As the speed of the motor is not constant, the frequency of an AC set driven by a generator is also variable, then, the converter is utilized to turn the variable frequencies of the AC set into constant ones.

• 由于发动机的转速不是恒定的,因而发电机输出的交流电的频率也是变化的,故再用变换器把变频交流电变换为恒频交流电。