Oil return algorithm for capacity modulated compressor

Abstract

A control for a compressor motor is programmed to operate the motor at at least one low capacity and at least one higher capacity. The control is operable to estimate an amount of oil which will have migrated from said compressor shell, at least when the compressor is operating at the lower capacity rate. The motor control moves the compressor motor from the lower capacity to at least one higher capacity once the estimated quantity of oil exceeds a predetermined limit. The capacity may be related to space.

Description

BACKGROUND OF THE INVENTION[0001]This application relates to an algorithm for ensuring adequate oil return in a refrigerant system including a capacity modulated compressor.[0002]Compressors are utilized as an integral part of a refrigerant system. In general, a compressor compresses a refrigerant and passes it downstream to a condenser. Refrigerant from the condenser passes through an expansion device, and then through an evaporator. From the evaporator, the refrigerant returns to the compressor.[0003]Lubricant is included in the refrigerant system, typically an Air Conditioner, Heat Pump or refrigeration application, and is particularly important to lubricate moving parts in the compressor. However, the lubricant becomes entrained in the refrigerant, and can flow with the refrigerant throughout the refrigerant system. As such, there may sometimes be an inadequate supply of lubricant returned to the compressor. Lubricant can sit in other areas of the refrigerant system, and in part...

AI Technical Summary

Benefits of technology

[0006]In a disclosed embodiment of this invention, system conditions are monitored to predict an amount of oil migration from the compressor during low capacity operation. When a particular amount of lubricant is deemed to have migrated from the compressor, an increased compressor capacity is run for a period of time. As an example of a particular application of the invention, a variable speed compressor is used.

Problems solved by technology

As such, there may sometimes be an inadequate supply of lubricant returned to the compressor.

However, at lower capacities, it may sometimes be difficult to adequately drive the lubricant back.

However, the increase in speed is not tied to any existing conditions in the refrigerant system, and thus may be operated too frequently, or not frequently enough.

Of course, operating at the increased speed too frequency somewhat defeats the purpose of operating the compressor at the lower speed.

On the other hand, running at the higher speed to return lubricant too infrequently would be even more undesirable.

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