AUTOMATIC BACKUP DEVICE FOR POWER SUPPLY Russian patent published in 2017 - IPC H02J9/06 H02H7/09 

FIELD: electrical industries.

SUBSTANCE: device has three undervoltage relays with normally closed and normally open contacts, two electrical circuits, a rectifier and a three-phase motor. The undervoltage relay of each phase is sequentially connected with the normally closed contact of the adjacent phase relay, while the first electrical circuit is turned in the first faulty phase between the working phase and the motor eponymous phase sequentially with the normally open contacts of the working phase undervoltage relay and the second electrical circuit sequentially connected with the said contacts is turned in the second phase between the working phase and the corresponding motor phase. The first circuit consists of a voltage divider, a phase shifter providing a phase shift of the working phase for -120 degrees, and a power amplifier. The second circuit consists of a voltage divider, a phase shifter providing a phase shift of the working phase for +120 degrees, and a power amplifier. The nominal output power maintenance of the three-phase motor shaft and the stability of its rotation is enabled by the symmetry of the generated three-phase voltage, which is achieved by power loss compensation as it passes through the active electrical circuits, fine adjustment of the phase shifts (-120 degrees and +120 degrees) via phase shifters on operational amplifiers with RC-filters, as well as the parameters identity of the active electrical circuits.

EFFECT: preservation of the nominal output power and stable functioning of the three-phase motor in case any two other phases of the network are lost.

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