| 摘要 |
PURPOSE:To improve AC motor drive characteristics, by selectively performing sine wave drive or rectangular wave drive by using a pulse width moldulation (PWM) inverter as an AC motor drive power source. CONSTITUTION:An AC motor 33 is driven through an inverter circuit consisting of the circuits of the switching elements 21-26 and rectifiers 27-32 of transistors, etc. connected to a direct current power source 34. The output of a signal generating circuit composed of a sine wave generating circuit 35, in which frequency and amplitude can be changed, a saw tooth wave generating circuit 8, comparators 9-11 and reversers 12-14 is applied to the bases of the transistors 21-26. The smooth revolution of the motor can be obtained by applying sine waves to the motor 33 in a region not higher than base speed; the lowering of a utilization rate of the power source can be prevented by applying rectangular waves to the motor 33 in a region not lower than the base speed. |
