Patent ID: 8253359

Claim:
An electric rotating machine control system comprising: an electric rotating machine; a driving circuit that is connected to a DC power supply, the driving circuit includes a frequency conversion unit configured such that: when the electric rotating machine is to be driven in a power running mode, the frequency conversion unit converts an output of the DC power supply into AC electric power, and when the electric rotating machine is to be driven in a regenerative operation mode, the frequency conversion unit converts an output of the electric rotating machine into DC electric power; and a control unit that controls the driving circuit, wherein the control unit judges whether a connection between the DC power supply and the driving circuit is being maintained, and is configured such that, when the connection is not being maintained, regenerative electric power generated by the electric rotating machine is reduced by controlling the driving circuit, wherein, when the connection between the DC Dower supply and the driving circuit is not being maintained, the control unit controls the driving circuit such that regenerative torque obtained by the electric rotating machine immediately becomes zero, wherein the control unit judges, based upon an input/output voltage at the connection that connects the driving circuit and the DC power supply, whether the connection between the DC power supply and the driving circuit is being maintained, wherein, when the input/output voltage is grater than a predetermined overvoltage threshold, the control unit judges that the connection between the DC power supply and the driving circuit is nor being maintained, and wherein, when a voltage change rate, at which the input/output voltage rises per unit of time, is greater than a predetermined change rate threshold, the control unit judges, based upon a rapid-change-state overvoltage threshold set to a smaller value than the predetermined overvoltage threshold, whether the connection between the DC power supply and the driving circuit is being maintained.