Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
1998-11-27
2001-12-04
Wayner, William (Department: 3744)
Refrigeration
Automatic control
Refrigeration producer
C062S230000, C310S053000, C318S473000, C417S423800
Reexamination Certificate
active
06324858
ABSTRACT:
BACKGROUND OF THE INVENTION
Electric motors are driven by supplying electricity to the motor windings. This results in the heating of the windings and associated motor structure due to losses in driving the motor. While motors are designed to operate at an elevated temperature, conventionally, motors are cooled responsive the motor windings reaching a predetermined temperature. For hermetic and semi-hermetic refrigerant compressors, cooling is achieved by causing refrigerant gas or liquid to flow through/over the motor structure before being supplied to the compressor with the suction or mid-stage pressure gas. Since the motor efficiency and equipment size requirements dictate limited flow path availability, the amount of cooling flow is somewhat limited. The motor structure, however, represents such a large thermal mass that the result is that there can be a significant time period before the motor cooling flow achieves the desired cooling effect to return the motor temperature to the desired level. During this time period the windings can experience a large deviation from the desired operating temperature.
SUMMARY OF THE INVENTION
The present invention uses the motor load to anticipate changes in motor cooling requirements and uses it as the primary process variable. Because of the time lag between changes in the motor load and a perceived temperature change, better motor temperature control is achieved than would be the case where cooling is responsive to motor temperature fluctuations from a set point. The motor winding temperature is used as a secondary variable to make minor corrections to the process output, i.e. the motor cooling flow. This mode of operation reduces operation at elevated temperatures above the design temperature and reduces the cooling requirement when the motor load has dropped but the motor is still at an elevated temperature due to the time lag in changes.
It is an object of this invention to reduce the time lag in a compressor motor cooling system.
It is another object of this invention to provide better motor temperature control by using motor load to anticipate changes in motor cooling requirements. These objects, and others as will become apparent hereinafter, are accomplished by the present invention.
Basically, motor power consumption and motor winding temperature are monitored and, responsive thereto, the flow of refrigerant to the motor is controlled so as to control the temperature of the motor.
REFERENCES:
patent: 3555356 (1971-01-01), Kaiser
patent: 4626753 (1986-12-01), Letterman
patent: 5298842 (1994-03-01), Vanek et al.
patent: 5475985 (1995-12-01), Heinrichs et al.
patent: 5582022 (1996-12-01), Heinrichs et al.
patent: 6041605 (2000-03-01), Heinrichs
Carrier Corporation
Wayner William
LandOfFree
Motor temperature control does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Motor temperature control, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Motor temperature control will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2595627