Patent ID: 9680462
Date: 2017-06-13
CPC Classifications: G05F,H02M,H03K

Claim:
1. A voltage regulator adapted to be electrically interposed between a utility power supply and a load, each having at least one phase, wherein the voltage regulator is configured to regulate the voltage supplied from the utility power supply to the load, the voltage regulator comprising: an autotransformer having, for each phase, a series winding and a regulating winding, the regulating winding having a plurality of taps and the series winding having a load side for connection to the load and a supply side for connection to the utility power supply; a controller coupled to the autotransformer, the controller configured to selectably operate the voltage regulator in at least a zero voltage reduction mode and an autotransformer mode; the controller having a zero voltage reduction mode switch connected between a first subset of at least two of the plurality of taps of the regulating winding of each phase; and the controller having a normally closed contactor that is biased, in the absence of power to the normally closed contactor, to electrically couple a second subset of at least two of the plurality of taps of the regulating winding of each phase to provide an alternate current path to the zero voltage reduction mode switch.