Abstract: A method of power control for an electrical motor using open-loop principles is disclosed. The method employs a desired control line function that determines hold-off time based on a detected phase lag of a motor drive signal. The motor to be controlled is driven with a motor drive signal at a given load for a first number of cycles to detect the phase lag of the motor drive signal. Controlling for phase lag for a second number of cycles is then accomplished by firing a thyristor according to the phase lag of the motor drive signal. Advantages include reduced power consumption of a motor controlled by an embodiment of the method or controller, and faster response time between the detection of load changes on the motor and the issuance of power control signals.

Abstract: Aspects of the present invention pertain to a method of power control for an electrical motor using a control bypass feature that allows for the delivery of full supply voltage to a motor when it is operating at or above a certain load threshold level. Advantages of the present invention include the ability to provide power savings at low loads while still a motor to operate at full rated capacity under high load conditions. Also, a load sensor and an override unit that are independent of the phase lag compensation portion of power control allows for faster response to rapid load changes.

Abstract: The present invention provides systems and methods for power factor control of a motor. A phase detector uses a line voltage of a power supply and a motor terminal voltage of a motor. The output of the phase detector is synchronized to a zero crossing of the motor current of the motor and a zero crossing of the line voltage. A digital microprocessor connected between the output of the phase detector and a rectifier driver senses a first time at which a phase of the motor voltage is crossing zero volts and a second time at which a phase of the motor current is crossing zero current. The digital microprocessor calculates the difference in time between the first and second times and uses the difference in time to calculate a phase lag of the motor. The digital microprocessor uses the phase lag to calculate a firing time of a rectifier to command power efficiently to the motor.