OT-88-06-1 -- Variable-Speed Compressor Performance PDF

The potential of a variable-speed compressor for providing enhanced load-matching capability in both cooling and heating modes is demonstrated. Heating and cooling capacity and energy-efficiency performance data are presented for five inverter-driven, nominal three-ton commercial compressors. Suitability of rotary, reciprocating, and scroll compressors for variable-speed application is discussed in terms of energy efficiency over the range of compression ratios that would be experienced when operating speeds are varied over the 30 Hz to 120 Hz range. The need to separate mechanical and electrical efficiency in order to maximize overall compressor efficiency is discussed. Inverter-driven compressor motor efficiency data are presented for motor operation over the 30 Hz to 60 Hz range. A more detailed understanding is needed to match compressor demand to electric motor/inverter output so as to achieve maximum efficiency over the speed range of operation for the compressor.

Units: Dual