To achieve OCP and current control accurately by simplifying hardware, which performs current detection without increasing the capacities of a power device and a motor.

This device comprises: an OCP 5 that is provided at a specified position of a DC link to perform the OCP; a phase current calculating part 6 that calculates a phase current of the motor 4 using a DC link current as an input; a driver 9 that supplies a switching signal to switching elements of a three-phase inverter circuit 3 and outputs output voltage information; a position and speed detecting part 7 that detects the rotational velocity and rotational speed of the rotor of the motor 4 using a phase current and an output voltage used as inputs; a speed controlling part 8 that performs speed control operation using a rotational speed command and the detected rotational speed as inputs to output an output current command; a current command limiting part 10 that clamps in such a way that the output current command, which is used as an input, becomes a current command equal to or less than the OCP; and a current controlling part 11 that compares the output current command outputted from the current command limiting part 10 with the detected phase current, creates a voltage command in such a way that the phase current becomes the output current command, and supplies the voltage command to the driver 9.