SU760375A1 - Device for regulating induction motor rotational speed - Google Patents

Description

The invention relates to electrical engineering and can be used in devices for regulating the speed of rotation of an asynchronous motor. five

Known devices for controlling the speed of rotation of an induction motor, which contain a constant current source, an inverter containing four thyristors, a switching capacitor, reverse current diodes, choke Γ д].

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The disadvantages of such devices are the impossibility of connecting in 15 the load of electric motors with predetermined parameters and the relative complexity of the converter.

Closest to the proposed 20 is a device for controlling the speed of rotation of an asynchronous motor, containing an inverter, made on the diodes and. thyristors, thyristor cathodes are combined 25 and connected to the negative output of the power source, the output load transformer e of the primary and secondary windings and the switching circuit composed of a series of 30

interconnected throttle and con-, capacitor, connected between the anodes of the thyristors [Υ | .

The disadvantage of such a device is complexity.

The purpose of the invention is to simplify the device.

This goal is achieved by the fact that in a device for controlling the rotational speed of an asynchronous electric motor containing an inverter consisting of diodes and thyristors, the cathodes of the thyristors of which are combined and connected to the negative terminal of the power source, an output load transformer with primary and secondary windings and a switching circuit composed of connected in series throttle and capacitor connected between the anodes of the thyristors, the anodes of the diodes are combined and connected to the positive terminal of the regular enrollment power load transformer is provided with additional primary winding, each primary winding one end is connected to the cathode of the diode, the other terminal - to the anode of the thyristor, said winding includes oppositely relative to each other.

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- - - FIG. 1 shows a block diagram of the proposed device; figure 2- ^: connection scheme of a single-phase electric motor; in fig. 3 - scheme

“Three-phase electrical connection”.

The device contains a constant current source 1 (Fig. 1), a parallel inverter 2, an output transformer 3 of the load of the controlled object 4.

To the output of a constant current source 1 (FIG. 2) a parallel inverter 2 is connected, consisting of diodes 5, b, thyristors 7, 8, a switching capacitor 9 and a choke 10. Positive terminal of constant source 1

'current is connected to the combined anodes of diodes 5, 6, the cathode of diode 5 is connected to the end of the first primary winding 11 of the output transformer 3, the beginning of which is connected to the output of the choke 10 and the anode of the thyristor 8. The cathodes of the thyristors 7, 8 are combined and connected to the negative terminal of the source 1 dc. The cathode of the diode 6 is connected to the beginning of the additional primary winding 12 of the transformer 3, the end of which is connected to the switching capacitor and the anode of the thyristor 7 of the inverter 2.

The switching capacitor 9 is connected in series with the choke 10. The end of the first secondary winding 13 of the load transformer and the beginning of the second secondary winding 14 are connected to the corresponding terminals of the working winding 15 of a single-phase electric motor. 16. The secondary windings of the transformer are connected in series with each other.

This device can also be used to control the rotational speed of an asynchronous three-phase electric motor (Fig. 3). In this case, the beginning of the secondary winding 13 of the transformer 3 is connected to the first phase .17 of the working winding of the electric drive, the combined end of the secondary windings 13, 14 of the transformer is connected to the beginning of the second phase 18 of the working winding of the motor. The beginning of the second secondary winding 14 of the transformer is connected through a capacitor 19 with the beginning of the third phase 20 of the motor winding.

The operation of the device is as follows.

When the thyristor 7 is closed, the thyristor * 8 is open and the current flows through the winding 11 in the direction from the end to the beginning. Capacitor 9 is charged through diode b and winding 12. When the control signal on the control electrode of the thyristor 8 is removed and the appearance of this signal on thyristor 7, the latter opens and capacitor 9 is connected in parallel to the thyristor 8, the current through the thyristor 8 stops, and thyristor 8 is closed. Capacitor 9 is recharging, i.e. acquires the opposite value of the charges, after which the current in the winding 11 stops and a current appears in the winding 12. In the future, the process repeats. So

⁵ , the current in the windings 11 and 12 is periodically switched with a frequency determined by the frequency of the control signal. Since in the winding 12 the current goes from the beginning to the end, and in the winding H from the end to the beginning, in the windings 13 and 14 EMF of different polarity is induced. ·

The presence of diodes 5, 6 ensures the flow of current only in one side, thereby preventing oscillation process. In practice, the presence of these diodes leads to the fact that the value of the capacitance of the capacitor 9 can be reduced

20 ^to 5 "10 times, ensures stable operation of the inverter both at idle and 'when the motor is started.

The load transformer has four windings. The corresponding inclusion of the primary windings 11 and 12 of the load transformer with a parallel inverter 2 allows you to get a half-wave in the windings 11 and 12

_ _N AC polar opposite Nost ^30, and the outputs of the secondary windings 13, 14 - a full-wave current that provides operation of single-phase AC motor

. from a constant current source. A half of a different frequency of motor power supply is provided by changing the frequency of the control signal applied to the control electrodes of the thyristors 7, 8 of the parallel inverter 2.

The operation of the device with a three-phase electric motor is as follows.

The outputs of the secondary 'windings 13,

45 14 of the transformer 3 is obtained full-wave current required to power the asynchronous motor 16 (Fig. 3). To provide a circular electric field, the average

50 point windings 13, 14 is connected to the second phase 18 of a three-phase electric motor 16. For security. phase shift between the applied voltage from the secondary winding 14 on

cr phase 20 of a three-phase electric motor, with respect to the applied voltage on phase 18, phase-shifting capacitor 19 is used.

This connection is a three-phase motor and secondary windings

60 load transformer allows to obtain a circular electric field in a three-phase electric motor and to ensure its normal operation at different frequencies of parallel operation

65 inverter. '

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Thus, the use of the invention makes it possible to simplify the proposed device, adjust the rotational speed of both Single-phase and three-phase electric motors, and reduce operating costs.

Claims (1)

Claim An apparatus for controlling sko- ".rOsti rotation asynchronous electric 'motor ^υ, comprising: an inverter configured with diodes and thyristors, the cathodes of thyristors coupled and connected to the negative terminal of the source of' power output transformer Nag I» manual ultrasonic inspection with primary and secondary windings, and A switching circuit made up of a choke and a capacitor connected in series, connected between the thyristor anodes, is connected with the fact that, in order to simplify the device, the anodes of the diodes are combined and connected to the field zhitelnomu conclusion power source load transformer is provided with additional primary winding, each primary winding with one terminal SO'o'dyyoyEG '~ diode cathode and another-terminal - to the anode of the thyristor, said winding includes oppositely relative to each other.