System and method for reducing windage losses in compressor motors

Abstract

A method and system for reducing windage losses in compressor motors is provided. The compressor motor is cooled by circulating refrigerant from a closed refrigerant loop incorporating the compressor. A pumping device coupled to a liquid expander in the closed refrigerant loop circulates refrigerant through the motor cavity and produces a motor cavity pressure lower than evaporating pressure. The lower pressure in the motor cavity reduces the density of the gasses in the motor cavity, resulting in reduced windage losses of the motor. Additionally, the pumping device is powered by the recovered liquid expansion energy between the condenser and the evaporator.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to a system and method of cooling a compressor motor by circulating refrigerant gas over the motor components. More specifically, the present invention is directed to reducing windage losses in a compressor motor by lowering the pressure and density of the refrigerant gas within the motor cavity.[0002]High-speed motors typically have large windage losses, in part because of the large amount of cooling gas induced windage friction caused during high-speed rotor rotation, which impacts the motor's performance and efficiency. To reduce the windage losses, factors directly related to the motor such as the peripheral speed of the rotor, the flow of motor cooling gas around the motor, the rotor surface area and the roughness of the rotor surface are manipulated and controlled to optimize the performance of the motor.[0003]One method for reducing energy losses in motors while cooling the motor is by suctioning refrigerant towar...

AI Technical Summary

Benefits of technology

[0011]One advantage of the present invention is the reduction in windage and energy losses in the motor.

[0012]Another advantage of the present invention is the recycling of discharged energy by the liquid expander.

[0013]Still another advantage of the present invention is that the system effectively lowers the pressure of refrigerant gas in the motor cavity, cools the motor, and keeps energy expenses at a minimum. All this optimizes the reduction of windage losses and increases the efficiency of the motor.

[0014]Additionally, another advantage of the present invention is that the compressor for the motor cooling loop is load dependant. Therefore, the system only operates at the necessary level for the current load of the system and does not consume unnecessary energy.

Problems solved by technology

High-speed motors typically have large windage losses, in part because of the large amount of cooling gas induced windage friction caused during high-speed rotor rotation, which impacts the motor's performance and efficiency.

However, this method uses mechanical equipment and is not optimal for maintaining a true constant pressure in the motor cavity.

Additionally, this method does not address the issue of the motor cavity temperature.

The preservation of oil in the motor bearing components allows for greater lubrication for the movement of parts thereby reducing friction while not allowing oil to escape into the motor cooling cavity, preventing excessive oil churning and reducing energy losses.

However, this system only holds the pressure in the motor cavity at a constant level, and only assists in reducing energy losses, rather than optimizing the motor efficiency.

For very high speed motors however, windage losses can still be substantial even after factors such as the peripheral speed of the rotor, the density and flow of motor cooling gas around the motor, the rotor surface area and / or the roughness of the rotor surface are optimized.

However, these systems lack the ability to both adequately cool the motor while providing a vacuum surrounding the motor cavity.

However in these systems, the auxiliary compressors consume more energy than they are saving in motor windage losses, therefore these systems are not a good solution to increasing motor efficiency.

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