RU223290U1 - Triac frequency converter for single-phase two-winding asynchronous electric motor - Google Patents

Abstract

The utility model relates to electrical engineering, namely to frequency converters driven by a single-phase alternating current network. The technical result of the claimed utility model is to create a triac frequency converter for a single-phase two-winding asynchronous electric motor of increased efficiency by reducing energy consumption, while simplifying the device control system. The triac frequency converter for a single-phase two-winding asynchronous electric motor is intended for use in an adjustable AC electric drive to control single-phase two-winding asynchronous electric motors powered from a single-phase AC network. The device contains two semiconductor switches, powered by a single-phase alternating current network, intended for connection to a load, which is the stator windings of a single-phase two-winding asynchronous electric motor. The first output of the first semiconductor switch is connected to the phase wire of the AC supply network, and the second output of the first semiconductor switch is intended for connection to the first output of the first stator winding of a single-phase two-winding asynchronous electric motor. The first output of the second semiconductor switch is connected to the phase wire of the AC supply network, and the second output of the second semiconductor switch is intended for connection to the first output of the second stator winding of a single-phase two-winding asynchronous electric motor. The combined second outputs of the stator windings of a single-phase two-winding asynchronous electric motor are connected to the neutral wire of the AC supply network. Triacs are used in semiconductor switches that pass current in both directions. 13 ill.

Description

The utility model relates to frequency converters driven by a single-phase AC network and can be used in an adjustable AC electric drive to control single-phase two-winding asynchronous electric motors powered by a single-phase AC network.

A device is known for starting a single-phase two-winding asynchronous motor from a single-phase network using a capacitor shift in the stator circuit, providing power from a single-phase network of an asynchronous motor, in which, to obtain a rotating stator field, one winding of the motor is connected to a single-phase network through capacitors, and the other winding is connected directly to the network (Kopylov I.P. Electrical machines. Textbook for universities / I.P. Kopylov. - M.: Higher School, 2006. - P. 343, Fig. 3.96).

The disadvantages of the described device for starting a single-phase two-winding asynchronous motor from a single-phase network using capacitor shift in the stator circuit are low reliability and increased dimensions due to the need to use high-capacity paper capacitors.

The closest to the proposed utility model in terms of technical essence and achieved result (prototype) is a semiconductor device for regulating the speed of a single-phase two-winding asynchronous electric motor, with the help of which the rotation speed is controlled. The device contains two reversible semiconductor switches on bipolar transistors, powered by a single-phase alternating current network, intended for connection to a load, which is the stator windings of a single-phase two-winding asynchronous electric motor. Each of the reversible semiconductor switches contains two bipolar transistors. One common connection point of the odd and even transistors of the first semiconductor switch is connected to the phase wire of the AC supply network, and the other common connection point of the odd and even transistors of the first semiconductor switch is intended for connection to the first output of the first stator winding of a single-phase two-winding asynchronous electric motor. One common connection point of the odd and even transistors of the second semiconductor switch is connected to the phase wire of the AC supply network, and the other common connection point of the odd and even transistors of the second semiconductor switch is intended for connection to the first output of the second stator winding of a single-phase two-winding asynchronous electric motor. The combined second outputs of the stator windings of a single-phase two-winding asynchronous electric motor are connected to the neutral wire of the AC supply network (patent RU 2420857, IPC N02R 1/42 (2006.01), N02R 25/04 (2006.01), N02R 27/04 (2006.01)).

The disadvantage of this semiconductor device for regulating the speed of a single-phase two-winding asynchronous electric motor is the increased energy consumption due to the use of bipolar transistors, which require control current to maintain the transistors in the on state, the complexity of the control system due to the need to take into account the polarity of the voltage passing through the transistors at each time.

The technical problem, the solution of which is provided by the implementation of the utility model, is to create a triac frequency converter for a single-phase two-winding asynchronous electric motor of increased efficiency by reducing energy consumption, while simplifying the device control system.

The solution to this technical problem is achieved by the fact that in a triac frequency converter for a single-phase two-winding asynchronous electric motor, containing two semiconductor switches powered from a single-phase alternating current network, intended for connection to a load representing the stator windings of a single-phase two-winding asynchronous electric motor, the first output of the first semiconductor the switch is connected to the phase wire of the AC supply network, and the second terminal of the first semiconductor switch is intended for connection to the first output of the first stator winding of a single-phase two-winding asynchronous electric motor, the first terminal of the second semiconductor switch is connected to the phase wire of the AC supply network, and the second terminal of the second semiconductor switch designed for connection to the first output of the second stator winding of a single-phase two-winding asynchronous electric motor, the combined second outputs of the stator windings of a single-phase two-winding asynchronous electric motor are connected to the neutral wire of the AC supply network, according to the utility model, triacs are used in semiconductor switches that pass current in both directions.

Reducing energy consumption and simplifying the device control system is due to the use of triacs as semiconductor switches that pass current in both directions without the need to take into account the polarity of the voltage passing through the triacs and without supplying a constant unlocking signal, since the triac is controlled by supplying an unlocking pulse and the triac will remain open as long as the current flowing through it exceeds the holding current, and closes when the voltage polarity changes.

The proposed utility model is illustrated by drawings, where in Fig. Figure 1 shows a schematic electrical diagram of a triac frequency converter for a single-phase two-winding asynchronous electric motor; in fig. 2 shows a vector diagram of the elliptical rotating field of the stator of the engine, consisting of four fixed positions of the magnetic induction vector of the stator field, when rotating clockwise; in fig. Figure 3 shows the flow of current through the stator windings at different times, as well as the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in Fig. 2; in fig. 4 shows a vector diagram of the elliptical rotating field of the stator of the engine, consisting of four fixed positions of the magnetic induction vector of the stator field, when rotating counterclockwise; in fig. Figure 5 shows the flow of current through the stator windings at different times, as well as the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in Fig. 4; in fig. 6 shows a vector diagram of the elliptical rotating field of the stator of the engine, consisting of three fixed positions of the magnetic induction vector of the stator field, when rotating clockwise; in fig. Figure 7 shows the flow of current through the stator windings at different times, as well as the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in Fig. 6; in fig. 8 shows a vector diagram of the elliptical rotating field of the stator of the engine, consisting of three fixed positions of the magnetic induction vector of the stator field, when rotating counterclockwise; in fig. Figure 9 shows the flow of current through the stator windings at different times, as well as the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in Fig. 8; in fig. 10 shows a vector diagram of the circular rotating field of the stator of the engine, consisting of four fixed positions of the magnetic induction vector of the stator field, when rotating clockwise; in fig. Figure 11 shows the flow of current through the stator windings at different times, as well as the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in Fig. 10; in fig. 12 shows a vector diagram of the circular rotating field of the stator of the engine, consisting of four fixed positions of the magnetic induction vector of the stator field, when rotating counterclockwise; in fig. Figure 13 shows the flow of current through the stator windings at different times, as well as the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in Fig. 12.

In addition, the following symbols are used in the drawing:

- F - phase;

- 0 - zero;

- L1, L2 - stator windings of the electric motor;

- VS1, VS2 - triacs;

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

- Umains - supply voltage;

- arcuate lines with an arrow - the direction of rotation of the stator magnetic field;

- t1, t2…t6 - moments of switching time of triacs;

- solid arrows along the stator windings of a single-phase asynchronous motor - forward direction of current in the windings of the electric motor;

- discrete arrows along the stator windings of a single-phase asynchronous motor - reverse direction of current in the windings of the electric motor.

A triac frequency converter for a single-phase two-winding asynchronous electric motor contains two semiconductor switches 1 and 2, powered by a single-phase alternating current network, intended for connection to a load representing the stator windings of a single-phase two-winding asynchronous electric motor. The first triac 3 (VS1) is used as the semiconductor switch of the semiconductor switch 1. The second triac 4 (VS2) is used as a semiconductor switch of the semiconductor switch 2. In the semiconductor switch 1, the first terminal 5 of the triac 3 (VS1) is connected to the phase wire of the AC supply network, the second terminal 6 of the triac 3 (VS1) is intended for connection to the first output 7 (C1) of the first stator winding 8 (L1). In the semiconductor switch 2, the first terminal 9 of the triac 4 (VS2) is connected to the phase wire of the AC supply network, the second terminal 10 of the triac 4 (VS2) is intended for connection to the first output 11 (C2) of the second stator winding 12 (L2). The second terminal 13 (NW) of the first stator winding 8 (L1) and the second terminal 14 (C4) of the second stator winding 12 (L2) are combined and connected to the neutral supply network.

The operation of a triac frequency converter for a single-phase two-winding asynchronous electric motor is carried out as follows. To ensure that the magnetic induction vector of the rotating elliptical field of the motor stator rotates clockwise, in accordance with the vector diagram shown in Fig. 2, it is necessary to apply control pulses to triacs 3 (VS1), 4 (VS2), in the following order (Fig. 3).

1. In the positive half-wave of the supply voltage, in the period from 0 to t1, triac 3 (VS1) opens, providing the first I fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the forward direction.

2. In the positive half-wave of the supply voltage, in the period from t1 to t2, triac 4 (VS2) opens, while triac 3 (VS1) remains open, providing a second II fixed position of the magnetic induction vector of the stator field when current flows through windings 8 (L1 ) and 12 (L2) in the forward direction.

When the polarity of the AC supply voltage changes, triacs 3 (VS1), 4 (VS2) close.

3. In the negative half-wave of the supply voltage, in the period from t2 to t3, triac 3 (VS1) opens, providing the third III fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the opposite direction.

4. In the negative half-wave of the supply voltage, in the period from t3 to t4, triac 4 (VS2) opens, while triac 3 (VS1) remains open, providing the fourth IV fixed position of the magnetic induction vector of the stator field when current flows through windings 8 (L1 ) and 12 (L2) in the opposite direction.

The stator field turns out to be rotating, elliptical, spatial, and time-varying. When the next positive half-wave passes, the cycle repeats, ensuring clockwise rotation of the stator field. In this case, the rotating stator field makes one revolution in one period of the supply network, that is, the rotation frequency fc of the stator field is 50 Hz.

To ensure that the magnetic induction vector of the rotating elliptical field of the motor stator rotates counterclockwise, in accordance with the vector diagram shown in FIG. 4, it is necessary to apply control pulses to triacs 3 (VS1), 4 (VS2), in the following order (Fig. 5).

1. In the positive half-wave of the supply voltage, in the period from 0 to t1, triac 4 (VS2) opens, providing the first I fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the forward direction.

2. In the positive half-wave of the supply voltage, in the period from t1 to t2, triac 3 (VS1) opens, while triac 4 (VS2) remains open, providing a second II fixed position of the magnetic induction vector of the stator field when current flows through windings 8 (L1 ) and 12 (L2) in the forward direction.

When the polarity of the AC supply voltage changes, triacs 3 (VS1), 4 (VS2) close.

3. In the negative half-wave of the supply voltage, in the period from t2 to t3, triac 4 (VS2) opens, providing the third III fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the opposite direction.

4. In the negative half-wave of the supply voltage, in the period from t3 to t4, triac 3 (VS1) opens, while triac 4 (VS2) remains open, providing the fourth IV fixed position of the magnetic induction vector of the stator field when current flows through windings 8 (L1 ) and 12 (L2) in the opposite direction.

The stator field turns out to be rotating, elliptical, spatial, and time-varying. When the next positive half-wave passes, the cycle repeats, ensuring counterclockwise rotation of the stator field. In this case, the rotating stator field makes one revolution in one period of the supply network, that is, the rotation frequency fc of the stator field is 50 Hz.

To ensure clockwise rotation of the magnetic induction vector of the rotating elliptical field of the motor stator at a reduced frequency, in accordance with the vector diagram shown in FIG. 6, it is necessary to apply control pulses to triacs 3 (VS1), 4 (VS2), in the following order (Fig. 7).

1. In the positive half-wave of the supply voltage, in the period from 0 to t1, triac 3 (VS1) and triac 4 (VS2) open, providing the first I fixed position of the magnetic induction vector of the stator field when current flows through windings 8 (L1) and 12 ( L2) in the forward direction.

When the polarity of the AC supply voltage changes, triacs 3 (VS1), 4 (VS2) close.

2. In the negative half-wave of the supply voltage, in the period from t1 to t2, triac 4 (VS2) opens, providing a second II fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the opposite direction.

When the polarity of the AC supply voltage changes, triac 4 (VS2) closes.

3. During the positive half-wave of the supply voltage, in the period from t2 to t3, all triacs are closed.

4. In the negative half-wave of the supply voltage, in the period from t3 to t4, triac 3 (VS1) opens, providing the third III fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the opposite direction.

The stator field turns out to be rotating, elliptical, spatial, and time-varying. When the next positive half-wave passes, the cycle repeats, ensuring clockwise rotation of the stator field. In this case, the rotating stator field makes one revolution in two periods of the supply network, that is, the rotation frequency fc of the stator field is 25 Hz.

To ensure rotation with a reduced frequency of the magnetic induction vector of the rotating elliptical field of the motor stator counterclockwise, in accordance with the vector diagram shown in Fig. 8, it is necessary to apply control pulses to triacs 3 (VS1), 4 (VS2), in the following order (Fig. 9).

1. In the positive half-wave of the supply voltage, in the period from 0 to t1, triac 3 (VS1) opens, providing the first I fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the forward direction.

When the polarity of the AC supply voltage changes, triac 3 (VS1) closes.

2. In the negative half-wave of the supply voltage, in the period from t1 to t2, triacs 3 (VS1) and 4 (VS2) open, providing a second II fixed position of the magnetic induction vector of the stator field when current flows through windings 8 (L1) and 12 (L2 ) in the opposite direction.

When the polarity of the AC supply voltage changes, triacs 3 (VS1), 4 (VS2) close.

3. In the positive half-wave of the supply voltage, in the period from t2 to t3, triac 4 (VS2) opens, providing the third III fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the forward direction.

4. During the negative half-wave of the supply voltage, in the period from t3 to t4, all triacs are closed.

The stator field turns out to be rotating, elliptical, spatial, and time-varying. When the next positive half-wave passes, the cycle repeats, ensuring counterclockwise rotation of the stator field. In this case, the rotating stator field makes one revolution in two periods of the supply network, that is, the rotation frequency fc of the stator field is 25 Hz.

To ensure clockwise rotation of the magnetic induction vector of the rotating elliptical field of the motor stator at a reduced frequency, in accordance with the vector diagram shown in FIG. 10, it is necessary to apply control pulses to triacs 3 (VS1), 4 (VS2), in the following order (Fig. 11).

1. During the positive half-wave of the supply voltage, in the period from 0 to t1, all triacs are closed.

2. In the negative half-wave of the supply voltage, in the period from t1 to t2, triac 4 (VS2) opens, providing the first I fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the opposite direction.

When the polarity of the AC supply voltage changes, triac 4 (VS2) closes.

3. In the positive half-wave of the supply voltage, in the period from t2 to t3, triac 3 (VS1) opens, providing a second II fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the forward direction.

When the polarity of the AC supply voltage changes, triac 3 (VS1) closes.

4. During the negative half-wave of the supply voltage, in the period from t3 to t4, all triacs are closed.

5. In the positive half-wave of the supply voltage, in the period from t4 to t5, triac 4 (VS2) opens, providing the third III fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the forward direction.

6. In the negative half-wave of the supply voltage, in the period from t5 to t6, triac 3 (VS1) opens, providing the fourth IV fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the opposite direction.

When the polarity of the AC supply voltage changes, triac 3 (VS1) closes.

The stator field turns out to be rotating, circular, spatial, and time-varying. When the next positive half-wave passes, the cycle repeats, ensuring clockwise rotation of the stator field. In this case, the rotating stator field makes one revolution in three periods of the supply network, that is, the rotation frequency fc of the stator field is 16.66 Hz.

To ensure clockwise rotation of the magnetic induction vector of the rotating elliptical field of the motor stator at a reduced frequency, in accordance with the vector diagram shown in FIG. 12, it is necessary to apply control pulses to triacs 3 (VS1), 4 (VS2), in the following order (Fig. 13).

1. In the positive half-wave of the supply voltage, in the period from 0 to t1, triac 3 (VS1) opens, providing the first I fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the forward direction.

When the polarity of the AC supply voltage changes, triac 3 (VS1) closes.

2. In the negative half-wave of the supply voltage, in the period from t1 to t2, triac 4 (VS2) opens, providing a second II fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the opposite direction.

When the polarity of the AC supply voltage changes, triac 4 (VS2) closes.

3. During the positive half-wave of the supply voltage, in the period from t2 to t3, all triacs are closed.

4. In the negative half-wave of the supply voltage, in the period from t3 to t4, triac 3 (VS1) opens, providing the third III fixed position of the magnetic induction vector of the stator field when current flows through winding 8 (L1) in the opposite direction.

When the polarity of the AC supply voltage changes, triac 3 (VS1) closes.

5. In the positive half-wave of the supply voltage, in the period from t4 to t5, triac 4 (VS2) opens, providing the fourth IV fixed position of the magnetic induction vector of the stator field when current flows through winding 12 (L2) in the forward direction.

When the polarity of the AC supply voltage changes, triac 4 (VS2) closes.

6. During the negative half-wave of the supply voltage, in the period from t5 to t6, all triacs are closed.

The stator field turns out to be rotating, circular, spatial, and time-varying. When the next positive half-wave passes, the cycle repeats, ensuring counterclockwise rotation of the stator field. In this case, the rotating stator field makes one revolution in three periods of the supply network, that is, the rotation frequency fc of the stator field is 16.66 Hz.

By changing the sequence of switching on the transistors, you can reduce the engine speed in accordance with the formula:

where f _reg - control frequency;

f _c - network frequency;

n is the number of periods of change in the supply voltage per revolution of the rotating stator field.

Thus, the proposed utility model has advantages over the prototype due to reduced power consumption and a simplified device control system.

Claims (1)

A triac frequency converter for a single-phase two-winding asynchronous electric motor, containing two semiconductor switches powered from a single-phase alternating current network, intended for connection to a load representing the stator windings of a single-phase two-winding asynchronous electric motor, with the first output of the first semiconductor switch connected to the phase wire of the alternating voltage supply network , and the second output of the first semiconductor switch is intended for connection to the first output of the first stator winding of a single-phase two-winding asynchronous electric motor, the first output of the second semiconductor switch is connected to the phase wire of the AC supply network, and the second output of the second semiconductor switch is intended for connection to the first output of the second stator winding single-phase two-winding asynchronous electric motor, the combined second outputs of the stator windings of the single-phase two-winding asynchronous electric motor are connected to the neutral wire of the AC supply network, characterized in that triacs are used in semiconductor switches that pass current in both directions.

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