THREE-PHASE SWITCHING UNIT Russian patent published in 2003 - IPC

FIELD: pulse engineering; on/off switching of three-phase load. SUBSTANCE: three-phase switching unit has diodes, thyristor optocouplers, current-limiting resistors, START and STOP push-buttons all inserted in phases being handled by this unit. Newly introduced in switching unit are contactor with three making contacts, additional thyristor, fourth diode, as well as additional thyristor optocouplers, fifth and sixth diodes and resistor whose number depends on number of phases being handled; making contacts of contactor are inserted between phases A, B, C and output leads of switching unit; contactor coil shorted out by fourth diode in backward direction is connected through its one lead to cathode of additional thyristor and through its other lead, to anodes of fifth diodes; cathodes of the latter are connected to respective phases of supply mains and to second leads of current-limiting resistors. Additional thyristor anode is connected to cathodes of sixth diodes and gate electrode, to cathode of third diode. Anode of light- emitting diode of additional optocoupler thyristor in each of phases A, B, C is connected through respective resistor to output lead of switching unit, and its cathode is connected to its output lead. Anode of photo switch of mentioned optocoupler thyristor is connected directly in two phases A and B to respective input of switching unit and through STOP push-button, to input in third phase. Photo switch cathode is connected to anodes of second and sixth diodes. Proposed design enables in-service detection of faulty (such as short-circuited) power diodes and load open circuits followed by disconnection of device. EFFECT: enhanced reliability. 1 cl, 1 dwg