SU1422354A1 - A.c. electric drive - Google Patents

Description

(21) 3954870 / 24-07

(22) 09/20/85

(46) 09/07/88. Bul Number 33

(71) Moscow Institute of Water Transport Engineers

(72) D.G. Vlasov

(53) 621.313.333.072 (088.8)

(56) Zhemerov GG Directly coupled thyristor frequency converters. - M .: Energie, 1977.

Firago et al. Thyristor cycloconverters. - Minsk: Science and technology, 1973, p. 23, Scheme IVa.

(54) AC ELECTRIC DRIVE

(57) The invention relates to electrical engineering and can be used in electric drives to reduce the impact loads during start-ups and to set when choosing the backlash in the driven mechanisms. The aim of the invention is to expand the control range and increase reliability. When two phases of the winding of a three-phase electric motor 1 are connected through corresponding pairs of anti-parallel connected thyristors 2, 3 to one terminal of a single-phase network and the third phase of electric motor 1 is connected to another terminal of the network and a node 4 consisting of series-connected is used to control the thyristors synchronization, a delay unit 6 and a three-channel pulse distributor 7, the first and second outputs of which are connected to the control of the respective thyristor pairs, are supplied with power motor winding of motor 1 by three-phase voltage with frequency

- where fc frequency is single phase

voltage and low voltage. In this way, the dynamic loads in the mechanisms are reduced, and the start and stop modes of the electric motor are facilitated, 2 sludge.

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The invention relates to electrical engineering and can be used in electric drives to reduce the impact loads during starting and stopping when selecting the backlash in the driven mechanisms.

The purpose of the invention is to expand the range of regulation and increase of the flexibility,

j FIG. 1 shows a structural (AC drive circuit; ka; in Fig. 2, time diagrams, explaining its operation.: AC drive; (FIG. 1) contains a three-phase asynchronous motor; 1 electric motor, thyristor i switch; two pairs of parallel thyristor JHBHHbrx, node 4 of the control of the thyristor switch consisting of OUT serially connected synchronization unit j5, delay unit 6 and three-channel distributor 7

: pulses, ONE CONCLUSIONS Pairs 2 and 3

: opposite-connected ti; resistors are combined and connected to a terminal for connecting a single-phase AC network to one terminal, other terminals of pairs 2 and 3 of anti-parallel connected thyristors are connected to the beginning of the first and second phases of the winding of the electric motor 1, respectively, beginning The third phase of the winding of the electric motor 1 is connected to the terminal for connecting a single-phase AC network to the other terminal, and the ends of all phases of the winding are combined. The inputs of the thyristor switch control unit 4, formed by the inputs of synchronization unit 5, are intended to be connected to the terminals of a single-phase AC network. The outputs of the thyristor switch control unit 4 are formed by two outputs of a three-channel pulse distributor 7, moreover, the output of the thyristor-switching control unit 4 is connected to the control circuits of the first pair of 2 parallel-connected thyristors, and the other output of the thyristor control unit 4 is connected to the control circuits of the second pair of parallel-connected thyristors of the switch.

The AC drive operates as follows.

For electric actuators used to drive double-wing gates

sluices, various hoisting-and-transport mechanisms, it is important to ensure reliable deceleration of the drive mechanisms in the area of the mill, as well as a reduced frequency of rotation of the drive motor at the beginning of the operating cycle, in particular, for. choice of possible backlash. When starting the motor 1 using a thyristor switch connected to a single-phase AC network. At the output of synchronization unit 5, pulses are formed when a single-phase mains voltage (Fig. 2) passes through zero, which through delay unit 6, which allows to change the phase of the pulses in accordance with the load angle of the electric motor, is fed to the input of the three-channel pulse distributor 7. The signals from the first two outputs of the distributor 7 pulses arrive at the control circuits of the corresponding pairs 2 and 3 of the switch thyristors in parallel with each other. In this case, the phases of the winding of the electric motor 1 are applied to a voltage (Fig. 2), the first harmonics of which (Fig. 2, dotted line) have a frequency that is three times lower than the frequency of a single-phase network voltage, and are shifted. . relative to each other at 17-0 ,. Thus, when connected to a single-phase network on the phase winding of the electric motor 1, a three-phase voltage is generated with a frequency

f -5, where fg is the frequency of a single-phase voltage, and undervoltage. After the motor is accelerated to the operating frequency at a given power frequency, the electric motor is further accelerated by switching it to three-phase voltage with a nominal frequency and voltage.

When the motor is stopped, switching from three-phase to single-phase voltage is performed.

Thus, the invention makes it possible to reduce dynamic shock loads in the mechanisms, to facilitate the starting and stopping of the electric motor by reducing the voltage and frequency applied to the electric motor, as well as to carry out short-term rotation modes at the required threefold speed when necessary. It does not require complex switching

and converter devices, which increases the reliability of the drive.

Claims (1)

Invention Formula AC drive containing a three-phase asynchronous motor, a thyristor switch made in the form of two pairs of anti-parallel connected thyristors, one outputs of which are combined and connected to a terminal for connecting a single-phase AC network to one terminal, the other terminals of the first and second pairs of counter-parallel connected thyristors are connected to the beginning, respectively, of the first and second phases of the motor winding, the ends of which are connected, the thyristor switch control unit, the inputs to torogo intended for connection to terminals of a single-phase AC network, characterized -Themes that, for the purpose of expansion ranging and A rise 25 1utatora com. reliability, the third phase of the motor winding is initially connected to a clamp for connecting a single-phase network to another terminal, and the end is connected to the ends of the first and second phases of the motor winding, the thyristor switch control unit is in the form of a series of synchronization unit, delay unit and three-channel pulse distributor , the inputs of the synchronization unit form the inputs of the control unit of the typifCTopHbiM switch, two outputs Five three-channel pulse distributors form the outputs of the thyristor switch control node, one of which is connected to the control circuits of the first pair oppositely in parallel 0 connected switch thyristors, another output of the r / evil control thyristor switch is connected to the control circuits of the second pair of counter-connected parallel thyristors fS) 2 (} 3 (P {2} Ui and with Exercise imfiy / fbCbi 2M W) (8) t J //; (2) / fj) (M) t st Jf3) ) ig. 2