| 摘要 |
A frequency changer has a semiconductor rectifier for converting commercial frequency AC to DC, a thyristor inverter for converting the DC to adjustable frequency AC, and a capacitor bank connected across the input to the inverter for reactive inverter load control. According to the invention, the inverter is started by charging the capacitor through a resistor from an auxiliary DC source at a voltage significantly higher than the rectifier DC voltage. A relay responsive to a capacitor voltage slightly above the rectifier voltage connects the rectifier to the capacitor-inverter combination and disconnects the capacitor charging circuit. The switchover takes place at a capacitor voltage equal to or slightly in excess of the rectifier voltage. |
