To solve the problem wherein a detection mask is conducted for a fixed postponement time to an nonconformity detecting signal in an abnormality detection system feeding back the driving operation of a main circuit for a power converter and monitoring the nonconformity of the operation of a main circuit element by a comparison with a control-command signal, but there is the case in which a detection delay for the postponement time is generated when an abnormality is generated in the main circuit, a driving circuit or the like driving the main circuit while the abnormality when an operation generating the abnormality of an oscillatory operation and repeating the abnormality in a short period of time for the postponement time, cannot be detected.

In the abnormality detection system, a detection is made even to the abnormality such as the oscillatory operation, and the lag time of an abnormal detection output is shortened largely, by waiting a detection postponement time only immediately after the control command signal is changed, paying attention to the fact that the nonconformity by the delay of a feedback signal under a normal state is only within a specified time range immediately after the control command signal is changed in the power converter.

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