An adaptive phase control (APC) scheme is proposed for three phase AC-to-DC converters to improve the power factor and minimize harmonic distortion. The APC scheme employs PWM principle and uses separated regulation loops for phase regulation and amplitude regulation to control the phase of the line current so that the converter draws nearly sine wave current with unity power factor. DC voltage regulation with fast dynamic response is achieved by the amplitude regulation loop. The inherent bidirectional power flow is an important property for motor drives with regenerative operation. Moreover, the converter is operated at a constant switching frequency around 1 kHz, which is favorable for high power applications.