Method and apparatus for controlling capacity of a multiple-stage cooling system

Claim 2

Apparatus for controlling the capacity of a refrigeration system having a variable speed compressor, said compressor having an associated suction pressure and a minimum operating oil pressure, said compressor being adapted to operate at variable speeds between a maximum and a minimum speed, said system coprising: (a) pressure selecting means for establishing an operating suction pressure range; (b) pressure detection means for sensing the suction pressure and for cooperating with said pressure selecting means to generate a first increase speed signal when said suction pressure exceeds the pressure range, and to generate a decrease speed signal when said suction pressure falls below the pressure range; (c) oil pressure detection means for providing a second increase speed signal when said oil pressure falls below said minimum operating oil pressure; and (d) selection means for receiving said first and second increase speed signals and causing the speed of the compressor to increase in respective response thereto, and for receiving the decrease speed signal and causing the speed of the compressor to decrease in response thereto.

Claim 3

Apparatus for controlling the capacity of a refrigeration system comprising a variable speed compressor for compressing a refrigerant, said compressor being adapted to operate between a maximum and a minimum speed, said compressor also utilizing oil and having an associated oil pressure, said refrigeration system further including a condenser for condensing the compressed refrigerant, an evaporator connected to said compressor and to said condenser for evaporating said condensed refrigerant and directing siad evaporated refrigerant to said compressor, pressure selection means for establishing a minimum operating oil pressure level, and an oil pressure detection means that generates an increase speed signal when said oil pressure falls below said minimum operating pressure level.

Claim 4

Apparatus for controlling the capacity of a refrigeration system comprising a variable speed compressor for compressing a refrigerant, said compressor being adapted to operate between a maximum and a minimum speed, said compressor also utilizing oil and having an associated oil pressure, said refrigeration system further including a condenser for condensing the compressed refrigerant, an evaporator connected to said compressor and to said condenser for evaporating said condensed refrigerant and directing siad evaporated refrigerant to said compressor, pressure selection means for establishing a minimum operating oil pressure level, and an oil pressure detection means that generates an increase speed signal when said oil pressure falls below said minimum operating pressure level.

Claim 5

A refrigeration system comprising: (a) a predetermined number of commonly piped compressors wherein one compressor being adapted to operate at variable speeds between a maximum and a minimum speed, said variable speed compressor also having an associated operating oil pressure; (b) oil pressure selection means for establishing a minimum operating oil pressure level for said variable speed compressor; (c) oil pressure detection means for determining the oil pressure associated with said variable speed compressor, said oil pressure detectiong means cooperating with said oil pressure selection means to generate a first increase speed signal when said oil pressure exceeds said minimum oil pressure level, and causing the variable speed compressor to increase the speed in response thereto; (d) pressure selection means for establishing a first and a second suction pressure range, each said pressure range having an upper and a lower limit, the first pressure range being associated with the variable speed compressor and the second pressure range being associated with the remaining compressors; (e) detection means for sensing the suction pressure and for cooperating with the pressure selection means to provide a second increase speed signal when the suction pressure exceeds the upper limit of the first pressure range, a decrease speed signal when the suction pressure falls below the lower limit of the first pressure range, an increase capacity signal when the suction pressure exceeds the upper limit of the second pressure range and that the variable speed compressor is operating at the maximum speed, and a decrease capacity signal when the suction pressure falls below the lower limit of the second pressure range and that the variable speed compressor is operating at the minimum speed; and (f) selection means for receiving the second increase speed and the decrease speed signals and in respective response thereto increasing and decreasing the speed of the variable speed compressor, and for receiving the increase capacity and decrease capacity signals and in respective response thereto energizing and de-energizing a compressor of the refrigeration system.

Claim 6

A refrigeration system comprising: (a) a predetermined number of commonly piped compressors wherein one compressor being adapted to operate at variable speeds between a maximum and a minimum speed, said variable speed compressor also having an associated operating oil pressure; (b) oil pressure selection means for establishing a minimum operating oil pressure level for said variable speed compressor; (c) oil pressure detection means for determining the oil pressure associated with said variable speed compressor, said oil pressure detectiong means cooperating with said oil pressure selection means to generate a first increase speed signal when said oil pressure exceeds said minimum oil pressure level, and causing the variable speed compressor to increase the speed in response thereto; (d) pressure selection means for establishing a first and a second suction pressure range, each said pressure range having an upper and a lower limit, the first pressure range being associated with the variable speed compressor and the second pressure range being associated with the remaining compressors; (e) detection means for sensing the suction pressure and for cooperating with the pressure selection means to provide a second increase speed signal when the suction pressure exceeds the upper limit of the first pressure range, a decrease speed signal when the suction pressure falls below the lower limit of the first pressure range, an increase capacity signal when the suction pressure exceeds the upper limit of the second pressure range and that the variable speed compressor is operating at the maximum speed, and a decrease capacity signal when the suction pressure falls below the lower limit of the second pressure range and that the variable speed compressor is operating at the minimum speed; and (f) selection means for receiving the second increase speed and the decrease speed signals and in respective response thereto increasing and decreasing the speed of the variable speed compressor, and for receiving the increase capacity and decrease capacity signals and in respective response thereto energizing and de-energizing a compressor of the refrigeration system.

Claim 7

The apparatus of claim 3 wherein said compressors have unequal capacity.

Claim 8

The apparatus of claim 3 wherein said compressors have equal capacity.

Claim 19

The method of claim 10 wherein the upper and the lower limits are the same.

Claim 20

The method of claim 10 wherein the compressors in said plurality of compressors have unequal capacity.

Claim 21

The method of claim 10 wherein the compressors in said plurality of compressors have equal capacity.