RU2538405C1 - Asynchronous motor with excluded idling - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: to device consisting of three-phase cage asynchronous motor, thyristor regulator for the purpose of reduced power consumption at idling by means of automatic transfer of the device to pulse mode in circuit of each stator phase downstream thyristors there are three in-series inductance coils and additional three capacitors coupled in parallel to stator windings of the caged asynchronous motor.

EFFECT: reduced power consumption at idling.

1 dwg

Description

The device relates to electrical engineering.

It is known "Device for welding" according to the patent of the Russian Federation No. 2032506, IPC B23K 9/00 dated 10.04.95, - [1], consisting of a welding transformer, a thyristor regulator in the circuit of its primary winding and a capacitor connected in parallel with the secondary winding. The device provides low power consumption in idle mode by switching the device to pulsed operation, but it is not possible to use such a circuit solution for a squirrel-cage induction motor due to the fact that the asynchronous motor has a secondary winding (rotor winding) that is always closed, even in idle mode.

Closest to the proposed is a "Thyristor voltage converter for controlling the speed of an induction motor" according to the patent of the Russian Federation No. 21115213, IPC Н02М 5/00 from 07/10/1998 - [2], consisting of a three-phase asynchronous motor with a squirrel-cage rotor and a thyristor regulator in a circuit stator windings. The disadvantage of this device is the significant power consumption in idle mode.

The proposed device (see Fig. 1) consists of a three-phase squirrel-cage induction motor, a thyristor regulator in the stator winding circuit, three additional inductors connected in series to each stator phase circuit after the thyristor regulator, and three capacitors connected in parallel to the stator windings of the induction motor.

The essence of the claimed technical solution is that an asynchronous motor with an excluded idle speed, consisting of a three-phase asynchronous motor with a squirrel-cage rotor, a thyristor regulator in the stator winding circuit, additionally connected in series to each stator phase circuit after the thyristor regulator of three inductors and three capacitors, connected in parallel to the stator windings of an induction motor, thanks to the additionally switched inductances and capacitors in idle mode turn automatically switches to pulse mode, which ensures reduction in power consumption.

The claimed invention solves the problem of reducing energy consumption in idle mode by automatically transferring the device to a pulsed idle mode.

When the device operates in the start-up mode and under load (the working mechanism creates a load), additional inductances and capacitances do not affect in any way. The device will work as with conventional thyristor regulation.

When switching to idle mode (the working mechanism has ceased to create braking torque on the motor shaft), the current consumption decreases and the influence of additional inductances and capacitors on the operation of the thyristors begins to affect. The thyristor control circuit supplies a short pulse to the control electrodes of all thyristors simultaneously. Opens those of the thyristors to which a positive voltage is applied. Mains voltage is applied to the motor windings. In this case, the charge of capacitors C begins through additional inductances L. As is known from the theory of transients (turning on the L-C circuit under voltage), the capacitor is charged to a double instantaneous value of the mains voltage during the transient. With the end of the charge, the current flowing through the thyristor will stop and it will close. The current consumed by the motor will be small, since the motor operates without load and is insufficient to keep the thyristors in the open state. After the capacitor is charged, it should be discharged to the motor winding. Moreover, the voltage across the capacitor is directed counter to the mains voltage and exceeds the mains voltage by 2 times (due to the transient process). Therefore, for a considerable period of time, until the voltage across the capacitor is equal to the mains voltage, the reverse voltage necessary for reliable locking of the thyristor will be applied to the thyristor.

Thus, in idle mode, the thyristors will open only for a very short period of time and then will be closed by a reverse voltage surge. As a result, only short-term voltage pulses with a duration of ~ 300 μs are sufficient on the motor windings, which are sufficient to maintain the engine idling. The engine continues to rotate, and power consumption is significantly reduced compared to normal idle mode.

When a load occurs or the engine slows down, the current consumed by the engine increases. The resistance of the motor windings shunting the capacitors is reduced. As a result of this, the charge voltage of the capacitor also decreases. The voltage on the capacitor can no longer reach the network level. Thyristors will not close. The device will work as with conventional thyristor regulation.

The inventive device for welding meets the requirement of "novelty", as it has new features:

1) three additional inductances connected in series in the circuit of each phase of the stator after the thyristors;

2) three capacitors connected in parallel with the stator windings of an induction motor.

Asynchronous motors with inductance in the stator circuit and with capacitors connected in parallel to the stator windings of the asynchronous motor are known from the existing level of technology and technical literature. But it is the application of such a combination of features that allows to obtain a new quality for the device - low power consumption at idle by switching to pulse mode. This allows us to conclude that the criterion of "inventive step".

The technical result of the proposed solution is the automatic reduction of power consumption when switching to idle mode by automatically switching the device mode to pulse operation. The technical result is achieved by the fact that three additional inductances are added to the device, connected in series to the circuit of each phase of the stator after the thyristors and three capacitors connected in parallel to the stator windings of the induction motor. Additional inductances and capacitances affect the transient processes when the thyristors are turned on in such a way that at a low load (low current consumption by the motor in idle mode), the reverse voltage surge when the thyristor is turned on leads to its blocking and, as a result, to the device operating in a pulsed mode, which provides energy saving. When the load on the motor increases, the current increases, the amplitude and duration of the reverse voltage surge decrease, and the thyristor regulator automatically switches to thyristor control mode.

The tests were carried out in a laboratory setup with a 4A80 V4 three-phase asynchronous motor with a rated power of 1.5 kW, rated rotation speed of 1400 rpm, rated voltage of 380 V. Antiparallel thyristors were T 142-80. To control the thyristors, a well-known scheme was used (Equipment for arc welding: a reference manual / Edited by V.V. Smirnov. L .: Energoatomizdat. Leningrad branch, 1986. -656 s: ill.) - [3], pp. 393-397 . A mandatory requirement for the control circuit is the short duration of the pulses that trigger the thyristors, which is achieved by the use of pulse transformers to form control signals. If this condition is not met, the implementation of the pulse mode will be impossible. Additional inductances were air coils wound with insulated wire. The inductance of each coil was 0.1 GN. Additional capacitors C of type MBGCH-1 had a capacitance of 4 μF, a nominal voltage of 500 V. In the pulse mode, the pulse amplitude reached 400 V, and the duration was 2 mS.

A decrease in the inductance L or capacitance C can lead to the fact that the pulse parameters are not enough to maintain rotation at idle, this will slow down the rotation of the motor, increase the current consumption and, as a result, switch from the pulse mode to the normal thyristor control mode.

Loss of idling in a pulsed mode amounted to 15 ... 25 W, instead of 60 ... 80 W in normal idle mode.

The tests carried out allow us to conclude that the claimed invention meets the criterion of "industrial applicability".

Information sources

1. RF patent No. 2032506, IPC B23K 9/00, “Device for welding”, authors: Gukov V., Gukov SV, bull. No 10 on 04/10/95

2. RF patent №2115213, IPC Н02М 5/00 "Thyristor voltage converter for controlling the speed of an induction motor", authors: Gladyshev SP, Bakin AA, Gladyshev PS, published July 10, 1998.

3. Equipment for arc welding: a reference guide / Edited by V.V. Smirnova. - L .: Energoatomizdat. Leningrad branch, 1986. - 656 p.: Ill.

Claims (1)

An asynchronous motor with an excluded idle mode, consisting of a three-phase squirrel-cage induction motor, a thyristor regulator in the stator winding circuit, characterized in that three inductors are additionally connected in series after each thyristor regulator in the circuit of each phase of the stator and three capacitors are connected in parallel to the stator windings of the asynchronous motor and additionally included inductors and capacitors in idle mode automatically turn the device into a pulse the first mode of operation.