This paper describes an auxiliary power supply employed to feed the control unit and gate drivers in a three-phase PWM micro inverter. The micro inverter feeds three-phase Tesla induction motor as mechanical actuator in small industrial water pumps. The proposed auxiliary power supply is based on a resonant serial half wave rectifier supplied from an output of the inverter. The rectifier provides output voltage of approximately 15 V at 30 mA load current. The analytical analysis was experimentally verified on the micro inverter TRISTALAN150