Carrier Corporation

Tathagata De

Alberto Vecchiotti

Tyler Joseph Ludwig

A system and method of freeze protection for a chiller including a metering device in flow communication with a condenser, a controller in electrical communication with the metering device, wherein the controller is configured to determine whether the difference between the fluid characteristic of the first liquid and the fluid characteristic of the second liquid is greater than a freezing limit, and enter a freeze protection mode if the difference between the fluid characteristic of the first liquid and the fluid characteristic of the second liquid is greater than the freezing limit.

System and method of freeze protection for a chiller

A refrigeration unit may include a first compressor constructed and arranged to compress a first refrigerant, and a second compressor constructed and arranged to compress a second refrigerant. A first condenser of the refrigeration unit is operatively coupled to the first compressor, and a second condenser is operatively coupled to the second compressor. An evaporator of the refrigeration unit is constructed and arranged to flow the first and second refrigerants received from the respective first and second condensers for chilling a heat transfer fluid. A controller of the refrigeration unit includes a computer processor and a storage media for executing a pre-programmed algorithm for initialing the second compressor when a predetermined crossover frequency of the first compressor is reached as a system load increases.

Dual-compressor refrigeration unit

A method for controlling a refrigeration system having a compressor, heat rejecting heat exchanger, expansion valve and heat absorbing heat exchanger circulating a refrigerant in series flow, the heat absorbing heat exchanger in thermal communication with working fluid, the method includes obtaining an expansion valve position set point; using a feedback control loop to generate a controlled expansion valve position; obtaining a rate of change of an operating parameter of the system; using the rate of change of the operating parameter to generate an adjustment; modifying the controlled expansion valve position using the adjustment; and controlling the expansion valve using the modified controlled expansion valve position.

Expansion valve control

There is a method for controlling a centrifugal compressor () having an inlet (), an outlet (), an impeller () mounted for rotation about an impeller axis (), a motor () coupled to the impeller to drive the impeller about the impeller axis (), and a variable inlet guide vane () array () controllable for movement between a relatively closed first condition and a relatively open second condition. A lift value is determined (). An allowable guide vane condition based upon the lift value is determined (). The guide vane array is closed () to the determined allowable guide vane condition. The impeller is accelerated () to an operational speed.

Centrifugal compressor startup control

A chiller system () includes a motor (), a motor controller () connected to the motor (), the motor controller () operative to send a control signal to the motor (), a rectifier () connected to an alternating current (AC) power source (), the rectifier () operative to receive AC power and output direct current (DC) power, a DC bus () connected to the rectifier (), a first inverter () connected to the DC bus () and the motor (), the first inverter () operative to receive DC power from the DC bus () and output AC power to the motor (), and a second inverter () connected to the DC bus () operative to receive DC power and output AC power to the motor controller ().

Chiller motor control system

A method of motor operation includes monitoring a voltage of a power bus supplying power to the motor, determining if a power failure is occurring or has occurred based on the monitoring, and lowering an operational capacity of the motor in response to the determining.

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Charlotte, NC, United States of America

Tathagata De