RU2507673C1 - Single-phase-three-phase semiconductor reversible switchboard driven by single-phase ac circuit - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: first outputs of the first and second semiconductor switches are connected with a phase of a single-phase AC circuit. The first outputs of the third and fourth semiconductor switches are connected with zero of a single-phase AC circuit. The second outputs of the first and third semiconductor switches are combined and connected with the start of the first stator winding and the end of the third stator winding. The second outputs of the second and fourth semiconductor switches are combined and connected with the end of the first stator winding and the start of the third stator winding. At the same time the start of the second stator winding of the motor is connected to zero, and its end - to the phase of the single-phase AC circuit.

EFFECT: invention provides for the possibility of increasing torque developed by a motor and capacity due to production of more even circular rotating magnetic flux of a stator field, simplified system of transistor control.

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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 to start and operate on a single-phase network of three-phase asynchronous motors.

A device is known for supplying a three-phase asynchronous 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 / AI Voldek -. L .: Energy, 1974. - S.612, ris.30-7).

The main disadvantages of the described device for supplying a three-phase asynchronous motor from a single-phase network using a capacitor shift in the stator circuit is the need to use large-capacity paper capacitors, as a result of which the motor torque usually decreases three times, the motor power drops to 50% of the nominal value.

The closest to the proposed invention in terms of technical nature and the achieved result (prototype) - power supply of a three-phase asynchronous motor from a single-phase AC network with reverse supply - is a single-phase-three-phase transistor reversing switch driven by a single-phase network, containing two semiconductor switches, each of which is connected with a phase of a single-phase alternating current network. 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 beginning of the second and third windings are connected to zero single-phase AC network. The first semiconductor switch is connected to the phase of the single-phase AC network and the end of the second winding of the three-phase asynchronous motor and the second semiconductor switch is connected to the phase of the single-phase AC network and the end of the third winding of the three-phase asynchronous motor. Two bipolar transistors are used as semiconductor switches, in which the emitters are connected to the phase of a single-phase alternating current network. So the collector of the first transistor is connected to the end of the second winding of a three-phase asynchronous motor, and the collector of the second transistor is connected to the end of the third winding of a three-phase induction motor (patent RU 109356, IPC H02P 27/16 (2006.01)).

The main disadvantages of the described single-phase-three-phase reversing switch, driven by a single-phase network, are the reduced value of the torque and power developed by the motor due to the ellipticity of the rotating magnetic flux of the stator field, as well as the complexity of the transistor control system due to the need to take into account the polarity of the voltage passing through the transistor at any time.

The present invention solves the problem of increasing the torque and power developed by the engine, obtaining a more uniform circular rotating magnetic flux of the stator field, as well as simplifying the transistor control system.

To solve this problem, in a single-phase-three-phase semiconductor reversing switch, driven by a single-phase AC network, equipped with two semiconductor switches, each of which is connected to the phase of the single-phase AC network, and one of the three stator windings is connected to zero and to the phase of the single-phase AC network , according to the invention, the device is further provided with two semiconductor switches, wherein a field effect transistor is used as each of the semiconductor switches. The first terminals of the first and second semiconductor switches are connected to the phase of the single-phase AC network, the first terminals of the third and fourth semiconductor switches are connected to the zero of the single-phase alternating current, the second terminals of the first and third semiconductor switches are combined and connected to the beginning of the first and the end of the third stator windings, the second the findings of the second and fourth semiconductor switches are combined and connected to the end of the first and the beginning of the third stator windings. In this case, the beginning of the second stator winding is connected to zero of the single-phase alternating current network, and the end of the second stator winding is connected to the phase of the single-phase alternating current network.

The possibility of increasing the torque and power developed by the motor, obtaining a more uniform circular rotating magnetic flux of the stator field, as well as simplifying the transistor control system in a single-phase three-phase semiconductor reversing switch driven by a single-phase AC network, is achieved by using four field-effect transistors as semiconductor switches, passing current in both directions, without the need to take into account the polarity of the voltage passing through the trans Orae and carried by the electrostatic field generated by charges that transistors considerably simplifies the control system without supplying a current control transistors, since control FET.

The invention is illustrated by drawings, in which Fig. 1 shows a circuit diagram of a single-phase-three-phase semiconductor reversing switch driven by a single-phase AC network; figure 2 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 vector; figure 3 - 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 shown in figure 2; figure 4 - phase-by-phase voltage change in the stator windings of the motor in accordance with the vector diagram shown in figure 2; figure 5 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, with the reverse direction of rotation of the motor; in Fig.6 - the direction of the magnetic flux and the flowing current along the stator windings of the motor in accordance with the vector diagram shown in Fig.5; in Fig.7 - phase-by-phase voltage variation in the stator windings of the motor in accordance with the vector diagram depicted in Fig.5.

In addition, the drawings show the following:

- f - phase;

- 0 - zero;

- A, B and C - stator windings A, B and C of a three-phase asynchronous electric motor, respectively;

- VT1 - VT4 - field effect transistors.

- 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;

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

- straight lines, solid and discrete, with arrows along the stator windings of the motor - the direction of magnetic flux and current in the stator windings;

t1-t7 are the times of switching transistors.

A single-phase-three-phase semiconductor reversing switch, driven by a single-phase AC network, contains four semiconductor switches, each of which uses a field effect transistor, and two of their four semiconductor switches are connected to the phase of a single-phase AC network. The first terminals of the first and second semiconductor switches are connected to a phase of a single-phase alternating current network. The first conclusions of the third and fourth semiconductor switches are connected to the zero of the single-phase AC network. The second terminals of the first and third semiconductor switches are combined and connected to the beginning of the first and end of the third stator windings. The second terminals of the second and fourth semiconductor switches are combined and connected to the end of the first and the beginning of the third stator windings. In this case, the beginning of the second stator winding is connected to zero of the single-phase alternating current network, and the end of the second stator winding is connected to the phase of the single-phase alternating current network.

An example of a single-phase-three-phase semiconductor reversing switch, driven by a single-phase AC network. The device is equipped with semiconductor switches, which are used four field-effect transistors. The first terminal 1 of the first transistor 2 (VT1) is connected to the phase of the single-phase AC network, the first terminal 3 of the third transistor 4 (VT3) is connected to the zero of the single-phase AC network, the second terminal 5 of the first transistor 2 (VT1) and the second terminal 6 of the third transistor 4 (VT3) are combined and connected to the beginning 7 of the first stator winding A and the end 8 of the third stator winding C of the electric motor. The first terminal 9 of the second transistor 10 (VT2) is connected to the phase of the single-phase AC network, the first terminal 11 of the fourth transistor 12 (VT4) is connected to the zero of the single-phase AC network, the second terminal 13 of the second transistor 10 (VT2) and the second terminal 14 of the fourth transistor 12 (VT4) are combined and connected to the end 15 of the first stator winding A and the beginning 16 of the third stator winding C of the electric motor. The beginning 17 of the second stator winding B of the electric motor is connected to zero, and its end 18 to the phase of a single-phase AC network.

The operation of a single-phase-three-phase semiconductor reversing switch, driven by a single-phase AC 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 semiconductor switches, which provide a rotating magnetic field of the stator. Initially, voltages are applied to the gates of the transistors, creating an electric field to close the transistors. Vector-algorithmic control is carried out by removing voltage from the gates of transistors in a certain sequence. To ensure rotation of the stator field in accordance with the vector diagram shown in figure 2, it is necessary to carry out the removal of voltage from the gates of transistors 2 (VT1), 4 (VT3), 10 (VT2), 12 (VT4) in the following sequence:

- at the initial moment of time t0, when the positive half-wave of the supply voltage passes, the voltage is removed from the gates of transistors 10 (VT2) and 4 (VT3), the current flows through the windings A and B in the opposite direction, along the winding C in the forward direction - obtaining I fixed position of the stator field magnetic flux vector;

- at time t1, the transistors 2 (VT1), 4 (VT3), 10 (VT2), 12 (VT4) are closed, the current flows through the winding B in the opposite direction - it provides II a fixed position of the stator field flux vector;

- at time t2, the voltage is removed from the gates of transistors 2 (VT1) and 12 (VT4), the current flows through the windings B and C in the opposite direction, along the winding A in the forward direction — III is obtained with a fixed position of the stator field flux vector;

- at time t3, when the negative half-wave of the supply voltage passes, the voltage is removed from the gates of transistors 10 (VT2) and 4 (VT3), the current flows through windings A and B in the forward direction, along winding C in the opposite direction - IV is obtained a fixed position of the stator field magnetic flux vector;

- at time t4, the transistors 2 (VT1), 4 (VT3), 10 (VT2), 12 (VT4) are closed, the current flows through the winding B in the forward direction, - V obtains a fixed position of the stator field flux vector;

- at time t5, the voltage is removed from the gates of transistors 2 (VT1) and 12 (VT4), the current flows through the windings B and C in the forward direction, along the winding A in the opposite direction - the VI obtains a 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 5, it is necessary to relieve the voltage from the gates of transistors 2 (VT1), 4 (VT3), 10 (VT2), 12 (VT4) in following sequence:

- at the initial moment of time t0, when the positive half-wave of the supply voltage passes, the voltage is removed from the gates of transistors 2 (VT1) and 12 (VT4), the current flows through windings B and C in the opposite direction, along winding A in the forward direction - it ensures I fixed position of the stator field magnetic flux vector;

- at time t1, the transistors 2 (VT1), 4 (VT3), 10 (VT2), 12 (VT4) are closed, the current flows through the winding B in the opposite direction - it provides II a fixed position of the stator field flux vector;

- at time t2, the voltage is removed from the gates of transistors 10 (VT2) and 4 (VT3), the current flows through the windings A and B in the opposite direction, along the winding C in the forward direction — the III fixed position of the stator field magnetic flux vector is obtained;

- at time t3, when the negative half-wave of the mains voltage passes, the voltage is removed from the gates of transistors 2 (VT1) and 12 (VT4), the current flows through windings B and C in the forward direction, along winding A in the opposite direction - IV is obtained a fixed position of the stator field magnetic flux vector;

- at time t4, transistors 2 (VT1), 4 (VT3), 10 (VT2), 12 (VT4) are closed, the current flows through the winding B in the forward direction - V receives a fixed position of the stator field flux vector;

- at time t5, the voltage is removed from the gates of the transistors 10 (VT2) and 4 (VT3), the current flows through the windings A and B in the forward direction, along the winding C in the opposite direction - the stator field magnetic flux vector VI is obtained.

Thus, on the basis of the foregoing, it can be concluded that the present invention has advantages over the known ones due to a more uniform circular rotating magnetic flux of the stator field, and hence the increased torque and power developed by the motor, as well as a simplified transistor control system.

Claims (1)

A single-phase-three-phase semiconductor reversing switch, driven by a single-phase AC network, equipped with two semiconductor switches, each of which is connected to the phase of the single-phase AC network, and one of the three stator windings is connected to zero and to the phase of the single-phase AC network, characterized in that the device is additionally equipped with two semiconductor switches, moreover, a field-effect transistor is used as each of the semiconductor switches, the first conclusions of the first and second semiconductor output keys are connected to the phase of a single-phase AC network, the first terminals of the third and fourth semiconductor switches are connected to zero of the single-phase AC network, the second terminals of the first and third semiconductor switches are combined and connected to the beginning of the first and end of the third stator windings, the second conclusions of the second and fourth semiconductor keys are combined and connected to the end of the first and the beginning of the third stator windings, while the beginning of the second stator winding is connected to zero single-phase AC network, and the end of the second stator winding is connected to the phase of a single-phase AC network.

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