5 Questions
How is capacity control of the compressor achieved?
Capacity control of the compressor is achieved primarily by speed modulation.
What is the first action of the compressor when unloading?
When unloading, the compressor’s first action is to reduce speed to slightly above the minimum (surge) speed for the pressure ratio present at the time.
What are IGVs and how do they contribute to capacity reduction and impeller stability?
IGVs are variable angle vanes installed in the suction inlet ahead of the first stage impeller. These guide vanes restrict the refrigerant from entering the impeller inlet, as well as imparting a “pre swirl” of the refrigerant in the direction of impeller rotation to increase energy efficiency during part load operation.
How is speed modulation achieved in the compressor?
Speed modulation is achieved by the use of “Inverter” control. To accomplish this, the incoming 3-phase AC supply is converted to high voltage DC, incorporating smoothing/storage capacitors, and then switched by the Inverter, utilizing 3-phase rectifiers, to give a simulated 3-phase AC supply of variable voltage and frequency.
What is the purpose of converting the incoming 3-phase AC supply to high voltage DC in the compressor's speed modulation process?
Converting the incoming 3-phase AC supply to high voltage DC incorporates smoothing/storage capacitors, and then switched by the Inverter, utilizing 3-phase rectifiers, to give a simulated 3-phase AC supply of variable voltage and frequency to achieve speed modulation.
Test your knowledge of compressor capacity control and speed modulation with this quiz. Explore the role of variable angle vanes in achieving shaft and impeller stability during unloading.
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