| 摘要 |
PROBLEM TO BE SOLVED: To provide a low-cost inverter device by lessening a load on an induction motor and then making an easy PWM-control of the motor. SOLUTION: Between a power supply line 18 and a ground line 19, switching elements 4a-4d are connected in the form of a full bridge. An inverter controller 9a, 11, 12 has a first mode at which when the switching elements 4b, 4c are in an off state, one of the switching elements 4a, 4d is turned on and the other is turned on or on/off-controlled and a second mode at which when the switching elements 4a, 4d are in an off state, one of the switching elements 4b, 4c is turned on and the other is turned on or on/off-controlled. The rectified waveform voltage from a rectifier 2 is directly inputted into the power supply line 18. The inverter controller 9a, 11, 12 divides a period of time to correspond to each half wave of the rectified waveform voltage and switches its mode between the first and the second one for eachdivided portion of the period and then outputs a PWM signal so that a pseudo AC voltage given to an induction motor 6 may have such a frequency zero-crossing at mode switching points. |
