RU139335U1 - NETWORK LOW FREQUENCY CONVERTER FOR A THREE-PHASE ASYNCHRONOUS ELECTRIC MOTOR - Google Patents

Abstract

A network-driven low-frequency frequency converter for a three-phase asynchronous motor equipped with three identical semiconductor modules containing semiconductor switches, the common connection points of the semiconductor switches of the semiconductor modules being connected to the corresponding windings of the three-phase asynchronous motor, and the semiconductor switch of each of the semiconductor modules connected to one of three phase three-phase voltage source, characterized in that as each of the tr x semiconductor switches of the semiconductor module, a bipolar transistor is used, the collectors of three bipolar transistors of each semiconductor module are combined, and their common connection point is connected to the beginning of one winding of a three-phase asynchronous motor and the end of the other winding of a three-phase asynchronous motor, and each emitter of the bipolar transistor in each semiconductor transistor is connected to each semiconductor corresponding phase of a three-phase voltage source.

Description

The proposed utility model relates to low-frequency frequency conversion devices driven by a network, and can be used in an electric drive to control the speed of three-phase asynchronous motors.

It is known a semiconductor device for converting an alternating voltage of one frequency into alternating voltage of another frequency, containing three identical semiconductor modules, each of which in turn contains twelve semiconductor switches. A thyristor is used as each of the twelve semiconductor switches of the semiconductor module. In this case, the semiconductor module consists of two thyristor groups. Three thyristors from six thyristors of each thyristor group form a cathode block, the other three thyristors from six thyristors of each thyristor group form an anode block. In one semiconductor module, all the cathodes of the cathode block of one thyristor group and all the anodes of the anode block of another thyristor group are combined through equalizing reactors and connected by a common point to the corresponding winding of a three-phase asynchronous motor. Thus, through common points, the semiconductor switches of each semiconductor module are connected to the corresponding windings of a three-phase asynchronous motor. In one thyristor group, each of the anodes of the cathode block and each of the cathodes of the anode block, that is, each semiconductor switch, is connected to one of the three phases of a three-phase voltage source (I. Ya. Bernstein. Thyristor frequency converters without a DC link / I.Ya. Bernstein . - M .: Energy, 1968. - S. 15, Fig. 1-86.).

The main disadvantages of the described semiconductor device for converting alternating voltage of one frequency into alternating voltage of another frequency are low reliability, large dimensions and cost, as well as the complexity of the control system due to the large number of thyristors used in semiconductor modules.

The closest to the proposed utility model in terms of technical nature and the achieved result (prototype) is a semiconductor device for converting an alternating voltage of one frequency into alternating voltage of another frequency, equipped with three identical semiconductor modules containing six semiconductor switches, each of which uses a thyristor. Three thyristors of six thyristors of each semiconductor module form a cathode block designed to form a positive half-wave of regulated voltage supplied to the corresponding winding of a three-phase asynchronous electric motor, and three thyristors of six thyristors of each semiconductor module form an anode block designed to form a negative half wave of voltage the corresponding winding of a three-phase asynchronous motor. In one semiconductor module, all the cathodes of the cathode block and all the anodes of the anode block are connected through equalizing reactors and connected by a common point to the beginning of the corresponding winding of a three-phase asynchronous electric motor. Thus, the common connection points of the semiconductor switches of the semiconductor modules are connected to the corresponding windings of a three-phase asynchronous motor. In one semiconductor module, each of the anodes of the cathode block and each of the cathodes of the anode block, that is, each semiconductor switch, is connected to one of the three phases of a three-phase voltage source. The ends of the three windings of a three-phase asynchronous electric motor are combined (Terekhov V.M. Elements of an automated electric drive / V.M. Terekhov. - M: Energoatomizdat, 1987. - P. 93, Fig. 3.9).

The main disadvantages of this semiconductor device for converting AC voltage of one frequency to AC voltage of another frequency are low reliability, large dimensions, and the complexity of the control system due to the large number of thyristors used in semiconductor modules.

The proposed utility model solves the problem of increasing reliability, reducing dimensions, and also simplifying the control system by reducing the number of commuting semiconductor elements.

To solve the problem in a low-frequency inverter driven by a network for a three-phase asynchronous motor equipped with three identical semiconductor modules containing semiconductor switches, the common connection points of the semiconductor keys of the semiconductor modules are connected to the corresponding windings of the three-phase asynchronous motor, and the semiconductor key of each of the semiconductor modules connected to one of the three phases of a three-phase voltage source, according to In this model, a bipolar transistor is used as each of the three semiconductor switches of the semiconductor module, the collectors of the three bipolar transistors of each semiconductor module are combined, and their common connection point is connected to the beginning of one winding of a three-phase asynchronous motor and the end of the other winding of a three-phase asynchronous motor, and each emitter of a bipolar in each semiconductor module is connected to the corresponding phase of a three-phase voltage source.

The increase in reliability, the reduction in size, and also the simplification of the control system are due to a decrease in the number of semiconductor elements in each semiconductor module by introducing bipolar transistors and using the property of transistors in the key mode to pass current in the forward and reverse directions due to the symmetrical structure of the bipolar transistor (p-n-p or n-p-n).

The proposed utility model is illustrated in the drawing, where in FIG. 1 shows a circuit diagram of the proposed low-frequency frequency converter driven by the network for a three-phase asynchronous electric motor; in FIG. 2 shows the opening transistors to obtain the calculated frequency of the regulated voltage of 50 Hz; in FIG. Figure 3 shows the opening transistors to obtain the calculated frequency of the regulated voltage of 30 Hz.

In addition, the following notation is used in the drawing:

- U - network voltage;

- Uc1, Uc3, Uc5 - voltage on the first, second and third stator windings of a three-phase asynchronous motor, respectively;

- C1-C2, C3-C4, C5-C6 - the beginning and end of the first, second and third stator windings of a three-phase asynchronous motor, respectively;

- A, B, C - phase three-phase voltage source;

- VT1-VT9 - bipolar transistors;

- t1-t20 - time intervals.

The low-frequency network-driven frequency converter for a three-phase asynchronous electric motor is equipped with three identical semiconductor modules containing three semiconductor switches each. A bipolar transistor is used as each of the semiconductor switches. The common connection points of the semiconductor switches of the semiconductor modules are connected to the corresponding windings of the three-phase asynchronous electric motor, namely, the common connection points of the combined collectors of the three bipolar transistors of each semiconductor module are connected to the beginnings of one of the windings of the three-phase asynchronous motor and the ends of the other of the windings of the three-phase asynchronous motor. The semiconductor switch of each of the semiconductor modules is connected to one of the three phases of the three-phase voltage source, namely, each emitter of the bipolar transistor in each semiconductor module is connected to the corresponding phase of the three-phase voltage source.

In the first semiconductor module 1, the collectors of three bipolar transistors 2 (VT1), 3 (VT2), 4 (VT3) are combined, and their common connection point is connected to the beginning 5 (C1) of the first stator winding and to the end 6 (C6) of the third stator winding three-phase asynchronous electric motor. In the second semiconductor module 7, the collectors of the three bipolar transistors 8 (VT4), 9 (VT5), 10 (VT6) are combined, and their common connection point is connected to the beginning 11 (C3) of the second stator winding and to the end 12 (C2) of the first stator winding three-phase asynchronous electric motor. In the third semiconductor module 13, the collectors of transistors 14 (VT7), 15 (VT8), 16 (VT9) are combined, and their common connection point is connected to the beginning 17 (C5) of the third stator winding and to the end 18 (C4) of the second stator winding of a three-phase asynchronous electric motor.

In the first semiconductor module 1, the emitter of bipolar transistor 2 (VT1) is connected to phase 19 (A) of a three-phase voltage source, the emitter of bipolar transistor 3 (VT2) is connected to phase 20 (B) of a three-phase voltage source, the emitter of bipolar transistor 4 (VT3) is connected to phase 21 (C) of a three-phase voltage source. In the second semiconductor module 7, the emitter of bipolar transistor 8 (VT4) is connected to phase 19 (A) of a three-phase voltage source, the emitter of bipolar transistor 9 (VT5) is connected to phase 20 (B) of a three-phase voltage source, the emitter of bipolar transistor 10 (VT6) is connected to phase 21 (C) of a three-phase voltage source. In the third semiconductor module 13, the emitter of bipolar transistor 14 (VT7) is connected to phase 19 (A) of a three-phase voltage source, the emitter of bipolar transistor 15 (VT8) is connected to phase 20 (B) of a three-phase voltage source, the emitter of bipolar transistor 16 (VT9) is connected to phase 21 (C) of a three-phase voltage source.

The work of a low-frequency frequency converter driven by the network for a three-phase asynchronous motor is as follows.

To obtain the calculated frequency of the regulated voltage of 50 Hz, at the initial time t0 (Fig. 2), transistor 2 (VT1) opens, the current goes from phase 19 (A) through the collector-emitter of transistor 2 (VT1) to the beginning of 11 (C3) second stator winding and to the end 12 (C2) of the first stator winding of a three-phase asynchronous motor. In the negative half-wave voltage, time t1 (Fig. 2), the transistor 2 (VT1) remains open. In the positive half-wave voltage, time t2, the period of operation of the first semiconductor module 1 is repeated. At time t3 (Fig. 2), transistor 9 (VT5) opens, current flows from phase 20 (B) through the collector-emitter of transistor 9 (VT5) to the beginning 11 (C3) of the second stator winding and the end 12 (C2) of the first stator winding of a three-phase asynchronous electric motor. In the negative half-wave voltage, time t4 (Fig. 2), the transistor 9 (VT5) remains open. In the positive half-wave voltage, time t5, the period of operation of the second semiconductor module 7 is repeated. At time t6 (Fig. 2), transistor 16 (VT9) opens, current flows from phase 21 (C) through the collector-emitter of transistor 16 (VT9) to the beginning 17 (C5) of the third stator winding and to the end 18 (C4) of the second stator winding of a three-phase asynchronous electric motor. In the negative half-wave voltage, time t7 (Fig. 2), the transistor 16 (VT9) remains open. In the positive half-wave voltage, time t8, the period of operation of the third semiconductor module 13 is repeated.

To obtain the calculated frequency of the regulated voltage of 30 Hz, at the initial time t0 (Fig. 3), transistor 2 (VT1) opens, the current goes from phase 19 (A) through the collector-emitter of transistor 2 (VT1) to the beginning of 11 (C3) second the stator winding and the end 12 (C2) of the first stator winding of a three-phase asynchronous motor. At time t1, transistor 2 (VT1) closes and transistor 3 (VT2) opens, the current goes from phase 20 (B) through the collector-emitter of transistor 3 (VT2) to the beginning 11 (C3) of the second stator winding and the end 12 (C2 ) the first stator winding of a three-phase asynchronous electric motor. In the negative half-wave voltage, time t2, the transistor 3 (VT2) remains open. At time t3, transistor 3 (VT2) closes and transistor 4 (VT3) opens. In the positive half-wave voltage, time t4, transistor 4 (VT3) remains open, the current goes from phase 21 (C) through the collector-emitter of transistor 4 (VT3) to the beginning 11 (C3) of the second stator winding and the end 12 (C2) of the first stator winding of a three-phase asynchronous electric motor. At time t5, transistor 4 (VT3) closes and transistor 2 (VT1) opens, current flows from phase 19 (A) through the collector-emitter of transistor 2 (VT1) to the beginning 11 (C3) of the second stator winding and the end 12 (C2 ) the first stator winding of a three-phase asynchronous electric motor. At time t6, the period of operation of the first semiconductor module 1 is repeated. At time t7 (Fig. 3), transistor 10 (VT6) opens, current flows from phase 21 (C) through the collector-emitter of transistor 10 (VT6) to the beginning 11 (C3) of the second stator winding and the end 12 (C2) of the first stator windings of a three-phase asynchronous electric motor. At time t8, transistor 10 (VT6) closes and transistor 8 (VT4) opens, current flows from phase 19 (A) through the collector-emitter of transistor 8 (VT4) to the beginning 11 (C3) of the second stator winding and the end 12 (C2 ) the first stator winding of a three-phase asynchronous electric motor. In the negative half-wave voltage, time t9, the transistor 8 (VT4) remains open. At time t10, transistor 8 (VT4) closes and transistor 9 (VT5) opens. In the positive half-wave voltage, time t11, transistor 9 (VT5) remains open, the current goes from phase 20 (B) through the collector-emitter of transistor 9 (VT5) to the beginning 11 (C3) of the second stator winding and the end 12 (C2) of the first stator winding of a three-phase asynchronous electric motor. At time t12, transistor 9 (VT5) closes and transistor 10 (VT6) opens, current flows from phase 21 (C) through the collector-emitter of transistor 10 (VT6) to the beginning 11 (C3) of the second stator winding and the end 12 (C2 ) the first stator winding of a three-phase asynchronous electric motor. At time t13, the period of operation of the second semiconductor module 13 is repeated. At time t14 (Fig. 3), transistor 15 (VT8) opens, current flows from phase 20 (B) through the collector-emitter of transistor 15 (VT8) to the beginning 17 (C5) of the third stator winding and to the end 18 (C4) the second stator winding of a three-phase asynchronous electric motor. At time t15, transistor 15 (VT8) closes and transistor 16 (VT9) opens, current flows from phase 21 (C) through the collector-emitter of transistor 16 (VT9) to the beginning 17 (C5) of the third stator winding and to the end of 18 ( C4) a second stator winding of a three-phase asynchronous electric motor. In the negative half-wave voltage, time t16, the transistor 16 (VT9) remains open. At time t17, transistor 16 (VT9) closes and transistor 14 (VT7) opens. In the positive half-wave voltage, time t18, transistor 14 (VT7) remains open, the current goes from phase 19 (A) through the collector-emitter of transistor 16 (VT9) to the beginning 17 (C5) of the third stator winding and to the end 18 (C4) the second stator winding of a three-phase asynchronous electric motor. At time t19, transistor 14 (VT7) closes and transistor 15 (VT8) opens, current flows from phase 20 (B) through the collector-emitter of transistor 16 (VT9) to the beginning 17 (C5) of the third stator winding and to the end of 18 ( C4) a second stator winding of a three-phase asynchronous motor. At time t20, the period of operation of the third semiconductor module 13 is repeated.

Thus, the proposed utility model has advantages over the known ones due to higher reliability indicators, smaller dimensions, and also a simplified control system by reducing the number of semiconductor elements in each semiconductor module.

Claims (1)

A network-driven low-frequency frequency converter for a three-phase asynchronous motor equipped with three identical semiconductor modules containing semiconductor switches, the common connection points of the semiconductor switches of the semiconductor modules being connected to the corresponding windings of the three-phase asynchronous motor, and the semiconductor switch of each of the semiconductor modules connected to one of three phase three-phase voltage source, characterized in that as each of the tr x semiconductor switches of the semiconductor module, a bipolar transistor is used, the collectors of three bipolar transistors of each semiconductor module are combined, and their common connection point is connected to the beginning of one winding of a three-phase asynchronous motor and the end of the other winding of a three-phase asynchronous motor, and each emitter of the bipolar transistor in each semiconductor transistor is connected to each semiconductor corresponding phase of a three-phase voltage source.

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