Patent ID: 6803741
Filing Date: 2004-10-12
Classification: H02P

Abstract:
A method for operating a motor controller to cause balanced positive and negative current half-cycles in a motor phase, the motor controller utilizing switching devices to periodically connect a motor phase stator winding to a current source supply line in which each switching device enters a non-conductive state during a notch period of each alternating current half-cycle, each notch period beginning at a shut-off angle when current through the respective switching device becomes zero and ending at a fire angle when the respective switching device is again placed in a conductive state, the controller identifying a desired fire angle, the method comprising the steps of:for an occurring half-cycle: (a) identify a next virtual zero crossing (VZC) angle corresponding to an angle estimate during the current half-cycle at which the magnitude of the fundamental component of the current will begin to decrease; (b) mathematically combining the next VZC angle and the desired notch period to identify the fire angle for the occurring half-cycle; and (c) repeating steps (a) and (b) for the next half-cycle as the occurring half-cycle.