| 摘要 |
PURPOSE:To reduce the cost of an induction motor by constructing in the manner so as to detect DC current and power factor only from a DC bus current. CONSTITUTION:A DC current transformer 9 is disposed in the state insulated from a DC bus 15 in the bus 15. The transformer 9 is connected to a DC current detector circuit 10, which is connected to an induction motor controller 7 which outputs a gate signal for controlling the gate of an inverter. A frequency instruction potentiometer 6 for setting a frequency f responsive to the target rotating speed of an induction motor and a microcomputer 8 as an arithmetic circuit are connected to the controller 7. The detecor circuit 10 has a DC current detector 10, an inverting amplifier 11 connected to the transformer 9, an inverter 12, the first half-wave rectifying filter 13, the second half-wave rectifying filter 14, a comparator 15, a gate switching circuit 16, an inflowing component amplifier 17 and an outflowing component amplifier 18. |
