| 摘要 |
PROBLEM TO BE SOLVED: To provide a power conversion device and a motor drive device having compact and low-cost overvoltage protection means for protecting equipment from an instantaneous overvoltage.SOLUTION: In a motor drive device 10, a control unit 40 turns off both switching elements on an upper and lower arms in the event of an overvoltage, so that the overvoltage is divided to both ends of the respective two switching elements connected in series, to decrease the overvoltage given to one transistor to the half of a voltage given when either one is operated. Thus, the switch elements can be protected from breakdown. Further, the control unit 40, after turning off both switching elements on the upper and lower arms, cuts off a connection between an inverter 25 and a motor 51 through a relay circuit 27, to thereby prevent one of the switching elements on the upper and lower arms from turned on by a current flowing from the motor 51, or when the switching element is already on, to shorten a time kept turned on. |
