RU2385527C1 - Semiconductor device of capacitor-free start-up of three-phase electric motor from single-phase grid - Google Patents

Abstract

FIELD: electric engineering.

SUBSTANCE: as semiconducting switch intended for short-circuiting of one of stator windings of motor when stator windings are connected as delta, two reversible semiconducting switchboards are used, every of which comprises two opposite connected transistors. In the first reversible semiconducting switchboard, collector of the first transistor is connected to emitter of the second transistor and connected to phase of supply grid, and emitter of the first transistor is connected to collector of the second transistor and to outputs of the first and second stator windings, and their common output is intended for connection to phase of supply grid. In the second reversible semiconducting switchboard, collector of the third transistor is connected to emitter of the fourth transistor, and their common output is intended for connection to phase of supply grid, and emitter of the third transistor is connected to collector of the fourth transistor, and their common output is intended for connection of outputs of the second and third stators windings. Common output of the first and third windings is connected to zero of single-phase grid.

EFFECT: increasing reliability and efficiency of device, reduction of its dimensions.

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Description

The present invention 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 asynchronous three-phase electric motors, the stator windings of which are connected according to the "triangle" scheme.

A device for the capacitor start of a three-phase electric motor from a single-phase network, containing a capacitor and inductance. The capacitor and inductance have a common output, which is designed to connect to the outputs of the windings, one of which is connected to the zero of the single-phase network, and the other is connected to the phase of the single-phase network. The other output of the capacitor is connected to the phase of the single-phase network and is designed to connect to the outputs of the windings, one of which is connected to the zero of the single-phase network. The other inductance output is connected to the zero of the single-phase network and the outputs of the windings, one of which is connected to the phase of the single-phase network. The motor windings are connected in the form of a "triangle" (S. Biryukov. Three phases - without loss of power / S. Biryukov // Radio. - M., 2000. - No. 7. - P.37, Fig. 1).

The main disadvantages of the described device for the capacitor starting of a three-phase electric motor from a single-phase network are the increased dimensions, due to the need to use paper capacitors of large capacity and inductances, as well as low reliability due to the presence of capacitors and inductances in the circuit.

Closest to the proposed invention in terms of technical nature and the achieved result (prototype) is a device for non-capacitor starting a three-phase electric motor from a single-phase network, containing a semiconductor key for shorting and a control system for this key, when connecting the stator windings according to the "triangle" circuit, connected in parallel to one winding. One output of the semiconductor switch is connected to the outputs of the first and second windings, the first winding designed to connect one output to zero of the single-phase network, and the other output to the phase of the single-phase network, and the second winding is designed to connect only to the phase of the single-phase network. The second output of the semiconductor switch is designed to connect to the outputs of the second and third windings, and the third winding is designed to connect to zero a single-phase network, and the second to the phase of a single-phase network. Thus, the common output of the first and third windings are designed to connect to zero the supply network, which is used as a uniform AC supply network to power a three-phase asynchronous motor. The control system for this semiconductor key consists of a diode bridge and two thyristors connected by cathodes in the opposite direction to one of the diagonals of the bridge. The common cathode point of these thyristors is connected to the minus of the other diagonal of the bridge (Golik V. Device for starting three-phase motors / V. Golik // M., Radio, 1996. - No. 6. - P.39, Fig. 1.3).

The main disadvantages of this device for capacitor-free starting of a three-phase electric motor from a single-phase network are reduced reliability, large dimensions and high cost due to the use of a complex control system for starting and introducing a large number of elements such as a diode bridge, a zener diode, two transistors, two thyristors.

The present invention solves the problem of increasing reliability and efficiency, as well as reducing the size of the device semiconductor non-capacitor starting three-phase electric motor from a single-phase network.

To solve this problem, in a semiconductor device for capacitor-free starting of a three-phase electric motor from a single-phase network, containing a semiconductor switch designed to short-circuit one of the stator windings of the motor when connecting the stator windings according to the "triangle" scheme, the single-phase AC mains for power supply is used a three-phase asynchronous motor according to the invention, two reversible semiconductors are used as a semiconductor switch single switches, each of which contains two counter-parallel connected transistors, and in the first reversible semiconductor switch, the collector of the first transistor is connected to the emitter of the second transistor and connected to the phase of the supply network, and the emitter of the first transistor is connected to the collector of the second transistor and to the terminals of the first and second stator windings, and in the second reverse semiconductor switch, the collector of the third transistor is connected to the emitter of the fourth transistor and is connected to the phase network, and the emitter of the third transistor is connected to the collector of the fourth transistor and to the terminals of the second and third stator windings, the common output of the first and third stator windings is connected to zero single-phase network.

Improving the reliability and efficiency, as well as reducing the size of the semiconductor device of the non-capacitor starting of a three-phase electric motor from a single-phase network, is due to a decrease in the number of semiconductor elements.

The invention is illustrated in the drawing, where figure 1 shows a circuit diagram of the proposed semiconductor device of a capacitor-free start-up of a three-phase electric motor from a single-phase network; figure 2 shows a vector diagram of rotation, consisting of six fixed positions of the magnetic flux of the stator field; figure 3 shows the phase-wise change in magnetic flux in the stator windings in accordance with the vector diagram shown in figure 2. In addition, the drawing shows the following:

- f - phase;

- 0 - zero;

- A, B, C - stator windings of the electric motor;

- VT1 - VT4 - transistors;

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

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

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

A semiconductor device for capacitor-free starting of a three-phase electric motor from a single-phase network contains a semiconductor switch, which is used as two reversing semiconductor switches, each of which contains two counter-parallel connected transistors. The first reversible semiconductor switch contains transistors 1 (VT1) and 2 (VT2). The collector of transistor 1 (VT1) is connected to the emitter of transistor 2 (VT2) and their common output is designed to connect to the phase of the supply network. The emitter of transistor 1 (VT1) is connected to the collector of transistor 2 (VT2) and their common output is designed to connect to the common output of the first and second windings 3 (winding A) and 4 (winding B), respectively. The second reversible semiconductor switch contains transistors 5 (VT3) and 6 (VT4). The collector of transistor 5 (VT3) is connected to the emitter of transistor 6 (VT4), and their common output is designed to connect to the phase of the supply network. The emitter of transistor 5 (VT3) is connected to the collector of transistor 6 (VT4), and their common output is designed to connect to the common output of the second and third windings 4 (winding B) and 7 (winding C), respectively. The common conclusion of the first and third windings 3 (winding A) and 7 (winding C) are intended to be connected to the supply network zero. Stator windings A, B, C of the electric motor are connected according to the "triangle" scheme.

The operation of the semiconductor device of the non-capacitor starting three-phase electric motor from a single-phase network is as follows. When the positive half-wave of the supply voltage passes, the transistor 1 (VT1) opens and the current passes through all three windings 3 (winding A), 4 (winding B), 7 (winding C) of the electric motor (Fig. 3). The first position of the stator magnetic field vector is formed. After a certain point in time, transistor 5 (VT3) opens and current flows through windings 3 (winding A) and 7 (winding C). The second position of the stator magnetic field vector is formed. After a certain point in time, transistor 1 (VT1) closes and the current goes through three windings 4 (winding B), 3 (winding A), 7 (winding C). A third position of the stator magnetic field vector is formed. When the negative half-wave of the supply voltage passes, the transistor 5 (VT3) closes and the transistor 2 (VT2) opens and the current flows through all three windings 3 (winding A), 4 (winding B), 7 (winding C). The fourth position of the stator magnetic field vector is formed. After a certain point in time, transistor 6 (VT4) opens and current flows through windings 3 (winding A) and 7 (winding C). The fifth position of the stator magnetic field vector is formed. After a certain point in time, transistor 2 (VT2) closes and the current goes through three windings 4 (winding B), 3 (winding A), 7 (winding C). The sixth position of the stator magnetic field vector is formed. The stator field is ellipsoidal, spatial, and changes in time. As the next positive half-wave passes, the cycle repeats.

Thus, reliability and economy are increased, as well as the dimensions of the device for non-capacitor starting of a three-phase electric motor from a single-phase network are reduced in the absence of using a complex control system for starting a three-phase electric motor.

Claims (1)

A semiconductor device for capacitor-free starting of a three-phase electric motor from a single-phase network, containing a semiconductor switch designed to short-circuit one of the stator windings of the motor when connecting the stator windings according to the "triangle" scheme, characterized in that two reversing semiconductor switches are used as a semiconductor switch, each of which contains two counter-parallel connected transistors, with a collector in the first reversing semiconductor switch the first transistor is connected to the emitter of the second transistor, and their common input is for connecting to the phase of the supply network, and the emitter of the first transistor is connected to the collector of the second transistor, and their common output is for connecting to the terminals of the first and second stator windings, and in the second reversing semiconductor The commutator of the third transistor is connected to the emitter of the fourth transistor, and their common output is designed to connect to the phase of the supply network and the emitter of the third transistor is connected to the collector one of the fourth transistors, and their common output is designed to connect to the terminals of the second and third stator windings, the common output of the first and third stator windings is connected to zero single-phase network.

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