RU200744U1 - Compact device for starting a three-phase motor from a single-phase network - Google Patents

Abstract

A compact device for starting a three-phase motor from a single-phase network refers to devices for starting three-phase asynchronous electric motors when powered from a single-phase network and can be used in an electric drive to start asynchronous three-phase electric motors, the stator windings of which are connected according to the "star" scheme. The semiconductor switch of the device contains two anti-parallel connected dynistors designed to power the stator windings of the motor when the stator windings are connected according to the "star" scheme, to connect with one common terminal to the terminal of the second stator winding, the other common terminal to the terminal of the third stator winding and to the phase supply network. The possibility of increasing the energy performance of the device is provided. 4 ill.

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 for starting asynchronous electric motors, the stator windings of which are connected according to the "star" scheme.

Known is a device for capacitor starting of a three-phase electric motor from a single-phase network, containing a paper capacitor and an inductance. The capacitor and inductance have a common output, which is designed to be connected 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 intended to be connected to the outputs of the windings, one of which is connected to the zero of the single-phase network. Another 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 according to the "triangle" type (Biryukov S. 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 capacitor starting of a three-phase electric motor from a single-phase network are increased dimensions due to the need to use paper capacitors of large capacity and inductance, as well as low reliability due to the presence of capacitors and inductors in the circuit.

The closest to the proposed utility model in terms of the technical essence and the achieved result (prototype) is a device for capacitor-free starting of a three-phase squirrel-cage electric motor from a single-phase network, containing semiconductor switches, which are two dynistors connected in opposite-parallel to connect one common terminal to the output of the stator winding , not connected to the phase and zero of the supply network, another common terminal - to the zero of the supply network and to the output of the stator winding connected to the zero of the supply network. The stator windings are connected according to the "star" scheme (patent RU No. 2370877, IPC Н02Р1 / 26 (2006.01)).

The main disadvantages of this device for capacitor-free starting of a three-phase squirrel-cage electric motor from a single-phase network are reduced energy characteristics due to the connection of dinistors in parallel with the stator windings. The proposed utility model solves the problem of increasing the energy characteristics of the device.

To solve the problem in a compact device for starting a three-phase electric motor from a single-phase network, containing a semiconductor switch, which is used as two anti-parallel connected dynistors connected to the supply network and the stator winding, when connecting the stator windings according to the "star" scheme, according to the utility model the semiconductor switch is connected with one common terminal to the terminal of the second stator winding, with the other common terminal to the terminal of the third stator winding and to the phase of the supply network.

An increase in the energy characteristics of a compact device for starting a three-phase motor from a single-phase network is due to a change in the connection diagram of a semiconductor switch.

The proposed utility model is illustrated by drawings, where figure 1 shows a schematic electrical diagram of the proposed compact device for starting a three-phase electric motor from a single-phase network; figure 2 is a vector diagram of rotation, which consists of four fixed positions of the magnetic flux vector of the stator field; figure 3 - directions of the vector of magnetic induction and current flowing through the stator windings of the motor in accordance with the vector diagram shown in figure 2; figure 4 - phase-by-phase change in voltage in the stator windings of the motor in accordance with the vector diagram shown in figure 2.

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

Phase - phase;

0 - zero;

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

VD1, VD2 - dinistors;

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

Unets - the change in the supply voltage over time;

Ua, Uv, Uc - voltage across the stator windings A, B and C, respectively;

t1, t2… t3 are the times of the circuit operation;

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

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

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

A compact three-phase motor starter from a single-phase network works as follows:

at the initial moment of time, when the positive half-wave of the supply voltage passes, the dinistor 1 (VD1) is closed, the current flows through two windings 2 (winding A), 3 (winding C) of the electric motor - the first position of the magnetic induction vector of the stator field is formed (figure 2);

at time t1, when the positive half-wave of the supply voltage passes and the threshold value of the supply voltage is reached, dinistor 1 (VD1) opens. The current passes through all three windings 2 (winding A), 4 (winding B), 3 (winding C) of the electric motor - the second position of the stator magnetic induction vector is formed;

at time t2, with a negative half-wave of the supply voltage, dinistor 5 (VD2) is closed, current flows through two windings 2 (winding A) and 3 (winding C) of the electric motor - the third position of the stator magnetic induction vector is formed;

at time t3, when the negative half-wave of the supply voltage passes and the threshold value of the supply voltage is reached, dinistor 2 (VD2) opens, the current flows through all three windings 2 (winding A), 4 (winding B), 3 (winding C) of the electric motor - the fourth is formed position of the magnetic induction vector of the stator field.

The stator field is ellipsoidal, spatial, time-varying. When the next positive half-wave passes, the cycle repeats.

Thus, the energy characteristics of a compact device for starting a three-phase electric motor from a single-phase network are increased.

Claims (1)

A compact device for starting a three-phase electric motor from a single-phase network, containing a semiconductor switch, in the capacity of which two anti-parallel-connected dinistors are used, connected to the supply network and the stator winding, when the stator windings are connected according to the "star" scheme, characterized in that the semiconductor switch is one common the terminal is connected to the terminal of the second stator winding, the other common terminal is connected to the terminal of the third stator winding and to the phase of the supply network.

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