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

Claim 1

A method of controlling the capacity of a preselected number of commonly piped compressors, comprising the steps of establishing an operation suction pressure range having an upper limit and a lower limit, detecting the suction pressure in the system for determining when said pressure exceeds said upper limit and when said pressure is below said lower limit, generating an increase capacity signal when said operating suction pressure exceeds said upper limit and a decrease capacity signal when said operation suction pressure is below said lower limit, and applying said increase capacity signal and said decrease capacity signal in tandem to respectively energize and deenergize the preselected number of compressors in a sequence where the first deenergized compressor is the first to be energized and the first energized compressor is the first to be deenergized.

Claim 2

A method of controlling the capacity of a preselected number of commonly piped compressors, comprising the steps of establishing an operation suction pressure range having an upper limit and a lower limit, detecting the suction pressure in the system for determining when said pressure exceeds said upper limit and when said pressure is below said lower limit, generating an increase capacity signal when said operating suction pressure exceeds said upper limit and a decrease capacity signal when said operation suction pressure is below said lower limit, and applying said increase capacity signal and said decrease capacity signal in tandem to respectively energize and deenergize the preselected number of compressors in a sequence where the first deenergized compressor is the first to be energized and the first energized compressor is the first to be deenergized.

Claim 5

A method of controlling a compressor system having a preselected number of commonly piped compressors of inequal capacity and a common suction pressure load, comprising the steps of establishing an operation suction pressure range having an upper limit and a lower limit, detecting the suction pressure in the system and determining when said pressure exceeds said upper limit and when said pressure is below said lower limit, providing an increase capacity signal when said operating suction pressure exceeds said upper limit and a decrease capacity signal when said operation suction pressure is below said lower limit, and selectively energizing and deenergizing compressors in response to the respective increase capacity signals and the decrease capacity signals to provide a combination of energized unequal capacity compressors that exceeds in number the preselected number of compressors in the system so that the capacity of the system matches the common pressure load.

Claim 6

A method of controlling a compressor system having a preselected number of commonly piped compressors of inequal capacity and a common suction pressure load, comprising the steps of establishing an operation suction pressure range having an upper limit and a lower limit, detecting the suction pressure in the system and determining when said pressure exceeds said upper limit and when said pressure is below said lower limit, providing an increase capacity signal when said operating suction pressure exceeds said upper limit and a decrease capacity signal when said operation suction pressure is below said lower limit, and selectively energizing and deenergizing compressors in response to the respective increase capacity signals and the decrease capacity signals to provide a combination of energized unequal capacity compressors that exceeds in number the preselected number of compressors in the system so that the capacity of the system matches the common pressure load.

Claim 9

A method of controlling the capacity of a preselected number of commonly piped compressors, comprising the steps of establishing an operating suction pressure range having an upper limit and a lower limit, detecting the suction pressure in the system and determining when said pressure exceeds said upper limit and when said pressure is below said lower limit, providing an increase capacity signal when said operating suction pressure exceeds said upper limit and a decrease capacity signal when said operating suction pressure is below said lower limit, and selectively energizing and deenergizing compressors in response to the respective increase capacity signals and the decrease capacity signals to provide a combination of energized compressors that exceeds in number the preselected number of compressors in the system so that the capacity of the system matches the common pressure load thereby allowing a close operating range.

Claim 10

A method of controlling the capacity of a preselected number of commonly piped compressors, comprising the steps of establishing an operating suction pressure range having an upper limit and a lower limit, detecting the suction pressure in the system and determining when said pressure exceeds said upper limit and when said pressure is below said lower limit, providing an increase capacity signal when said operating suction pressure exceeds said upper limit and a decrease capacity signal when said operating suction pressure is below said lower limit, and selectively energizing and deenergizing compressors in response to the respective increase capacity signals and the decrease capacity signals to provide a combination of energized compressors that exceeds in number the preselected number of compressors in the system so that the capacity of the system matches the common pressure load thereby allowing a close operating range.

Claim 13

The method as described in claims 1 or 3 or 5, further including the step of providing a time delay prior to energizing or deenergizing a subsequent compressor in the system.

Claim 22

The system as described in claims 4 or 6, wherein said selection means comprises sequencing means connected to said detection means for establishing a first-off first-on sequence for energizing the compressors in response to an increase capacity signal and for establishing a first-on first-off sequence for deenergizing the compressors in response to a decrease capacity signal, and control circuit means connected to said sequencing means for tandemly connecting energizing signals to said compressors in a first-off first-on sequence and tandemly disconnecting said energizing signals from said compressors in a first-on first-off sequence.

Claim 33

An apparatus for controlling the capacity of a preselected number of compressors having a common suction pressure load, comprising: (a) a voltage source; (b) at least one variable resistance means connected to said voltage source for supplying a voltage signal representative of each of the operating suction pressure range limits; (c) a pressure transducer cooperating with the system suction pressure for measuring said pressure and generating an electrical signal representative of the measure pressure; (d) a comparator circuit receiving said voltage signals representative of said operation suction pressure range limits and said transducer signal for comprising said transducer signal with said pressure limit voltage signals for determining when said transducer signal is outside of said operations suction pressure range limits and generating increase capacity and decrease capacity signals in response thereto; (e) strategy means receiving said increase capacity and decrease capacity signals from said comparator circuit and generating in response to each of said received signals an energizing control or a deenergizing control signal, said energizing control signals occurring in a first-off first-on sequence and said deenergizing control signals occurring in a first-on first-off sequence; and (f) control circuit means for tandemly connecting said energizing control signals to said compressors in a first-off first-on sequence and tandemly disconnecting said energizing signals from said compressors in a first-on first-off sequence to provide a combination of energized compressors that exceeds in number the preselected number of compressors in the system and so that the capacity of the system matches the suction pressure load.

Claim 34

An apparatus for controlling the capacity of a preselected number of compressors having a common suction pressure load, comprising: (a) a voltage source; (b) at least one variable resistance means connected to said voltage source for supplying a voltage signal representative of each of the operating suction pressure range limits; (c) a pressure transducer cooperating with the system suction pressure for measuring said pressure and generating an electrical signal representative of the measure pressure; (d) a comparator circuit receiving said voltage signals representative of said operation suction pressure range limits and said transducer signal for comprising said transducer signal with said pressure limit voltage signals for determining when said transducer signal is outside of said operations suction pressure range limits and generating increase capacity and decrease capacity signals in response thereto; (e) strategy means receiving said increase capacity and decrease capacity signals from said comparator circuit and generating in response to each of said received signals an energizing control or a deenergizing control signal, said energizing control signals occurring in a first-off first-on sequence and said deenergizing control signals occurring in a first-on first-off sequence; and (f) control circuit means for tandemly connecting said energizing control signals to said compressors in a first-off first-on sequence and tandemly disconnecting said energizing signals from said compressors in a first-on first-off sequence to provide a combination of energized compressors that exceeds in number the preselected number of compressors in the system and so that the capacity of the system matches the suction pressure load.

Claim 35

The system as described in claims 25 or 26, wherein said control circuit means comprises: (a) circuit means for receiving each of said energizing control signals and generating in response thereto a signal for energizing a corresponding compressor, said circuit means further receiving each of said deenergizing control signals for generating in response thereto a signal for deenergizing a corresponding compressor; and (b) relay means cooperating with each of the compressors for receiving said energizing and deenergizing signals from said circuit means and energizing or deenergizing the corresponding compressor in response thereto.

Claim 40

The system as described in claims 28 or 29, wherein said control circuit means comprises: (a) circuit means receiving each of said energizing control signals and generating in response thereto a signal for energizing a corresponding compressor, said circuit means further receiving each of said deenergizing control signals and generating in response thereto a signal for deenergizing a corresponding compressor; and (b) relay means cooperating with each of the compressors for receiving said energizing and deenergizing signals from said circuit means and energizing or deenergizing the corresponding compressor in response thereto.

Claim 41

An apparatus for adjusting the capacity of a commonly-piped multi-compressor cooling system to maintain common suction pressure within preselected limits, comprising: (a) measurement means for detecting the level of suction pressure in the cooling system and generating an increase capacity signal if the suction pressure exceeds the preselected limits and for generating a decrease capacity signal if the suction pressure drops below the preselected limits; (b) strategy means for generating an energizing signal for the compressor which has been turned off the greatest period of time in response to an increase capacity signal from said measurement means and for generating a deenergizing signal for the compressor which has been turned on the greatest period of time in response to a decrease capacity signal from said measurement means; and (c) switch means connected to each of the compressors in tandem for receiving said increase capacity signals and decrease capacity signals and for independently energizing a compressor selected by said strategy means in response to an increase capacity signal and for independently deenergizing a compressor selected by the strategy means in response to a decrease capacity signal, whereby a new combination of energized compressors is created out of a total number of combinations greater than the number of compressors available so as to match the system capacity to the cooling load.

Claim 42

An apparatus for adjusting the capacity of a commonly-piped multi-compressor cooling system to maintain common suction pressure within preselected limits, comprising: (a) measurement means for detecting the level of suction pressure in the cooling system and generating an increase capacity signal if the suction pressure exceeds the preselected limits and for generating a decrease capacity signal if the suction pressure drops below the preselected limits; (b) strategy means for generating an energizing signal for the compressor which has been turned off the greatest period of time in response to an increase capacity signal from said measurement means and for generating a deenergizing signal for the compressor which has been turned on the greatest period of time in response to a decrease capacity signal from said measurement means; and (c) switch means connected to each of the compressors in tandem for receiving said increase capacity signals and decrease capacity signals and for independently energizing a compressor selected by said strategy means in response to an increase capacity signal and for independently deenergizing a compressor selected by the strategy means in response to a decrease capacity signal, whereby a new combination of energized compressors is created out of a total number of combinations greater than the number of compressors available so as to match the system capacity to the cooling load.

Claim 47

A method for adjusting the capacity of a commonly-piped multi-compressor cooling system to maintain common suction pressure within preselected limits: (a) establishing high and low suction pressure limits for the cooling system; (b) measuring the suction pressure; (c) comparing the suction pressure to the established pressure limits; (d) generating an increase capacity signal if the suction pressure is above the established limits and a decrease capacity signal if the suction pressure is below the established limits; (e) incrementing a first register to determine which compressor has been deenergized the longest period of time in response to an increase capacity signal; (f) incrementing a second register to determine which compressor has been energized the longest period of time in response to a decrease capacity signal; (g) connecting each compressor in tandem to said first register and to said second register; (h) generating an energizing control signal to the compressor which has been deenergized the longest in response to incrementing said first register; (i) generating a deenergizing control signal to the compressor which has been energized the longest period of time in response to incrementing said second register; (j) energizing the compressor designated by said first register in response to said energizing signal; and (k) deenergizing the compressor designated by said second register in response to said deenergizing signal.

Claim 48

A method for adjusting the capacity of a commonly-piped multi-compressor cooling system to maintain common suction pressure within preselected limits: (a) establishing high and low suction pressure limits for the cooling system; (b) measuring the suction pressure; (c) comparing the suction pressure to the established pressure limits; (d) generating an increase capacity signal if the suction pressure is above the established limits and a decrease capacity signal if the suction pressure is below the established limits; (e) incrementing a first register to determine which compressor has been deenergized the longest period of time in response to an increase capacity signal; (f) incrementing a second register to determine which compressor has been energized the longest period of time in response to a decrease capacity signal; (g) connecting each compressor in tandem to said first register and to said second register; (h) generating an energizing control signal to the compressor which has been deenergized the longest in response to incrementing said first register; (i) generating a deenergizing control signal to the compressor which has been energized the longest period of time in response to incrementing said second register; (j) energizing the compressor designated by said first register in response to said energizing signal; and (k) deenergizing the compressor designated by said second register in response to said deenergizing signal.