Patent ID: 7733616

Claim:
An abnormality detecting device for detecting an abnormality in an electric power converting device supplying a drive current to an AC motor, said electric power converting device including: first and second power supply lines supplying a DC power from a power supply, and first to n-th (n is a natural number) switching circuits connected in parallel between said first and second power supply lines, and connected to coils of first to n-th phases of said AC motor, respectively; each of said first to n-th switching circuits having first and second switching elements connected in series together at a connection point which is connected to a coil of a corresponding phase of said AC motor; said abnormality detecting device comprising: a first switching control unit turning on the first switching element of the i-th (i is a natural number not exceeding n) switching circuit for a first predetermined time period, and a short fault determining unit determining that the second switching element of said i-th switching circuit has a short fault, when an overcurrent exceeding a predetermined threshold is detected within said first predetermined time period; wherein said first predetermined time period is shorter than a time period, in the case where the short fault is present in any one of the second switching elements of the remaining switching circuits other than said i-th switching circuit, from a time point of turning on the first switching element of said i-th switching circuit to a time point of attaining said predetermined threshold by a current flowing through a short circuit path extending from said first power supply line through said AC motor and the second switching element of said remaining switching circuit to said second power supply line.