SU1460764A1 - Method of self-starting a synchronous motor - Google Patents

Abstract

The invention relates to electrical engineering. The aim of the invention is to facilitate the conditions for the self-launching path. reducing the duration of the self-starting process and preventing the synchronous motor from operating in the asynchronous mode with the excitation turned on. The self-starting method of the synchronous motor is carried out as follows. With short circuits on adjacent elements 3 or 4, accompanied by a decrease in voltage to the minimum value that ensures the stability of this engine, measuring body 6 triggers time delay 7. If a short circuit causing the synchronous engine to drop from synchronism occurred on an adjacent element 3, with o (L

Description

/one . . The invention relates to electrical engineering and can be used for self-starting synchronous motors dropped out of synchronicity due to short-term deep voltage drops due to short-circuits on adjacent network elements.

The aim of the invention is to facilitate the start-up conditions by reducing the duration of the process by the start-up process and preventing the synchronous motor from operating in asynchronous-running modes with the drive on. . ..

The drawing shows a functional diagram of the device that implements the method of self-start synchronous motor.

The device contains a synchronous motor 1, powered by substation busbars 2, to which adjacent elements 3 and 4 are connected, equipped with protections acting respectively with both a voltage and without time delay, as well as a voltage transformer 5, to the output of which the measuring element is connected 6 voltage to which the time transducer 7 is sequentially connected, the resynchronization unit 8, the exciter 9, is connected to the excitation winding 10 of the synchronous motor by an output.

The method is carried out as follows.

When there are short circuits on adjacent elements 3 and 4, accompanied by a decrease in voltage to the minimum that ensures the stability of the given engine, the voltage measuring unit 6 triggers the time-longer organ 7. Further, the operation of the device proceeds in different ways, depending on where the short circuit occurred on the adjacent element 3 or 4. When

five

0

five

thirty

35

40

short circuit on the element 3, causing the synchronous motor to turn out of synchronization, since this element is equipped with a protection acting on time, the organ 7 of the delay time of 0.2 s starts the resynchronization unit 8, acts on the exciter 9 and turns off the excitation winding 10 from the driver. After this, the short-circuit and the following are disconnected: J power recovery causes the engine to self-start, followed by excitation when the motor reaches the subsynchronous rotation frequency.

With a short circuit on the element 4, which does not cause the synchronous motor to fall out of synchronicity, since this element is equipped with protection acting without a time delay, the resynchronization unit does not start, since the latter is started by the authority 7 with a delay sufficient for complete shutdown of the short closing and restoring power. This prevents the wear resistance during short circuits on adjacent elements equipped with protection without a time delay.

As a voltage measuring unit, you can use a voltage relay with a set value of srabatse, equal to UKO. those. minimum voltage ensuring the stability of a given engine at a given load determined by the well-known expression

  t, v

XP NK.C.M.K

where K „is the reliability coefficient, taken equal to 1.1-1.2;

-

force, excitation coefficient;

engine load factor;

SMK - maximum engine overload on a static characteristic with a nominal excitation.

A time relay is used as a time lag.

The time delay setting is determined depending on the own time of the element switches off, the network and the specific type of time relay. For reliable off. setting of protection without time delay, and the use of switches in the network, the intrinsic time of deactivation of which does not exceed 0.1 s, the time delay setting is sufficient to take 0.2 seconds for a relay with a setting limit of 0.1-1 , 3 s, the response time spread of which is 0.06 s.

At the same time, in order to ensure reliable operation of the device during short circuits on adjacent elements equipped with time-active protection, the time-delay setting of these protection must be at least 0.5 s. The relay with a setting limit of 0.25-3.5 s The scatter of response times of which the composition is. O, 12 s.

The proposed method allows, compared with the previous method, to significantly reduce the duration of the self-starting process and to prevent the operation of synchronous motors in the asynchronous mode with excitation turned on,; which leads to a decrease in currents and electromagnetic moments and a significant relief in the conditions of self-starting ..

In addition, with this method of self-starting, the residual voltage on the tires of the substation, from which synchronous motors are powered, is comparatively higher than with the known method,. which favorably affects other consumers,

Claims (1)

Invention Formula The method of self-starting of a synchronous motor when powered from a substation, from which adjacent elements are simultaneously supplied with protection, both with time delay and 0 uh d five 0 without exceeding the time out of synchronicity due to short-term deep reductions in substation voltage caused by short-circuits on adjacent network elements with protection with maintenance time at which the excitation of the synchronous motor is disconnected and the excitation is re-enabled when the motor reaches the subsynchronous rotation frequency, This is so that, in order to ease the conditions for self-starting by reducing the duration of the self-starting process and to prevent asynchronous operation when enabled, excitation, control the national station substation and when 1P (voltage reaches the minimum value ensuring the stability of the synchronous motor, the specified excitation of the synchronous motor excitation with time delay adjusted from the time of disconnection of the short circuit on adjacent network elements with protection without time delay to the side increase and from time off short circuit on adjacent network elements with protection with a time delay in the direction of decrease.