| 摘要 |
PURPOSE:To eliminate fluctuation in the rotation of an induction motor by detecting output voltage from an inverter at a level substantially half that of DC input voltage at high speed under noise-free state. CONSTITUTION:The voltage detecting circuit for inverter comprises voltage dividing circuits Ru, Rx for halving DC voltage Vdc of an inverter, diode bridges DUA1, DXA1, DUA2, DXA2 connected in reverse parallel with a detecting power supply(drive power supply) E1+E2 and receiving output voltage VA from the inverter and a divided voltage VB, a comparator CP for comparing the output voltage VA with the divided voltage VB, and a photocoupler connected through a resistor R4 with the power supply E1+E2 and subjected to ON/OFF control through the comparator CP. When output voltage from main circuit deviates from the range of Vdc/2-Vcc-Vdc/2+Vdc, differential input voltage to the comparator CP becomes + or -Vcc and the output voltage VA is detected with robust detection characteristics where the voltage varies abruptly in the vicinity of Vdc/2. |
