SU425262A1 - DEVICE FOR LOCKING THERMAL PROTECTION OF MULTI-SPEED ELECTRIC MOTORS OF NON-TIME CURRENT - Google Patents

Description

one

This invention relates to devices for thermal protection of multi-speed AC motors with a load having large inertia moments.

The known devices containing power contactors of individual speeds, interlocked with each other by interlocking block contacts, thermal relays with heating elements connected in series to the common power circuit of the electric motor through current transformers do not have an automated blocking.

The proposed device for automation. The interlocking system is equipped with a time relay, the winding of which is connected to the operative circuits through parallel-connected closing contacts of power contactors, and its instantaneous closing contact and opening contact with opening delay time are connected in series with the winding of the intermediate contactor.

The drawing shows a schematic diagram of a device for blocking thermal protection of myog-speed AC motors, for example, a four-speed motor, designed to drive a mechanism with a large moment of inertia.

The device consists of a four-speed asynchronous motor D with a short-circuited rotor, a BI switch with an electromagnetic release; speed switch BZ, which is set in position 1-4; power contactors

Pi, PZ, P3, Pi with closing and opening contacts; current transformers Tr, Tpz; bipolar thermal relays P, Pb, PT, PS with opening contacts and with settings corresponding to the currents of the individual

engine speeds; relay time RV with a closing contact and a break contact with an open time delay; A wearer contactor RD, with closure contacts; control buttons / Sn

Kn2; ryu voltage relay with closure contacts.

The heating elements of the RE-PS relays are connected in series to the secondary circuits of the current transformers Tpi, Tpz and are triggered by the opening contacts of the corresponding contactors PI-Pi. Contactors Pi-Pi are interlocked. The block co-tacts of the PS-PS thermal relays are connected in series to the ryu voltage relay circuit. Timer PB enabled through parallel connected auxiliary contacts of contactors Pb P-, RZ, PV

Intermediate contactor RD is connected through a series-connected relay contact

RV time. acting instantly and contact acting with time delay. The contacts of the intermediate contactor RD are connected in parallel with the heating elements of the tenl relays. The primary windings of current transformers are included in two phases of the common power circuit of the engine D.

When the automatic switch BI is turned on, power is applied to the control circuits. If the BZ speed selector is in position 1, pressing the Sleep button generates the power supply circuit of the RYV relay. This relay turns on the first speed contactor PI, which opens its block contacts, bypassing the heating elements of the thermal relay P, and by its closing block switch turns on the time relay RV, which instantaneously closes the relay contactor through the intermediate contactor of the thermal relay PS-PS. After a certain period of time, the RV relay breaks its contact, de-energizes the intermediate contactor Rd, which introduces the heating elements of the thermal relay PS, which has a first-speed current setting, to the circuits of current transformers Tpi, Tpz.

When switching the speed switch Vy from position 1 to position 2, the contactor PI is de-energized and the contactor PZ-circuit is prepared. The contactor PI de-energizes the time relay PB with its normally open contact. This relay comes to its initial position, the auxiliary contact of the PI contactor turns on the second-speed PZ contactor, and by other auxiliary contacts it shunts the heating elements of the thermal relay Rd. The second-speed contactor PZ breaks its block contacts, shunting the heating elements of the thermal relay Re, and closing

The auxiliary switch turns on the PB time relay. The time relay by its closing contact turns on, and the opening contact switches off the intermediate contactor Rd after a certain period of time. The contactor first bypasses, and then enters the heating elements of the second-speed thermal relay Re into the current transformer circuit Gy Tpz.

When other speeds are enabled, the circuit operates in the same way.

When any thermal relay PS-PS is overheated, the voltage relay circuit is broken and the engine is turned off.

Subject invention

Device for blocking thermal protection of multi-speed electric motors of alternating current with a load having large moments of inertia, containing power contactors of individual speeds interlocked with each other by interlocking contact contacts, thermal relays with heating

elements connected in series to a common power circuit of an electric motor through current transformers and bypassing contactors of power contactors and closing contacts of an additional intermediate contactor, characterized in that, in order to automate blocking, it is equipped with a time relay, the winding of which is connected to operational circuits through parallel connected closing circuits blocking contacts of power contactors, and its instantaneous closing contact and opening contact with time delay p The circuit is connected in series with the coil of the intermediate contactor. 5RbR7. / 5 Re PI tni-nr ft