RU192777U1 - Semiconductor device for starting a three-phase asynchronous electric motor from a single-phase network - Google Patents

Abstract

A semiconductor device for starting a three-phase asynchronous electric motor from a single-phase network is intended for use in an electric drive to power asynchronous three-phase electric motors, the stator windings of which are connected according to the "broken star" scheme. Two semiconductor switches of the device are formed by counter-parallel pairs of semiconductor elements made in the form of transistors. The stator windings of the electric motor are connected as a “torn star”. In the first semiconductor key, the collector of the first transistor is connected to the emitter of the second transistor and connected to the beginning of the second stator winding, and the emitter of the first transistor is connected to the collector of the second transistor and with zero supply network made in the form of a single-phase AC network for supplying a three-phase asynchronous motor. In the second semiconductor key, the collector of the third transistor is connected to the emitter of the fourth transistor and connected to the beginning of the third stator winding, and the emitter of the third transistor is connected to the collector of the fourth transistor and with zero supply network. The end of the second stator winding is connected to the end of the third stator winding and is connected to the phase of the supply network. The end of the first stator winding is connected to zero of the supply network, and the beginning of the first stator winding is connected to the phase of the supply network. Significantly increases the reliability of the device with increased efficiency.

Description

The proposed utility model relates to devices for starting three-phase asynchronous electric motors from a single-phase network and can be used in an electric drive to power three-phase asynchronous electric motors, the stator windings of which are connected according to the “broken star” scheme.

A device for controlling the rotational speed of a three-phase asynchronous electric motor from a single-phase network, containing semiconductor switches, which are used power semiconductor elements, such as three triacs or six thyristors, forming counter-parallel pairs, for switching the motor windings. One of the outputs of each triac or one of the common outputs of each counter-parallel pair of semiconductor elements made in the form of thyristors is connected to the mains phase, and the other output of each triac or other common output of each counter-parallel pair of semiconductor elements made in the form of thyristors connected to the corresponding stator winding. In this case, the stator windings of the electric motor are connected to a star, and the zero output of the electric motor is connected to zero of the supply network (Glazenko T.A. Semiconductor systems of a pulsed asynchronous electric drive of low power. / T.A. Glazenko. - Leningrad: ENERGOATOMIZDAT, 1983. - P. 61 Fig. 2-12, diagram No. 12).

The main disadvantages of the described device for controlling the rotational speed of a three-phase asynchronous electric motor from a single-phase network are low reliability, which is explained by a significant number of power semiconductor elements.

Closest to the proposed device in technical essence and the achieved result (prototype) is a device for capacitor starting a three-phase electric motor from a single-phase network, containing a high-capacity paper capacitor, an inductance and a semiconductor switch formed by a counter-parallel pair of semiconductor elements made in the form of two thyristors. One output of the semiconductor switch is connected to zero power supply, made in the form of a single-phase AC network to power a three-phase asynchronous motor, and the other output of the semiconductor switch is connected to the inductance. The capacitor and inductance have a common output, which is designed to connect to the output, that is, with the beginning, of the first stator winding. The other output of the capacitor is connected to a common point of two thyristors connected counter-parallel, that is, with one output of the semiconductor switch, with zero supply network and with one output, that is, with the beginning, of the second stator winding. Another output, that is, the end, of the second stator winding is connected to one of the outputs, namely the end of the third stator winding, forming a common point. Another output, that is, the beginning, of the third winding is connected to the phase of the supply network and to another output, namely the end of the first stator winding. The stator windings of this electric motor are connected according to the “broken star” type (Glazenko T. A. Semiconductor systems of a pulsed asynchronous electric drive of low power. / T. A. Glazenko. - Leningrad: ENERGOATOMIZDAT, 1983. - P. 61, Fig. 2-12, Scheme No. 13).

The main disadvantage of the described device for capacitor starting a three-phase electric motor from a single-phase network is low reliability due to the need to use both paper capacitors of large capacity and inductance, as well as due to the unpredictability of the direction of rotation of the motor.

The technical problem, the solution of which is provided by the implementation of the utility model, is to create a semiconductor device for starting a three-phase asynchronous electric motor from a single-phase network with increased reliability.

The solution to this technical problem is achieved by the fact that a semiconductor device for starting a three-phase asynchronous electric motor from a single-phase network, containing a semiconductor switch formed by a counter-parallel pair of semiconductor elements, one output of which is connected to zero power network, made in the form of a single-phase AC network for supplying a three-phase asynchronous motor, and the end of the third stator winding is connected to the end of the second stator winding, and the stator windings of the electric motor with dineny by "broken star" type, according to the utility model the semiconductor device is provided with a key formed anti-parallel pairs of semiconductor elements, wherein the anti-parallel pair of semiconductor elements of both semiconductor switches are in the form of transistors. In this case, in the first semiconductor key, the collector of the first transistor is connected to the emitter of the second transistor and connected to the beginning of the second stator winding, and the emitter of the first transistor is connected to the collector of the second transistor and to zero supply network, and in the second semiconductor key the collector of the third transistor is connected to the emitter of the fourth transistor and connected to the beginning of the third stator winding, and the emitter of the third transistor is connected to the collector of the fourth transistor and to zero supply network, the end of the second hydrochloric winding is connected to the end of the third stator winding and is connected to a phase of a power line, a first end of the stator winding is connected to a power line zero, and the beginning of the first stator winding is connected to the mains phase.

Improving the reliability of a semiconductor device for starting a three-phase asynchronous electric motor from a single-phase network is due to the use of two semiconductor switches with a simplified control system for opening and closing them in the absence of a capacitor and inductance.

The proposed utility model is illustrated by drawings, where in FIG. 1 shows a circuit diagram of a semiconductor device for starting a three-phase asynchronous electric motor from a single-phase network; in FIG. 2 is a vector diagram of a circular rotating field of a stator of an electric motor, which consists of six fixed positions of the magnetic induction vector of the stator field; in FIG. 3 - directions of the magnetic induction vector and the flowing current along the stator windings of the electric motor in accordance with the vector diagram depicted in FIG. 2; in FIG. 4 - phase-by-phase voltage variation in the stator windings of the electric motor in accordance with the vector diagram depicted in FIG. 2.

In addition, the drawings show the following:

- f - phase;

- 0 - zero;

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

- VT1-VT4 - transistors;

- I, II, III, IV, V, VI - sequential fixed positions of the magnetic induction vector of the circular rotating field of the stator of a three-phase asynchronous motor;

- straight lines with arrows - the directions of the magnetic induction vector of the circular rotating field of the stator of the electric motor;

- arcuate lines with arrows - directions of rotation of the stator magnetic field;

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

- U _A , U _B , U _C - voltage on the stator windings A, B, C;

- fat dots - the beginning of the stator windings;

- straight lines with arrows along the stator windings of the electric motor - the directions of the magnetic induction vector and current in the stator windings;

- t1-t6 are the times of switching transistors.

A semiconductor device for starting a three-phase electric motor from a single-phase network contains two semiconductor switches formed by two counter-parallel pairs of semiconductor elements, each of which is made in the form of two transistors.

In the first semiconductor key 1, the collector of the first transistor 2 (VT1) is connected to the emitter of the second transistor 3 (VT2), and their common output is connected to the beginning of the second stator winding 4 (B). The emitter of the first transistor 2 (VT1) is connected to the collector of the second transistor 3 (VT2) and their common output is connected to the supply network zero.

In the second semiconductor key 5, the collector of the third transistor 6 (VT3) is connected to the emitter of the fourth transistor 7 (VT4) and their common output is connected to the beginning of the third stator winding 8 (C). The emitter of the third transistor 6 (VT3) is connected to the collector of the fourth transistor 7 (VT4), and their common output is connected to the supply network zero.

The end of the second stator winding 4 (B) is connected to the end of the third stator winding 8 (C) and connected to the phase of the supply network. The beginning of the first stator winding 9 (A) is connected to the phase of the supply network. The end of the first stator winding 9 (A) is connected to zero supply network. Stator windings 9 (A), 4 (B), 8 (C) of the electric motor are connected according to the “broken star” scheme. The power network is made in the form of a single-phase AC network for supplying a three-phase asynchronous motor.

The semiconductor device for starting a three-phase induction motor from a single-phase network for six fixed positions of the magnetic flux of the stator field is as follows.

Vector-algorithmic control is carried out by opening transistors 2 (VT1), 3 (VT2), 6 (VT3), 7 (VT4) in a certain sequence. To ensure rotation of the magnetic induction vector of the circular rotating field of the stator of the electric motor in accordance with the vector diagram shown in FIG. 2, in the sequence I-II-III-IV-V-VI, it is necessary to open the transistors 2 (VT1), 3 (VT2), 6 (VT3), 7 (VT4) in the following sequence:

- at the initial moment of time, when the positive half-wave of the supply voltage passes, the transistor 2 (VT1) opens, and the current passes through the winding 9 (A) and the motor winding 4 (B) - the first position of the stator field magnetic induction vector is formed (Fig. 2, Fig. . 3, Fig. 4);

- at time t1, with a positive half-wave of the supply voltage, transistor 6 (VT3) opens, transistor 2 (VT1) remains open, and the current goes through windings 9 (A), 4 (B) and 8 (C) - the second position of the magnetic vector is formed induction of the stator field (Fig. 2, Fig. 3, Fig. 4);

- at time t2, with a positive half-wave of the supply voltage, transistor 2 (VT1) closes, transistor 6 (VT3) remains open, and the current flows through windings 9 (A) and 8 (C) - the third position of the stator field magnetic induction vector is formed (Fig. . 2, Fig. 3, Fig. 4);

- at time t3, when the negative half-wave of the supply voltage passes, the transistor 6 (VT3) closes and the transistor 3 (VT2) opens, and the current flows through two windings 9 (A), 4 (B) - the fourth position of the stator field magnetic induction vector is formed (Fig. 2, Fig. 3, Fig. 4);

- at time t4, transistor 7 (VT4) opens, transistor 3 (VT2) remains open, and the current flows through windings 9 (A), 4 (B) and 8 (C) - the fifth position of the stator field magnetic induction vector is formed (Fig. . 2, Fig. 3, Fig. 4);

- at time t5 the transistor 3 (VT2) closes, the transistor 7 (VT4) remains open, and the current goes through the windings 9 (A) and 8 (C) - the sixth position of the stator field magnetic induction vector is formed (Fig. 2, Fig. 3, Fig. 4).

The stator field turns out to be rotating, ellipsoidal, spatial, changing in time. With the passage of the next positive half-wave at time t6, the cycle repeats.

Thus, based on the foregoing, we can conclude that the proposed semiconductor device for starting a three-phase asynchronous electric motor from a single-phase network has advantages compared to the known ones: increased reliability and efficiency, as well as reduced dimensions.

Claims (1)

A semiconductor device for starting a three-phase asynchronous motor from a single-phase network, containing a semiconductor switch formed by a counter-parallel pair of semiconductor elements, one output of which is connected to zero power network, made in the form of a single-phase AC network for supplying a three-phase asynchronous motor, and the end of the third stator winding is connected to the end of the second stator winding, and the stator windings of the electric motor are connected by the type of "torn star", characterized in that that the device is equipped with a semiconductor key formed by counter-parallel pairs of semiconductor elements, and counter-parallel pairs of semiconductor elements of both semiconductor switches are made in the form of transistors, while in the first semiconductor key, the collector of the first transistor is connected to the emitter of the second transistor and connected to the beginning of the second stator winding , and the emitter of the first transistor is connected to the collector of the second transistor and to zero supply network, and in the second semiconductor In the key, the collector of the third transistor is connected to the emitter of the fourth transistor and connected to the beginning of the third stator winding, and the emitter of the third transistor is connected to the collector of the fourth transistor and to zero supply network, the end of the second stator winding is connected to the end of the third stator winding and connected to the phase of the supply network, end the first stator winding is connected to zero of the supply network, and the beginning of the first stator winding is connected to the phase of the supply network.

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