Variable speed rotary compressor and adjustable speed drive efficiencies measured in the laboratory

Conference · Tue Sep 01 04:00:00 EDT 1992

OSTI ID:10175225

Miller, W A

Two state-of-the-art variable-speed rotary compressors, of nominal one ton cooling capacity, were instrumented and tested in the laboratory. Both compressors were identical except for their respective variable-speed drive systems (i.e., motor and inverter). One compressor had an inverter driven induction motor (IDIM) drive, and the other had a permanent magnet electronically commutated motor drive (PM-ECM). The laboratory study evaluated the compressor`s efficiency under representative variable-speed conditions. Testing was conducted as a function of compressor drive frequency and of refrigerant condensing and evaporating conditions. Saturated refrigerant conditions, inlet superheat, and subcooling were controlled using a secondary refrigerant calorimeter. Spectrum analysis was conducted on the current input to one phase of the three- phase drive systems to measure motor speed and characterize harmonic content of the inverters. An optimal volt per Hz ratio was determined at 120-, 90-, 60-, and 30-Hz drive frequencies and at different load conditions for the rotary with induction motor as driven by a PWM inverter and also by a motor generator set (ideal induction motor drive). Variation of voltage input to the compressor had the largest effect at the lowest drive frequency (30Hz). A 5% variation about the optimal voltage at 30 Hz frequency caused a roughly 5% drop in compressor isentropic efficiency. Calorimeter data were used to develop modulating compressor and drive system performance maps. Performances of the two compressors were compared and the rotary with PM-ECM drive showed better efficiency trends at 30-Hz drive frequency. Above the 30-Hz drive frequency no clear advantage was observed for the PM-ECM vs the IDIM, possibly due to oversizing of the PM-ECM inverter.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10175225
• Report Number(s): CONF-921110--26; ON: DE92040026
• Country of Publication: United States
• Language: English

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32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
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42 ENGINEERING
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BUILDING EQUIPMENT
COMPONENTS
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COMPRESSORS
EFFICIENCY
ELECTRIC MOTORS
ENERGY EFFICIENCY
EQUIPMENT AND PROCESSES
EVAPORATION
HEAT PUMPS
REFRIGERANTS
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VAPOR CONDENSATION