| 摘要 |
PURPOSE:To provide a PWM cycloconverter which is operated smoothly even in a state that an output current is very small by a method wherein a commutation overlap period is provided between individual gate signals of four semiconductor switching elements constituting two sets of bidirectional switches and the dead time is provided in such a way that the PWM cycloconverter is operated normally without any troubles even when the detection delay of an HCT is generated. CONSTITUTION:In a PWM cycloconverter, a P-type IGBT 1 and a P-type IGBT 2 are connected in series, a P-type IGBT 3 and a P-type IGBT 4 are connected in series, and an arm which is composed of two bidirectional switches is constituted. At this time, gate signals Su, Su', SL, SL' drive the P-type IGBTs 1 to 4, a commutation overlap period ta for current commutation is provided between the gate signals Su, and SL', and the dead time td of the bidirectional switches is provided between the Su and the SL as well as the Su, and the SL. Thereby, even when an output current to is very small and the detection of a current polarity by an HCT is delayed, the bidirectional switches can be changed over reliably. |
