Patent Description:
HVACR systems are generally used to heat, cool, and/or ventilate an enclosed space (e.g., an interior space of a commercial building or a residential building, an interior space of a refrigerated transport unit, or the like). A HVACR system may include a heat transfer circuit that utilizes a working fluid for providing cooled or heated air to an area. The heat transfer circuit can include a compressor for compressing the working fluid. The compressor can include a motor that rotates a driveshaft to compress the working fluid. The compressor can include gas bearing(s) that support the driveshaft as the driveshaft rotates within the compressor. A building HVACR system (e.g., a residential HVACR system, a residential HVACR system, or the like) can utilize utility electrical power to power its electrical components (e.g., the compressor, the controller, valve(s), and the like).

<CIT> discloses a heat transfer circuit with a compressor that includes a shaft, a gas bearing for supporting the shaft, a motor configured to rotate the shaft, and a variable frequency drive electrically connected to the motor.

A HVACR system can include a heat transfer circuit configured to heat or cool a process fluid (e.g., air, water and/or glycol, or the like). The heat transfer circuit includes a compressor that compresses a working fluid circulated through the heat transfer circuit. The compressor can include a driveshaft and one or more gas bearings for supporting the driveshaft. The compressor compresses the working fluid by rotating the driveshaft within the compressor. The gas bearing(s) support the driveshaft while the driveshaft rotates.

In an embodiment, the compressor includes a variable frequency drive (VFD) configured to utilize utility power, a permanent magnet motor electrically connected to the VFD and that rotates the driveshaft, one or more gas bearings to support the drive shaft, a backup gas supply fluidly connected to the one or more gas bearings, and a switch-mode power supply electrically connected to the VFD. During an interruption in the utility power, the switch-mode power supply is configured to utilize DC electrical power generated by a back electromotive force of the permanent magnet motor to operate the backup gas supply to provide a flow of compressed working fluid to the one or more gas bearings.

In an embodiment, the compressor includes a controller. The controller has a utility power mode and a backup power supply mode. In the utility power mode, the VFD receives the utility power and supplies power to the permanent magnet motor to rotate the driveshaft and compress the working fluid. In the backup power supply mode, the VFD generates the DC electrical power utilizing the back electromotive force of the permanent magnet motor, and the DC electrical power is used to power the controller to activate the backup gas supply.

In an embodiment, in the backup power supply mode, the controller operates the backup gas supply utilizing electrical power supplied from the switch-mode power supply utilizing the DC electrical power.

In an embodiment, the DC electrical power is supplied from the VFD to the switch-mode power supply.

In an embodiment, the back electromotive force causes the permanent magnet motor to supply an AC electrical power to the VFD, and the VFD converts the AC electrical power into the DC electrical power.

In an embodiment, the back electromotive force generates the DC electrical power in the VFD, and the DC electrical power is supplied from the VFD to the switch-mode power supply.

In an embodiment, the compressor includes a controller. The switch-mode power supply is configured to supply electrical power to the controller with a lower voltage than the DC electrical power.

In an embodiment, the switch-mode power supply receives the DC electrical power generated by the back electromotive force at a first voltage and the DC electrical power supplied from the switch-mode power supply to the controller is at a second voltage lower than the first voltage.

In an embodiment, the backup gas supply includes a second compressor. The second compressor is configured to operate by being powered by the switch-mode power supply utilizing the DC electrical power generated by the back electromotive force of the permanent magnet motor.

In an embodiment, the VFD includes an inverter electrically connected to the permanent magnet motor. The back electromotive force of the permanent magnet motor generates AC electrical power that is supplied from the permanent magnet motor to the inverter of the VFD. The inverter is configured to convert the AC electrical power into the DC electrical power.

In an embodiment, the VFD includes a rectifier, a DC link, and an inverter in series. The rectifier is configured to receive the utility power. The switch-mode power supply is electrically connected to the VFD between the DC link and the inverter.

In an embodiment, a method directed to operating an electric power supply system for a compressor in a heat transfer circuit. The compressor includes a permanent magnet motor, a driveshaft, and one or more gas bearings for supporting the driveshaft. The method includes operating the electrical power supply system in a utility power mode and operating the electrical power supply system in a backup power mode during an interruption of utility power. Operating in the utility power mode includes a VFD receiving utility power, supplying AC electrical power from the VFD to the permanent magnet motor to rotate the driveshaft and compress working fluid, and providing a flow of the compressed working fluid to the one or more gas bearings. Operating in the backup power mode during an interruption of the utility power includes supplying to a switch-mode power supply DC electrical power generated in the VFD by a back electromotive force of the permanent magnet motor, and utilizing, via the switch-mode power supply, the DC electrical power generated by the back electromotive force to operate a backup gas supply. The operation of the backup gas supply provides a flow of compressed working fluid to the one or more gas bearings.

In an embodiment, supplying the DC electrical power to the switch-mode power supply includes the back electromotive force causing the permanent magnet motor to supply AC electrical power to the VFD, and the VFD converting the AC electrical power into the DC electrical power.

In an embodiment, utilizing the DC electrical power generated by the back electromotive force includes: the switch-mode power supply receiving the DC electrical power generated by the back electromotive force at a first voltage, and the switch-mode power supply supplying DC electrical power at a second voltage lower than the first voltage.

In an embodiment, utilizing the DC electrical power generated by the back electromotive force to operate the backup gas supply includes: converting, with the switch-mode power supply, the DC electrical power into electrical power with a lower voltage, and utilizing the electrical power with the lower voltage to operate the backup gas supply.

In an embodiment, the backup gas supply includes a second compressor. In the backup power mode, the second compressor is configured to be powered by the switch-mode power supply to supply the flow of the compressed working fluid to the one or more gas bearings.

In an embodiment, the VFD includes an inverter electrically connected to the permanent magnet motor. Supplying the DC electrical power generated to the switch-mode power supply includes: generating, by the back electromotive force of the permanent magnet motor, AC electrical power that is supplied from the permanent magnet motor to the inverter of the VFD, and the inverter converting the AC electrical power into the DC electrical power.

In an embodiment, operating the electrical power supply system in the backup power mode includes initiating a shutdown of the compressor.

Both described and other features, aspects, and advantages of a compressor for a heat transfer circuit, an electric power supply system for a heat transfer circuit, a method of operating an electric power supply system for a heat transfer circuit will be better understood with the following drawings:.

A heating, ventilation, air conditioning, and refrigeration ("HVACR") system is generally configured to heat and/or cool an enclosed space (e.g., an interior space of a commercial or residential building, an interior space of a refrigerated transport unit, or the like). The HVACR system includes a heat transfer circuit that includes a compressor and a working fluid (e.g., a refrigerant, a refrigerant mixture, or the like) that circulates through the heat transfer circuit. The working fluid is utilized to heat or cool a process fluid (e.g., air, water and/or glycol, or the like).

The compressor includes a driveshaft, a motor that when powered rotates the driveshaft to compress the working fluid, and gas bearing(s) that support the driveshaft while it rotates. A gas bearing can be an aerostatic type of gas bearing. An aerostatic gas bearing relies upon the incoming flow of compressed gas to maintain the levitation of the driveshaft. When not provided with compressed gas, an aerostatic bearing is unable to keep the driveshaft levitated. The aerostatic gas bearing without the incoming compressed gas cannot maintain the layer of pressurized gas that prevents solid contact between the driveshaft and the aerostatic gas bearing. When compressed gas is no longer flowing to an aerostatic gas bearing, it can cause damage to the driveshaft and/or the gas bearing(s) due to the rotating driveshaft directly contacting the aerostatic gas bearing(s). An interruption in the utility power to the compressor can interrupt the operation of the compressor and the flow of the compressed gas to the gas bearing(s) resulting in damage to compressor. For example, a portion of the working fluid compressed by the compressor is supplied to the gas bearing(s), which means an interruption in the power to the compressor also interrupts the flow of compressed working fluid to the gas bearing(s). In some conventional configurations, a battery in the form of an uninterruptable power supply or the like, can be used to ensure that the compressor keeps compressing working fluid and supplying the compressed working to the gas bearing(s). However, this increases both the cost and maintenance of the compressor.

Embodiments described herein are directed to compressors, HVACR systems, heat transfer circuits, and power electric power supply systems for a heat transfer circuit that utilize the back electromotive force of the permanent magnet motor of the compressor to power and operate a backup gas supply when the utility power is interrupted. The powered backup gas supply providing a flow of compressed working fluid to the gas bearing(s) during the utility power interruption.

<FIG> is a schematic diagram of an embodiment of a heat transfer circuit <NUM>. In an embodiment, the heat transfer circuit <NUM> is utilized in a HVACR system. The heat transfer circuit <NUM> includes a compressor <NUM>, a condenser <NUM>, an expansion device <NUM>, and an evaporator <NUM>. In an embodiment, the heat transfer circuit <NUM> can be modified to include additional components, such as, for example, an economizer heat exchanger, one or more valve(s), sensor(s) (e.g., a flow sensor, a temperature sensor, and the like), a receiver tank, or the like.

The components of the heat transfer circuit <NUM> are fluidly connected. The heat transfer circuit <NUM> can be configured as a cooling system that can be operated in a cooling mode (e.g., a fluid chiller of an HVACR system, an air conditioning system, or the like), or the heat transfer circuit <NUM> may be configured as a heat pump system that can be run in a cooling mode or a heating mode.

A working fluid flows through the heat transfer circuit <NUM>. The main flow path <NUM> of the working fluid through the heat transfer circuit <NUM> extends through the compressor <NUM>, the condenser <NUM>, the expansion device <NUM>, the evaporator <NUM>, and back to the compressor <NUM>. In an embodiment, the main flow path <NUM> extends from a discharge outlet <NUM> of the compressor <NUM> back to a suction inlet <NUM> of the compressor <NUM>, and through the compressor <NUM> from the suction inlet <NUM> to the discharge outlet <NUM>. The working fluid in the main flow path <NUM> enters the compressor <NUM> through the suction inlet <NUM> and exits the compressor <NUM> through the discharge outlet <NUM>. The working fluid includes one or more refrigerant(s).

Dotted lines are provided in the Figures to indicate fluid flows through some components (e.g., condenser <NUM>, evaporator <NUM>) for clarity, and should be understood as not specifying a specific route in each component. Dashed dotted lines are provided in <FIG> to illustrate electronic communications between different features. For example, a dashed dotted line extends from a controller <NUM> to a flow sensor <NUM> as the controller <NUM> receives measurements (e.g., flowrate measurements) from the flow sensor <NUM>. For example, a dashed-dotted line extends from the controller <NUM> to the compressor <NUM> as the controller <NUM> controls the compressor <NUM>. In an embodiment, the controller <NUM> includes memory for storing information and a processor. The controller <NUM> in <FIG> and described below is described/shown as a single component. However, it should be appreciated that a "controller" as shown in <FIG> and described herein may include multiple discrete or interconnected components that include a memory and a processor in an embodiment. In an embodiment, the controller <NUM> may be disposed within the compressor <NUM> (e.g., the controller <NUM> being an integral compressor controller).

Working fluid in a lower pressure gaseous state or mostly gaseous state is drawn into the suction inlet <NUM> of the compressor <NUM>. The working fluid is compressed as it flows through the compressor <NUM>. The working fluid flows from the discharge outlet <NUM> of the compressor <NUM> through the main flow path <NUM> to the condenser <NUM>.

A first process fluid PF<NUM> flows through the condenser <NUM> separate from the working fluid. The condenser <NUM> is a heat exchanger that allows the working fluid and the first process fluid PF<NUM> to be in a heat transfer relationship without physically mixing as they each flow through the condenser <NUM>. As the working fluid flows through the condenser <NUM>, the working fluid is cooled by the first process fluid PF<NUM>. Accordingly, the first process fluid PF<NUM> is heated by the working fluid and exits the condenser <NUM> at a higher temperature relative to temperature at which it entered the condenser <NUM>. In an embodiment, the first process fluid PF<NUM> may be air, water and/or glycol, or the like that is suitable for absorbing and transferring heat from the working fluid and the heat transfer circuit <NUM>. For example, the first process fluid PF<NUM> may be ambient air circulated from an outside atmosphere, water to be heated as hot water, or any suitable fluid for transferring heat from the heat transfer circuit <NUM>. The working fluid is cooled by the condenser <NUM> and becomes liquid or mostly liquid as it is cooled in the condenser <NUM>.

The liquid/gaseous working fluid flows from the condenser <NUM> to the expansion device <NUM>. The expansion device <NUM> allows the working fluid to expand. The expansion causes the working fluid to significantly decrease in temperature. An "expansion device" as described herein may also be referred to as an expander. In an embodiment, the expander may be an expansion valve, expansion plate, expansion vessel, orifice, or the like, or other such types of expansion mechanisms. It should be appreciated that the expander may be any type of expander used in the field for expanding a working fluid to cause the working fluid to decrease in temperature. The gaseous/liquid working fluid has a lower temperature after being expanded by the expansion device <NUM>.

The lower temperature gaseous/liquid working fluid then flows from the expansion device <NUM> to and through the evaporator <NUM>. A second process fluid PF<NUM> also flows through the evaporator <NUM> separately from the working fluid. The evaporator <NUM> is a heat exchanger that allows the working fluid and the second process fluid PF<NUM> to be in a heat transfer relationship within the evaporator <NUM> without physically mixing. As the working fluid and the second process fluid PF<NUM> flow through the evaporator <NUM>, the working fluid absorbs heat from the second process fluid PF<NUM> which cools the second process fluid PF<NUM>. Accordingly, the second process fluid PF<NUM> exits the evaporator <NUM> at a lower temperature than the temperature at which it entered the evaporator <NUM>. The working fluid is gaseous or mostly gaseous as it exits the evaporator <NUM>. The working fluid flows from the evaporator <NUM> to the suction inlet <NUM> of the compressor <NUM>.

In an embodiment, the second process fluid PF<NUM> is air cooled by the HVACR system and ventilated to the enclosed space to be conditioned. In an embodiment, the second process fluid PF<NUM> is an intermediate fluid (e.g., water, heat transfer fluid, or the like), and the cooled second process fluid PF<NUM> may be utilized by the HVACR system to cool air in or ventilated to the enclosed space to be conditioned.

The compressor <NUM> includes one or more gas bearing(s) <NUM>. The gas bearing(s) <NUM> are aerostatic gas bearing(s) that provide support by utilizing an incoming flow of fluid. For example, a flow of the compressed working fluid F<NUM> is supplied to the gas bearing(s) <NUM> (e.g., the compressed working fluid discharged from the compressor <NUM> before passing through the expander <NUM>, the working fluid in the main flow path <NUM> after the compressor <NUM> and before the expander <NUM>). The gas bearing(s) <NUM> include one or more radial gas bearing(s) that radially support the driveshaft of the compressor <NUM> while it rotates. The heat transfer circuit <NUM> includes a backup gas supply <NUM> configured to supply compressed working fluid to the gas bearing(s) <NUM> when compressor <NUM> is unable to supply sufficient compressed working fluid for gas bearing(s) <NUM>. For example, the second compressed gas supply <NUM> is used during a utility power interruption that stops the operation of the compressor <NUM>.

In an embodiment, the backup gas supply <NUM> may be a vessel 61A which has been charged with compressed gaseous working fluid during normal operation of the compressor <NUM>. An outlet valve (e.g., the valve <NUM> between the back gas supply <NUM> and gas bearing(s) <NUM>) can be used to open and control discharge of the compressed gaseous working fluid from the vessel 61A to the gas bearing(s).

In an embodiment, the backup gas supply <NUM> may include a second compressor 61B smaller than the compressor <NUM> which is operable to provide compressed gaseous working fluid to the gas bearing(s) <NUM>. In an embodiment, the backup gas supply <NUM> may include a pump for pumping compressed working fluid (e.g., liquid working fluid) to the gas bearing(s) <NUM>.

In an embodiment, the backup gas supply <NUM> may include a condenser valve 61C that fluidly connects the condenser <NUM> to the compressor bearing(s) <NUM>. For example, the condenser valve 61C fluidly connects to the condenser <NUM> between its inlet <NUM> and its outlet <NUM>. The opened condenser valve 61C is configured to supply pressurized working fluid within the condenser <NUM> to the gas bearing(s) <NUM>. In such an embodiment, the controller <NUM> upon sensing a utility power interruption can be configured to close valve(s) in the main flow path <NUM> to prevent depletion of the pressurized working fluid from the condenser <NUM> until supplied to the gas bearing(s) <NUM> (e.g., closing a valve 35A to stop flow through the inlet <NUM> of the condenser <NUM>, closing a valve 35B to stop flow through the outlet <NUM> of the condenser <NUM> to the expander <NUM> and/or the expander <NUM> being an electronic expansion valve that is closed to stop flow from the outlet <NUM> through the expander <NUM>, or the like).

In an embodiment, the backup gas supply may include a vessel with an electric heater 61D that is charged with liquid or a mixture of liquid and gaseous working fluid (e.g., charged with the liquid and/or gaseous working fluid from the condenser <NUM>, or the like). The heater is powered to heat/vaporize the liquid within the vessel and provide compressed working fluid to the gas bearing(s) <NUM>. The vessel with an electric heater 61D may be charged with working fluid during normal operation.

In an embodiment, to conserve power during a utility power interruption, the backup gas supply <NUM> may include the condenser valve 61C in combination with the second compressor 61B or the vessel with a heater 61D. For example, the controller <NUM> configured to supply pressurized working fluid to the gas bearing(s) <NUM> by using the available compressed gas within the condenser <NUM>, and then powering a second compressor 61A or a vessel with an electric heater 61D to generate the compressed working fluid (e.g., compressed gas). The controller <NUM> powers the secondary compressor 61A or the electric heater of the vessel with the electric heater 61D to generate compressed working fluid once the pressurized gaseous working fluid stored in the condenser <NUM> is consumed (e.g., gaseous working fluid stored in the condenser <NUM> is no longer at a sufficient pressure for operating the gas bearing(s) <NUM>).

One or more valve(s) <NUM> (e.g., outlet valve, flow control valve, check valve, or the like) can be utilized to ensure that the compressed gaseous work fluid discharged from backup gas supply <NUM> flows to the gas bearing(s) <NUM>.

In an embodiment, the backup gas supply <NUM> may be used to supply pressurized working fluid to the gas bearing(s) <NUM> during startup and/or shutdown of the compressor <NUM>. For example, during the startup of the compressor <NUM>, the controller <NUM> operates the backup gas supply <NUM> to supply compressed working fluid from the backup gas supply <NUM> to the gas bearing(s) <NUM> until the gas discharged from the outlet <NUM> of the compressor <NUM> is at a predetermined pressure (e.g., at a pressure sufficient for the gas bearing(s) to levitate the driveshaft of the compressor <NUM>).

The heat transfer circuit <NUM> includes an electrical power supply system <NUM>. The electrical power supply system <NUM> is configured to supply for supplying electrical power to the electrical components for operating the heat transfer circuit <NUM>. For example, the electrical components for operating the heat transfer circuit can include, but not limited to, a motor <NUM> of the compressor <NUM>, the valve(s) <NUM>, the controller <NUM>, fan(s), sensor(s), and the like). For simplicity, "power" as described hereafter refers to "electrical power" unless specified otherwise.

<FIG> is block diagram of an electrical power supply system <NUM> for a compressor of a heat transfer circuit. For example, the electrical power system <NUM> may be the electrical power system <NUM> in <FIG>. The heat transfer circuit includes a compressor <NUM> that compresses the working fluid that flows flow through the heat transfer circuit. The dashed-dotted arrows in <FIG> indicate the flow of electricity when utility power P<NUM> is flowing and is being supplied to the electrical power system <NUM>. For example, the compressor <NUM> in <FIG> is being powered using utility power P<NUM>. This can be referred to as a "utility power mode" or a "normal operation" of the electrical power system <NUM>. <FIG> illustrates the electrical power system <NUM> in the utility power mode. The electrical power system <NUM> supplies/provides electrical power to the electrical components of the heat transfer circuit.

The compressor <NUM> includes a permanent magnet motor <NUM>, a compression mechanism <NUM> (e.g., intermeshed screw, scroll, impeller, or the like), a driveshaft <NUM>, gas bearing(s) <NUM> (e.g., gas bearings <NUM> in <FIG>, or the like), and a variable frequency drive ("VFD") <NUM>. The electrical power system <NUM> includes the VFD <NUM>. The compression mechanism <NUM> is mounted to the driveshaft <NUM>. The electrical power system <NUM> powers the motor <NUM> by the VFD <NUM> supplying AC power P<NUM> to the motor <NUM>. The motor <NUM> operates using known principles to rotate the driveshaft <NUM>. The AC power P<NUM> powers the motor <NUM> to rotate the driveshaft <NUM> which rotates/orbits the affixed compression mechanism <NUM> to compress the working fluid. In an embodiment, the AC power P<NUM> supplied by the inverter <NUM> is multiphase AC power (e.g., three-phase AC power, or the like). The AC power P<NUM> supplied from the VFD <NUM> to the motor <NUM> can also be referred to as motor input power. The controller <NUM> controls the VFD <NUM> and adjusts the speed of the motor <NUM> by controlling the frequency of the motor input power P<NUM> supplied by the VFD <NUM> to the motor <NUM>. The use of the VFD <NUM> allows the motor <NUM> to be a variable speed motor.

The rotating driveshaft <NUM> is supported by the gas bearing(s) <NUM>. The gas bearing(s) <NUM> are aerostatic gas bearing(s) that provide support by utilizing an incoming flow of compressed gas F<NUM>. An aerostatic gas bearing relies upon the incoming flow of compressed gas to maintain the levitation of the driveshaft. The aerostatic bearing is unable to keep the driveshaft levitated when not being supplied with the flow of compressed gas (e.g., the aerostatic gas bearing without the incoming compressed gas cannot maintain the layer of pressurized gas that prevents solid contact between the driveshaft and the aerostatic gas bearing). As shown in <FIG>, in the utility power mode, the flow of compressed gas F<NUM> supplied to the gas bearing(s) <NUM> is a portion of the working fluid compressed by the compressor <NUM>.

Generally, utility power P<NUM> is supplied to the electrical power system <NUM>. In an embodiment, the utility power P<NUM> is multiphase AC electrical power (e.g., three-phase AC electrical power, or the like). The utility power P<NUM> is used by the electrical power system <NUM> to supply electrical power to each electrical component of the heat transfer circuit at its specified type and voltage (e.g., 24V DC, 120V AC, and the like). The VFD <NUM> receives utility power P<NUM> and converts the utility power P<NUM> into the motor input power P<NUM>. In an embodiment, the voltage of the utility power P<NUM> is about 690V or less.

In an embodiment, the VFD <NUM> includes a rectifier <NUM>, a DC link <NUM>, and an inverter <NUM>. The rectifier <NUM>, DC link <NUM>, and the inverter <NUM> are electrically connected in series in the VFD <NUM>. For example, the DC link <NUM> electrically connects the output of the rectifier <NUM> to the input of the inverter <NUM>. The rectifier <NUM>, DC link <NUM>, and inverter <NUM> converts the utility power P<NUM> into the motor input power P<NUM>. The rectifier <NUM> of the VFD <NUM> receives the utility power P<NUM>. The rectifier <NUM> converts the AC three-phase power P<NUM> into DC power P<NUM> which is supplied to the DC link <NUM>. The DC link <NUM> filters/smooths the voltage of DC power P<NUM> received from the rectifier <NUM> and outputs filtered DC power P<NUM>. The filtered DC power P<NUM> is supplied from the DC link <NUM> to the inverter <NUM>. The filtered DC power P<NUM> supplied to the inverter <NUM> is converted by the inverter <NUM> into the AC motor input power P<NUM> which is supplied from VFD to the motor <NUM>. The inverter <NUM> of the VFD <NUM> supplies the motor input power P<NUM> to motor <NUM>.

The electrical power system <NUM> includes a switch-mode power supply <NUM> that is electrically connected to the VFD <NUM>. The switch-mode power supply <NUM> is electrically connected between the rectifier <NUM> and the inverter <NUM>. In the illustrated embodiment, the switch-mode power supply <NUM> is electrically connected after the rectifier <NUM> and before the inverter <NUM> within the VFD <NUM>. For example, the inlet <NUM> of the switch-mode power supply <NUM> is connected after the rectifier <NUM> and before the inverter <NUM> within the VFD <NUM>. In another embodiment, the switch-mode power supply <NUM> may be electrically connected after the rectifier <NUM> and before the DC link <NUM>. For example, the inlet <NUM> of the switch-mode power supply <NUM> is connected after the rectifier <NUM> and before the DC link <NUM> within the VFD <NUM>.

The HVACR system can include other various electrical components used in operating the heat transfer circuit. An electrical power load <NUM> is the electrical power consumed in the activating/operating of the other electrical components. Examples of such electrical components can include, but not limited to, controller <NUM> (e.g., controller <NUM> in <FIG>, or the like), solenoid(s) 106A, valve(s) 106B (e.g., valve(s) <NUM>, or the like), actuators 106C, a backup gas supply <NUM> (e.g., backup gas supply <NUM> in <FIG>, or the like), fan(s) (e.g., evaporator fan, condenser fan, etc.), and/or sensor(s) (e.g., temperature sensor(s), pressure sensor(s), and the like). It should be appreciated that the electrical power load <NUM> can vary based on how the heat transfer circuit is operating (e.g., operating at maximum capacity, operating at minimum capacity, operating in a defrost mode, operating in a ventilation mode, and the like). The electrical power system <NUM> supplies power P<NUM> to meet the electrical load <NUM> of the other electrical components.

In the illustrated embodiment, the electrical power system <NUM> includes a utility power supply <NUM>. The utility power supply <NUM> receives utility power P<NUM> and supplies power P<NUM> to power the other electrical components for operating the heat transfer circuit. The utility power supply <NUM> supplies power P<NUM> that meets the electrical load <NUM>. The utility power supply <NUM> can supply electrical power for each electrical component of the heat transfer circuit at its specified type and voltage. In an embodiment, the power P<NUM> supplied by utility power supply <NUM> can include DC power (e.g., 24V DC power, or the like) for the DC powered electrical components and/or AC power (e.g., 120V AC power, or the like) for the AC powered electrical components. In another embodiment, the switch-mode power supply <NUM> may be configured to supply the power P<NUM> for the electrical load <NUM> in the utility power mode. In such a configuration, the electrical power system <NUM> may not include the utility power supply <NUM> (e.g., the utility power supply <NUM> being incorporated into the switch-mode power supply <NUM>, etc.) The switch-mode power supply <NUM> can be configured to utilize the utility power P<NUM> directly (e.g., the switch-mode power supply <NUM> receives the utility power P<NUM>) or indirectly via the VFD <NUM> (e.g., the switch-mode power supply <NUM> receiving the DC electrical power from DC link <NUM>).

In some instances, the flow of utility power P<NUM> to the utility power system <NUM> can be interrupted (e.g., a building power outage, a utility transmission line outage, a power plant outage, and the like). The utility power system <NUM> is configured to operate in a backup power mode when the utility power P<NUM> is interrupted. For example, the utility power system <NUM> starts operating in the backup power mode when the utility power system <NUM> unexpectedly stops receiving utility power P<NUM>. In the backup power mode, utility power is not being supplied to the utility power system <NUM>.

<FIG> illustrates the electrical power supply system <NUM> when operating in the backup power mode. The backup power mode does not utilize a battery backup (e.g., an uninterrupted power supply, or the like). When the utility power is interrupted, the VFD <NUM> stops powering the permanent magnet motor <NUM> (e.g., no power is being supplied from the VFD <NUM> to the motor <NUM>). When electrical power is suddenly no longer being provided to supplied to the motor <NUM>, the back electromotive force from the permanent magnet motor <NUM> causes the permanent magnet motor <NUM> to generate and supply electrical power P<NUM> to the VFD <NUM>. The back electromotive force results from the interaction of the still rotating driveshaft <NUM> (e.g., the still rotating rotor affixed to the driveshaft <NUM>) and the motor <NUM>. For example, the back electromotive force causes the permanent magnetic motor <NUM> to temporary operate as an electrical generator. The voltage of the electrical power P<NUM> generated via the electromotive force varies with the speed of the still rotating driveshaft <NUM>. The amount of electrical power P<NUM> decreases as the speed/rotation of the driveshaft <NUM> slows down. For example, the voltage of the electrical power P<NUM> generated by the motor <NUM> is at a maximum voltage when a utility power interruption occurs and then decreases as the rotation of the driveshaft <NUM> slows down.

The inverter <NUM> is configured to convert DC electrical power into AC electrical power in the forward direction (e.g., convert DC electrical power into three-phase AC electrical power during normal operation) and to convert AC electrical power into DC electrical power in the reverse direction (convert the multiphase AC electrical power into DC electrical power during the backup power mode). For example, the motor supplies the multiphase AC power P<NUM> (e.g., three-phase AC power, or the like) to the inverter <NUM> which converts the multiphase AC power P<NUM> into DC power P<NUM>. The voltage of the DC power P<NUM> generated in the VFD <NUM> from the back electromotive force of the motor <NUM> is at least 200V. In an embodiment, the voltage of the DC power P<NUM> is at least 400V. In an embodiment, the voltage of the DC power P<NUM> is at least 600V. For example, the voltage of the DC power P<NUM> may be at or about 650V.

In the backup power mode, the switch-mode power supply <NUM> utilizes the DC power P<NUM> generated in the VFD <NUM> from the motor <NUM>. The switch-mode power supply <NUM> is electrically connected to the VFD <NUM> such the VFD <NUM> supplies the generated DC power P<NUM> to the switch-mode power supply. The DC power P<NUM> is supplied from the inverter <NUM> to the switch-mode power supply <NUM>. The switch-mode power supply <NUM> utilizes the DC power P<NUM> to supply power P<NUM>, P<NUM> to electrical components used for operating the heat transfer circuit. In particular, the DC power P<NUM> generated by motor <NUM> and inverter <NUM> has a voltage that is higher than the voltage used by the electrical components for controller operation of the compressor <NUM>. For example, the DC power P<NUM> can have a voltage over 600V while the electrical components use voltage(s) that are below 150V. The switch-mode power supply <NUM> is configured to convert the DC power P<NUM> to electrical power with a lower voltage (e.g., a voltage reduction of at least <NUM>%). The higher and lower voltage may be significantly different. In an embodiment, the switch-mode power supply <NUM> converts the DC electrical power P<NUM> to DC electrical power P<NUM> (e.g., 24V DC electrical power, or the like). In some embodiments, the switch-mode power supply <NUM> converts the DC electrical power P<NUM> to the DC electrical power P<NUM> and AC electrical power P<NUM> (e.g., 120V AC electrical power, or the like).

The electrical load <NUM> can include a DC load 103A and/or an AC load 130B. In an embodiment, the DC load 103A is for powering DC powered component(s) used in controlling operation of the compressor <NUM>. In an embodiment, the AC load 103B is for powering AC powered component(s) used in controlling operation of the compressor <NUM>. For example, the DC load 103A and/or the AC load 103B may be limited to only electrical component(s) that are critical for compressor control to conserve the limited amount of electrical power P<NUM> available from the motor <NUM>. The switch-mode power supply <NUM> supplies DC power P<NUM> to power the DC load 103A and/or AC power P<NUM> to power the AC load 103B.

In particular, the switch-mode power supply <NUM> supplies electrical power P<NUM>, P<NUM> to activate/operate the backup gas supply <NUM> to provide a flow of compressed gas F<NUM> to the gas bearing(s) <NUM> of the compressor <NUM>. For example, the switch-mode power supply <NUM> provides DC power P<NUM> to power the controller <NUM>. The controller <NUM> is configured to active/operate the backup gas supply <NUM>. For example, the switch-mode power supply <NUM> provides AC power P<NUM> for activating/operating the backup gas supply <NUM>.

In another embodiment, the backup gas supply <NUM> includes a vessel (e.g., vessel 61A in <FIG>, or the like) containing compressed working fluid. The vessel is charged with compressed gaseous working fluid during normal operation of the compressor <NUM>. In such an embodiment, the valve(s) 106B can include a flow control valve for controlling the flow output of the vessel. When a power interruption occurs, the switch-mode power supply <NUM> provides electrical power P<NUM>, P<NUM> sufficient for operating the vessel to provide compressed working fluid F<NUM> to gas bearing(s) <NUM>. For example, the switch-mode power supply <NUM> supplies electrical power P<NUM>, P<NUM> to power the controller <NUM> and the flow control valve for the vessel. The controller <NUM> detects that a utility power interruption is occurring and opens the flow control valve to supply the compressed working fluid F<NUM> to the gas bearings <NUM>. In some embodiments, the controller <NUM> may also activate one or more of the other valves(s) 106B (e.g., valves <NUM> in <FIG>, or the like) so that the compressed working fluid F<NUM> correctly flows from the vessel to the gas bearing(s) <NUM> (e.g., flows from the backup gas supply <NUM> to the gas bearing(s) <NUM>).

In one embodiment, the backup gas supply <NUM> includes a secondary compressor (e.g., secondary compressor 61B in <FIG>, or the like) that compresses working fluid and provides the compressed working fluid to the gas bearing(s) <NUM> during the backup power supply mode. The secondary compressor of the backup gas supply <NUM> being smaller than the main compressor <NUM>. When a power interruption occurs, the switch-mode power supply <NUM> provides electrical power P<NUM>, P<NUM> to power the second compressor to provide a flow of compressed working fluid F<NUM> to the gas bearing(s) <NUM>. For example, the switch-mode power supply <NUM> supplies DC electrical power P<NUM> to power the controller <NUM> and AC electrical power P<NUM> for powering the second compressor (e.g., for operating the motor of the second compressor). The controller <NUM> detects that a utility power interruption is occurring and activates the second compressor to begin compressing working fluid and provide the flow of compressed working fluid F<NUM> to the gas bearings <NUM>. In some embodiments, the controller <NUM> also activates one or more of the valves(s) 106B (e.g., valves <NUM> in <FIG>, or the like) so that the compressed working fluid F<NUM> correctly flows from the second compressor to the gas bearing(s) <NUM> (e.g., flows from the backup gas supply <NUM> to the gas bearing(s) <NUM> in <FIG>, doesn't flow into the outlet of the compressor <NUM>, doesn't flow into the condenser, or the like).

In another embodiment, the backup gas supply <NUM> include a vessel with a heater (e.g., vessel with a heater 61D in <FIG>, or the like) for containing liquid and/or gaseous working fluid. The vessel can be charged with liquid and/or gaseous working fluid during normal operation of the compressor <NUM>. In such an embodiment, the valve(s) 106B may include a flow control valve for controlling the flow output of the vessel. When a power interruption occurs, the switch-mode power supply <NUM> provides electrical power P<NUM>, P<NUM> sufficient for operating the vessel and its heater to provide compressed working fluid F<NUM> to the gas bearing(s) <NUM>. For example, the switch-mode power supply <NUM> supplies electrical power P<NUM>, P<NUM> to power the controller <NUM>, to power the heater, and to power the flow control valve for the vessel. The heater heats the liquid and/or gaseous working fluid within the vessel to generate compressed working fluid within the vessel. For example, the powered heater vaporizes liquid working fluid in the vessel to generate compressed gaseous working fluid within the vessel which is then supplied to the gas bearing(s) <NUM>). The controller <NUM> detects that a utility power interruption is occurring, turns on the heater to generate the compressed working fluid within the vessel, and opens the flow control valve to supply the generated compressed working fluid F<NUM> from the vessel to the gas bearings <NUM>. In some embodiments, the controller <NUM> may also activate one or more of the other valves(s) 106B (e.g., valves <NUM> in <FIG>, or the like) so that the compressed working fluid F<NUM> correctly flows from the vessel to the gas bearing(s) <NUM> (e.g., flows from the backup gas supply <NUM> to the gas bearing(s) <NUM>. In an embodiment, the backup gas supply <NUM> may include a condenser valve (e.g., condenser valve 61C in <FIG>, or the like) that fluidly connects a condenser of the heat transfer circuit (e.g., condenser <NUM> in <FIG>, or the like) to the gas bearing(s) <NUM>. When a power interruption occurs, the switch-mode power supply <NUM> provides electrical power P<NUM>, P<NUM> sufficient for the controller <NUM> to activate the condenser valve (e.g., open/operate the condenser valve) to supply compressed working fluid F<NUM> to the gas bearing(s) <NUM>. The condenser valve of the backup gas supply <NUM> supplies a flow of compressed working fluid contained in the condenser to the gas bearing(s) <NUM>. In some embodiments, when a power interruption occurs, the controller <NUM> can also be configured to close valve(s) in the main flow path of the heat transfer circuit (e.g., main flow path <NUM> in <FIG>, or the like) to prevent depletion of the pressurized working fluid from the condenser <NUM> until supplied to the gas bearing(s) <NUM> (e.g., close valve 35A, close valve 35B, the expander <NUM> being an electronic expansion valve that is closed to stop flow from the outlet <NUM> through the expander <NUM>, or the like).

In an embodiment, to conserve power during a utility power interruption, the backup gas supply <NUM> may include the condenser valve or the charged vessel in combination with the second compressor or the vessel with a heater. For example, the controller <NUM> configured to supply pressurized working fluid to the gas bearing(s) <NUM> by using the available compressed gas within the condenser and/or the charged vessel, and then powering a second compressor 61A and/or a vessel with an electric heater to generate the additional compressed working fluid (e.g., compressed gas). The controller <NUM> is configured to operate the secondary compressor and/or the electric heater to generate compressed working fluid once the pressurized gaseous working fluid stored in the condenser is consumed (e.g., gaseous working fluid stored in the condenser <NUM> is no longer at a sufficient pressure for operating the gas bearing(s) <NUM> in <FIG>, the gaseous working fluid in the condenser is less than a predetermined pressure).

In the backup power mode, the backup gas supply <NUM> is powered and operates to supply the flow of compressed working fluid F<NUM> to the gas bearing(s) <NUM> of the compressor <NUM>. The utility power system <NUM> is configured so as to maintain the flow of compressed gas to the gas bearing(s) <NUM> when a utility power interruption occurs. This advantageously allows the rotating driveshaft <NUM> to slow down/stop before contacting the gas bearing(s) <NUM>, or the gas bearing(s) <NUM> to maintain their support/levitation of the driveshaft <NUM> by the gas bearing(s) <NUM> during a short utility power interruption.

<FIG> is a block flow diagram of a method <NUM> of controlling an electrical power supply system of a heat transfer circuit. In an embodiment, the method <NUM> may be applied to the electrical power supply system <NUM> of the heat transfer circuit <NUM> in <FIG> and/or the electrical power supply system <NUM> in <FIG> and <FIG>. The method <NUM> begins at <NUM>.

At <NUM>, the electrical power system operates in a utility power mode. For example, the electrical power system <NUM> in <FIG> is operating in the utility power mode. The utility power mode utilizes utility power (e.g., utility power P<NUM>) to electrically power the electrical components of the heat transfer circuit. As shown in <FIG>, operating in the utility power mode <NUM> includes <NUM> - <NUM> for operation of a compressor of the heat transfer circuit (e.g., compressor <NUM>, compressor <NUM>).

At <NUM>, the utility power is received by a variable frequency drive (VFD) of the compressor (e.g., VFD <NUM>). At <NUM>, the VFD uses the utility power to supply the electrical power (e.g., electrical power P<NUM>) to an electric motor of the compressor (e.g., permanent magnet motor <NUM>, permanent magnet motor <NUM>). As discussed above, the VFD can include a rectifier (e.g., rectifier <NUM>), DC link (e.g., DC link <NUM>), and an inverter (e.g., inverter <NUM>) in series to convert the utility power to the electrical power supplied to the motor. At <NUM>, the electric motor is powered by the supplied electrical power from the VFD. The powered electric motor rotates a driveshaft (e.g. driveshaft <NUM>) to compress the working fluid in the heat transfer circuit. In particular, the driveshaft is affixed to a compression mechanism (e.g., compression mechanism <NUM>) and the rotating of the driveshaft moves the coupled compression mechanism to compress the working fluid. At <NUM>, a flow of the compressed working fluid (e.g., flow of compressed working fluid F<NUM>, flow of compressed working fluid F<NUM>) is provided to the gas bearing(s) of the compressor (e.g., gas bearing gas bearing(s) <NUM>). A portion of the compressed working fluid is supplied to the gas bearing(s). The gas bearing(s) utilize the compressed working fluid to support the rotating driveshaft.

Operating in the utility power mode <NUM> can also include a power supply (e.g., utility power supply <NUM>, switch-mode power supply <NUM>) supplying electrical power (e.g., electrical power P<NUM>) to other electrical components of the heat transfer circuit <NUM>. For example, supplying electrical power to other electrical components <NUM> can include the power supply (e.g., utility power supply <NUM>) receiving the utility power (e.g., utility power P<NUM>) and supplying DC electrical power and/or the AC electrical power to meet the electrical load of the other electrical components (e.g., electrical load <NUM>). For example, supplying electrical power to the other electrical components <NUM> can include the power supply (e.g., switch-mode power supply <NUM>) receiving DC electrical power generated by the VFD (e.g., the DC electrical power supplied from the DC Link <NUM>) and supplying the DC electrical power and/or the AC electrical power to meet the electrical load of the other electrical component(s). The method <NUM> then proceeds to <NUM>.

At <NUM>, the electrical power system operates in a backup power mode. For example, the electrical power system <NUM> in <FIG> is operating in the backup power mode. The backup power mode occurs when the flow of utility power is interrupted. The electrical power system switches from the utility power mode to the backup power mode when the utility power is no longer being supplied to the electrical power system. The backup power mode utilizes electrical power generated by the back electromotive force of the motor (e.g., electrical power P<NUM>) to electrically power electrical components of the heat transfer circuit. In particular, the backup power mode utilizes the back electromotive force generated electric power to ensure that the feed of compressed gas to the gas bearing(s) does not suddenly stop while the driveshaft is still rotating (e.g., prevents the power interruption from causing failure of the gas bearing(s) due to no longer being fed compressed gas).

Operating the electrical power system in the backup power mode <NUM> includes <NUM>, <NUM>, <NUM>, and <NUM>. At <NUM>, DC electrical power generated in the VFD by the back electromotive force (e.g., DC electrical power P<NUM>) is supplied to a switch-mode power supply (e.g., switch-mode power supply <NUM>). Supplying the DC electrical power <NUM> can include the inverter of the VFD receiving from the motor the AC electrical power generated by the motor's back electromotive force (e.g., electrical power P<NUM>), and the inverter converting into the DC electrical power. The method <NUM> then proceeds from <NUM> to <NUM>.

At <NUM>, the DC electrical power supplied from the VFD to the switch-mode power supply is utilize to operate a backup gas supply (e.g., and provide compressed fluid to the gas bearing(s). Utilizing the DC electrical power to operate the backup gas supply at <NUM> can include the switch-mode power supply supplying DC electrical power (e.g., DC electrical power P<NUM>) to DC powered electrical component(s) of the heat transfer circuit <NUM>. In particular, the switch-mode power supply supplying the DC electrical power to DC powered electrical component(s) at <NUM> includes supplying DC electrical power to a controller of the heat transfer circuit (e.g., controller <NUM>, controller <NUM>). The powered controller can activate the backup gas supply to begin the flow of the compressed fluid (e.g., compressed fluid F<NUM>) from the backup gas supply to the gas bearing(s). In an embodiment, the backup gas supply can be a second smaller compressor, and the powered controller can initiate the startup of the second smaller compressor. In another embodiment, the backup gas supply can be a vessel containing compressed working fluid, and the powered controller can open an outlet valve for the vessel so the compressed working fluid flows from the vessel to the gas bearing(s).

Utilizing the DC electrical power to operate the backup gas supply <NUM> can include the switch-mode power supply supplying AC electrical power (e.g., AC electrical power P<NUM>) to AC powered electrical component(s) of the heat transfer circuit <NUM>. In particular, the switch mode power supply supplies AC electrical power <NUM> to AC electrical components used for operating/activating the backup gas supply. For example, in an embodiment in which the backup gas supply is a second smaller compressor, supplying the AC electrical power at <NUM> can include supplying the AC electrical power to the power the second smaller compressor (e.g., AC electrical power for powering the motor of the second smaller compressor). For example, in an embodiment in which the backup gas supply is a vessel containing compressed working fluid, supplying the AC electrical power at <NUM> can include supplying the AC electrical power to power the valve(s) for directing the working fluid from the outlet of the vessel to the gas bearing(s) (e.g., valve(s) <NUM>, valve(s) 106B). The method <NUM> then proceeds to <NUM>.

At <NUM>, when the utility power is restored (e.g., the utility power flows to the electrical power supply system after being interrupted, the utility power interruption ends, etc.), the method <NUM> returns to operating in the utility power mode at <NUM>. In returning to the utility power mode <NUM>, the method can include resetting any adjustments to the heat transfer circuit made by operating in the backup power mode. For example, shutting down the second smaller compressor used to supply compressed working fluid to the gas bearing(s) at <NUM> in an embodiment. For example, opening and/or closing valves to recharge the vessel used to supply compressed working fluid to the gas bearing(s) at <NUM> in another embodiment. If utility power is still interrupted, the method <NUM> proceeds to <NUM>.

At <NUM>, the controller compares the length of the utility power interruption to a predetermined time period. If the utility power interruption is shorter than the predetermined time period, the method <NUM> returns to <NUM>. For example, when the utility power interruption is shorter than the predetermined time period at <NUM>, the electrical power system continues its utilization of the back electromotive force generated electrical power to have the backup gas supply provide the flow of compressed gas to the gas bearing(s). If the utility power interruption is equal to or longer than the predetermined time period, then the method <NUM> proceeds to <NUM>. The predetermined time period can be amount of time that indicates that a utility power interruption is a significant power outage (e.g., a building power outage, a utility transmission line outage, a power plant outage, etc.). The predetermined time period may be based on the amount of time the backup gas supply is able to supply compressed gas to the gas bearing(s) (e.g., length of time until the vessel is empty, length of time that the electromotive force generates power sufficient to power the second smaller compressor, or the like). At <NUM>, the controller initiates a shutdown of the compressor. The shutdown of the compressor at <NUM> can include the shutdown of heat transfer circuit. In an embodiment, the shutdown of the compressor at <NUM> includes the adjustments made during a normal shutdown of the compressor (e.g., closing the vanes of the compressor, closing a solenoid valve(s) in the heat transfer circuit to perform a pump down, etc.).

In an embodiment, the controller at <NUM> may be configured to initiate the shutdown when the electrical power generated by the back electromotive force (e.g., electrical power P<NUM> supplied from the motor <NUM>, electrical power P<NUM> generated in the VFD <NUM>) decreases to a predetermined amount (e.g., a predetermined voltage, or the like). For example, the controller initiates the shutdown of the compressor when the voltage of the electrical power generated by the back electromotive force is at a predetermined voltage threshold (e.g., the voltage of the electrical power P<NUM>, the voltage of the electrical power P<NUM>, or the like). The electrical power system may include an electrical power sensor (e.g., a voltage sensor, a current sensor, or the like) that is utilized by the controller to detect the voltage of the electrical power generated by the back electromotive force. The predetermined amount/voltage threshold can be based on the minimum amount of power needed for completing the shutdown of the compressor. In such an embodiment, <NUM> in the illustrated embodiment of <FIG> may be replaced with comparing electrical power generated by the back electromotive force (e.g., electrical power P<NUM> supplied from the motor <NUM>, electrical power P<NUM> generated in the VFD <NUM>) to a predetermined threshold (e.g., a predetermined voltage, or the like). For example, when the amount of electrical power generated by the back electromotive force (e.g., the present voltage of the electrical power P<NUM>, the present voltage of the electrical power P<NUM>, or the like) equal to or greater than a predetermined power threshold (e.g., a predetermined voltage threshold), the method <NUM> goes back to <NUM>. For example, when the amount of electrical power generated by the back electromotive force is less than the predetermined power threshold, the method <NUM> proceeds to <NUM> at which the controller initiates the shutdown of the compressor.

The method <NUM> can allow for the heat transfer circuit and the compressor to be shut down in a normal manner when an interruption in the utility power occurs unexpectedly without utilizing a battery backup, such as an uninterrupted power supply. This advantageously prevents the high speed rotating driveshaft from contacting and damaging the gas bearing(s) during an unexpected power outage. The method <NUM> can advantageously provide for a faster restart time as the heat transfer circuit is in a known shutdown state (e.g., can startup from a known shutdown instead of a diagnostic startup to account for pressure(s) and component(s) being left in an unknown state).

It should be appreciated that the method <NUM> in an embodiment may be modified based on the heat transfer circuit <NUM> as shown in <FIG> and/or the electrical power system <NUM> in <FIG> and <FIG> and as discussed above.

It should be appreciated that that heat transfer circuit <NUM>, the compressor for compressing working fluid in a heat transfer circuit (e.g., compressor <NUM>, compressor <NUM>), the electrical power supply system <NUM> for a compressor of a heat transfer circuit, and the method <NUM> of controlling an electrical power supply system of a heat transfer circuit as described herein may be modified in other embodiments to be for a climate controlled transport unit. For example, in an embodiment, the utility power and the utility power mode as described above can instead be internal electrical power and an internal power mode. In the internal power mode, an internal power source of the climate controlled transport unit (e.g., an internal combustion engine and generator, a battery, or the like) supplies the electrical power to power the electrical components for the heat transfer circuit. For example, in an embodiment, an internal combustion engine (e.g., diesel engine, or the like) can drive a generator which supplies the electrical power in the internal power mode, and the backup power mode is used when the engine and generator unexpectedly stop generating and supplying electrical power. For example, a battery (e.g., a battery pack, a single battery, or the like) supplies the electrical power in the internal power mode, and the backup power mode is used when the battery unexpectedly stops supplying electrical power.

The terminology used in this specification is intended to describe particular embodiments and is not intended to be limiting. The terms "a," "an," and "the" include the plural forms as well, unless clearly indicated otherwise. The terms "comprises" and/or "comprising," when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or components. The use of "(s)" as applied herein is intended to mean "one or more" of the corresponding feature.

Claim 1:
A compressor (<NUM>; <NUM>) for compressing a working fluid in a heat transfer circuit (<NUM>), comprising:
a variable frequency drive (VFD) (<NUM>) configured to utilize utility power (P<NUM>);
a motor electrically connected to the VFD, the motor configured to rotate a driveshaft (<NUM>) and
one or more gas bearings (<NUM>; <NUM>) to support the driveshaft;
characterized in that
the motor is a permanent magnet motor (<NUM>; <NUM>);
a backup gas supply (<NUM>; <NUM>) is fluidly connected to the one or more gas bearings; and
a switch-mode power supply (<NUM>) is electrically connected to the VFD,
wherein during an interruption in the utility power, the switch-mode power supply is configured to utilize DC electrical power (P<NUM>) generated by a back electromotive force of the permanent magnet motor to operate the backup gas supply to provide a flow (F<NUM>) of compressed working fluid to the one or more gas bearings.