RU89789U1 - A TRANSISTOR REDUCER FOR POWERING A THREE-PHASE SHORT-CIRCUITED MOTOR, STATOR WINDINGS WHICH ARE CONNECTED BY TYPE "STAR", FROM ONE-PHASE NETWORK - Google Patents

Abstract

A transistor gear for powering a three-phase squirrel-cage motor, the stator windings of which are connected in the form of a star, from a single-phase network, containing a semiconductor first valve group based on diodes and a second valve group based on transistors connected to a supply single-phase network, characterized in that the first valve a group based on diodes is made in the form of a diode bridge, in which the first AC output is designed to connect to the phase of the mains, the second AC output voltage is designed to connect to zero the supply network and the negative DC output is designed to connect to zero a three-phase squirrel-cage motor, the second valve group is made of the first, second and third transistors designed to provide vector-algorithmic switching of the windings, the emitters of which are designed to connect to the stator windings of a three-phase squirrel-cage motor, and the collectors are connected to the positive DC output of the diode one hundred.

Description

The present invention relates to single-phase-three-phase frequency converters driven by a single-phase network, and can be used * in an electric drive to power asynchronous three-phase and synchronous motors.

A three-phase low-frequency semiconductor * converter is known, a frequency driven by a three-phase network, formed of three three-phase zero thyristor rectifiers, outputs connected to the inputs of three stator windings included in the star. The anodes of the thyristors are connected to the corresponding phases of the three-phase network, and the cathodes are connected to each other, forming a zero point, which is connected to the input of the corresponding winding. The outputs of the stator windings are designed to connect to zero power supply network (Bernstein I.Ya. Thyristor frequency converters without a DC link / I.Ya. Bernshtein. - M .: Energy, 1968. - P.42, Fig. 2-10a .).

The main disadvantages of this low-frequency semiconductor frequency converter, driven by a three-phase network, are the inability to use in a single-phase network, as well as low reliability and increased dimensions due to the use of a large number of thyristors.

Closest to the proposed invention in technical essence and the achieved result (prototype) is a low-frequency frequency converter driven by a network for an induction motor, the stator windings of which are connected in the form of a "star" containing three valve groups. The first valve group is made on the basis of three diodes. The second valve group contains three bipolar transistors of the n-p-n structure, the emitters of which are designed to connect to zero the supply of a single-phase network. The third valve group contains three field effect transistors, the sources of which are connected to the corresponding anodes of the three diodes forming the first valve group, the cathodes of which are designed to connect the phase and outputs of the three stator windings, which in turn have a common input connected to the phase. The collectors of the three bipolar transistors are connected to the corresponding gates of the field effect transistors. Thus, the converter is made on three field-effect transistors, three bipolar transistors and three diodes (Dubrovsky A. / Radio No. 11. Dubrovsky A - M.: Rospechat, 2002. - C41).

The main disadvantages of the described low-frequency semiconductor frequency converter are reduced reliability, increased dimensions and cost due to the need to use a large number of transistors and diodes.

The present invention solves the problem of increasing reliability and efficiency, as well as reducing the size of the device.

To solve the problem in a transistor gearbox for supplying a three-phase squirrel-cage motor, the stator windings of which are connected in the form of a "star", from a single-phase network containing a semiconductor first valve group based on diodes and a second valve group based on transistors connected to a supply single-phase network, according to According to the invention, the first valve group based on diodes is made in the form of a diode bridge, in which the first AC voltage output is designed to connect to the supply phase network, the second AC output is designed to connect to zero the mains supply, and the negative DC output is designed to connect to zero a three-phase squirrel-cage motor. The second valve group is made of the first, second and third transistors designed to provide vector-algorithmic switching of the windings, the emitters of which are designed to connect to the stator windings of a three-phase squirrel-cage motor, and the collectors are connected to the positive DC output of the diode bridge.

Improving the reliability of the transistor gearbox for powering a three-phase squirrel-cage motor, the stator windings of which are connected in the form of a star, from a single-phase network is due to the simplification of the control system due to the reduction in the number of power switching elements.

The reduction in size and increased efficiency of the device are due to the implementation of the first valve group in the form of a diode bridge, in which the first AC output is designed to connect to the phase of the supply network, the second AC output is designed to connect to zero supply network, and the negative DC output is designed to connect with zero three-phase squirrel-cage motor, and the second valve group of three transistors designed to provide a vector-algorithm manual switching of the windings, the emitters of which are designed to connect to the stator windings of a three-phase short-circuited motor, and the collectors are connected to the positive DC output of the diode bridge, that is, instead of six thyristors and three diodes, only three transistors and four diodes are used.

The invention is illustrated in the drawing, where Fig. 1 shows a circuit diagram of a transistor gearbox for powering a three-phase squirrel-cage motor, the stator windings of which are connected in the form of a "star", from a single-phase network; figure 2 is a vector diagram of rotation consisting of three fixed positions of the magnetic flux of the stator field; figure 3-vector diagram of rotation consisting of four fixed positions of the magnetic flux of the stator field; figure 4 is a vector diagram of rotation consisting of six fixed positions of the magnetic flux of the stator field; figure 5 - phase-by-phase change in the magnetic flux in the stator windings, as well as the direction of the magnetic flux and the flowing current through the stator windings in accordance with the vector diagram shown in figure 2; Fig.6 is a phase-by-phase change in the magnetic flux in the stator windings, as well as the direction of the magnetic flux and the flowing current through the stator windings in accordance with the vector diagram shown in Fig.3; in Fig.7 - phase-by-phase change in the magnetic flux in the stator windings, as well as the direction of the magnetic flux and the flowing current through the stator windings in accordance with the vector diagram shown in Fig.4, Fig.8 is the same as in Fig.5, when passing two half-waves of constant voltage for one position vector of the magnetic flux of the stator field.

In addition, the drawing shows the following:

- Ф - phase;

- 0 - zero;

- C1-C3 - inputs of stator windings;

- VD1-VD4 - diodes;

- VT1-VT3 - transistors;

- I, II, III, IV, V, VI - consecutive fixed positions of the magnetic flux of the stator;

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

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

- Trigger = f (t) - change in the rectified voltage in time;

- straight lines with arrows - directions of the magnetic flux and current in the stator windings.

A transistor gearbox for supplying a three-phase squirrel-cage motor, the stator windings of which are connected in the form of a star, from a single-phase network, contains a semiconductor first valve group based on diodes and a second valve group based on transistors connected to a supply single-phase network. The first valve group based on diodes is made in the form of a diode bridge, in which the first AC output is designed to connect to the mains phase, the second AC output is designed to connect to the mains zero and the negative DC output is intended for connecting to zero a three-phase squirrel-cage motor . The second valve group based on transistors is made of the first, second and third transistors designed to provide vector-algorithmic switching of the windings. The emitters of these transistors are designed to be connected to the stator windings of a three-phase squirrel-cage motor, and the collectors are connected to the positive DC output of the diode bridge.

As the supply network, a single-phase phase-zero alternating current supply network was used to supply a three-phase squirrel-cage motor and switching power transistors.

An example of a transistor gearbox for powering a three-phase short-circuit motor, the stator windings of which are connected in the form of a "star", from a single-phase network assembled on transistors.

The device contains a first valve group, made in the form of a diode bridge, consisting of 1,2,3,4 diodes (VD1, VD2, VD3, VD4), and a second valve group, made of 5,6,7 transistors (VT2, VT1, VT3). The cathode of diode 1 (VD1) and the anode of diode 2 (VD2), that is, the first AC output of the diode bridge, are connected to the mains phase, and the cathode of diode 3 (VD3) and the anode of diode 4 (VD4), that is, the second AC output diode bridge connected to zero mains supply. The cathode of diode 2 (VD2) and the cathode of diode 4 (VD4) are connected to the plus, that is, to the positive DC output of the diode bridge, which is connected to the collectors of 5,6,7 transistors (VT2, VT1, VT3). The emitter of the first transistor 5 (VT2) is connected to the input 8 (C2) of the stator winding of the motor. The emitter of the second transistor 6 (VT1) is connected to the input 9 (C1) of the stator winding of the motor. The emitter of the third transistor 7 (VT3) is connected to the input 10 (C3) of the stator motor winding. The windings with the inputs 9,8,10 (C1, C2, C3) of the motor are connected in the form of a "star" (Fig. 1), the zero point of which is connected to the minus, that is, to the negative DC output of the diode bridge. The transistors 5,6,7 (VT2, VT1, VT3) have either an n-p-p structure, as shown in Fig. 1, or a p-n-p structure.

A transistor gear for powering a three-phase squirrel-cage motor, the stator windings of which are connected in the form of a "star", from a single-phase network operates as follows.

To obtain a rotating magnetic field by the method of vector-algorithmic lowering the frequency in the stator winding, it is necessary to turn on transistors in a certain sequence.

To ensure the rotation of the stator field in the sequence I-II-III, shown in figure 2 by the vector diagram of the rotation of the stator field (fixed position of the magnetic flux), it is necessary to turn on the transistors 5,6,7 (VT2, VT1, VT3) as follows:

in I half-period of the rectified voltage (Fig.5.) VT1 - I position of the stator field vector, then in the II half-period of the rectified voltage (Fig. 5.) VT2 - II position of the stator field vector, then in III half-period of the rectified voltage (Fig.5.) VT3 - III position of the stator field vector

To ensure the rotation of the stator field in the sequence I-II-III-IV, shown in Fig. 3 by the vector diagram of the rotation of the stator field (fixed position of the magnetic flux), it is necessary to turn on the 5,6,7 transistors (VT2, VT1, VT3) as follows:

in I half-period of the rectified voltage (Fig.7.) simultaneously VT1, VT3 - I position of the stator field vector, then in II half-period of the rectified voltage (Fig.7.) simultaneously VT1, VT2 - II position of the stator field vector, then in III half-period of the rectified voltage (Fig.7.) VT2 - III position of the stator field vector, then in IV half-period of the rectified voltage (Fig.7.) VT3 - IV position of the stator field vector, then

To ensure the rotation of the stator field in the sequence I-II-III-IV-V-VI, shown in Fig. 4 by the vector diagram of the rotation of the stator field (fixed position of the magnetic flux), it is necessary to turn on 5,6,7 transistors (VT2, VT1, VT3 ) in the following way:

in IV half-period of the rectified voltage (Fig.9) simultaneously VT1, VT3 - I position of the stator field vector, then

in II half-period of the rectified voltage (Fig.9) VT1 - II position of the stator field vector, then in III half-period of the rectified voltage (Fig.9) simultaneously VT1, VT2 - III position of the stator field vector, then in IV half-period of the rectified voltage (Fig.9) VT2 - IV position of the stator field vector, then in V half-period of the rectified voltage (Fig.9) simultaneously VT2, VT3 - V position of the stator field vector, then in VI half-period of the rectified voltage (Fig.9) VT3 - VI position of the stator field vector.

To lower the frequency, one half-wave of the supply voltage can be skipped on one cycle of the vectors, but two, three, and so on. The sequence of turning on the transistors when passing two half-waves on one clock cycle for the mode (Fig. 5) is shown in Fig. 8; to pass three, four and further half-waves the work will be similar. In the same way, the operation of a three-phase squirrel-cage motor is formed while passing two, three, and so on half-waves for the operating modes shown in Fig.6,7.

Thus, the present invention can be used in a single-phase network for adjusting the speed of household appliances having a three-phase asynchronous squirrel-cage motor, with high reliability and efficiency and small dimensions.

Claims (1)

A transistor gear for powering a three-phase squirrel-cage motor, the stator windings of which are connected in the form of a "star", from a single-phase network, containing a semiconductor first valve group based on diodes and a second valve group based on transistors connected to a single-phase supply network, characterized in that the first valve the diode-based group is made in the form of a diode bridge, in which the first AC output is designed to connect to the phase of the supply network, the second AC output is voltage is designed to connect to zero the supply network and the negative DC output is designed to connect to zero a three-phase squirrel-cage motor, the second valve group is made of the first, second and third transistors designed to provide vector-algorithmic switching of the windings, the emitters of which are designed to connect to the stator windings of a three-phase squirrel-cage motor, and the collectors are connected to the positive DC output of the diode one hundred.