| 摘要 |
PURPOSE: To obtain an effective starting method for a square wave inverter as rush current restricting means during start of a single-phase or three-phase square wave inverter. CONSTITUTION: Starting is initiated with a switching frequency fK higher than the rated switching frequency fn only during the initial section Tn of the predetermined time zone from a starting moment T0 of a square wave inverter to time point T1 for starting at rating, this switching frequency fK is gradually lowered up to the rated switching frequency fK, and shifting to rated operation by the rated switching frequency fK is started from the rated operation start point T1 . In the start method in the whole start section including a start initial section Tn, the pulse width at each period of a start pulse is fixed to 120 deg. and the square wave inverter is started by PAM(pulse amplitude modulation) method. By this starting, an increase in magnetic flux in an early stage of start of a transformer at the inverter output side can be restricted and the occurrence of a rush current can be restricted. |
