Introduction
A frequency inverter allows the stepless control of the refrigerating capacity to the cooling demand of the system by speed control. The following guidelines explain the design, operation, application range and special characteristics of
- Bitzer scroll compressors
- in combination with external frequency inverters for speed control, e.g. the Bitzer Varipack.
All Bitzer scroll compressors are suitable for operation above and below the supply frequency and can thus run over an exceptionally broad capacity range.
Features of the operation with a frequency inverter (FI):
- higher system efficiency, especially in part-load
- more exact temperature control possible
- precise coolant temperature for sensitive process cooling resp. heat-transfer fluid temperature for heat pumps
- fewer compressor starts
- less strain on the motor and the power network due to integrated soft start: starting current is lower than with direct start, softstarter, star-delta or part-winding start
- higher refrigerating capacity often possible by operation above supply frequency (allows use of a compressor with lower displacement at supply frequency 50 or 60 Hz, i.e. possibly lower costs per kW refrigerating capacity)
- reduced sound emissions (e.g. fans, pumps)
The figure below shows the smaller temperature fluctuations with frequency inverter control:
- On/Off regulation, left third: large temperature fluctuations, relatively low average effective evaporation temperature (fine dotted line)
- Stepped mechanical regulation, middle third: reduced temperature fluctuations due to faster regulation, higher average effective evaporation temperature and thus higher efficiency
- Regulation with frequency inverter, right third: very steady room resp. coolant temperature (± 0,5 K possible) due to stepless control, higher average effective evaporation temperature and thus higher efficiency
With frequency inverter operation, the average evaporation temperature can be raised e.g. from -7 to -4.5°C. Rising the evaporation temperature by 1 K increases system efficiency by up to 3%.
Also observe the following technical documents
- ESB-100: Operating instructions Hermetic scroll compressors ESH
- ESB-110: Operating instructions Hermetic scroll compressors ELH and ELA
- ESB-130: Operating instructions Hermetic scroll compressors Orbit 6 and Orbit 8
- CB-110 and CB-111: Operating instructions Varipack - external Bitzer frequency inverters
- AT-660: Application of R290 and R1270, A3 refrigerants