Electronic control transformer using DC link voltage
First Claim
1. A drive system to power a plurality of components of a chiller system having different voltage requirements, the drive system comprising:
- a converter stage connected to an AC power source to receive an input AC power at a fixed input AC voltage and a fixed input frequency, the converter stage being configured to convert the fixed 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; and
a first inverter stage connected to the DC link, the first inverter stage being configured to convert the boosted DC voltage from the DC link to provide an output power at a variable voltage and variable frequency to a motor of a chiller system, 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;
wherein the first inverter stage is configured to reverse power flow through the first inverter stage to the DC link stage to transfer electrical power from energy stored in a rotating mass of a motor connected to the first inverter stage to maintain a voltage level of the DC link in response to a decreasing fixed input AC voltage; and
a second inverter stage connected to the DC link, the second inverter stage being configured to convert the boosted DC voltage from the DC link into an auxiliary output power source having a fixed output AC voltage and a fixed output frequency for at least one component of a chiller system, the fixed output AC voltage being less than the fixed input AC voltage; and
, wherein the fixed output AC voltage and fixed output frequency of the second inverter stage is maintained in the event of a temporary decrease in the fixed input AC voltage.
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Accused Products
Abstract
In a chiller system, an electronic control transformer is powered by the DC link of a variable speed drive that drives a compressor motor. The electronic control transformer converts the DC voltage to a constant 120 VAC at 60 Hz, for providing power to auxiliary electrical devices associated with the chiller system. The electronic transformer includes four semiconductor switches to convert the DC voltage to AC. The energy stored in the compressor motor is transferred to the DC link of the VSD during an input voltage sag. The electronic control transformer maintains the control voltage and prevents the system auxiliary loads from dropping out during a voltage sag. The chiller system is able to ride through the input voltage sag or interruption. A boost converter may be provided at the input of the VSD to increase ride through capability.
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Citations
28 Claims
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1. A drive system to power a plurality of components of a chiller system having different voltage requirements, the drive system comprising:
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a converter stage connected to an AC power source to receive an input AC power at a fixed input AC voltage and a fixed input frequency, the converter stage being configured to convert the fixed 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; and
a first inverter stage connected to the DC link, the first inverter stage being configured to convert the boosted DC voltage from the DC link to provide an output power at a variable voltage and variable frequency to a motor of a chiller system, 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;
wherein the first inverter stage is configured to reverse power flow through the first inverter stage to the DC link stage to transfer electrical power from energy stored in a rotating mass of a motor connected to the first inverter stage to maintain a voltage level of the DC link in response to a decreasing fixed input AC voltage; and
a second inverter stage connected to the DC link, the second inverter stage being configured to convert the boosted DC voltage from the DC link into an auxiliary output power source having a fixed output AC voltage and a fixed output frequency for at least one component of a chiller system, the fixed output AC voltage being less than the fixed input AC voltage; and
, wherein the fixed output AC voltage and fixed output frequency of the second inverter stage is maintained in the event of a temporary decrease in the fixed input AC voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 9, 10)
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8. The drive system of claim 8, wherein the at least one auxiliary electrical component is selected from the group consisting of:
- pumps, relays, solenoids, heaters, contactors, fans, and combinations thereof.
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11. A chiller system comprising:
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a refrigerant circuit comprising compressor, a condenser, and an evaporator connected in a closed refrigerant loop;
a motor connected to the compressor to power the compressor;
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; and
a first inverter stage connected to the DC link, the first inverter stage being configured to convert the boosted DC voltage from the DC link into the output power for the motor, the first inverter stage also being configured to reverse power flow through the first inverter stage to the DC link stage to transfer electrical power from energy stored in a rotating mass of the motor to maintain the voltage level of the DC link stage in response to a decreasing input AC voltage; and
an electronic control transformer connected to the DC link, the electronic control transformer being configured to convert the boosted DC voltage from the DC link into an auxiliary output power source having a fixed output AC voltage and a fixed output frequency, the fixed output voltage being less than the fixed input AC voltage, wherein the fixed output AC voltage and fixed output frequency of the electronic control transformer is maintained in the event of a temporary decrease in the input AC voltage. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An electronic control transformer for powering at least one auxiliary device associated with a chiller system, the electronic control transformer comprising:
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an inverter module to convert a DC voltage to provide a fixed output AC voltage and fixed frequency to power the at least one auxiliary device;
the inverter module comprising a plurality of pairs of power switches, wherein each pair of power switches includes an insulated gate bipolar transistor connected in anti-parallel to a diode;
an input DC connection for connecting the electronic control transformer to a DC link of a variable speed drive; and
an output AC connection for connecting the at least one auxiliary device to the inverter module. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28)
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Specification