Capacity control in piston compressors
Large piston-type compressors (as a rule, above 7.5 kW motor rated power) can be supplied with power control. This is usually accomplished by using one of the following methods:
- lock suction pairs in one or more cylinders (suction pair stopped one or more cylinders, thus reducing pumping speed compressor);
- the intake valve lift (suction valve is raised that allows vaporous to go back into the intake chamber during the compression stroke);
- discharge recirculation vapour (pair discharged from the piston returned directly to the suction pair, thus reducing the amount of the refrigerant is pumped around the system, but not the volume of the pumped compressor).
The latter method is the least efficient - input power supply compressor usually a part load and full load. With other methods of input power falls almost in line with a capacity reduction...
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