Out-of-step detection device and out-of-step detection method

摘要

This step-out detection device includes an alternating current component calculation unit, a harmonic component calculation unit, a rotational speed calculation unit, and a determination unit. The alternating current component calculation unit calculates the alternating current component of the torque current component of an electric motor as obtained from the current passing through the electric motor. The harmonic component calculation unit calculates the second-order harmonic component of the alternating current component in terms of electric angle from the alternating current component calculated by the alternating current component calculation unit. The rotational speed calculation unit calculates the rotational speed of the electric motor in terms of electric angle from the alternating current component calculated by the alternating current component calculation unit. The determination unit compares the threshold value determined in accordance with the rotational speed calculated by the rotational speed calculation unit and the second-order harmonic component calculated by the harmonic component calculation unit, and outputs a signal showing the step-out of the electric motor if the second-order harmonic component is the threshold value or more.