Variable speed compressor motor control for low speed operation
AssigneeCarrier Corporation
InventorsAlexander Lifson, Michael F. Taras
Life of this patent
Estimating the term…
Abstract
A variable speed drive is provided for a compressor in a refrigerant system. When a low load situation has been determined by the refrigerant system controls, the variable speed drive moves the compressor to a lower speed mode of operation. In this case, if a speed is so low that it cannot ensure adequate oil lubrication of the compressor elements, then the motor speed is periodically increased to a level that will ensure proper lubrication. In this manner, a variable speed drive compressor can be operated at an extremely low speed to precisely match load demand on a refrigerant system. The invention can be extended beyond refrigerant system applications and to any oil-lubricated compressors whose lubrication is speed dependant.
Claims31
A refrigerant system comprising:
- a compressor and an electric motor for driving said compressor, a variable speed drive for varying a speed of operation of said electric motor;
- a condenser downstream of said compressor, an expansion device downstream of said condenser, and an evaporator downstream of said expansion device;
- and
- said variable speed drive moving said compressor to low speed operation, and said variable speed drive being operable for entering a low speed mode should a speed of said compressor drop below a predetermined minimum, and said variable speed drive operating said compressor at low level of speed, and then periodically increasing the speed of said compressor toward a higher level of speed, with said higher level of speed being selected to ensure adequate lubrication of the compressor elements when in said low speed mode.
A compressor comprising:
- a compressor pump unit and an electric motor for driving said compressor pump unit, said electric motor being provided with a variable speed drive;
- and
- entering a low speed mode should a speed of said compressor pump unit drop below a predetermined minimum, said variable speed drive moving said compressor to low speed operation, and said variable speed drive operating said compressor at a low level of speed, and then periodically increasing the speed of said compressor toward a higher level of speed, with said second higher level of speed being selected to ensure adequate lubrication of the compressor elements when in said low speed mode.
A method of operating a refrigerant system comprising the steps of:
- (1) providing a compressor with a variable speed drive, and monitoring a load on a refrigerant system associated with said compressor;
- (2) identifying a low load situation, and moving said compressor to a low speed operation when a low load situation has been identified;
- and
- (3) operating said compressor at a low level of speed, entering a low speed operation mode should a speed of said compressor drop below a predetermined minimum, and periodically moving said compressor speed upwardly to a higher level of speed with said higher level of speed being selected to ensure adequate lubrication of compressor elements while in said low speed mode.
Dependencies are inferred from the claim text.