverter 7, a transformer 14, and a synchronous motor 41, and operates by receiving power supply from the DC power supply 8.

The DC power supply 8 is a DC power supply obtained by rectifying a power supply system or a battery type DC power supply. Examples of the battery type DC power source include a secondary power source such as nickel metal hydride or lithium ion.
The inverter 7 is a voltage type inverter circuit, and is composed of switching elements Q1 to Q6. Switching elements Q1 and Q2 form a U-phase arm, switching element Q3 forms a Q-phase arm, and switching element Q5 forms a W-phase arm. Power semiconductor elements represented by IGBT (Insulated Gate Bipolar Transistor) and MOSFET (Metal Oxide Semiconductor Field Effect Transistor) are applied to the switching elements Q1 to Q6. The AC powers 100a, 100b, 100c output from the U-phase arm, V-phase arm, and W-phase arm are out of phase with each other by 2π / 3 radians.

  In addition, diodes D1 to D6 for flowing current from the emitter side (source side) to the collector side (drain side) are connected between the collector and emitter (or between the drain and source) of each switching element Q1 to Q6. Yes. Further, a MOSFET parasitic diode may be used as the diodes D1 to D6. The AC power of each phase of the three-phase AC power output from the inverter 7 is supplied to the corresponding coil of the primary side coil 12 of the transformer 14.

The transformer 14 includes a primary side coil 12, a shield 13, and secondary side coils 50, 51, 52.
The primary side coil 12 includes coils corresponding to the respective phases of the three-phase AC power and is star-connected.
The shield 13 protects the synchronous motor 41 when an abnormal voltage such as a magnetic interruption between the primary coil 12 and each secondary coil, a magnetic interruption between the coil and peripheral devices, or a lightning impulse is applied. .

The secondary coil 50 has an electrical angle of π / 9 radians in terms of the phase of each phase of the three-phase AC power output to the corresponding phase of the three-phase AC power input to the primary coil 12. This is a staggered coil that has been adjusted to be delayed.
The secondary coil 51 is star-connected in the same manner as the primary coil 12, and outputs three-phase AC power having the same phase for each phase of the three-phase AC power input to the primary coil 12.

The secondary coil 52 has an electrical angle of π / 9 radians in terms of the phase of each phase of the three-phase AC power output to the corresponding phase of the three-phase AC power input to the primary coil 12. It is a staggered coil that has been adjusted to advance.
The staggered type coil will be described more specifically with reference to FIG. FIG. 5 shows the case of the secondary coil 52. Each phase of the secondary coil is composed of two coils, and one winding of each phase is connected in series to one winding of the other phase, and is connected in series with the coil length of the own phase. By adjusting the ratio of the coil lengths of the phases, AC power in which a desired phase difference is generated with respect to the AC power input to the primary coil can be output.

For example, when the coil length is set to 1: 1 as shown in FIG. 5A, the phase of the output power is shifted by π / 6 radians.
In this embodiment, the phase of Eu1 + Ev2 is set to 1: 0.53 by setting the coil length ratio of Eu1 and Ev2, the ratio of the coil length of Ev1 and Ew2, and the ratio of the coil length of Ew1 and Eu2 to 1: 0.53, respectively. The phase of π / 9 radians can be advanced with respect to Eu1, the phase of Ev1 + Ew2 can be advanced by π / 9 radians with respect to Ev1, and the phase of Ew1 + Eu2 can be advanced with respect to Ew1 by π / 9 radians.

5 illustrates the case where the phase is advanced as in the secondary side coil 52, but in the case where the phase is delayed as in the secondary side coil 50, the combination of secondary coil connections is changed. Specifically, Eu1 may be connected to Ew2, Ev1 may be connected to Eu2, and Ew1 may be connected to Ev2.
Here, the AC power output from each secondary coil will be described. The output currents 101a, 101b, and 101c of the secondary coil 50 are out of phase by 2π / 3 radians. The same applies to the output currents 102a, 102b, 102c of the secondary coil 51, and the same applies to the output currents 103a, 103b, 103c of the secondary coil 52.

The output currents 101a, 102a, and 103a are out of phase by π / 9 radians. The same applies to the output currents 101b, 102b, and 103b, and the same applies to the output currents 101c, 102c, and 103c.
The synchronous motor 41 will now be described in detail with reference to the drawings. FIG. 2 is a plan view of the synchronous motor constituting the synchronous motor drive system according to the first embodiment of the present invention. FIG. 3 is a detailed view of the synchronous motor of FIG.

FIG. 2 is a cross-sectional view of the synchronous motor 41 cut along a plane perpendicular to the rotation axis.
The synchronous motor 41 includes the rotor 2 and the stator 43.
The rotor 2 includes a rotor core 4 and a plurality of permanent magnets 5. The permanent magnets 5 are arranged on the rotor core 4 at equal intervals in the circumferential direction of the rotor. The magnetic pole 6 constituted by the permanent magnet 5 constitutes a magnetic pole pair in which N poles and S poles are alternately arranged with respect to the stator 43. The magnetic pole pair N pole and S pole have an electrical angle of 2π radians, and the arrangement interval of adjacent magnetic poles has an electrical angle of π radians. In this embodiment, the rotor has 20 magnetic poles, and the electrical angle is 10 times the mechanical angle. In FIG. 2, in order to make the drawing of the permanent magnet 5 and its magnetic pole 6 easy to see, no lead wire is drawn from all the permanent magnets. Similarly, the stator winding 9 and the stator teeth 47 are not drawn from all the stator windings and teeth.

The stator 43 includes a plurality of stator teeth 47 disposed to face the rotor 2 and a stator winding 9 wound around each stator tooth 47 in a concentrated manner. The plurality of stator teeth 47 constitutes a stator tooth group 48 in units of three arranged in the circumferential direction of the stator. In the present embodiment, six sets of stator teeth 48 are arranged at equal intervals of 60 ° in mechanical angle.
The number of magnetic poles arranged in the circumferential direction of the rotor 2 is 20 in total, and the number of stator teeth is 18 in total, which are shifted by 10/9 per half circumference.

  In FIG. 2, when the counterclockwise rotation direction is the + direction, the stator teeth set 48b is arranged with a mechanical angle of −60 ° and an electrical angle of + 2π / 3 radians with respect to the stator teeth set 48a. Further, the stator teeth group 48c is disposed with a mechanical angle of + 60 ° and an electrical angle of + 4π / 3 radians (−2π / 3 radians) with respect to the stator teeth group 48a. Therefore, the stator teeth group 48a, the fixed teeth group 48b, and the stator teeth group 48c are arranged at an electrical angle of 2π / 3 radians.

In the synchronous motor of the present embodiment, the combination of the stator teeth group 48a, the stator teeth group 48b, and the stator teeth group 48c is two sets in the circumferential direction (the stator teeth group 48a ′ and the stator teeth group 48b ′). , Stator teeth group 48c ′) is repeated arrangement.
The configuration of the stator tooth group 48a will be described in detail with reference to FIG. Hereinafter, the mechanical angle between the stator windings will be discussed, and the angle between the centers (one-dot chain lines) of the stator teeth around which the respective stator windings are wound is expressed. The stator teeth group 48a is composed of three adjacent stator teeth 61a, 62a, 63a. The stator teeth 61a, 62a, 63a are arranged with stator windings 81a, 82a, 83a wound in concentrated winding so that the winding directions are opposite to each other. The stator teeth 61a around which the stator winding 81a is wound are arranged at a mechanical angle of + 20 ° with respect to the stator teeth 62a around which the stator winding 82a is wound. That is, they are arranged with a deviation of + π / 9 radians from the electrical angle π radians (mechanical angle 18 °), which is the magnetic pole spacing. Similarly, the stator winding 83a is disposed at a mechanical angle of −20 ° with respect to the stator winding 82a. That is, they are arranged with a deviation of −π / 9 radians from the electrical angle π radians, which is the magnetic pole interval. Here, the stator teeth are arranged at equal intervals of 360/18 = 20 ° in the circumferential direction. On the other hand, 20 magnetic poles of the rotor are arranged at equal intervals in the circumferential direction, and the interval is 360/20 = 18 °.

Similarly to the stator teeth set 48a, the other two sets of stator teeth sets 48b and 48c shown in FIG. 2 are electrically connected from the electrical angle π radians in which the three windings are magnetic pole intervals. They are offset by + π / 9 radians and −π / 9 radians.
FIG. 4 is a diagram for explaining the connection of the stator windings of the synchronous motor shown in FIG.
The a, b, and c at the end of the illustrated winding terminal numbers correspond to the windings that constitute the stator tooth groups 48a, 48b, and 48c, respectively.

  The terminals 31a, 32a, 33a of the three stator windings 81a, 82a, 83a in the stator tooth set 48a are individually connected to the outside, and the secondary coils 50, 51, It is individually connected to 52 connection terminals. Similarly, the terminals 31b, 32b, 33b of the three windings in the stator tooth set 48b and the terminals 31c, 32c, 33c of the three windings of the stator tooth set 48c are also individually brought out to the outside. And connected to the connection terminals of the secondary side coils 50, 51, 52 of the transformer 14 individually.

  In addition, terminals of the stator windings having a phase difference of 2π / 3 radians in different stator tooth groups 48a, 48b, 48c are commonly connected to a neutral point. That is, the terminals 34a, 34b, and 34c are connected to the first neutral point, the terminals 35a, 35b, and 35c are connected to the second neutral point, and the terminals 36a, 36b, and 36c are connected to the third neutral point. Is connected to the neutral point. In this example, the first, second and third neutral points are electrically separated, but any two neutral points or all neutral points can be electrically connected. Good.

  In the present embodiment, there are two sets of stator teeth 48a, stator teeth 48b, and stator teeth 48c. Are in the same positional relationship in terms of electrical angle. For this reason, a neutral point connection may be configured between three adjacent stator teeth groups among the six stator teeth groups, or a neutral point connection between every other three stator teeth groups. Further, the neutral point connection may be constituted by all six sets of stator teeth.

The 18 stator teeth are arranged at a different arrangement interval from the magnetic pole interval of the rotor, and constitute a stator teeth group in units of 3 arranged in the circumferential direction. Further, the three stator windings in each stator tooth group are individually connected to independent external terminals.
Here, “individual” indicates the relationship between the stator windings included in one stator tooth group, and the relationship between the stator windings included in different stator teeth groups. It does not indicate. Accordingly, the stator windings included in different stator teeth groups may be connected in common if conditions permit. For example, currents of the same phase are supplied to the stator winding 81a included in the stator teeth set 48a and the stator winding 81a ′ included in the stator teeth set 48a ′. It is good also as connecting to the external terminal. Of course, there is no problem even if it is individually connected to the external terminal.

How AC power is supplied to the synchronous motor 41 configured as described above will be described with reference to FIGS. 6 and 7.
FIG. 6 shows the positional relationship between the stator and the rotor according to the first embodiment of the present invention. FIGS. 6 (a), 6 (b), and 6 (c) show that the rotor 2 is counterclockwise. The positional relationship between the stator and the rotor when rotated by 2 ° in mechanical angle (π / 9 radians in electrical angle) is shown. FIG. 5 is a diagram showing a time change of the current flowing through each stator winding in the first embodiment. The times indicated by (a), (b), and (c) in FIG. 7 correspond to the positional relationships shown in FIGS. 6 (a), 6 (b), and 6 (c), respectively.

  2 and 3, the distance between the magnetic poles of the rotor is indicated by 10 and 11. The distance between the magnetic poles 10 and 11 of the rotor means the position of the magnetic neutral point between the magnetic pole N and the magnetic pole S which are composed of permanent magnets arranged on the rotor. Here, it is mechanically located between the magnets. Reference numeral 10 denotes the distance between the magnetic poles changing from the N pole to the S pole in the counterclockwise direction, and reference numeral 11 denotes the distance between the magnetic poles changing from the S pole to the N pole in the counterclockwise direction. The inter-magnetic pole 11 ′ is at the same electrical angle as the inter-magnetic pole 11 but at a different mechanical angle.

  In FIG. 6A, as indicated by the alternate long and short dash line, the center of the stator teeth 63a and the rotor magnetic poles 11 are opposed to each other in a matching positional relationship. When the current is supplied by adjusting the phase so that the current flowing through the stator winding 83a is maximized in this positional relationship, the magnet torque that is the torque generated by the permanent magnet is maximized. As described with reference to FIG. 2, the angle between adjacent magnetic poles (18 °) and the angle between adjacent stator teeth (20 °) are different. Are opposed to each other in a positional relationship that coincides with each other, the center of the stator teeth 62a and the rotor magnetic pole 10 and the center of the stator teeth 61a and the rotor magnetic pole 11 'are opposed to each other with a shifted positional relationship.

  In FIG. 6 (b), the rotor is rotated counterclockwise by 2 ° in mechanical angle (π / 9 radians in electrical angle) from FIG. 6 (a), and the stator teeth as shown by the one-dot chain line. The center of 62a and the rotor magnetic pole 10 face each other in a positional relationship that coincides. When the current is supplied by adjusting the phase so that the current flowing through the stator winding 82a is maximized in this positional relationship, the magnet torque that is the torque generated by the permanent magnet is maximized. At this time, the center of the stator teeth 63a and 11 between the rotor magnetic poles, and the center of the stator teeth 61a and 11 'between the rotor magnetic poles face each other in a shifted positional relationship.

  6 (c), the rotor is rotated counterclockwise by a mechanical angle of 2 ° (electrical angle π / 9 radians) from FIG. 6 (b). The center of 61a and the rotor magnetic pole 11 'are opposed to each other in a matching positional relationship. When the current is supplied by adjusting the phase so that the current flowing through the stator winding 81a is maximized in this positional relationship, the magnet torque that is the torque by the permanent magnet is maximized. At this time, the center of the stator teeth 63a and 11 between the rotor magnetic poles, and the center of the stator teeth 62a and 10 between the rotor magnetic poles face each other in a shifted positional relationship.

  6A, 6B, and 6C, that is, each of the stator teeth of the stator teeth 61a, 62a, and 63a facing each other between the rotor magnetic poles. In time, the current is supplied by adjusting the phase so that the currents flowing through the stator windings 81a, 82a, and 83a become maximum. As a result, the magnet torque can be maximized for each stator tooth, and the overall torque can be increased.

  In FIG. 7, the currents flowing through the winding terminals 31a, 32a, 33a (and the currents flowing through the stator windings 81a, 82a, 83a) are shown on the vertical axis, and the time is shown on the horizontal axis. As shown in FIG. 5, the current passed through the winding terminal 31a is advanced by π / 9 radians relative to the current passed through the winding terminal 32a, and the current passed through the winding terminal 33a relative to the current passed through the winding terminal 32a. Is delayed by π / 9 radians.

The relationship between the arrangement of the stator windings and the current flowing through the stator windings are as follows.
The stator winding 83a is disposed with a deviation of −π / 9 radians from π radians in electrical angle with respect to the stator winding 82a. With such an arrangement relationship, AC current that is advanced by π / 9 radians is supplied to the current that flows through the stator winding 83a relative to the current that flows through the stator winding 82a. On the other hand, the stator winding 81a is arranged with a deviation of + π / 9 radians from π radians in electrical angle with respect to the stator winding 82a. With such an arrangement relationship, the AC current delayed by π / 9 radians is supplied to the current flowing through the stator winding 81a with respect to the current flowing through the stator winding 82a. This deviation of π / 9 radians is caused by the function of the transformer 14. The inverter 7 controls ON and OFF of the switching elements Q1 to Q6 so that current is supplied at the timing shown above.

  In this way, at the timing when each stator tooth comes between the magnetic poles, the AC power supplied to the stator teeth is supplied to the maximum, and the number of magnetic poles and the number of stator teeth are determined. In consideration of the mechanical angle deviation caused by the difference, in order to supply AC power having a phase deviation, the transformer 14 is arranged between the inverter 7 and the synchronous motor 41, and the phase is adjusted by the staggered winding type secondary coil. The shift is a feature of the present embodiment.

By using a relatively reliable component as compared with the power semiconductor such as the transformer 14, it is possible to prevent an increase in the number of inverters 7 and, as a result, an increase in the number of switching elements, thereby reducing the reliability of the synchronous electric drive system. Can be suppressed.
In addition, due to fluctuations in the potential between the inverter and ground and the ground potential of the shaft of the synchronous motor, a common mode current is generated in the shaft of the synchronous motor, and electric corrosion is generated in the bearing, resulting in damage. However, by using the transformer 14, it is possible to prevent the common mode current from being supplied to the synchronous motor 41, and it is possible to provide a synchronous motor drive system having high noise resistance.
<Embodiment 2>
In the first embodiment, a plurality of three-phase AC powers whose phases are shifted from each other are supplied to the synchronous motor 41 via the transformer 14 to rotate the synchronous motor so as to obtain the maximum torque. showed that. However, it cannot be denied that a loss, that is, an effect as a resistance of the coil, conversion of electric power into heat, or the like is generated through the transformer 14.

Therefore, the second embodiment shows that this loss is suppressed.
<Configuration>
FIG. 8 is a circuit diagram showing the configuration of the synchronous motor drive system in the present embodiment.
As can be seen from FIG. 8, a path is provided through which AC power can be supplied directly from the inverter to the synchronous motor. On this path, a switch is provided. When the switch 27 is turned OFF and the switch 28 is turned ON, the AC power output from the inverter is directly supplied to the synchronous motor.

  The switches 27 and 28 are turned on and off by a control device of a device (for example, an automobile) on which the synchronous motor drive system is mounted. The timing for turning on and off differs depending on the system used and is determined by the designer. For example, if a synchronous motor drive system is used to rotate the wheels of an automobile, the three-phase AC power is synchronized via a transformer to obtain maximum torque when starting to rotate from a state where the wheels are not rotating. The switch 27 is turned on and the switch 28 is turned off so as to be supplied to the electric motor. Then, when the rotation of the wheel is stabilized to a certain level or more, the switch 27 is turned off and the switch 28 is turned on in order to reduce the loss caused by the transformer 14 instead of obtaining the maximum torque. Basically, when a large torque is required, the switch 27 is turned on and the switch 28 is turned off. In a state where the rotation is stable, the switch 27 is turned off and the switch 28 is turned on.

By providing a path for supplying the three-phase AC power to the synchronous motor 41 via the transformer 14 and a path for supplying the three-phase AC power to the synchronous motor 41 without passing through the transformer 14, Selection of whether to supply a plurality of shifted three-phase AC power to obtain the maximum torque in the synchronous motor 41 or to supply the three-phase AC power to the synchronous motor 41 without passing through the transformer 14 to reduce the loss in the transformer 14 Therefore, a more flexible synchronous motor drive system can be configured.
<Embodiment 3>
In the third embodiment, a case will be described in which the winding method for the teeth is different from that of the first embodiment. Since the basic configuration is the same as that shown in the first embodiment, a different part from the first embodiment will be described in the third embodiment.

  FIG. 9 is a circuit diagram illustrating a configuration of a synchronous motor drive system according to the third embodiment. FIG. 11 is a detailed view showing how the winding is wound in one stator tooth set of the synchronous motor 41 in the third embodiment. The third embodiment is different from the first embodiment in the winding method, the wiring for supplying AC power, the configuration of the transformer, and the like by changing the winding method.

As shown in FIG. 9, unlike the first embodiment, the transformer 14 does not include the secondary coil 51. Accordingly, the number of windings in the synchronous motor 41 is six fewer than that of the first embodiment.
The secondary coil 50 has an electrical angle of π / 9 radians in terms of the phase of each phase of the three-phase AC power output to the corresponding phase of the three-phase AC power input to the primary coil 12. This is a staggered coil that has been adjusted to be delayed.

The secondary coil 52 has an electrical angle of π / 9 radians in terms of the phase of each phase of the three-phase AC power output to the corresponding phase of the three-phase AC power input to the primary coil 12. It is a staggered coil that has been adjusted to advance.
Here, the AC power output from each secondary coil will be described. The output currents 101a, 101b, and 101c of the secondary coil 50 are out of phase by 2π / 3 radians. The same applies to the output currents 103a, 103b, and 103c of the secondary coil 52.

The output currents 101a and 103a are out of phase by 2π / 9 radians. The same applies to the output currents 101b and 103b, and the same applies to the output currents 101c and 102c.
FIG. 10 is a plan view of the synchronous motor 41 according to the third embodiment. The basic configuration is the same as that shown in the first embodiment. Here, the reference numerals used for the winding sets are different from those in the first embodiment.

FIG. 11 is a detailed view of the synchronous motor in the third embodiment, and is a diagram for illustrating that the winding method of the winding is different from that in the first embodiment.
As shown in FIG. 11, a portion of the stator winding 91a (number of turns N1) is wound around the stator teeth 71a, and a portion of the stator winding 92a (number of turns N2) is wound around the stator teeth 73a. The remaining portion of the stator winding 91a (the number of turns N21) and the remaining portion of the stator winding 92a (the number of turns N22) are wound around the stator teeth 72a.

  In the stator winding 91a, the portions wound around the stator teeth 71a and 72a generate magnetic fields having opposite polarities. Similarly, in the stator winding 92a, the portions wound around the stator teeth 72a and 73a generate magnetic fields having opposite polarities. Further, when currents of the same phase are supplied to the stator windings 91a and 92a, the portions wound around the stator teeth 72a generate magnetic fields having the same polarity.

Further, the following relationship is satisfied with respect to the number of turns of the stator windings 91a and 92a.
N1 = N2
N21 = N22 = (N1) / {2cos (π / 9)}
By satisfying the above relationship, the maximum value of the magnetic flux generated in the stator teeth 71a, 72a, 73a can be made equal. Note that the equal sign (=) is used here for convenience, but in reality, it is often difficult to completely match. When the right side is a decimal, the equal symbol includes a match that uses an integer close to the decimal, and further includes a match that can be ignored as a design error.

FIG. 12 is a diagram for explaining the connection of the stator windings of the synchronous motor according to the third embodiment.
The a, b, and c at the end of the illustrated winding terminal numbers correspond to the windings that constitute the stator tooth groups 8a, 8b, and 8c, respectively.
The respective winding terminals 21a and 23a of the two stator windings 91a and 92a in the stator teeth set 8a are individually connected to the outside and are connected to the secondary side coils 50 and 52 of the transformer 14. It is connected to the. Similarly, the two winding terminals 21b and 23b in the stator teeth set 8b and the two winding terminals 21c and 23c in the stator teeth set 8c are individually connected to the outside of the transformer 14. The secondary side coils 50 and 52 are individually connected to the connection terminals.

  The terminals of the stator windings having a phase difference of 2π / 3 radians in different stator tooth groups 8a, 8b, 8c are commonly connected to the neutral point. That is, the winding terminal 22a, the winding terminal 22b, and the winding terminal 22c are connected to the first neutral point, and the winding terminal 24a, the winding terminal 24b, and the winding terminal 24c are connected to the second neutral point. ing. In this example, the first and second neutral points are electrically separated, but they may be electrically connected.

  In this embodiment, there are two sets of stator teeth 8a, stator teeth 8b, and stator teeth 8c, and stator teeth sets having the same a, b, and c at the end of the stator teeth Are in the same positional relationship in terms of electrical angle. For this reason, a neutral point connection may be configured between three adjacent stator teeth groups among the six stator teeth groups, or a neutral point connection between every other three stator teeth groups. Further, the neutral point connection may be constituted by all six sets of stator teeth.

  As shown in FIG. 13, AC power is supplied to the synchronous motor configured as described above. In FIG. 13, currents that flow through the winding terminals 21 a and 23 a (currents that flow through the stator windings 91 a and 92 a) are shown on the vertical axis, and time is shown on the horizontal axis. As shown in FIG. 13, the current flowing through the winding terminal 23a is advanced by 2π / 9 radians relative to the current flowing through the winding terminal 21a. This deviation of 2π / 9 radians is caused by the function of the transformer 14.

The relationship between the arrangement of the stator windings and the current flowing through the stator windings are as follows.
The stator teeth 73a are arranged with a deviation of −π / 9 radians from π radians in electrical angle with respect to the stator teeth 72a. On the other hand, the stator teeth 71a are arranged with a deviation of + π / 9 radians from π radians in electrical angle with respect to the stator teeth 72a. With such an arrangement relationship, the current passed through the stator winding 92a is advanced by 2π / 9 radians relative to the current passed through the stator winding 91a.

Even when the winding is wound as shown in FIG. 11, one winding is wound around at least two stator teeth of the plurality of stator teeth constituting the stator teeth group. And the other stator teeth, with respect to the synchronous motor 41 that generates the magnetic field in such a manner that two magnetic fields generated by the AC power supplied to the two windings are combined, In the case of supplying AC power in which the phases of two mutually corresponding phases are shifted, a phase shift can be caused by the transformer 14.
<Other variations>
In the above embodiment, the method of implementing the present invention has been described, but it is needless to say that the embodiment of the present invention is not limited to this. Hereinafter, various modified examples included in the concept of the present invention other than the above embodiment will be described.
(1) In the above embodiment, the switching element and the diode have been described as being a Si (silicon) device. However, this may be a SiC (silicon carbide) device or a GaN (gallium nitride) device to obtain a wide band gap. In recent years, SiC (silicon carbide) devices and GaN (gallium nitride) devices have been attracting attention as devices capable of high heat resistance and low loss. Effects such as heat resistance can be obtained.
(2) In the above embodiment, the synchronous motor 41 is described as an outer rotor type synchronous motor in which the rotor is arranged outside the stator, but the inner rotor type in which the rotor is arranged inside the stator. The same effect can be obtained even with a synchronous motor of this type, a so-called face-facing axial gap synchronous motor in which the rotor and stator are arranged with a gap in the axial direction, and a synchronous motor with a combination of them. Needless to say.
(3) In the above embodiment, the synchronous motor 41 has been described in the case where the number of stator teeth 47 is 18 and the number of permanent magnets 5 is 20. However, the number of stator teeth 47 and the number of permanent magnets 5 are described. And the number of stator teeth 47 may be any number as long as the condition for rotating the rotor is satisfied. For example, the number of stator teeth 47 may be 9 and the number of permanent magnets 5 may be 10. A combination in which the number of stator teeth 47 is 15 and the number of permanent magnets is 12 may be used.

In this case, the phase shift generated in the transformer 14 is determined based on the difference between the angle formed by the adjacent magnetic pole and the center of the synchronous motor and the angle formed by the adjacent tooth and the center of the synchronous motor. The winding length ratio of the two coils of the staggered connection of the secondary coil of the transformer 14 is adjusted so that a phase shift occurs.
(4) In the above embodiment, the voltage value of the AC power output from the inverter 7 is not particularly described. However, since the transformer 14 is used in the above embodiment, the number of turns of the secondary coil is adjusted. Thus, the AC power input to the primary coil can be boosted and output from the secondary coil, so that the voltage of the AC power generated by the inverter 7 can be reduced. As a result, a large design margin for the switching element breakdown voltage can be secured, and the reliability of the system can be improved.

By reducing the voltage generated by the inverter 7 to a low voltage (for example, 42 V or less), the risk of electric shock is reduced, thereby providing a fail-safe effect. Moreover, since it becomes possible to arrange | position a cable close by making it low voltage, a freedom degree arises in the routing of a cable.
Furthermore, although an excessive surge voltage may be generated due to the high-speed switching of the inverter 7 and the influence of the cable impedance, the voltage level including the surge voltage can be lowered by reducing the voltage. Thereby, the possibility of breakage of the switching element of the inverter 7 can be reduced, and the deterioration of the insulation performance of the coil in the transformer can be moderated.
(5) In the first embodiment, the AC power having the same phase may be directly supplied to the synchronous motor 41 without using the transformer 14.
(6) Although the cable length is not particularly mentioned in the above embodiment, when the cable between the inverter 7 and the transformer 14 and between the transformer 14 and the synchronous motor are long, high-speed switching by the switching element of the inverter 7 and the cable An excessive surge voltage is generated due to the influence of the impedance. Due to the surge voltage, the insulation of the transformer or motor coil may deteriorate and burn out. Therefore, it is desirable to shorten the cable length in view of safety and performance.
(7) In the above embodiment, the number of stator teeth belonging to the stator teeth group is set to 3, but this may be 2 or more.
(8) In the third embodiment, in order to make it easier to compare with the first embodiment, the phase of the AC power output from the secondary coil 50 is set to the phase of the AC power input to the primary coil. The phase of the AC power output from the secondary coil 52 is delayed by π / 9 radians relative to the AC power input to the primary coil.

  However, this is because the phase of each phase of the three-phase AC power output from the secondary coil 50 and the phase of each corresponding phase of the three-phase AC power output from the secondary coil 52 are 2π / For example, the secondary coil 50 is configured by star connection in the same manner as the primary coil 12, and the three-phase AC is in phase with the three-phase AC power input to the primary coil 12. Electric power is output, and each of the phases of the three-phase AC power output from the secondary-side coil 52 with respect to the phase of each phase of the three-phase AC power input to the primary-side coil 12 through the secondary-side coil 52 You may comprise a zigzag connection type coil in which the phase of the phase is delayed by 2π / 9 radians.

  The synchronous motor drive system according to the present invention can be used as, for example, a motor for turning automobile wheels, as a motor that can obtain the maximum torque in the synchronous motor.

It is the circuit diagram which showed the system configuration | structure of the synchronous motor drive system. It is a top view of a synchronous motor. It is detail drawing of a part of synchronous motor. It is a figure for demonstrating the connection of the stator winding | coil of the synchronous motor shown in FIG. (A) shows the connection configuration of the coils of each phase of the staggered winding type coil in the transformer, and (b) shifts the phase of the AC power of each phase by synthesizing the phases of each phase. It is a vector diagram for showing. The positional relationship of the stator and rotor of Embodiment 1 is shown, and the passage of time is shown in the order of (a), (b), and (c). FIG. 3 is a diagram showing a change over time of a current flowing through each stator winding in the first embodiment. FIG. 6 is a circuit diagram showing a configuration of a synchronous motor drive system in a second embodiment. FIG. 5 is a circuit diagram showing a configuration of a synchronous motor drive system in a third embodiment. FIG. 6 is a plan view of a synchronous motor according to a third embodiment. FIG. 10 is a diagram showing a winding method of one stator tooth set in the third embodiment. FIG. 10 is a diagram for explaining connection of stator windings of the synchronous motor in the third embodiment. FIG. 10 is a diagram showing a change over time of a current flowing through each stator winding in the third embodiment.

Explanation of symbols

2 Rotor 4 Rotor core 5 Permanent magnet 6 Magnetic pole 7 Inverter 8 DC power supply 9 Stator winding 12 Primary coil 14 Transformer 27, 28 Switch 41 Synchronous motor 48a, 48a ', 48b, 48b', 38c, 48c ' Stator teeth set 50, 51, 52 Secondary coil

Claims (8)

An inverter that converts DC power into three-phase AC power and outputs it;
The three-phase AC power output from the inverter is input to output a plurality of three-phase AC power, and the phase of the AC power of a specific phase of the one three-phase AC power to be output, and the output A phase conversion unit that is out of phase with the phase of the specific phase AC power in the other three-phase AC power to be
A synchronous motor that rotates by receiving a plurality of three-phase AC power output from the phase converter;
A synchronous motor drive system comprising: The synchronous motor is
A rotor including a plurality of magnetic poles, wherein the plurality of magnetic poles are arranged at equal intervals in the circumferential direction;
Including a plurality of stator windings wound in a concentrated winding, the stator windings being arranged in parallel in the circumferential direction,
The plurality of stator windings constitute a stator winding set in units of m arranged in the circumferential direction (m is an integer of 2 or more),
In each stator winding set, each stator winding is individually connected to an independent external terminal,
In supplying three-phase AC power from the phase conversion unit to the plurality of stator windings, one stator winding set is connected to one stator winding in the one stator winding set. AC power of a specific phase of one three-phase AC power is supplied, and AC power of a specific phase of the other three-phase AC power is supplied to the other stator windings in the one stator winding set The synchronous motor drive system according to claim 1, wherein the phase converter and the external terminal are connected as described above. The synchronous motor drive system according to claim 2, wherein the phase conversion unit has an insulating function that insulates the inverter from the synchronous motor. The synchronous motor drive system according to claim 2, wherein the phase converter boosts the voltage of the input three-phase AC power and outputs the boosted voltage to the synchronous motor. The phase conversion unit is a transformer including a primary coil connected to the inverter and a plurality of secondary coils connected to the synchronous motor and corresponding to the plurality of three-phase AC powers, respectively.
At least one of the plurality of secondary side coils includes a staggered winding type coil, and the staggered winding type coil has a three-phase phase that is shifted in phase with respect to the three-phase AC power input to the primary side coil. 3. The synchronous motor drive system according to claim 2, wherein AC power is output. The synchronous motor drive system further includes:
A direct path for supplying the three-phase AC power output from the inverter to the synchronous motor without passing through the phase converter, and the synchronous motor for supplying the three-phase AC power output from the inverter via the phase converter. A switching means for selecting any of the indirect paths to be supplied to and supplying three-phase AC power to the synchronous motor through the selected path;
The synchronous motor drive system according to claim 1, wherein the synchronous motor rotates in response to three-phase AC power supplied from the direct path. The phase difference between the specific phase of the one three-phase AC power and the specific phase of the other three-phase AC power is an angle formed between an adjacent magnetic pole in the synchronous motor and the center of the synchronous motor, and The synchronous motor drive system according to claim 1, wherein the shift is determined based on an angle formed by an adjacent winding in the synchronous motor and a center of the synchronous motor. The inverter includes a plurality of switching elements,
The synchronous motor drive system according to any one of claims 1 to 7, wherein the switching element is configured by a wide band gap semiconductor containing silicon carbide or gallium nitride.

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