| 摘要 |
PURPOSE:To eliminate a damage to a switching element and a circuit element near the switching element even if noise is introduced by providing a relay switch for electrically opening a rectifier and the two switching elements when a signal from a driving circuit to the switching element is OFF. CONSTITUTION:A DC relay 13 is connected to a circuit disposed at a rear stage of an electrolytic capacitor 6 to apply a voltage of the capacitor 6 to a series circuit of IGBTs 7, 8 through the relay 13. As a result, a manual switch 10 is opened by a user in a state that an AC from a commercial power source 1 remains supplied to stop supply of a DC to the relay 12 at a moment when an operation of a driving circuit 9 is stopped, and its contact is immediately opened. Accordingly, even if spikelike noise is introduced from the power source 1 at the time of stopping the circuit 9, the noise is effectively cut OFF by the relay 13 in which its contact is opened. Thus, malfunctions of the IGBTs 7, 8 can be effectively prevented. |
