| 摘要 |
PROBLEM TO BE SOLVED: To prevent the failure of elements which constitute an inverter. SOLUTION: When a breaker 10 is closed, the voltage (15 V) of a transistor driving power source 23 rises, but a voltage VA at a point A and a voltage VB at a point B (detected voltage) do not. Thus, an LED 21 of a photocoupler 20 remains in an 'off' state, emitting no light. With a phototransistor 22 in an 'off' state, the voltage of the collector of the phototransistor 22, i.e., a voltage VC at a point C, becomes 15 V, the voltage of the driving power source 23. A diode Da turns into an 'on' state, and switches SW6, SW5 are interlocked to turn them into an 'off' state. A three-phase rectifier circuit 4 consisting of SCR1, SCR2, SCR3 and diodes D4, D5, D6 and a switching signal generating circuit 4 stop operating, thereby causing a current to stop flowing in switching transistors. |
