Method and apparatus for controlling the operation of a centrifugal compressor in a refrigeration system

• US 4,404,812 A
• Filed: 11/27/1981
• Issued: 09/20/1983
• Est. Priority Date: 11/27/1981
• Status: Expired due to Fees

• Current Assignee: Carrier Corporation (Carrier Global Corporation)
• Original Assignee: Carrier Corporation (Carrier Global Corporation)
• Inventors: Zinsmeyer, Thomas M.
• Primary Examiner(s): Makay, Albert J.
• Assistant Examiner(s): TANNER, HARRY B
• Application Number:
  US06/325,617
• Time in Patent Office: 662 Days
• Field of Search: 62/217, 62/224, 62/225, 62/231, 62/469, 62/84, 62/192, 62/193, 62/228 D, 62/157, 417/13, 417/281, 417/902, 73/861.61, 73/861.63, 340/606, 340/611
• US Class Current: 62/84
• CPC Class Codes: F25B 1/053 of turbine type
• CPC Class Codes: F25B 31/002 Lubrication

Abstract

A method and apparatus to prevent oil pump cavitation in a hermetically sealed vapor compression refrigeration system are disclosed. A hermetically sealed housing containing the refrigeration compressor transmission and oil supply reservoir is connected to the suction side of the compressor to equalize the pressure in the housing and the suction to the compressor is constructed with a restriction such as an orifice or a venturi to create a pressure drop or is of a size small enough to create a pressure drop when refrigerant flows through the line. The pressure drop is sensed by a pressure differential switch to anticipate sharp drops in pressure in the housing. The flow of refrigerant to the compressor is throttled in response to predetermined pressure drops to prevent a sharp drop in pressure within the transmission housing and thus prevent vigorous boiling of refrigerant from the oil reservoir. Prevention of vigorous boiling of the refrigerant from the oil prevents oil pump cavitation and loss of oil to the transmission and bearings of the compressor.

Claims

1. A compressor control for use in vapor compression refrigeration system for controlling the operation of a hermetic centrifugal compressor having a transmission enclosed in a housing said housing having an oil reservoir for lubricating the transmission and an atmosphere of refrigerant, said control comprising:

means to equalize the pressure between the compressor suction and the atmosphere of refrigerant in the housing,

means to detect a pressure differential between the compressor suction and the housing before equalization of the pressure in the housing occurs, and

means to throttle the suction to the compressor upon the detection of a predetermined pressure differential between the compressor suction and the housing.

2. A compressor control for use in a vapor compression refrigerant system for controlling the operation of a hermetic centrifugal compressor having a transmission enclosed in a housing said housing having an oil reservoir for lubricating the transmission and an atmosphere of refrigerant, said control comprising:

a pressure equalization line between the compressor suction and the housing,

means in the pressure equalization line to produce a pressure drop when refrigerant is flowing in the pressure equalization line,

a pressure differential switch operatively associated with the pressure equalization line to detect a predetermined pressure drop across the pressure equalization line and to generate an electrical signal when a predetermined pressure drop is detected, and

means to throttle the suction to the compressor in response to the signal generated by the pressure differential switch.

3. The compressor control of claim 2 wherein the means in the pressure equalization line to produce a pressure drop in an orifice.

4. The compressor control of claim 2 wherein the means in the pressure equalization line to produce a pressure drop is a venturi type restriction.

5. A compressor control for use in a vapor compression refrigeration system for controlling the operation of a hermetic centrifugal compressor of the type having a compressor casing housing a rotating impeller, a suction line connected to the inlet of the casing, a discharge line connected to the outlet of the casing, inlet guide vanes in the suction line to control the flow of refrigerant to the comprssor, control means to open and close the inlet guide vanes, and a housing hermetically enclosing a transmission for driving the impeller, and a lubrication oil reservoir, said control comprising

a pressure equalization line connecting the suction line to the housing to equalize the pressure of vaporous refrigerant in the housing and the suction line to the compressor

restriction means positioned in the pressure equalization line to localize the pressure drop between the housing and the suction line when there is flow of refrigerant from the housing to the suction line,

a pressure differential switch connected across the restriction means and set to make or break electrical contacts when a predetermined pressure exists across the restriction means, said pressure differential switch being connected to the inlet guide vane control means to close the inlet guide vanes upon occurrence of the predetermined pressure differential across the restriction means and to allow said guide vanes to be opened when said predetermined pressure differential does not exist.

6. A method of controlling operation of a hermetically sealed centrifugal compressor in a vapor compression refrigeration system comprising the steps of

maintaining pressure in a housing containing the compressor transmission and the oil supply of the compressor, at substantially the same pressure as the suction to the compressor

detecting the occurrence of a predetermined pressure difference between the suction of the compressor and the housing

throttling the suction to the compressor upon detection of the predetermined pressure difference to prevent a sharp drop in pressure in the housing.

7. In a vapor compression refrigeration system a method of controlling operation of a hermetically sealed centrifugal compressor to prevent rapid vaporization of refrigerant entrained in a supply of lubricating oil comprising the steps of

providing pressure equalization between the suction to the compressor and a housing enclosing a supply of oil for the compressor

determining when a pressure differential exists between the compressor suction and the housing

closing guide vanes in the compressor suction when a predetermined pressure differential exists to increase the pressure in the suction to the compressor and to retard pressure drop in the housing, and

allowing the guide vanes in the compressor suction to open when the pressure differential is reduced below a predetermined amount.