SU402115A1 - DEVICE RESINCHRONIZATION AND PROTECTION AGAINST - Google Patents

Description

one

The device is designed to control and protect synchronous motors.

The operation of a synchronous electric motor (DM) when the voltage is disconnected and then restored is disrupted due to the non-synchronization of the LED and the network, which leads to the appearance of high currents and an accident or shutdown of the LED. In addition, when recovering the voltage, the diaphragm turns out to be asynchronous and may, if it does not provide unloading, do not get in sync, which entails a violation of the technological process. Therefore, when disconnecting the supply voltage, it is necessary to resynchronize the LEDs, i.e., disconnect the excitation current.

When reducing the supply voltage or asynchronous mode, it is necessary, on the contrary, to force the excitation to increase the stability of the LED.

Existing methods of controlling the operation of the LEDs provide protection against asynchronous operation (for example, relays tuned to the variable component of the excitation current), but do not respond to disconnection of the supply voltage. Conventional voltage control methods using a voltage relay are not suitable in this case, since the coasting SD continuously maintains a voltage sufficient to hold the specified relay.

The purpose of this invention is to monitor the asynchronous mode and resynchronize the LEDs for all violations of its operation mode (load change, change, shutdown and subsequent restoration of the supply voltage), improving the reliability and selectivity of the protection. The goal is achieved by the fact that one input contact of the asynchronous mode control unit is connected to the asynchronous protection circuit, and in parallel with the power direction relay contact to the resynchronization circuit.

The scheme of the proposed device is shown

in the drawing. An excitation winding of the LED and control circuits that are not related to the invention are not conventionally shown. The drawing shows the control circuit of the asynchronous mode on the variable component in the excitation current, although in principle any device can be used to control the asynchronous mode.

In the drawing, the following notation is accepted: P - disconnector; VM - oil switch; TH - voltage transformer; TT - current transformer; CD - synchronous motor; B - pathogen; SG - quenching resistor; SD1-SD4 - resistors; D - straightener; CB - field contactor; KVZ - electromagnet latch KB; Ci, € 2 - capacitors; IPB, 2PB - time relay; RK - frequency control relay; RP - relay intermediate; ROME. - power voltage relay; PPC - resynchronization relay; PAP - asynchronous relay; RPT - starting current relay.

The proposed device operates as follows.

The LED is connected to the mains with a VM switch, the RPT relay is activated, the 1PB relay is turned on, which turns on the 2PB relay. When the stator current decreases at the subsynchronous speed, the RPT contacts are disconnected, the 1PB is disconnected, and the contactor KB is turned on, connecting the excitation to the LED winding. After the 2PB relay is disconnected, the KB contactor is held on the latch. When an asynchronous mode appears, the RK relay turns on the control of the variable component in the excitation current, which pulls its measles with a slip frequency. By contacting the relay, the RC switches on the RP relay, which remains on due to the discharge of the capacitor C2 for the RK off-time. The RP relay contacts force the excitation and turn on the PAP asynchronous relay, which deactivates via the SD time delay. In asynchronous mode, the PHM power direction relay can be turned on (depending on the power factor), which opens its contact in the PPC resynchronization relay circuit. However, the latter remains switched on, since its power is supplied through normally open contacts turned on during the asynchronous mode of the RP relay. When the supply voltage is disconnected, the LED goes into a generator mode. In this case, the RNM relay is turned on, and the RC and RP remain de-energized, which causes the PPC relay to turn off. The latter, with a time delay, disconnects the excitation contactor KB, affecting its latch n and activates the relay 1РВ, 2РВ, preparing the contactor KB for reclosing. When the KB is turned off, the LED field winding turns on the discharge resistance of the SG, due to which the field is extinguished. When the voltage is restored, the SD is turned on as an asynchronous motor with subsequent connection of the exciter B. Thus, the combination of the power direction relay and the asynchronous mode control unit provides not only the control of the asynchronous mode, but also the resynchronization of the SD when the supply voltage is disconnected and subsequently restored.

Subject invention

A resynchronization and protection device against asynchronous operation of a synchronous electric motor, comprising an asynchronous mode control unit and a power direction relay, included in the stator motor circuit, characterized in that, in order to increase the reliability and selectivity of the protection, one output contact of the asynchronous mode control unit is included in the circuit protection from asynchronous mode, and the second in parallel with the contact of the power direction relay - to the resynchronization circuit.