Importance

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Abstract

A capacity control system for a refrigeration system including a compressor, a condensor, and an evaporator, all connected in a closed refrigeration circuit is provided. The compressor includes a plurality of adjustable inlet guide vanes, a motor connected to regulate the inlet guide vanes position, and an electrical speed motor connected to drive the compressor. The capacity control system includes a microprocessor responsive to continual measurements of a PRV signal, a compressor head signal and a suction flow signal for calculating a current operating point. The microprocessor determines whether the operating point is sufficiently away from a surge surface. The microprocessor will cause the operating point to move to a new operating point of a lower compressor speed and a more open PRV position if the operating point is sufficiently away from surge. In order to accomplish this, the microprocessor generates control signals to adjust both the speed of the compressor drive motor and the position of the inlet guide vanes. In an alternate embodiment, the microprocessor is responsive to continual measurements of a PRV signal, a motor speed signal, and a suction flow signal for generating such control signals.

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First Claim