Variable speed drive for a chiller system
First Claim
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1. A drive system for a compressor of a chiller system, the drive system comprising:
- a variable speed drive, the variable speed drive being configured to receive an input AC voltage at a fixed AC input voltage and provide an output AC power at a variable voltage and variable frequency, the variable speed drive comprising;
a converter stage connected to an AC power source providing the input AC voltage, the converter stage being configured to convert the input AC voltage to a boosted DC voltage;
a DC link connected to the converter stage, the DC link being configured to filter and store the boosted DC voltage from the converter stage; and
an inverter stage connected to the DC link, the inverter stage being configured to convert the boosted DC voltage from the DC link into the output AC power having the variable voltage and the variable frequency; and
a motor connected to the inverter stage and powered by the output AC power from the inverter stage, the motor being connectable to a compressor of the chiller system to power the compressor;
wherein the converter stage comprises a three-phase pulse width modulated boost rectifier having insulated gate bipolar transistors and is configured to maintain a boosted DC voltage greater than the input AC voltage when the input AC voltage falls below the fixed AC input voltage.
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Abstract
A variable speed drive with a boost converter is provided for a chiller system driven by an induction motor. The boost converter can be a diode or thyristor rectifier followed by a boost DC/DC converter or a three-phase pulse width modulated boost converter. The boost converter provides a boosted voltage to the DC link, which results in a boosted voltage being applied to the induction motor by the inverter of the variable speed drive.
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Citations
20 Claims
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1. A drive system for a compressor of a chiller system, the drive system comprising:
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a variable speed drive, the variable speed drive being configured to receive an input AC voltage at a fixed AC input voltage and provide an output AC power at a variable voltage and variable frequency, the variable speed drive comprising;
a converter stage connected to an AC power source providing the input AC voltage, the converter stage being configured to convert the input AC voltage to a boosted DC voltage;
a DC link connected to the converter stage, the DC link being configured to filter and store the boosted DC voltage from the converter stage; and
an inverter stage connected to the DC link, the inverter stage being configured to convert the boosted DC voltage from the DC link into the output AC power having the variable voltage and the variable frequency; and
a motor connected to the inverter stage and powered by the output AC power from the inverter stage, the motor being connectable to a compressor of the chiller system to power the compressor;
wherein the converter stage comprises a three-phase pulse width modulated boost rectifier having insulated gate bipolar transistors and is configured to maintain a boosted DC voltage greater than the input AC voltage when the input AC voltage falls below the fixed AC input voltage. - View Dependent Claims (2, 5, 6, 7, 8, 9, 10)
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3-4. -4. (canceled)
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11. A chiller system comprising:
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a compressor, a condenser, and an evaporator connected in a closed refrigerant loop;
a motor connected to the compressor to power the compressor; and
a variable speed drive connected to the motor, the variable speed drive being configured to receive an input AC power at a fixed input AC voltage and a fixed input frequency and provide an output power at a variable voltage and variable frequency to the motor, the variable voltage having a maximum voltage greater in magnitude than the fixed input AC voltage and the variable frequency having a maximum frequency greater than the fixed input frequency, the variable speed drive comprising;
a converter stage connected to an AC power source providing the input AC power, the converter stage being configured to convert the input AC voltage to a boosted DC voltage, the boosted DC voltage being greater than the fixed input AC voltage;
a DC link connected to the converter stage, the DC link being configured to filter the boosted DC voltage and store energy from the converter stage;
an inverter stage connected to the DC link, the inverter stage being configured to convert the boosted DC voltage from the DC link into the output power for the motor having the variable voltage and the variable frequency; and
wherein the converter stage comprises a three-phase pulse width modulated boost rectifier having insulated gate bipolar transistors. - View Dependent Claims (12, 15, 16, 17, 18, 19, 20)
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13-14. -14. (canceled)
Specification