| 摘要 |
PROBLEM TO BE SOLVED: To reduce the contained harmonic components of the input current of a direct frequency conversion circuit. SOLUTION: In this direct type frequency conversion circuit that is composed of series switch parts 12, 22, and 32, snubber capacitors C1, C2, and C3, and three-phase bridge inverter circuits 13, 23 and 33, the instantaneous value of the sinusoidal input current command value of each phase is used as a center for setting the maximum and minimum values by giving fixed width to positive and negative sides, and the pulse pattern of a control signal to the switching element of the series switching part of the phase is determined for turning on and off at a point when an input current detection value to the direct type frequency conversion circuit reaches the maximum and minimum values.
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