RU2402863C1 - Device for capacitor-free start of three-phase asynchronous motor supplied power to from single-phase mains - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in the device for capacitor-free start two reversible semiconductor switches are formed by parallel-opposition pairs represented by transistors. In the first reversible semiconductor switch the first transistor collector is connected to the second transistor emitter and to the power-supply mains phase. The first transistor emitter is connected to the second transistor collector and to the first stator winding beginning. In the second reversible semiconductor switch the third transistor collector is connected to the fourth transistor emitter and to the power-supply mains phase. The third transistor emitter is connected to the fourth transistor collector and to the second stator winding beginning The end of the second and the beginning of the third stator windings are connected to the single-phase power-supply mains neutral. The end of the first stator winding is connected to that of the third stator winding.

EFFECT: higher reliability and cost-efficiency and downsizing.

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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 "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 as power 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 anti-parallel pair made in the form of thyristors is connected to the phase of the mains supply, and the other output of each triac or other common output of each anti-parallel pair made in the form of thyristors is 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, scheme 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, complexity of the power circuit, large dimensions and high cost, which is explained by a significant number of power 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 capacitor, inductance and a semiconductor switch formed by an anti-parallel pair made in the form of two thyristors. One output of the semiconductor switch is connected to the phase of the supply network, made in the form of a single-phase AC network for supplying a three-phase asynchronous motor, and the other output of the semiconductor switch is connected to the beginning of the first stator winding. 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 in opposite parallel, that is, with one output of the semiconductor switch, with the phase of the 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 zero of the supply network and to another output, namely the end of the first stator winding. By another output, the common point of the thyristors is connected to another output of the inductance. The stator windings of this electric motor are connected as a broken star (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 disadvantages of the described device for the non-capacitor starting of a three-phase asynchronous electric motor from a single-phase network are low reliability, high cost and increased dimensions due to the need to use both large-capacity paper capacitors and inductance, as well as due to the unpredictability of the direction of rotation of the motor.

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

To solve the problem in a device for non-capacitor starting a three-phase asynchronous electric motor from a single-phase network, containing a semiconductor switch formed by a counter-parallel pair, one output of which is connected to a phase of the supply network made in the form of a single-phase AC network for supplying a three-phase asynchronous motor, and another output which is connected to the beginning of the first stator winding, and the beginning of the third stator winding is connected to zero supply network, and the stator windings of the electric motor STUDIO connected torn type "star", according to the invention two reversing semiconductor switch are semiconductor switches are formed by anti-parallel pairs, are constructed as transistors. 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 beginning of the first stator winding. In the second reverse semiconductor switch, the collector of the third transistor is connected to the emitter of the fourth transistor and connected to the phase of the supply network, and the emitter of the third transistor is connected to the collector of the fourth transistor and to the beginning of the second stator winding. The end of the first stator winding is connected to the end of the third stator winding. The end of the second stator winding is connected to zero supply network.

The increase in reliability and economy, as well as the reduction in the dimensions of the device for non-capacitor starting a three-phase asynchronous electric motor from a single-phase network, is due to the use of two reversible semiconductor switches as semiconductor switches, using a simpler control system for opening and closing them in the absence of a capacitor and inductance.

The invention is illustrated by drawings, where Fig. 1 shows a circuit diagram of a semiconductor device of a non-capacitor starting 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 a vector diagram of rotation, consisting of four fixed positions of the magnetic flux of the stator field; figure 4 shows a vector diagram of rotation, consisting of four fixed positions of the magnetic flux of the stator field, in which the motor torque is greater than the motor moment shown in figure 3; figure 5 shows the phase-by-phase change of the magnetic flux in the stator windings in accordance with the vector diagram depicted in figure 2; figure 6 shows the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram depicted in figure 3; in Fig.7 shows the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram depicted in Fig.4.

In addition, the drawing shows the following:

F - phase;

0 is 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 arrows - directions of rotation of the stator magnetic field;

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

bold points - the beginning of the stator windings;

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

A semiconductor device for capacitorless starting of a three-phase electric motor from a single-phase network contains two reversible semiconductor switches, which are semiconductor switches. Reversible semiconductor switches are formed by two counter-parallel pairs, each of which is made in the form of two transistors. In the first reversible semiconductor switch, the collector of the first transistor 1 (VT1) is connected to the emitter of the second transistor 2 (VT2), and their common output is connected to the phase of the supply network. The emitter of the first transistor 1 (VT1) is connected to the collector of the second transistor 2 (VT2) and their common output is connected to the beginning of the first stator winding 3 (winding B). In the second reversible semiconductor switch, the collector of the third transistor 4 (VT3) is connected to the emitter of the fourth transistor 5 (VT4) and their common output is connected to the phase of the supply network. The emitter of the third transistor 4 (VT3) is connected to the collector of the fourth transistor 5 (VT4), and their common output is connected to the beginning of the second stator winding 6 (winding C).

The end of the second stator winding 6 (winding C) is connected to the supply network zero. The end of the first stator winding 3 (winding B) is connected to the end of the third stator winding 7 (winding A). The beginning of the third stator winding 7 (winding A) is connected to the supply network zero. Stator windings A, B, C of the electric motor are connected according to the scheme of a torn "star".

The power network is made in the form of a single-phase AC network for supplying a three-phase asynchronous motor.

The operation of the device of the capacitorless start of a three-phase asynchronous electric motor from a single-phase network for six fixed positions of the magnetic flux of the stator field is as follows. With the passage of the positive half-wave of the supply voltage, the transistor 1 (VT1) opens and the current passes through two windings 3 (winding B) and 7 (winding A) of the electric motor (Fig. 2 and Fig. 5). Formed the first position of the vector of the magnetic field of the stator (figure 2). After a given moment, with a positive half-wave of the supply voltage, transistor 4 (VT3) opens and the current passes through windings 3 (winding B), 7 (winding A) and 6 (winding C). The second position of the stator magnetic field vector is formed. After a given time, with a positive half-wave of the supply voltage, transistor 1 (VT1) closes and the current flows only through winding 6 (winding C). A third position of the stator magnetic field vector is formed. With the passage of the negative half-wave of the supply voltage, transistor 4 (VT3) closes and transistor 2 (VT2) opens, and the current flows through two windings 7 (winding A), 3 (winding B). The fourth position of the stator magnetic field vector is formed. After a given point in time, transistor 5 (VT4) opens and the current flows through windings 7 (winding A), 3 (winding B) and 6 (winding C). The fifth position of the stator magnetic field vector is formed. After a given point in time, transistor 2 (VT2) closes and the current goes through winding 6 (winding C). The sixth position of the stator magnetic field vector is formed. The stator field turns out to be rotating, ellipsoidal, spatial, changing in time. As the next positive half-wave passes, the cycle repeats.

The operation of the device of the capacitorless start of a three-phase electric motor from a single-phase network for four fixed positions (Fig. 3) of the magnetic flux of the stator field is as follows. When the positive half-wave of the supply voltage passes, the transistor 1 (VT1) opens and the current passes through two windings 3 (winding B) and 7 (winding A) of the electric motor (Fig. 1 and Fig. 6). Formed the first position of the stator magnetic field vector (Fig.3). After a given point in time, transistor 4 (VT3) opens and transistor 1 (VT1) closes, and current flows through winding 6 (winding C). The second position of the stator magnetic field vector is formed. With the passage of the negative half-wave of the supply voltage, transistor 4 (VT3) closes and transistor 2 (VT2) opens, and the current flows through two windings 7 (winding A), 3 (winding B). A third position of the stator magnetic field vector is formed. After a given point in time, transistor 5 (VT4) opens and transistor 2 (VT2) closes, and current flows through winding 6 (winding C). The fourth position of the stator magnetic field vector is formed. The stator field turns out to be rotating, ellipsoidal, spatial, changing in time. As the next positive half-wave passes, the cycle repeats.

The operation of the device of the capacitorless start of a three-phase electric motor from a single-phase network, in which the electric motor torque is greater than the electric motor moment (Fig. 4) for four fixed positions of the stator field magnetic flux, is as follows. When the positive half-wave of the supply voltage passes, the transistor 1 (VS1) opens and the current passes through two windings 3 (winding B) and 7 (winding A) of the electric motor (Fig. 1 and Fig. 7). Formed the first position of the stator magnetic field vector (figure 4). After a given point in time, transistor 4 (VS3) will open, and transistor 1 (VS1) will still be open, and the current will go through windings 3 (winding B), 7 (winding A) and 6 (winding C). The second position of the stator magnetic field vector is formed. With the passage of the negative half-wave of the supply voltage, transistor 4 (VS3) and transistor 1 (VS1) will close, and transistor 2 (VS2) will open, and the current will go through two windings 7 (winding A), 3 (winding B). A third position of the stator magnetic field vector is formed. After a given point in time, transistor 5 (VS4) will open, and transistor 2 (VS2) will still be open, and the current will go through windings 7 (winding A), 3 (winding B) and 6 (winding C). The fourth position of the stator magnetic field vector is formed. The stator field turns out to be rotating, ellipsoidal, spatial, changing in time. As the next positive half-wave passes, the cycle repeats.

By changing the switching order of the windings, it is possible to reverse the motor. Thus, firstly, this device for the non-capacitor starting of a three-phase electric motor from a single-phase network allows you to get a predictable direction of rotation of the motor and its reverse, secondly, the possibility of the absence of a capacitor and inductance in the circuit, thirdly, reliability and efficiency are increased, and also the dimensions of the device are reduced.

Claims (1)

A device for capacitorless starting of a three-phase asynchronous electric motor from a single-phase network, containing a semiconductor switch formed by a counter-parallel pair, one output of which is connected to a phase of the supply network made in the form of a single-phase AC network for supplying a three-phase asynchronous motor, and the other output of which is connected to the beginning of the first stator winding, and the beginning of the third stator winding is connected to zero power supply, and the stator windings of the electric motor are connected as a broken the third "star", characterized in that two reversing semiconductor switches, which are semiconductor switches, are formed by counter-parallel pairs made in the form of transistors, and in the first reversing 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 beginning of the first stator winding, and in the second reverse semiconductor switch, the collector the third transistor is connected to the emitter of the fourth transistor and connected to the phase of the supply network, and the emitter of the third transistor is connected to the collector of the fourth transistor and the beginning of the second stator winding, while the end of the first stator winding is connected to the end of the third stator winding, and the end of the second stator winding is connected to zero mains supply.

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