To operate a current-type inverter without generating any surge voltage due to current interruption and with less switching loss and a high power factor on commutation.
A load voltage V and a load current I are detected by detectors 91 and 92 and a commutation reactance X is calculated from an inductance Lx and a frequency (f) by a commutation reactance operator 93. A commutation overlapping time operator 74 performs operation using a trigonometric function based on V, I, X, and f, ignites an element at a commutation destination, and then calculates a time T, until an element current at a commutation source reaches zero at the zero cross point of a load voltage. Gate amplifiers 71 and 72 send a gate control signal for igniting the element at the commutation destination at a time that is earlier than the zero cross point of the load voltage by TU and for arc-extinguishing the element at the commutation source at the zero cross point of the load voltage to a current-type inverter element.
ONUMA HITOSHI
KAWADA NORIYUKI
TSURUSAKI KAZUYA
HIYAMA MAMORU
