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

Claim 2

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.

Claim 3

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.

Claim 4

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.

Claim 5

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

Claim 6

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

Claim 7

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.

Claim 8

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.

Claim 11

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.

Claim 12

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.