Patent ID: 8618757

Claim:
A method comprising: determining an applied armature voltage supplied to a polyphase synchronous machine having a pull-out torque, the armature voltage being supplied from a power source via one of a plurality of taps of a regulating transformer, a first tap of the plurality of taps supplying a voltage at a different level than a second tap of the plurality of taps; determining an estimated pull-out torque based on physical parameters of the polyphase synchronous machine, a power angle, and the applied armature voltage, wherein the power angle is based on real and reactive power monitored at an armature; and changing the armature voltage being supplied from the power source to the synchronous machine by selecting one of the voltage levels from the plurality of taps of the regulating transformer, the selecting one of the voltage levels being based on the estimated pull-out torque and the determined applied armature voltage to minimize power consumption of the machine while ensuring based on a predetermined confidence level that the pull-out torque of the synchronous machine will not be exceeded.