22 May 2002
This paper describes a variable speed two stage 30HP centrifugal compressor developed for refrigerant R134a. Rotational speed of three phase AC induction compressor motor is regulated by varying the applied frequency of inverter. Two impellers are attached at both ends of the single shaft. The rotor section of motor is located in the middle of the shaft. The desired speed of the compressor motor is achieved via direct drive instead of gearbox. This makes the variable speed centrifugal compressor simple and compact.
Variable speed centrifugal compressor can change rotational speed when in operation. Thus capacity and pressure ratio can be adjusted by changing the drive frequency. This characteristics of the variable speed centrifugal compressor matches the real operating conditions of heat pumps and air conditioners. This can extend the operation range and reliability of space conditioning heat pump especially in a cold climate.