Asynchronous motor with excluded idling

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

 

The unit refers to the electromechanics.

It is known Device for welding" RF patent No. 2032506, IPC B23K 9/00 from 10.04.95,, - [1], consisting of a welding transformer, thyristor regulator circuit of the primary winding and capacitor, connected in parallel to the secondary winding. The device provides low power consumption in idle mode by placing the device in burst mode, but to use this schematic for asynchronous motor with squirrel-cage winding is not possible due to the fact that the induction motor secondary winding (rotor winding) is always closed, even in idle mode.

Closest to the proposed is "Thyristor voltage Converter for speed control of induction motor" in patent RF №2115213, IPC NM 5/00 from 10.07.1998, - [2], consisting of three-phase asynchronous motor with squirrel-cage rotor and the thyristor regulator in the circuit of the stator winding. The disadvantage of this device is a significant power consumption in idle mode.

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

The essence of the proposed technical solution is that the induction motor is excluded from the idling mode, consisting of three-phase asynchronous motor with squirrel-cage rotor, the thyristor regulator in the circuit of the stator winding, is additionally connected in series in the circuit of each phase of the stator after the thyristor regulator three inductors and three capacitors connected in parallel stator windings of an induction motor, thanks also includes the inductances and capacitors in idle mode automatically switches to burst mode, which ensures lower energy consumption.

The claimed invention solves the problem of reducing power consumption in the idle mode by the automatic transfer device in a pulsed mode at idle.

When the device is in the mode of start-up and operation under load (load creates a working mechanism) additional inductance and capacitance has no impact. The device will work as normal thyristor regulation.

When switching to idle mode (working mechanism ceased to create a braking torque on the motor shaft) reduced current consumption and affecting effects the additional inductances and capacitances on the operation of the thyristors. The control circuit of thyristor delivers a short pulse to the control electrodes of all of the SCRs at the same time. Open the thyristors to which is applied a positive voltage. The voltage applied to the motor windings. This starts a charge capacitors through additional inductance L. As is well known from theory of transients (the inclusion of the L-C circuit under voltage), the capacitor during the transition process is charged to a dual instantaneous value of the mains voltage. With the end of the charge current flowing through the thyristor, will cease, and it will close. The current drawn by the motor will be small, because the engine runs without load and insufficient to hold the thyristor in an open state. After the charge of the capacitor should discharge to the motor winding. Moreover, the capacitor voltage is directed oppositely to the network voltage exceeds the voltage in 2 times (due to the transition process). Therefore, for a considerable period of time until the voltage on the capacitor is compared with the network voltage, the thyristor will be applied reverse voltage necessary for reliable locking of the thyristor.

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

When load or slowing down the rotation of the motor increases, the current drawn by the motor. Decreases the resistance of the motor winding, shunt capacitors. The result is reduced and the charging voltage of the capacitor. The capacitor voltage can not reach the level of the network. The thyristors will not be closed. The device will work as normal thyristor regulation.

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

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

2) three capacitor, connected in parallel to the windings of the stator of an induction motor.

The current level of technology and technical literature known asynchronous motors, with the inductance in the circuit of the stator and capacitors, connected in parallel to the windings of the stator of an induction motor. But the use of this combination of features allows you to get a new quality is the equip - low power consumption at idle by moving in a pulsed mode. This allows to conclude that the criterion of "inventive step".

The technical result of the proposed solutions - automatically reduce power consumption when switching to the idle mode by the automatic transfer device mode in pulse mode. The technical result is achieved that the device adds three additional inductance, connected in series in the circuit of each phase of the stator after thyristors and three capacitor, connected in parallel to the windings of the stator of an induction motor. Additional inductance and capacitance affect transients when switching the thyristors so that at low load (low current consumption of the engine is in the idling mode) release reverse voltage when turning on the thyristor leads to its locking and result in operation of the device in a pulse mode that conserves energy. With increasing motor load current increases, reduced the amplitude and duration of the reverse discharge voltage and the thyristor controller automatically switches to the mode of thyristor control.

The tests were conducted in a laboratory setting with three-phase asynchronous motor A B4 BONDS with nominal is through the power of 1.5 kW, rated speed 1400 rpm, rated voltage 380 Century Antiparallel thyristors had mark T 142-80. To control the thyristors used a well-known scheme (Equipment for arc welding: a reference Handbook / edited by centuries Smirnova. HP: Energoatomizdat.Leningrad branch, 1986. -656 with: ill.) - [3], pp. 393-397. A requirement for the control circuit is the short duration pulses, triggering thyristors, which is achieved by use of a pulse transformer, for generating control signals. If this condition is not met, the implementation of the pulse mode will not be possible. Additional inductance represented air coil, wound with insulated wire. The inductance of each coil was 0.1 MT. Additional capacitors type MGC-1 had a capacity of 4 µf, rated voltage 500 C. In a pulsed mode, the pulse amplitude was reached 400 V, and the duration is 2 MS.

A decrease in the inductance L or the capacitance C can cause the parameters of the pulses will not be enough to sustain rotation at idle, it will cause slowing of the rotation of the engine, the increase in the current consumption and, as a result, the transition from pulse mode to the normal thyristor regulation.

Idling losses in pulsed mode with the left 15...25 W, instead of 60...80 watts in normal idle mode.

The tests allow us to conclude on the compliance of the claimed invention, the criterion of "industrial applicability".

Sources of information

1. RF patent №2032506, IPC B23K 9/00, "Device for welding", authors: Gukov Century, Gukov, S. C., bull. No. 10 from 10.04.95,

2. RF patent №2115213, IPC NM 5/00 "Thyristor voltage Converter for speed control of induction motor", authors: Gladyshev, S. P., A. Bakin, A., Gladyshev P.F., published 10.07.1998,

3. Equipment for arc welding: a reference Handbook / edited by centuries Smirnova. - L.: Energoatomizdat. Leningrad branch, 1986. - 656 S.: ill.

Induction motor with excluded idling mode, consisting of three-phase asynchronous motor with squirrel-cage rotor, the thyristor regulator in the circuit of the stator winding, characterized in that in the circuit of each phase of the stator sequentially after the thyristor regulator included three inductance and parallel to the windings of the stator of an induction motor is connected with the three capacitor, with the added inductance and capacitors in idle mode automatically put the device in a pulsed mode.



 

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