RU121406U1 - SINGLE-PHASE-THREE-PHASE TRANSISTOR FREQUENCY CONVERTER, LED BY THE NETWORK - Google Patents

Abstract

A single-phase-three-phase transistor frequency converter driven by a network, containing semiconductor switches based on transistors that pass current in both directions, connected to the phase of the supply network and to the stator windings of an asynchronous three-phase motor, connected to a star, and a single-phase AC supply network is used as the supply network current to power an asynchronous three-phase motor, and the zero point of the star is connected to the zero of the supply network, characterized in that field-effect transistors are used as transistors that pass current in both directions.

Description

The proposed utility model relates to frequency converters driven by a single-phase alternating current network, and can be used in an adjustable AC electric drive to power asynchronous three-phase motors, the stator windings of which are connected to a star.

A device for controlling the rotational speed of an asynchronous three-phase electric motor from a single-phase network, containing semiconductor switches, which are used as power elements such as three triacs or six thyristors for switching motor windings. One of the outputs of the triac or thyristor is connected to the phase of the supply network, and the other output of the thyristor or triac is connected to the corresponding stator winding. In this case, the stator windings of an asynchronous three-phase 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 device for controlling the speed of an asynchronous three-phase electric motor from a single-phase network are low reliability and large dimensions due to the use of a large number of semiconductor switches.

The closest to the proposed utility model in technical essence and the achieved result (prototype) is an adjustable single-phase three-phase semiconductor frequency converter driven by a network containing semiconductor switches based on transistors connected to the phase of the supply network and to the stator windings of an asynchronous three-phase motor connected to a star . As a supply network, a single-phase AC supply network was used to power an asynchronous three-phase motor, and the star's zero point is connected to zero of the supply network. As transistors, bipolar transistors are used, passing current in both directions in a pulsed key mode at an adjustable frequency, based on a symmetric internal structure. (Patent RU 95198 IPC H02M 5/297 (2006.01)).

The main disadvantages of this regulated single-phase-three-phase semiconductor frequency converter driven by the network are low reliability due to increased heating due to the consumption of control current in the key mode due to the operation of bipolar transistors on alternating current, as well as the complexity of the control system due to the need to take into account the polarity of the voltage passing through a transistor at every moment in time.

The proposed utility model solves the problem of increasing the reliability of the device and simplifying the control system.

To solve the problem in a single-phase-three-phase transistor frequency converter driven by a network containing semiconductor switches based on transistors that transmit current in both directions, connected to the phase of the supply network and to the stator windings of an asynchronous three-phase motor connected to a star, and as a supply network a single-phase AC mains is used to power an asynchronous three-phase motor, and the star’s zero point is connected to zero the mains supply, according to the useful mode Whether as a transistor, a current is passed in both directions, FETs are used.

Improving the reliability and simplifying the control system of a single-phase-three-phase transistor frequency converter driven by the network is achieved by using field-effect transistors in the absence of the need to take into account the polarity of the voltage passing through the transistors and supplying current to the transistors, since the field-effect transistor is controlled by an electrostatic field created by charges.

The proposed utility model is illustrated in the drawing, where Fig. 1 shows a circuit diagram of the proposed single-phase-three-phase transistor frequency converter driven by the network; figure 2 is a vector diagram of rotation, for the positive half-wave of the supply voltage, consisting of three fixed positions of the magnetic flux of the stator field; figure 3-vector diagram of rotation, for the negative half-wave of the supply voltage, consisting of three 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 of the magnetic flux in the stator windings in accordance with the vector diagrams depicted in figure 2 and figure 3, depending on the half-wave voltage, the direction of the magnetic flux and the current flowing through the stator windings; figure 6 - change in voltage in the stator windings in time, in accordance with the vector diagrams depicted in figure 2 and figure 3, depending on the half-wave of the supply voltage; Fig.7 - for a higher frequency, the phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagrams depicted in Fig.2 and Fig.3, depending on the half-wave voltage, the direction of the magnetic flux and the current flowing through the stator windings; on Fig - for a higher frequency, the voltage change in the stator windings in time, in accordance with the vector diagrams depicted in figure 2 and figure 3, depending on the half-wave of the supply voltage; figure 9 - for a frequency of 16.67 Hz phase-by-phase change in the magnetic flux in the stator windings in accordance with the vector diagram shown in figure 4, depending on the half-wave voltage, the direction of the magnetic flux and the current flowing through the stator windings; figure 10 - for the control frequency of 16.67 Hz, the voltage change in the stator windings in time, in accordance with the vector diagram depicted in figure 4.

In addition, the drawing shows the following:

F - phase;

- 0 - zero;

- C1-C3 - stator windings;

- VT1 -VT3 - field effect transistors;

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

- t0-t12 - time instants;

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

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

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

The single-phase-three-phase transistor frequency converter driven by the network contains semiconductor switches based on field-effect transistors that transmit current in both directions. Field-effect transistors are used as field-effect transistors that transmit current in both directions. Semiconductor switches are connected to the phase of the supply network and to the stator windings of an asynchronous three-phase motor connected to a star. As a supply network, a single-phase AC supply network was used to power an asynchronous three-phase motor, and the star's zero point is connected to zero of the supply network.

The drain of transistor 1 (VT1) is connected to the phase of the supply network, and the source of transistor 1 (VT1) is connected to the beginning 2 of the stator winding (C1) of the motor. The drain of transistor 3 (VT2) is connected to the phase of the supply network, and the source of transistor 3 (VT2) is connected to the beginning 4 of the stator winding (C2) of the motor. The drain of transistor 5 (VT3) is connected to the phase of the supply network, and the source of transistor 5 (VT3) is connected to the beginning 6 of the stator winding (C3) of the motor. The ends of the three stator windings of the motor are interconnected as the zero point of a 7 star, which is connected to zero of the supply network.

Transistors 1 (VT1), 3 (VT2) and 5 (VT3), passing current in both directions, are field.

The operation of a single-phase-three-phase transistor frequency converter driven by the network is as follows. A single-phase alternating voltage is supplied to the stator windings of an asynchronous three-phase motor in a sequence providing a rotating magnetic field of the stator with the required characteristics.

Using a single-phase-three-phase transistor frequency converter driven by the network, it is possible to carry out vector-algorithmic control of a three-phase asynchronous electric motor, creating several types of rotating stator fields in series, for example, passing three (see figure 2 and figure 3) positions of the circular magnetic flux vector rotating field of stator motor.

Initially, the gates of transistors 1, 3, 5 (VT1, VT2, VT3) were supplied with voltage, which creates an electric field to close the transistors. Vector-algorithmic control is carried out by removing voltage from the gates of transistors 1, 3, 5 (VT1, VT2, VT3), providing vector control of an asynchronous three-phase electric motor by passing three consecutive fixed positions of the magnetic flux vector of the circular rotating field of the motor stator for a positive half wave and three consecutive fixed positions the magnetic flux vector of the circular rotating field of the stator of the engine for the negative half-wave:

- at time t0 of the positive half-cycle of the supply voltage, the voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current;

- at time t1 of the positive half-cycle of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current;

- at time t2 of the positive half-period of the supply voltage, voltage is applied to the gate of transistor 3 (VT2) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 5 (VT3) and they begin to pass current;

- at time t3 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, the voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current;

- at time t4 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 3 (VT2) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 5 (VT3) and they begin to pass current;

- at time t5 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 5 (VT3) and it ceases to pass current, the voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current.

Here, the proposed converter allows for this algorithm to power the motor with a voltage of 2f / _NET and is a high-frequency frequency converter.

Vector-algorithmic control is carried out by removing voltage from the gates of transistors 1, 3, 5 (VT1, VT2, VT3), which provides vector control of an asynchronous three-phase electric motor when two consecutive fixed three positions of the magnetic flux vector of the circular rotating field of the stator of the motor for a positive half-wave and double the passage of three consecutive fixed positions of the magnetic flux vector of the circular rotating field of the stator of the motor for the negative floor wave:

- at time t0 of the positive half-cycle of the supply voltage, the voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current;

- at time t1 of the positive half-cycle of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current;

- at time t2 of the positive half-period of the supply voltage, voltage is applied to the gate of transistor 3 (VT2) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 5 (VT3) and they begin to pass current;

- at time t3 of the positive half-cycle of the supply voltage, the voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current; the position of the stator rotating field vector for the first (I) time interval is repeated;

- at time t4 of the positive half-cycle of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current; the position of the stator rotating field vector for the second (II) time interval is repeated;

- at time t5 of the positive half-cycle of the supply voltage, voltage is applied to the gate of transistor 3 (VT2) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 5 (VT3) and they begin to pass current; the position of the stator rotating field vector for the third (III) time interval is repeated;

- at time t6 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current; the position of the stator rotating field vector for the first (I) time interval is repeated;

- at time t7 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 3 (VT2) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 5 (VT3) and they begin to pass current; the position of the stator rotating field vector for the second (II) time interval is repeated;

- at time t8 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 5 (VT3) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current; the position of the stator rotating field vector for the third (III) time interval is repeated;

- at time t9 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, the voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current; the position of the stator rotating field vector for the first (I) time interval is repeated;

- at time t10 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 3 (VT2) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 5 (VT3) and they begin to pass current; the position of the stator rotating field vector for the second (II) time interval is repeated;

- at time t11 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 5 (VT3) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current; the position of the stator rotating field vector for the third (III) time interval is repeated.

With this algorithm, a single-phase-three-phase transistor frequency converter driven by the network allows you to power the motor with a frequency of 4f _NETWORK .

Vector-algorithmic control is carried out by removing the voltage from the gates of transistors 1, 3, 5 (VT1, VT2, VT3), which provide vector control of an asynchronous three-phase electric motor by passing six consecutive fixed positions of the magnetic flux vector of a circular rotary stator field per motor revolution:

- at time t0 of the positive half-cycle of the supply voltage, the voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current;

- at time t1 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 5 (VT3) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current;

- at time t2 of the positive half-period of the supply voltage, voltage is applied to the gate of transistor 3 (VT2) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 5 (VT3) and they begin to pass current;

- at time t3 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, the voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current;

- at time t4 of the negative half-period of the supply voltage, voltage is applied to the gate of transistor 5 (VT3) and it ceases to pass current, voltage is removed from the gate of transistors 1 (VT1) and 3 (VT2) and they begin to pass current;

- at time t5 of the negative half-cycle of the supply voltage, voltage is applied to the gate of transistor 1 (VT1) and it ceases to pass current, voltage is removed from the gate of transistors 3 (VT2) and 5 (VT3) and they begin to pass current.

That is, the proposed converter allows, with this algorithm, to power the motor with voltage with a frequency and is a low frequency frequency converter.

Thus, the proposed utility model has advantages over the known frequency converters due to the higher reliability and simplified control system.

Claims (1)

A single-phase-three-phase transistor frequency converter driven by a network, containing semiconductor switches based on transistors that transmit current in both directions, connected to the phase of the supply network and to the stator windings of an asynchronous three-phase motor connected to a star, and a single-phase alternating supply network is used as the supply network current to power an asynchronous three-phase motor, and the star’s zero point is connected to zero of the supply network, characterized in that as transistors I skip current in both directions, field effect transistors are used.