Variable speed drive chiller system
First Claim
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1. A refrigeration system having:
- a closed fluid circuit serially including a screw compressor, a discharge line, a condenser, an expansion device, a chiller and a suction line leading back to said compressor;
water passing through said chiller in a heat exchange relationship and being cooled;
said compressor being unloaded solely by regulating the speed of said compressor;
motor means for driving said compressor;
means for varying the speed of said motor means by controlling the frequency of electrical current supplied to said motor;
means for providing cooling to said means for varying the speed;
means for sensing the temperature of water leaving said chiller;
means for controlling said means for varying the speed responsive to the sensed temperature of water leaving said chiller.
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Abstract
The compressor in a refrigeration system is controlled solely by a variable speed drive which controls the motor of the compressor by virtue of the varying of the frequency of the electricity provided to the motor. To minimize the initial cost and to minimize operating costs, the variable speed drive is cooled by refrigerant from the refrigeration system which permits the use of a smaller drive, and the variable speed drive is operated at, or approaching, a unity power factor.
196 Citations
17 Claims
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1. A refrigeration system having:
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a closed fluid circuit serially including a screw compressor, a discharge line, a condenser, an expansion device, a chiller and a suction line leading back to said compressor;
water passing through said chiller in a heat exchange relationship and being cooled;
said compressor being unloaded solely by regulating the speed of said compressor;
motor means for driving said compressor;
means for varying the speed of said motor means by controlling the frequency of electrical current supplied to said motor;
means for providing cooling to said means for varying the speed;
means for sensing the temperature of water leaving said chiller;
means for controlling said means for varying the speed responsive to the sensed temperature of water leaving said chiller. - View Dependent Claims (2, 3, 4, 5, 11, 12, 13)
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6. A refrigeration system having:
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a closed fluid circuit serially including a screw compressor, a discharge line, a condenser, a first expansion device, an economizer, a second expansion device, a chiller and a suction line leading back to said compressor;
a branch line connected to said economizer and extending into said compressor;
water passing through said chiller in a heat exchange relationship and being cooled;
said compressor being unloaded solely by regulating the speed of said compressor;
motor means for driving said compressor;
means for varying the speed of said motor means by controlling the frequency of electric current supplied to said motor;
means for providing cooling to said means for varying the speed;
means for sensing the temperature of water leaving said chiller;
means for controlling said means for varying the speed responsive to the sensed temperature of water leaving said chiller. - View Dependent Claims (7, 8, 14, 15)
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9. A method for selecting the compressor, motor and variable speed drive for refrigeration system comprising the steps of:
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for a given design refrigeration requirement, selecting a compressor having a design speed and being capable of providing the necessary refrigerant delivery;
selecting a motor operating at the compressor design speed with a power factor of at least 0.89 when delivering the design amount of refrigerant;
selecting a variable speed drive for controlling said motor by varying the frequency of electric power supplied to said motor such that said variable speed drive operates at an input power factor of at least 0.99 when driving said motor to drive said compressor to deliver the design amount of refrigerant. - View Dependent Claims (10, 16, 17)
selecting means for sensing the temperature of water leaving the chiller; and
selecting means for controlling the speed of said motor solely responsive to the sensed temperature of the water leaving the chiller.
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Specification