RU2344540C2 - One-phase-three-phase reversing switchboard - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: one-phase-three-phase reversing switchboard semi-conductor keys form antiparallel pairs with one outputs connected to the AC one-phase mains phase, the said keys being built around turn-off thyristors. The other outputs of the keys are connected to the outputs of the second and third windings of three-phase induction motor. The inputs of the aforesaid windings are connected to the AC one-phase mains zero, while the three-phase induction motor first winding input is connected to the phase while its output is connected to the one-phase AC mains zero. The switchboard carries out vector control over three-phase induction motor by creating a rotating field of the stator.

EFFECT: feeding three-phase induction motor from single-phase mains with rotor rpm adjustment.

8 dwg

Description

The present invention relates to reversible semiconductor switches driven by a single-phase AC network, and can be used in an unregulated AC drive for powering a single-phase network of three-phase asynchronous motors.

A device is known for supplying a three-phase induction motor from a single-phase network using a capacitor shift in the stator circuit, supplying power from a single-phase network of a three-phase asynchronous motor with windings connected to a star, in which one winding of a three-phase asynchronous motor is connected to a single-phase network through a capacitor to obtain a rotating stator field , and the other two windings - directly to a single-phase network (Voldek A.I. Electrical machines. A textbook for students of higher technical educational institutions tions / A.I.Voldek -. L .: Energy, 1974. - S.612, ris.30-7).

The disadvantage of this device is the need to use paper capacitors of large capacity, as a result of which the engine torque is usually reduced by three times, the engine power drops to 50% of the nominal.

The closest to the proposed invention in terms of technical nature and the achieved result (prototype) - supplying a three-phase asynchronous motor from the mains with reverse supply - is a three-phase reversing switch containing semiconductor switches that connect the windings of a three-phase asynchronous motor to the mains. A three-phase alternating current network was used as the supply network, and semiconductor switches are made in the form of eight thyristors, forming four counter-parallel connected pairs. In this case, two counter-parallel connected pairs of thyristors are connected by one terminal to one phase of the supply network, and the other, respectively, to the ends of the second and third windings of a three-phase asynchronous motor and two counter-parallel connected pairs of thyristors are connected by one terminal to the other phase of the supply network, and the others respectively to the ends of the second and third windings of a three-phase induction motor. The third winding of a three-phase asynchronous motor is directly connected to the network (Petrov L.P. Thyristor voltage converters for an asynchronous electric drive / L.P. Petrov. - M.: Energoatomizdat, 1986. - P.155, Fig. 6.1.a.).

The main disadvantages of the described three-phase reversible switch are the inability to supply from a single-phase network, which limits the use of three-phase asynchronous motors in a single-phase power supply system, as well as the need to use a large number of semiconductor switches (eight thyristors), which reduces the reliability of a three-phase reversible switch and increases its size and cost.

The present invention solves the problem of providing the possibility of powering a three-phase asynchronous motor from a single-phase network without adjusting the speed of the electric motor while increasing reliability and efficiency, as well as reducing the size.

To solve the problem, in a single-phase-three-phase reversing switch containing network-driven semiconductor switches that form counter-parallel pairs, some of the terminals of which are connected to the phase of the network, made in the form of a single-phase AC network, the semiconductor switches are made on lockable thyristors, and the other conclusions of the semiconductor switches connected to the ends of the second and third windings of a three-phase asynchronous motor, respectively, the beginning of the second and third windings are connected to zero single-phase AC network current, and the beginning of the first winding of a three-phase asynchronous motor is connected to the phase, and its end to zero of the single-phase AC network.

The increase in reliability, reduction in size and increase in efficiency of a single-phase-three-phase reversing switch is due to a decrease in the number of semiconductor switches (four lockable thyristors or transistors instead of eight thyristors).

The invention is illustrated by drawings, where Fig. 1 shows a circuit diagram of a single-phase-three-phase reversing switch when executing semiconductor switches on lockable thyristors; figure 2 is the same when performing semiconductor switches on transistors with diode protection; figure 3 is a vector diagram of a circular rotating field of the stator of the engine, which consists of six fixed positions of the magnetic flux; figure 4 - the direction of the magnetic flux and the flowing current through the windings of the stator of the motor in accordance with the vector diagram depicted in figure 3; figure 5 - phase-by-phase change in magnetic flux in the stator windings of the motor in accordance with the vector diagram depicted in figure 3; figure 6 is a vector diagram of a circular rotating field of the stator of the motor, which consists of six fixed positions of the magnetic flux in the opposite direction of rotation of the motor; Fig.7 - the direction of the magnetic flux and the flowing current along the stator windings of the motor in accordance with the vector diagram depicted in Fig.6; on Fig - phase-by-phase change in magnetic flux in the stator windings of the motor in accordance with the vector diagram depicted in Fig.6.

In addition, the drawings show the following:

- Ф - phase;

- 0 - zero;

- C1-C6 - the findings of the stator windings of a three-phase asynchronous motor;

- V1-V4 - lockable thyristors;

- VT1-VT4 - transistors;

- VD1-VD4 - protective diodes;

- I, II, III, IV, V, VI - sequential fixed positions of the magnetic flux vector of the circular rotating field of the motor stator;

- straight lines with arrows - the direction of the magnetic flux vector of the circular rotating field of the stator of the motor;

- U network = f (t) - change in supply voltage in time;

- straight lines with arrows along the stator windings of the motor - the direction of magnetic flux and current in the stator windings.

The single-phase, three-phase reversing switch contains network-driven semiconductor switches that form counter-parallel pairs. The semiconductor switches are made on lockable thyristors, one of the terminals of which are connected to a phase of a network made in the form of a single-phase alternating current network, while the other terminals are connected to the ends of the second and third windings of a three-phase asynchronous motor, respectively. The beginning of the second and third windings are connected to zero of the single-phase AC network, and the beginning of the first winding of the three-phase asynchronous motor is connected to the phase, and its end is to zero of the single-phase AC network.

An example of a single-phase-three-phase reversing switch containing semiconductor switches made in the form of lockable thyristors. The switch contains lockable semiconductor switches, which are used as four lockable thyristors 1, 2, 3, 4 (V1-V4), two lockable thyristors connected in opposite-parallel fashion on the second and third windings of a three-phase asynchronous motor. In this case, the first motor winding is connected to the single-phase AC network by the beginning of the winding 5 (C1) to the phase and the end of the winding 6 (C2) to zero directly, the second winding is connected to the beginning of the winding 7 (C3) to zero and the end of the winding 8 (C4) through lockable thyristors to phase, the third winding is connected to the beginning of winding 9 (C5) to zero and the end of winding 10 (C6) through lockable thyristors to phase.

The cathode of the lockable thyristor 1 (V1) and the anode of the lockable thyristor 2 (V2) are connected to the mains phase, the cathode of the lockable thyristor 2 (V2) and the anode of the lockable thyristor 1 (V1) are connected to terminal 8 (C4) of the motor stator winding. The cathode of the lockable thyristor 3 (V3) and the anode of the lockable thyristor 4 (V4) are connected to the mains phase, the cathode of the lockable thyristor 4 (V4) and the anode of the lockable thyristor 3 (V3) are connected to terminal 10 (C6) of the stator motor winding.

An example of a single-phase-three-phase reversible switch with lockable semiconductor switches, driven by a network containing semiconductor switches made in the form of transistors. The switch contains lockable semiconductor switches, which are used as four transistors 11, 12, 13, 14 (VT1-VT4), two transistors connected between each other in parallel in parallel to the second and third windings of a three-phase asynchronous motor. Also, protective diodes 15, 16, 17, 18 (VD1-VD4) are included in the collector circuits of transistors 11, 12, 13, 14 (VT1-VT4). In this case, the first motor winding is connected to the single-phase AC network by the beginning of the winding 19 (C1) to the phase and the end of the winding 20 (C2) to zero directly, the second winding is connected to the beginning of the winding 21 (C3) to zero and the end of the winding 22 (C4) through transistors to the phase, the third winding is connected by the beginning of the winding 23 (C5) to zero and the end of the winding 24 (C6) through transistors to the phase.

The emitters of transistors 11 and 12 (VT1 and VT2) are connected to the mains phase, the collectors of transistors 11 and 12 (VT1 and VT2) are connected to terminal 22 (C4) of the stator motor winding through protective diodes 15 and 16 (VD1 and VD2) as follows: the anode of the diode 15 (VD1) and the cathode of the diode 16 (VD2) are connected to the stator winding terminal 22 (C4), the cathode of the diode 15 (VD1) is connected to the collector of transistor 11 (VT1), and the anode of the diode 16 (VD2) is connected to the collector of transistor 12 (VT2). The emitters of transistors 13 and 14 (VT3 and VT4) are connected to the phase of the supply network, the collectors of transistors 13 and 14 (VT3 and VT4) are connected to terminal 24 (C6) of the stator motor winding through protective diodes 17 and 18 (VD3 and VD4) as follows: the anode of the diode 17 (VD3) and the cathode of the diode 18 (VD4) are connected to the output 24 (C6) of the stator winding, the cathode of the diode 17 (VD3) is connected to the collector of transistor 13 (VT3), and the anode of the diode 18 (VD4) is connected to the collector of transistor 14 (VT4).

Transistors 11, 13 (VT1, VT3) have an n-p-n structure. Transistors 12, 14 (VT2, VT4) have a p-n-p structure.

The operation of a single-phase-three-phase reversible switch on a lockable semiconductor switch, driven by the network, is as follows. A single-phase alternating voltage is supplied to the stator windings of a three-phase asynchronous motor by switching the corresponding lockable semiconductor switches, which provides a rotating magnetic field of the stator.

Using a single-phase-three-phase reversible switch with lockable semiconductor switches driven by the network, it is possible to vector control a three-phase asynchronous electric motor, creating a rotating stator field by passing six (see Fig. 3 and Fig. 6) consecutive fixed positions of the magnetic flux vector of a circular stator rotating field forward and reverse engine.

Vector motor control of the passage of six consecutive fixed positions of the stator field magnetic flux vector per one forward rotation of the motor

To ensure the rotation of the magnetic flux vector of the circular rotating field of the stator of the motor in accordance with the vector diagram shown in figure 3, in the sequence I-II-III-IV-V-VI, it is necessary to apply control pulses to the lockable thyristors 1, 2, 3, 4 (V1, V2, V3, V4) in the following sequence:

unlocking control pulse on V2 - I fixed position of the stator field magnetic flux vector;

unlocking control pulse on V4 - II fixed position of the stator field magnetic flux vector;

locking control pulse on V2 - III fixed position of the stator field magnetic flux vector;

unlocking control pulse on V1 - IV fixed position of the stator field magnetic flux vector;

unlocking control pulse on V3 - V fixed position of the stator field magnetic flux vector;

locking control pulse on V1 - VI fixed position of the stator field magnetic flux vector.

To ensure the rotation of the magnetic flux vector of the circular rotating field of the stator of the motor in accordance with the vector diagram shown in figure 3, in the sequence I-II-III-IV-V-VI, it is necessary to apply control pulses to the transistors 11, 12, 13, 14 (VT1, VT2, VT3, VT4) in the following sequence:

unlocking control pulse on VT2 - I fixed position of the stator field magnetic flux vector;

unlocking control pulse on VT4 - II fixed position of the stator field magnetic flux vector;

locking control pulse on VT2 - III fixed position of the stator field magnetic flux vector;

unlocking control pulse on VT1 - IV fixed position of the stator field magnetic flux vector;

unlocking control pulse on VT3 - V fixed position of the stator field magnetic flux vector;

locking control pulse on VT1 - VI fixed position of the stator field magnetic flux vector.

Vector motor control of the passage of six consecutive fixed positions of the stator field magnetic flux vector for one revolution of the motor in the opposite direction

To ensure the rotation of the magnetic flux vector of the circular rotating field of the stator of the motor in accordance with the vector diagram shown in Fig.6, in the sequence I-II-III-IV-V-VI, it is necessary to apply control pulses to the lockable thyristors 1, 2, 3, 4 (V1, V2, V3, V4) in the following sequence:

unlocking control pulse on V4 - I fixed position of the stator field magnetic flux vector;

unlocking control pulse on V2 - II fixed position of the stator field magnetic flux vector;

locking control pulse on V4 - III fixed position of the stator field magnetic flux vector;

unlocking control pulse on V3 - IV fixed position of the stator field magnetic flux vector;

unlocking control pulse at V1 - V fixed position of the stator field magnetic flux vector;

locking control pulse on V3 - VI fixed position of the stator field magnetic flux vector.

To ensure the rotation of the magnetic flux vector of the circular rotating field of the stator of the motor in accordance with the vector diagram shown in figure 3, in the sequence I-II-III-IV-V-VI, it is necessary to apply control pulses to the transistors 11, 12, 13, 14 (VT1, VT2, VT3, VT4) in the following sequence:

unlocking control pulse on VT4 - I fixed position of the stator field magnetic flux vector;

unlocking control pulse on VT2 - II fixed position of the stator field magnetic flux vector;

locking control pulse on VT4 - III fixed position of the stator field magnetic flux vector;

unlocking control pulse on VT3 - IV fixed position of the stator field magnetic flux vector;

unlocking control pulse on VT1 - V fixed position of the stator field magnetic flux vector;

locking control pulse on VT3 - VI fixed position of the stator field magnetic flux vector.

This single-phase, three-phase reversible switch with lockable semiconductor switches, driven by the network, allows the three-phase asynchronous motor to operate at a frequency f _NETWORK from a single-phase network.

Thus, the present invention can be used in a single-phase network with high reliability and efficiency, as well as small dimensions.

Claims (1)

A single-phase-three-phase reversing switch containing network-driven semiconductor switches that form counter-parallel pairs, some of which are connected to a phase of a network made in the form of a single-phase alternating current network, characterized in that the semiconductor switches are made on lockable thyristors, the other terminals of the semiconductor switches are connected with the ends of the second and third windings of a three-phase induction motor, respectively, the beginning of the second and third windings are connected to zero single-phase AC network, and on alo first winding three-phase induction motor is connected to a phase and its end - to zero-phase AC.

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