FI72404B - RADIOAVSTOERNINGSDROSSEL FOER FASVINKELSTYRDA HALVLEDAROMKOPPLARE - Google Patents

Description

|. * £ ta ^ 7] rB1 nn ADVERTISEMENT ΠΟΛΚΑ wSHi ™ 11 utlAggningsskrift / Z4 U4 C Patent my 3-liietty (45) Patcnt «cJ.'elat 11 05 133 / <51) Kv.lk.4 / lnt.a . * H 01 F 17/06 // H 01 F 3/08 (21) Patent application - Patent »öknlng 781513 (22) Filing date - Ansökningidag 12.05.78 (FI) (23) Starting date - Glltighetidig 12.05.78 (41) to the public - BHvit offentlig 15-11.78

National Board of Patents and Registration / 44) Date of display and publication. - 30.01.87 patent · och registerstyrelsen '' Ansökan utlagd och utl.skrlften publicerad (86) Kv. application - Int. ansökan (32) (33) (31) Privilege claimed - Begärd priority 1 ^ .05.77

Federal Republic of Germany Förbundsrepub1i ken Tyskland (DE) P 2721967.6 (71) V0GT GmbH S Co KG, Erlautal 7> Erlau, Federal Republic of Germany Förbunds-republiken Tyskland (OE) (72) Erich Lechky, Erlau DE) (7 * 0 Berggren Oy Ab (5 ^) Radio interference suppressor for phase angle controlled semiconductor switches -Radioavstörningsdrossel för fasvinkelstyrda haivledaromkopplare

The invention relates to a radio interference suppression choke for phase angle-controlled semiconductor switches, which comprises a ring core combination of two sub-ring cores, the first sub-core being a high-permeability core compressed with iron powder-secreting binders.

Phase angle-controlled semiconductor switches are increasingly used in various fields of electrical engineering to control load currents or powers in alternating current circuits, e.g., to control motors or to adjust the brightness of light sources.

The rapid switching event of such switches causes significant interference voltages which, according to VDE (Verband der Deutschen Elektro-Techniker) regulation 0875, must be attenuated by suitable interference suppression devices in the frequency range 0.15-30 MHz to the specified permissible level.

A suitable radio interference canceller for such semiconductor switches is a series connection of a ring core choke and a capacitor, taking into account the space requirements and costs. This interference suppression member acts as a voltage divider alongside the semiconductor switch and thus attenuates the interference signals generated in the switch and propagating to the supply conductors of the load circuit.

The load current passes through a choke which, due to the low frequency of the load circuit, usually 50 Hz, does not represent the inductive resistance mentioned in terms of the load current. However, at high frequencies of interference voltages, the inductive resistance must be high, especially at 150 kHz, because the interference voltage is highest at this frequency. The choke must therefore have the highest possible inductance at a frequency of 150 kHz, which means the highest possible permeability of the choke core at this frequency.

There is a harmful side effect associated with this interference suppression circuit. The choke and the capacitor form an oscillation circuit which closes via a semiconductor switch made conductive and in which a switching event generates an intrinsic oscillation. The frequency of the self-oscillation is between 5-20 kHz. The summation of the load and oscillation current in a semiconductor switch causes current fluctuations that can cause unintended interfering switching phenomena. For example, in dimmers, they cause light variation resembling the flicker of connected light sources.

This side effect can be avoided by adequate damping of said self-oscillations. It has been found that the required attenuation can only be achieved by means of sufficiently large losses in the choke core, because additional connections of the semiconductor switch, such as the connection of a resistor, overload the consumption circuit or weaken the interference suppression effect too much. The core material is thus required to have large losses in the frequency range 5-20 kHz.

The two requirements mentioned, namely high permeability at 150 kHz and high losses compared to the former at lower frequencies of 5-20 kHz, are opposite when using a homogeneous magnetically soft material. The material is either broadband and retains its permeability up to high frequencies, in which case the material always has small losses at low frequencies, or the material has high losses at low frequencies, which, however, is always associated with a sharp decrease in permeability at high frequencies.

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Although in some uses of homogeneous cores a good usable compromise can be reached between the two requirements, in many applications it is not possible to find a suitable core material that meets said opposite requirements. This is especially the case when the load circuit is required to be small in size at high power.

In these cases, combined choke cores are used, assembled from two sub-cores made of different magnetically soft materials: 1. a "permeability-providing" sub-core that is broadband and provides sufficient permeability at 150 kHz, 2. a "loss-providing" sub-core that has large losses in the range of 5-20 kHz and thus ensures adequate attenuation of harmful self-oscillations. However, it does not significantly increase permeability at 150 kHz.

In addition, the radio interference suppression choke is required to be reasonable in cost compared to the total cost of the semiconductor switch. Since the circuit elements mainly used in semiconductor switches, e.g. capacitors, resistors, thyristors, etc., have become considerably cheaper in recent years, low costs are also required for the radio interference suppression choke. This means e.g. that expensive materials and complex manufacturing methods must be increasingly avoided.

DE-A-2 119 950 discloses a two-part choke, the permeability-providing sub-core of which consists of a ferrite ring provided with an air gap. The loss-producing part consists of stamped and stacked electrical or deep-drawing plates. The manufacturing costs of this solution are high due to grinding the air gap and stacking the plates. The requirement for reasonably priced interference suppressors cannot therefore be met. In addition, the plates cause audible magnetostrictive vibrations, which in many applications, such as dimmers in dwellings, are perceived as acoustic interference.

DE-A-1 813 643 also discloses a choke with a two-part core. The permeability-providing sub-core 4 72404 consists of a nickel-copper-iron alloy rolled into thin strips to which manganese, molybdenum and chromium have been added. The loss-producing part consists of strips or plates of iron to which silicon or aluminum has been added. The composition of the permeability-providing sub-core alloys is selected so that the magnetostriction is very low. This avoids the disadvantage of interfering noise, but the alloys used, which contain 74 to 84% nickel, are too expensive to be rolled into strip material as a core material and cannot be used to produce a cost-effective radio interference suppression choke.

DE-A-2 505 080 further discloses a two-part choke core with which the use of expensive materials can be avoided. The permeation-providing part in this case is iron powder which is compressed together with an insulating binder. The loss-causing portion of the core forms an annular iron wire coil which is placed in a mold before pressing so that it is embedded in the ring core after pressing and surrounded on all sides by iron powder. This solution undoubtedly reduces the cost in terms of the material used, but the individual installation and manufacture of the wire windings require additional equipment and measures which must be carried out in addition to simple powder pressing. In particular, iron powder must be added to the compression sheet both before and after the insertion of the wire coil, i.e. the filling must be carried out in two stages. In addition, a device is needed for manufacturing and positioning the wire windings precisely centrally.

The present invention is based on the idea of manufacturing both partial cores by a conventional pulp core pressing method without additional steps.

Indeed, it has surprisingly been found that by compressing insulating binders without using conventional commercially available and inexpensive magnetically soft iron powder grades with particle sizes between 10 and 600 μm, lossy sub-cores can be made so as to provide the required high attenuation in the frequency range 5-20 kHz. with a partial heart. The properties of the particle in question can then be influenced and set to the desired values by compression force, particle size and particle size distribution of the powder, and gentle heat treatment. It has been found that the electromagnetic properties of such cores, in particular losses in the range of 5-20 kHz, can be kept within the manufacturing accuracies required for mass production. Similarly, it has been shown that the strength of cores compressed without a binder is sufficient and differs only insignificantly from the strength of cores normally used in chokes as binder-containing pulp cores.

The radio interference suppression choke according to the invention is characterized in that the second sub-core is compressed from iron powder without the use of an insulating binder in order to optimize the permeability and the frequency curve of the losses of the entire ring core assembly.

A significant advantage of the invention is that the permeability and losses of the combined two-part core can be influenced by the volume ratios of both core cores in addition to the above-mentioned compression factors and the heat treatment of the lossy sub-core. From a manufacturing point of view, this can be achieved very simply by selecting the heights of the partial cores during compression. A change in the volume ratio is required, for example, when two types of capacitors with different capacitance values are used in the semiconductor switch for interference suppression. Higher capacitance values require higher attenuation in the range of 5-20 kHz, inductance at 150 kHz may be lower. At lower capacitance values, on the other hand, the attenuation may be lower, and a higher inductance at 150 kHz is required. The properties of the choke can be adapted to meet different requirements simply by making the compression heights suitable for the manufacture of sub-cores.

The sub-cores are assembled, coated together in a known manner with an insulating protective layer and wound.

The accompanying drawing shows an embodiment of the invention.

In the figure, reference numerals 1 and 2 denote partial cores coated together with insulation 3. 4 is a winding. The choke represents an implementation suitable for dimmers to control powers between 60-600 W. The assembled and coated core has an outer diameter of 39 mm, an inner diameter of 20 mm and a height of 8.5 mm. The volume ratio of the permeability-providing sub-core to the loss-providing sub-core is 1.5 in this example. The winding is 140 turns of 0.75 mm copper lacquer wire. This choke, together with a 0.22 μF capacitor, attenuates the interference of the semiconductor switch so that the interference level N remains in accordance with VDE regulation 0875. The choke according to the invention thus meets the requirements imposed on it, despite the inexpensive materials used and the considerably simplified manufacturing method.