Washing machine motor drive device

Abstract

A washing machine motor drive device drives a motor using an inverter circuit, which implements a constant torque control through a change in the torque-revolution speed characteristic of the motor. This facilitates an easy control of braking torque (negative torque), thereby providing a maximized braking torque. An easy control of regenerative energy is also provided, and back electromotive force is consumed by the internal resistance of the motor. Practically described, DC power of a rectifier circuit connected to an alternating current source is converted by an inverter circuit into AC power for driving the motor for operating an agitator or a washing/spinning tub. Motor rotor position is detected by rotor position detector, motor current is detected by current detector, and a control device controls the inverter circuit for resolving the motor current into a current component corresponding to magnetic flux and a current component corresponding to torque. At a motor braking operation, the current component corresponding to magnetic flux and the current component corresponding to torque are controlled independently. As a result, the torque at high speed revolution can be increased, or the efficiency at low speed revolution can be improved. This leads to the use a downsized and energy-conscious motor, and contributes to the prevention of an abnormal rise of DC voltage in the inverter circuit.