| 摘要 |
PROBLEM TO BE SOLVED: To remove a power source harmonic component easily for cost reduction by inserting, into respective phases on AC side of a diode-bridged rectifier, a two-way switching element which switches at a high speed according to a prescribed pattern. SOLUTION: A rectifier 2 of diode-bridge constitution is connected to a three-phase AC power source 1. The output of the rectifier 2, which is smoothed by a DC reactor 3 and a smoothing capacitor 4, to which an inverter 5 for controlling PWM is connected to convert direct current into alternating current for supply to a load motor 6. To phases R to T of the power source 1, two-way switching elements 7 to 9 constituted of transistors and so on are provided to switch at a high speed. A zero cross detection means 10 and a frequency detection means 11 for AC power source 1 are provided between the phase R and the phase S. By both the outputs of the detection means 10, 11, a switch control means 12 is driven, and at the same frequency as a line voltage, the two-way switching elements 7 to 9 are switched at a high speed. It is thus possible to eliminate a power source harmonic component easily for cost reduction. |
