RU136260U1 - SWITCH FOR CONNECTING A THREE-PHASE ASYNCHRONOUS MOTOR TO A SINGLE-PHASE AC NETWORK - Google Patents

Abstract

A switch for connecting a three-phase asynchronous motor to a single-phase AC network, equipped with a semiconductor key connecting the windings of the three-phase asynchronous motor to a single-phase AC network, with the beginning of the first winding of the three-phase asynchronous motor connected to the phase, and its end connected to zero of the single-phase AC network, the second winding connected to a semiconductor switch, in turn, connected to the phase, and to zero single-phase AC network, the beginning of the third winding is connected to a single-phase AC network, characterized in that the first and second dinistors are connected in parallel as a semiconductor switch, in which the anode of the first dinistor and the cathode of the second dinistor are combined and connected to the phase of the single-phase AC network, the cathode of the first dinistor and the anode of the second dinistor combined and connected to the beginning of the second winding, while the end of the second winding is connected to zero single-phase AC network, and the end of the third winding is connected to the phase of the single-phase AC network current.

Description

The proposed utility model relates to non-reversible semiconductor switches driven by a single-phase AC network, and can be used in an unregulated AC drive to power three-phase asynchronous motors from a single-phase network.

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 / AI Voldek -. L .: Energy, 1974. - S. 612, Figure 30-7)..

The main disadvantage 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 is reduced by three times, and the motor power drops to 40% of the nominal.

The closest to the proposed utility model in terms of technical nature and the achieved result (prototype) is a single-phase-three-phase transistor reversing switch, which supplies the three-phase asynchronous motor from a single-phase AC network with a reverse, containing two semiconductor switches connecting the windings of a three-phase asynchronous motor to a single-phase supply AC power. The beginning of the first winding of a three-phase induction motor is connected to the phase, and the end of the first winding is connected to zero of the single-phase AC network. The beginning of the second winding of a three-phase asynchronous motor is connected to zero of the single-phase AC network, and the end of the second winding is connected to the first semiconductor switch connected to the phase. Thus, the second winding is connected to the first semiconductor switch and to zero single-phase AC network. The beginning of the third winding of a three-phase induction motor is connected to zero of the single-phase AC network, and the end of the third winding of a three-phase induction motor is connected to the second semiconductor switch. Two field effect transistors are used as semiconductor switches. The first terminals of the field effect transistors are connected to the phase of a single-phase AC network. The second terminal of the first field-effect transistor is connected to the end of the second winding of a three-phase induction motor. The second terminal of the second field-effect transistor is connected to the end of the third winding of a three-phase induction motor. To control semiconductor switches on field-effect transistors, a single-phase-three-phase transistor reversing switch is additionally equipped with a stabilized power supply and a programmable logic device (patent RU 121976, IPC Н02Р 27/16 (2006.01)).

The main disadvantages of the described single-phase-three-phase transistor reversing switch, driven by a single-phase network, are reduced reliability, increased dimensions and high cost, due to the need to control semiconductor switches on field effect transistors, based on additional equipment containing a stabilized power source and a programmable logic device, preferably when using devices for mechanisms that do not require reverse and speed control, and t ebuyuschih only up and running.

The proposed utility model solves the problem of increasing reliability and reducing the dimensions of the device with increasing its efficiency, when used for mechanisms that do not require reverse and speed control, but require only start-up and operation.

To solve this problem, in the switch for switching a three-phase induction motor into a single-phase AC network, equipped with a semiconductor key connecting the windings of the three-phase asynchronous motor to a single-phase AC network, the beginning of the first winding of the three-phase asynchronous motor is connected to the phase, and its end is connected to zero of the single-phase network alternating current, the second winding is connected to a semiconductor switch, in turn, connected to the phase, and to zero single-phase AC network, n the beginning of the third winding is connected to zero of the single-phase AC network, according to the utility model, the first and second dinistors connected in parallel are used as a semiconductor switch, in which the anode of the first dinistor and the cathode of the second dinistor are combined and connected to the phase of the single-phase AC network, the cathode of the first dinistor and the anode of the second dinistor are combined and connected to the beginning of the second winding. The end of the second winding is connected to zero of the single-phase AC network, and the end of the third winding is connected to the phase of the single-phase AC network.

The introduction of dynistors instead of field-effect transistors as a semiconductor key, which is used in the device selected as a prototype, leads to the absence of the need for equipment for controlling semiconductor switches and contributes to the possibility of increasing reliability, reducing overall dimensions and increasing the cost-effectiveness of the switch for switching a three-phase asynchronous motor into a single-phase network alternating current. The lack of need for equipment for controlling semiconductor switches is due to the use of the dynistor property during direct connection, not to pass current until the voltage on it reaches a certain value; this property of the dinistor is due to the fact that the dinistor is not a control thyristor, and it does not have a third control output when used for mechanisms that do not require reverse and speed control, but require only start-up and operation.

The proposed utility model is illustrated by drawings, where in FIG. 1 shows a circuit diagram of a semiconductor switch for switching a three-phase asynchronous motor into a single-phase AC network; in FIG. 2 is a vector diagram of an elliptical rotating field of a motor stator, which consists of four fixed positions of the magnetic flux; in FIG. 3 shows the directions of the magnetic flux and the current flowing through the stator windings of the motor in accordance with the vector diagram shown in FIG. 2; in FIG. 4 - phase-by-phase voltage variation in the stator windings of the motor in accordance with the vector diagram depicted in FIG. 2.

In addition, the drawings show the following:

- Φ is the phase;

- About - zero;

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

- VS and VS2 - dinistors.

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

- straight lines with arrows, indicated by Roman numerals, - the direction of the magnetic flux vector of the circular rotating field of the motor stator;

- 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;

- t1-t5 - times of switching transistors.

The switch for switching a three-phase induction motor into a single-phase AC network is equipped with a semiconductor switch 1 connecting the first winding 2, the second winding 3, and the third winding 4 of the three-phase asynchronous motor to a single-phase AC network. As the semiconductor switch 1, the first dinistor 5 (VS1) and the second dinistor 6 (VS2) are used, which are connected in opposite directions.

The anode of the first dinistor 5 (VS1) and the cathode of the second dinistor 6 (VS2) are combined and connected to the phase of a single-phase AC network. The cathode of the first dinistor 5 (VS1) and the anode of the second dinistor 6 (VS2) are combined and connected to the beginning 7 (C3) of the second winding 3 of the three-phase asynchronous motor. Thus, the beginning 7 (C3) of the second winding 3 is connected to the semiconductor switch 1.

The beginning 8 (C1) of the first winding 2 of the three-phase asynchronous motor is connected to the phase, and the end 9 (C2) of the first winding 2 is connected to zero of the single-phase AC network. The end 10 (C4) of the second winding 3 is connected to zero single-phase AC network. The beginning 11 (C5) of the third winding 4 is connected to zero of the single-phase AC network, and the end 12 (C6) of the third winding 4 is connected to the phase of the single-phase AC network.

The switch to include a three-phase asynchronous motor in a single-phase AC network operates as follows. Vector-algorithmic control is carried out by the operation of the dinistors in a certain sequence. 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 2, in the sequence I-II-III-IV, it is necessary that the dynistor 5 (VS1) operate at a lower voltage than the dynistor 6 ( VS2). Then dinistor 5 (VS1) and dinistor 6 (VS2) will operate in the following sequence:

- at the initial moment of time, a positive half-wave of voltage passes through the first winding 2, and a current flows through the third winding 4 - I fixed position of the stator field magnetic flux vector;

- at time t1, the dinistor 6 (VS2) is triggered, and the current begins to flow along the second winding 3, while in the first winding 2 and in the third winding 4 the current flows - II fixed position of the stator field magnetic flux vector;

- at time t2, a negative half-wave of voltage passes through the first winding 2, and current flows through the third winding 4, the dynistor 5 (VS1) is closed — III fixed position of the stator field magnetic flux vector;

- at time t3, the dinistor 6 (VS2) is triggered - IV fixed position of the stator field magnetic flux vector.

Thus, the proposed utility model has advantages over the known one due to the absence of the need for additional control elements for semiconductor switches and, as a result, due to higher reliability and economy, as well as smaller dimensions. Therefore, the proposed device is preferably used for mechanisms that do not require reverse and speed control, but only start-up and operation.

Claims (1)

A switch for connecting a three-phase asynchronous motor to a single-phase AC network, equipped with a semiconductor key connecting the windings of the three-phase asynchronous motor to a single-phase AC network, with the beginning of the first winding of the three-phase asynchronous motor connected to the phase, and its end connected to zero of the single-phase AC network, the second winding connected to a semiconductor switch, in turn, connected to the phase, and to zero single-phase AC network, the beginning of the third winding is connected to a single-phase AC network, characterized in that the first and second dinistors are connected in parallel as a semiconductor switch, in which the anode of the first dinistor and the cathode of the second dinistor are combined and connected to the phase of the single-phase AC network, the cathode of the first dinistor and the anode of the second dinistor combined and connected to the beginning of the second winding, while the end of the second winding is connected to zero single-phase AC network, and the end of the third winding is connected to the phase of the single-phase AC network current.

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