A device according to an embodiment includes an circuit; a detector for detecting a current response output from the circuit; a vector converter for converting the current response into a d-axis current and a q-axis current by using a rotational phase angle of a motor connected to the circuit; a calculator for calculating, based on a torque command and a current phase angle command, a current amplitude command of the current response output from the circuit; a dq-axes converter for calculating a d-axis current command and a q-axis current command from the current amplitude command and the current phase angle command; and a controller for calculating a voltage command so that the d-axis current command and the q-axis current command are equal to the d-axis current and the q-axis current.