A frequency changer or frequency inverter is an electronic or electromechanical device that converts alternating current (AC) of one frequency to alternating current of another frequency. 

Frequency changers are typically used to control the speed of motors, primarily oxygen blowers and induce fans. In crematorium machine application,  significant energy savings are achieved. It workes together with PLC to control the speed of fan running, volume of intake and out take air from the cremation machine.