| 摘要 |
PURPOSE:To suppress generation of an overcurrent at the time of switching and to synchronously start in a safe state by switching control of an inverter from a separate-excitation type to a synchronizing type to drive it when the output frequency of the inverter is lowered. CONSTITUTION:A control circuit 7 of a microcomputer for supplying a switching signal to switching elements TU-TZ of an inverter 1 to control the operation of an inverter 1, etc., is provided. The inverter 1 is controlled with a separate- excitation type when a brushless DC motor 2 is started, the output frequency of the inverter 1 is raised or lowered within a predetermined range. When the output frequency is lowered, the control of the inverter 1 is switched from the separate-excitation type to a synchronization type to drive the motor 2. Thus, an overcurrent can be suppressed at the time of switching, and a synchronization start can be effectively performed with a low frequency in a safe state. |
