SU580619A1 - Device for switching transformer taps without disconnection of load current - Google Patents

Description

contactors practically do not leak. After the switching command is given, contact 23 opens and the load current, depending on polarity, flows from contact 19 to output 22 through diodes 15 and 17 and contacts 3 and 5. Then, in accordance with the received contact sequence of contacts of parallel contactors 1 and 2, contacts open 3 and 5. Assume that at the moment of opening of these contacts the direction of the current coincides with the direct direction of diode 15. Then contact 5 is opened without current. The restoring voltage is applied to it only after the next passage of current through zero, when the contacts already disperse for some distance. Considering that the contact divergence rate is 1 or more meters per second (or 1 or more mm / ms), after 1-2 ms after the contact divergence, the gap strength will be sufficient to withstand a voltage of several thousand volts.

Thus, if the opening of the contacts occurs within one or more milliseconds before the current passes through zero, then an arc does not occur on the contacts that are opened without current.

The opening of contact 3 is accompanied by an arc due to the load current. The arc on this contact exists before the next current passing through zero. After that, it goes out as the reverse half-wave of the current flows through the contacts of the odd shoulder of contactor 2. The restoring voltage to the open contact 3 is applied when the current direction coincides with the conductive direction of the diode 15. During the next half-period, the recovery occurs the strength of this gap, so re-ignition of the arc at these contacts is excluded.

After opening contacts 3 and 5, contacts 8 and 10 are closed, forming a circuit between adjacent taps of the control winding. The circulating current flows, coinciding with the conductive direction of the diode 15, from pin 19 to pin 20 through diode 15, resistor 11, pins 4 and 10, resistor 14 and diode 18. The reverse half-wave flows from pin 20 through diode 16, resistor 12, contacts eight

and 6, a resistor 13 and a diode 17 to pin 19.

Contacts 4 and 6 are then opened, breaking the sum or difference of the load current and circulating current depending on the direction of the switch. The process of opening contacts 4 and 6 is similar to the opening of contacts 3 and 5. Contacts 7 and 9 are closed, and then contacts 24 are closed. Switching is complete. An arc on breakable contacts practically cannot exist for more than one half period, and this determines the high breaking capacity of such a contactor.

Claims (2)

Invention Formula A device for switching transformer taps without opening the load current, containing two contactors with contacts in the even and odd arms connected to the bypassing contacts and a selector, characterized in that, in order to increase the breaking capacity by shortening the arc time at the contacts when switching, it additionally equipped with four separation diodes and two by shunt contacts, the contactors of the same name are connected to each other through two successively connected separation diodes, the middle points of the diodes are connected directly to the contacts of the even and odd shoulders of the voters, and through additional bypass contacts to the line terminal for connecting the load. Sources of information taken into account in the examination I. AM Ryvkin. “Parallel operation of contacts in the contactors of transformer on-load tap-changers,“ Electrical Engineering, № 7, 1965. 2. Porudominsky V.V. Transformer switching device under load. M., ed. “Energie, 1974, p. 78-98.