| 摘要 |
PURPOSE:To protect the inverter from a short-circuit current by a method wherein a reactor and a resistor inserted at detecting an overcurrent are provided between a DC power source and the inverter, in the inverter having the DC power source small in an internal impedance. CONSTITUTION:The DC power source 13 is obtained by means of a diode bridge 15 and a capacitor 16 from an AC power source 10. To the DC power source 13, a reactor 1 to which a diode inverse to the polarity of the power source is connected in parallel, and a resistor 3 to which a transistor 4 is connected in parallel are connected, and the inverter is connected between output terminals 19 and 20. If a load is shortened or a commutation of the inverter is failed, the short-circuit current is suppressed in the rate of rise by the reactor 1 and increases. If the current increases to a predetermined value, the outputs of an overcurrent detdctor 6 and a comparator 5 cause the transistor 4 to be turned OFF and effect insertion of the resistor 3, and at the same time, release an electromagnetic contactor from the excitation, open contacts 21, 12 and close a contact 17. |
