A power converter comprising: an electric power converting unit configured to convert direct-current power into desired alternating-current power; an electric current detecting unit configured to detect an electric current outputted from the electric power converting unit to an alternating-current motor; an electric current converting unit configured to convert electric current information detected at the electric current detecting unit into an excitation current, a torque current, and a primary electric current; characterised in that the power converter comprises: an overexcitation determining unit configured to: compare a specified current value with the primary electric current, and only in the case of where the primary electric current is greater than or equal to the specified current value, the overexcitation determining unit compares the excitation current with the torque current, the excitation current and the torque current being converted at the electric current converting unit, and output overexcitation determination information when the excitation current is greater than the torque current, and a control unit configured to give a control signal to the electric power converting unit and control an output supplied from the electric power converting unit to the alternating-current motor, such that based on the overexcitation determination information from the overexcitation determining unit the control unit is further configured to select preset setting information to suppress overexcitation of the output supplied from the electric power converting unit. an electric power converting unit configured to convert direct-current power into desired alternating-current power; an electric current detecting unit configured to detect an electric current outputted from the electric power converting unit to an alternating-current motor; an electric current converting unit configured to convert electric current information detected at the electric current detecting unit into an excitation current, a torque current, and a primary electric current; characterised in that the power converter comprises: an overexcitation determining unit configured to: compare a specified current value with the primary electric current, and only in the case of where the primary electric current is greater than or equal to the specified current value, the overexcitation determining unit compares the excitation current with the torque current, the excitation current and the torque current being converted at the electric current converting unit, and output overexcitation determination information when the excitation current is greater than the torque current, and a control unit configured to give a control signal to the electric power converting unit and control an output supplied from the electric power converting unit to the alternating-current motor, such that based on the overexcitation determination information from the overexcitation determining unit the control unit is further configured to select preset setting information to suppress overexcitation of the output supplied from the electric power converting unit. compare a specified current value with the primary electric current, and only in the case of where the primary electric current is greater than or equal to the specified current value, the overexcitation determining unit compares the excitation current with the torque current, the excitation current and the torque current being converted at the electric current converting unit, and output overexcitation determination information when the excitation current is greater than the torque current, and a control unit configured to give a control signal to the electric power converting unit and control an output supplied from the electric power converting unit to the alternating-current motor, such that based on the overexcitation determination information from the overexcitation determining unit the control unit is further configured to select preset setting information to suppress overexcitation of the output supplied from the electric power converting unit.