JP4021803B2 - Multi-pulse rectifier transformer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-pulse rectifier transformer suitable for converting three-phase alternating current into direct current with less harmonics.
[0002]
[Prior art]
When three-phase alternating current is converted into direct current, the most common method is to use one three-phase full-wave rectifier circuit in which six rectifier elements are bridge-connected. In such a three-phase full-wave rectifier circuit, the rectifying element that is energized sequentially every 60 degrees switches and outputs a DC voltage. The DC voltage rectified by this method has a period of 6 times the power supply frequency. A large voltage ripple is included, which becomes a harmonic and causes various obstacles.
[0003]
As a countermeasure, a main full-wave rectifier circuit for full-wave rectification of a three-phase AC voltage, a three-phase AC voltage whose phase is advanced by a predetermined angle with respect to the three-phase AC voltage, and a three-phase whose phase is delayed by a predetermined angle A transformer that outputs an AC voltage, and two auxiliary full-wave rectifier circuits (hereinafter simply referred to as a full-wave rectifier circuit) that supply two loads of three-phase AC voltages output from the transformer to the load after full-wave rectification. An 18-pulse rectifier is proposed (see, for example, Patent Document 1).
[0004]
FIG. 5 is a transformer vector diagram showing the winding structure of the transformer constituting the 18-pulse rectifier circuit. In the figure, the three-phase AC voltage of the power supply is represented by equilateral triangles R1, S1, and T1. Two points obtained by equally dividing the arc drawn by connecting the remaining two vertices S1 and T1 around the vertex R1 of the equilateral triangle as S3 and T2, respectively. Further, two points obtained by equally dividing the arc drawn by connecting the remaining two vertices T1 and R1 with the vertex S1 of the equilateral triangle as the center are defined as T3 and R2, respectively. Furthermore, two points obtained by equally dividing the arc drawn by connecting the remaining two vertices R1 and S1 around the vertex T1 of the equilateral triangle as R3 and S2, respectively.
[0005]
Next, the intersections of the straight line passing through the vertex R1 of the equilateral triangle and parallel to the opposite side and the straight line passing through the two points T3 and R2 on the arc and the straight line passing through the two points R3 and S2 on the arc are R4, respectively. R5. Further, the intersection points of a straight line passing through the vertex S1 of the equilateral triangle and parallel to the opposite side, a straight line passing through the two points R3 and S2 on the arc, and a straight line passing through the two points S3 and T2 on the arc are respectively S4 and S5. And Furthermore, the intersections of a straight line passing through the vertex T1 of the equilateral triangle and parallel to the opposite side, a straight line passing through the two points S3 and T2 on the arc, and a straight line passing through the two points T3 and R2 on the arc are respectively T4 and T5. And
[0006]
As a result, a hexagonal transformer vector diagram formed by connecting the points R4-R5-S4-S5-T4-T5-R4 is formed. Of these, the line segment R4-R5 corresponds to the R-phase first coil 2, the line segment S5-T4 corresponds to the R-phase second coil 3, and the line segment S4-S5 corresponds to the S-phase first coil 5, respectively. T5-R4 corresponds to the S-phase second coil 6, line segment T4-T5 corresponds to the T-phase first coil 8, and line segment R5-S4 corresponds to the T-phase second coil 9, respectively. The length of the line segment corresponds to the number of turns of the coil with respect to the iron cores of the R, S, and V phases.
[0007]
FIG. 6 is a winding structure diagram of the transformer 10 satisfying this transformer vector diagram, and the reference numerals indicating the dividing points and intersections in FIG. 5 are represented as corresponding winding terminals or taps. In the drawing, an R-phase first coil 2 and an R-phase second coil 3 are wound around an R-phase iron core 1, and an R-phase first coil 2 is provided with an intermediate tap R1, and an R-phase second coil. 3, intermediate taps T2 and S3 are provided. In addition, an S-phase first coil 5 and an S-phase second coil 6 are wound around the S-phase iron core 4, and among these, the S-phase first coil 5 is provided with an intermediate tap S <b> 1. Are provided with intermediate taps R2, T3. Further, a T-phase first coil 8 and a T-phase second coil 9 are wound around the T-phase iron core 7, and among these, the T-phase first coil 8 is provided with an intermediate tap T <b> 1. Are provided with intermediate taps S2, R3.
[0008]
One end R4 of the R-phase first coil 2 is one end of the S-phase second coil 6, one end of the S-phase first coil 5 is one end of the T-phase second coil 9, and one end of the T-phase first coil 8 is one end. The other end of the R-phase first coil 2 is connected to the other end of the T-phase second coil 9 and the other end of the S-phase first coil 5 is connected to the R-phase second coil 3. The other end of the T-phase first coil 8 is connected to the other end of the S-phase second coil 6. Then, the conducting wire is drawn out from the intermediate taps R1, S1, and T1 to become three-phase AC input terminals R1, S1, and T1, and the conducting wire is drawn out from the intermediate taps R2, S2, and T2, and the first three-phase AC output terminal R2 is drawn. , S2, and T2, and the lead wires are drawn out from the intermediate taps R3, S3, and T3 to form second three-phase AC output terminals R3, S3, and T3.
[0009]
Therefore, a full-wave rectifier circuit is connected to the first three-phase AC output terminals R2, S2, and T2, and another full-wave rectifier circuit is connected to the second three-phase AC output terminals R3, S3, and T3. 18-pulse rectifier that reduces harmonics generated on the power supply side by connecting the output terminals of the full-wave rectifier circuit in parallel to the output terminal of the main three-phase full-wave rectifier circuit that converts three-phase alternating current into direct current Is configured.
[0010]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-10646 (page 6, FIG. 8)
[0011]
[Problems to be solved by the invention]
The 18-pulse rectifier has two rectifiers that full-wave rectify the above-described transformer and two types of three-phase AC voltages output from the transformer, respectively, with respect to the main rectifier circuit that directly full-wave rectifies the three-phase AC voltage. Many configurations that add a multi-pulse rectifier transformer including a circuit have been adopted. In this case, the transformer generally uses natural air cooling, and no positive protection means against self-heating is provided. Further, since the winding structure of the transformer is complicated, it is relatively difficult to detect the temperature, and it is difficult to provide a protection means.
[0012]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-pulse rectifier transformer capable of reliably protecting a transformer from overheating with a simple configuration.
[0013]
Another object of the present invention is to provide a multi-pulse rectifier transformer capable of easily and reliably detecting the temperature of the transformer.
[0014]
Another object of the present invention is to provide a multi-pulse rectifier transformer that can be reduced in size, weight, and unitized, and that can extend its life.
[0015]
[Means for Solving the Problems]
The invention according to claim 1
A three-phase AC voltage received from a three-phase AC power source is input, and a first three-phase AC voltage whose phase is advanced by a predetermined angle with respect to this three-phase AC voltage and a second whose phase is delayed by a predetermined angle A transformer that outputs a three-phase AC voltage, and first and second rectifier circuits that supply a load to the load by full-wave rectifying the first and second three-phase AC voltages output from the transformer, respectively. In multi-pulse rectifier transformer,
A relay is provided that detects the temperature of the transformer and opens the input path for one phase of the three-phase AC voltage input to the transformer when the detected value exceeds a predetermined value.
[0016]
The invention according to claim 2 is the multi-pulse rectifier transformer according to claim 1, wherein the multi-pulse rectifier transformer is attached to a case that integrally houses the transformer, the first and second rectifier circuits, and a side wall of the case. And a heat sink having first and second rectifier circuits mounted on the inner surface, and the relay indirectly detects the temperature of the transformer from the temperature of the heat sink.
[0017]
The invention according to claim 3 is the multi-pulse rectifier transformer according to claim 1, wherein the multi-pulse rectifier transformer is attached to a housing that integrally accommodates the transformer, the first and second rectifier circuits, and a side wall of the housing. A heat sink in which the first and second rectifier circuits are mounted on the inner surface, a fan for ventilating the air in the housing, a temperature of the heat sink is detected, and the fan is closed when the detected value exceeds a predetermined value. And a relay that opens and stops the fan when the detected value falls below a predetermined value.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a multi-pulse rectifier transformer according to the present invention in combination with a main circuit for driving a three-phase AC motor as an 18-pulse rectifier. In the figure, an input end of a full-wave rectifier circuit 12 is connected to a three-phase AC power source 11, a smoothing capacitor 13 is connected to an output end thereof, and an input end of an inverter 14 is connected. A three-phase AC motor 15 is connected to the output terminal of the inverter 14.
[0019]
The input terminal of the multi-pulse rectifier transformer 20 is connected to the three-phase AC power supply 11, and the output terminal of the multi-pulse rectifier transformer 20 is connected to the output terminal of the full-wave rectifier circuit 12. The multi-pulse rectifier transformer 20 receives a three-phase AC voltage, generates a three-phase AC voltage whose phase is advanced by a predetermined angle, and a three-phase AC voltage whose phase is delayed by a predetermined angle. Each voltage is full-wave rectified and output, and together with the full-wave rectifier circuit 12, an 18-pulse rectifier is configured.
[0020]
The multi-pulse rectifier transformer 20 includes a terminal block 21 connected to the three-phase AC power source 11. The three-phase AC input terminal R1 of the transformer 10 is connected to the R-phase terminal of the terminal block 21 via the fuse 22A and the bimetal 23A, and the three-phase AC terminal S1 of the transformer 10 is directly connected to the S-phase terminal. The AC input terminal T1 of the transformer 10 is connected to the T phase via a fuse 22B. The load end of the fuse 22A is connected to one input end of the ventilation fan 24, and the other input end of the ventilation fan 24 is connected to the S-phase terminal of the terminal block 21 via the bimetal 23B.
[0021]
As described above, the transformer 10 is a three-phase AC output terminal R2, which outputs a three-phase AC voltage whose phase is advanced by 40 degrees with respect to the three-phase AC voltage applied to the three-phase AC input terminals R1, S1, T1. S2 and T2 and three-phase AC output terminals R3, S3 and T3 for outputting a three-phase AC voltage whose phase is delayed by 40 degrees are provided. The three-phase AC output terminals R2, S2, T2 are connected to the input terminal of the full-wave rectifier circuit 25. The output terminal of the full-wave rectifier circuit 25 is connected to the fixed side of the connector 27. The input terminal of the full-wave rectifier circuit 26 is connected to the three-phase AC output terminals R3, S3, and T3. The output terminal of the full-wave rectifier circuit 26 is connected to the fixed side of the connector 27. The positive side and the load side of the connector 27 are connected in parallel to the output terminal of the full-wave rectifier circuit 12. The bimetals 23A and 23B and the full-wave rectifier circuits 25 and 26 are attached to the heat sink 28 as will be described later.
[0022]
In FIG. 2, the multi-pulse rectifier transformer 20 is housed in a housing and unitized. The transformer 10 is housed in a housing 31. An air inlet 32 is formed in the lower part of one side wall of the casing 31, and an air outlet 33 is formed in the upper part of the other side wall. A ventilation fan 24 is attached to the inner central portion of the air exhaust port 33. Further, a substantially central portion of the other side wall of the casing 31 is cut out, and a heat sink 28 is attached thereto. Full-wave rectifier circuits 25 and 26 and bimetals 23A and 23B are mounted inside the heat sink 28, and a lead wire inlet / outlet 34 formed between the heat sink 28 and the air outlet 33 is used for three-core three-phase AC input. A lead wire and a two-core DC output lead wire are passed through.
[0023]
The operation of the present embodiment configured as described above will be described below. First, the three-phase AC voltage of the three-phase AC power supply 11 is full-wave rectified by the full-wave rectifier circuit 12, smoothed by the smoothing capacitor 13, and supplied to the inverter 14. The inverter 14 converts the direct current supplied thereto into alternating current of variable voltage and variable frequency, adds it to the three-phase alternating current motor 15, and drives the three-phase alternating current motor 15. In the multi-pulse rectifier transformer 20, a three-phase AC voltage is applied to the three-phase AC input terminals R1, S1, and T1 of the transformer 10 through the terminal block 21, the fuse 22A, the fuse 22B, and the bimetal 23A. As a result, a three-phase AC voltage whose phase is advanced by 40 degrees with respect to the three-phase AC voltage is output from the three-phase AC output terminals R2, S2, and T2, and a phase is 40 degrees from the three-phase AC output terminals R3, S3, and T3. A delayed three-phase AC voltage is output. These three-phase AC voltages are full-wave rectified by the full-wave rectifier circuits 25 and 26, respectively, and are supplied to the output terminal of the full-wave rectifier circuit 12 via the connector 27. As a result, the full-wave rectifier circuits 25 and 26 are conducted so as to fill the direct current ripple output through the full-wave rectifier circuit 12, so that the current ripple is reduced and the harmonics appearing on the power supply side are also reduced.
[0024]
Here, the transformer 10 is housed inside the casing 31, and the ventilation fan 24 sucks external air from the air inlet 32 and exhausts it from the air outlet 33. The heat sink 28 promotes cooling of the full-wave rectifier circuits 25 and 26. However, since the temperature change is equivalent to that of the transformer 10, the temperature of the heat sink 28 is detected instead of directly detecting the temperature of the transformer 10. However, temperature detection equivalent to direct detection is possible. This will be described below.
[0025]
Generally, in order to protect a transformer, it is optimal to directly detect the winding temperature, but it is difficult to attach a temperature sensor or a bimetal to the iron core or winding. Even if a temperature sensor, bimetal, etc. are attached to the iron core or winding, if the position is below the transformer, the detected temperature is low, and the change with respect to the temperature rise is small. A large difference is likely to occur between the temperature and the detected value. However, since the same current flows through the full-wave rectifier circuits 25 and 26 constituting the multi-pulse rectifier transformer 20, the temperature increase tendency of the transformer 10 and the temperature increase tendency of the heat sink 28 are substantially proportional. Therefore, by detecting the temperature of the heat sink 28, although indirectly, the temperature of the transformer 10 can be reliably detected with high accuracy. Further, the heat sink 28 to which the full-wave rectifier circuits 25 and 26 are attached has an advantage that the bimetal 23A can be easily attached.
[0026]
FIG. 4 is a diagram obtained by actually measuring the relationship between the temperature of the heat sink 28 and the temperature of the transformer 10. As is apparent from this diagram, the temperature of the heat sink and the temperature of the transformer have a linear relationship. For example, as the bimetal 23A attached to the heat sink 28, the contact is opened at 90 ° C. or higher, and at 70 ° C. or lower. By using the one that is closed, it is equivalent to directly detecting the temperature of the transformer 10 and opening the contact at 150 ° C. or higher and closing at 120 ° C. or lower. Note that point A indicates that the temperature of the heat sink 28 is 90 ° C. when the ventilation fan 24 fails and the temperature of the transformer 10 reaches 150 ° C.
[0027]
Therefore, in this embodiment, the bimetal 23A is attached to the heat sink 28 so that the three-phase voltage supply path to the transformer 10 is cut off when the temperature rises. The bimetal 23A has the operating characteristics shown in FIG. In other words, if the temperature tends to rise, it switches to the off state at 90 ° C., and if the temperature tends to fall, it returns to the on state at 70 ° C. Accordingly, the temperature of the heat sink 28 rises in accordance with the temperature rise of the transformer 10, and when the temperature exceeds 90 ° C., the R-phase path for supplying the three-phase voltage to the transformer 10 is interrupted. Only a single-phase AC voltage is supplied to the phase AC input terminals S1 and T1. As a result, the three-phase AC output terminals R2, S2, T2 and R3, S3, T3 of the transformer 10 have the same phase as the AC applied to the three-phase AC input terminals S1, T1, and a value greater than the input voltage. Only a small voltage is output. This means that only the voltage that is smaller than the rectified voltage between the S and T phases rectified by the full-wave rectifier circuit 12 and smaller than the rectified voltage is output from the full-wave rectifier circuits 25 and 26.
[0028]
As a result, no current flows through the transformer 10, and its function is substantially stopped. In general, when a load is connected to a three-phase AC transformer, the one-phase voltage supply path is opened. It is necessary to plan. However, in the multi-pulse rectifier transformer constituting the 18-pulse rectifier, the transformer can be reliably protected from overheating only by opening the input path for one phase.
[0029]
On the other hand, the bimetal 23B provided in the power supply path of the ventilation fan 24 has the operating characteristics shown in FIG. That is, if the temperature tends to rise, it is switched to the on state at 70 ° C., and if the temperature tends to fall, it returns to the off state at 50 ° C. Accordingly, as the temperature of the transformer 10 rises, the temperature of the heat sink 28 also rises. When the temperature exceeds 70 ° C., the ventilation fan 24 starts the ventilation operation, and when the temperature drops below 50 ° C., the ventilation operation. To stop. As a result, the ventilation fan 24 is operated only in a temperature range in which the temperature of the transformer 10 rises and exceeds 120 ° C. where cooling is necessary and then drops to 100 ° C. The rate can be lowered and the lifetime of the device can be increased depending on its lifetime.
[0030]
Thus, according to the present embodiment, the temperature of the transformer 10 is detected, and when the detected value exceeds a predetermined value, the input path for one phase of the three-phase AC voltage input to the transformer is opened. Since 23A is provided, the transformer 10 can be reliably protected from overheating with a simple configuration.
[0031]
In addition, according to the present embodiment, the transformer 10 is housed in the casing 31, and the full-wave rectifier circuits 25 and 26 and the bimetal 23 </ b> A are attached to the heat sink 28 attached to the side wall of the casing 31. Therefore, the temperature of the transformer can be detected easily and reliably.
[0032]
Further, a ventilation fan 24 for ventilating the air in the housing 31 is provided, and the ventilation fan 24 is operated when the temperature of the heat sink 28 exceeds a predetermined value by the bimetal 23B attached to the heat sink 28. Since the ventilation fan 24 is stopped when it is lowered, it is possible to realize a reduction in size, weight, and unitization, and it is possible to extend the life of the device including the life of the ventilation fan 24. It is done.
[0033]
In the above embodiment, the temperature of the transformer 10 is indirectly detected, and the bimetal 23A that opens the input circuit for the three-phase AC voltage and the bimetal 23B that opens and closes the power supply path of the ventilation fan 24 are used. However, the present invention is not limited to this. Even if the microcomputer (MCU) controls the on / off of the switching element according to the output of the temperature sensor, the point is to detect the temperature of the transformer. Any relay that opens and closes the power path may be used.
[0034]
【The invention's effect】
As is apparent from the above description, according to the present invention, a multi-pulse rectifier transformer capable of reliably protecting a transformer from overheating with a simple configuration is provided.
[Brief description of the drawings]
FIG. 1 is a block diagram showing the configuration of an embodiment of a multi-pulse rectifier transformer according to the present invention in combination with a main circuit for driving a three-phase AC motor as an 18-pulse rectifier.
FIG. 2 is a schematic configuration diagram in which the multi-pulse rectifier transformer shown in FIG. 1 is housed in a housing and unitized.
3 is a diagram showing operating characteristics of two types of bimetals constituting the multi-pulse rectifier transformer shown in FIG. 1 or FIG.
4 is a diagram showing the relationship between the transformer temperature and the heat sink temperature in the multi-pulse rectifier transformer shown in FIG. 2;
FIG. 5 is a transformer vector diagram showing a winding structure of a transformer of an 18-pulse rectifier circuit to which the present invention is applied.
6 is a winding structure diagram of a transformer that satisfies the transformer vector diagram shown in FIG. 5. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Transformer 11 Three-phase alternating current power supply 12, 25, 26 Full wave rectification circuit 20 Multi-pulse rectification transformer 23A, 23B Bimetal 24 Ventilation fan 28 Heat sink 31 Case 32 Air intake port 33 Air exhaust port

Claims (3)

A three-phase AC voltage received from a three-phase AC power source is input, and a first three-phase AC voltage whose phase is advanced by a predetermined angle with respect to this three-phase AC voltage and a second whose phase is delayed by a predetermined angle A transformer that outputs a three-phase AC voltage; and first and second rectifier circuits that supply first and second three-phase AC voltages output from the transformer to a load by full-wave rectification, respectively. In multi-pulse rectifier transformer,
A relay is provided that detects the temperature of the transformer and opens an input path for one phase of the three-phase AC voltage input to the transformer when the detected value exceeds a predetermined value. Pulse rectifier transformer. A case that integrally houses the transformer and the first and second rectifier circuits; a heat sink that is attached to a side wall of the case and has the first and second rectifier circuits mounted on an inner surface; The multi-pulse rectifier transformer according to claim 1, wherein the relay indirectly detects the temperature of the transformer from the temperature of the heat sink. A case that integrally houses the transformer and the first and second rectifier circuits; a heat sink that is attached to a side wall of the case and has the first and second rectifier circuits mounted on an inner surface; When the temperature of the fan for ventilating the air in the housing and the heat sink is detected, and the detected value exceeds a predetermined value, the fan is operated and the detected value falls below the predetermined value The multi-pulse rectifier transformer according to claim 1, further comprising a relay that opens to stop the fan.

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