Abstract: A refrigeration compressor system using a reciprocating compressor with continuously variable capacity. The speed of the compressor can be varied substantially continuously over predefined range of speeds. A controller for the compressor monitors one or more physical parameters indicative of the temperature of the application being refrigerated, such as the temperature itself and/or the pressure in the compressor's refrigerant suction line. Using a predefined algorithm, the controller adjusts the speed of said compressor so as to keep said monitored parameter within a predefined target range. In a preferred embodiment, the compressor is an open direct drive compressor. The compressor's motor has a substantially continuous range of useable operating speeds which varies by a ratio of more than two to one.

Abstract: An apparatus and method for controlling a multi-compressor refrigeration system. The controller is designed to maintain a target temperature in a specified area. It achieves this goal by selecting compressor configurations which will maintain a target pressure on the common compressor suction line directing refrigerant into the compressors. As part of the process, the controller first establishes a record of the load handling capabilities of all useable configurations of the compressors. Then, periodically, it detects the current temperature and line pressure; selects a preferred configuration of compressors in accordance with a predetermined algorithmic function of the target pressure, the current line pressure, and the record of the load handling capabilities; and activates the preferred configuration if different from the currently active configuration.