Capacity control compressor
General methods of control power on reciprocating compressors compressor cylinder unloading and motor speed control. For compressors 10 tons and under, the compressor is used most frequently, but the control of the motor speed is increasing in popularity. Systems under 20 tons, power cooling often use several welded hermetic compressors that open and close or adjustable speed to achieve the desired compressor capacity control. All methods of performance management match below cooling, reducing the bandwidth and power requirements.
Cylinder unloading traditionally used weld sealants. On the other hand, it is commonplace on serviceable sealants exceeds 10 tons. The two most common types of cylinder unloading, suction bypass discharge and suction slice unloading. The latter method has become more popular in recent years.
In handling cylinders, pistons keep moving up and down in the cylinder, but they are pumping the refrigerant in the cooling system.
This reduces the cooling capacity and reducing energy consumption at partial load. Suction bypass style unloading system uses a special cylinder head and unloader valve control. The valve can be pressure-activated valve, as shown here, or electrically-activated valve. In this view, we see the flow of the refrigerant, and cylinder is loaded. This pumping of refrigerant cylinder, or a pair of cylinders, the system in the usual way.
As the heat absorbed by the evaporator falls (since the cooling system load drops), temperature and pressure of the refrigerant in the evaporator and the compressor suction pipe also fall. Pressure, activation of the flux regulator, as shown here, feels the pressure drop and draws station piston in the given point. The unloader is activated (piston pulled back), and the cylinder is said to be unloaded at this point. Please note that the suction gas is not compressed, but simply pumped through the bypass of the passage back to the compressor. The gas for this cylinder, or a pair of cylinders, goes round and round, without going into the discharge line or system.
Electrically-activated flux regulator works in a similar manner, but receives a signal from the thermostat, which measures the temperature of the evaporator. As the temperature drops due to the cooling load reduction valve station in a preset point.
Suction slice style unloader is activated in a similar manner. The difference is that the suction gas allowed unloaded cylinder, rather than recycling, and bypassing-type station. In this view, we see suction slice unloader is activated, i.e. the cylinder(s) unloaded...
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Refrigeration 
