Methods are directed towards dynamically determining refrigerant film thickness at the rolling-element bearing and for dynamically controlling refrigerant film thickness at the rolling-element bearing. Further, an oil free chiller system is configured for dynamically determining refrigerant film thickness at the rolling-element bearing of the oil free chiller system, wherein the oil free chiller system is also configured for dynamically controlling refrigerant film thickness at the rolling-element bearing of the oil free chiller system.

Method for protecting an electric motor of a motor driven consumer equipped with a controller for controlling the capacity or the power of the consumer, comprises the following steps: the determination of the thermal condition of the motor by direct measurement on the motor; and the limitation of the maximum capacity or the maximum power of the consumer as a function of the aforementioned determined thermal condition.

Systems and methods are provided and include a compressor for a refrigeration system and a duct assembly that includes a duct frame and a sensor unit. The duct frame provides a path for evaporating refrigerant from a lubricant sump of the compressor. The sensor unit obtains temperature measurements of the refrigerant and a lubricant within the lubricant sump and heats and evaporates the refrigerant located within the duct frame of the duct assembly. A control module receives temperature measurements from the sensor unit, determines a presence of liquid refrigerant within the lubricant sump of the compressor in response to a determination that an actual temperature change does not correspond with an expected temperature change for the lubricant, and in response to a determination that the actual temperature change corresponds with the expected temperature change for the lubricant, operates the compressor.

An inverter control device that controls an inverter unit that converts a DC voltage from a converter unit to an AC voltage and supplies the AC voltage to the DC motor includes a storage unit that stores therein information regarding a synchronization-loss limit; a synchronization-loss limit-current calculation unit that calculates the limitation value on the synchronization-loss limit current on the basis of the magnet temperature of the DC motor, the bus voltage to be applied to the inverter unit, and the information regarding a synchronization-loss limit; and a control unit that compares the primary current to be input to the converter unit with the limitation value and that, when the primary current exceeds the limitation value, outputs an adjustment command to adjust the operating frequency of the DC motor such that the primary current becomes equal to or less than the limitation value.

A method for controlling an economizer circuit is provided. The economizer circuit includes a valve to regulate refrigerant flow between the economizer and the compressor. The valve can be opened to engage the economizer circuit or closed to disengage the economizer circuit based on the output frequency provided to the compressor motor by a variable speed drive and an operating condition of the economizer.

Systems and methods for controlling a cooling circuit for a variable frequency drive (VFD) in an HVACR system are disclosed. The method includes determining, by a controller, an operating condition of a heat sink associated with the VFD. The controller determines whether a temperature of the heat sink is greater than or equal to a heat sink temperature threshold. The method further includes enabling a bypass flow control device in response to the heat sink temperature being greater than or equal to the heat sink temperature threshold.

A vapor compression system includes a primary loop and a secondary loop. The primary loop includes a dynamic compressor operable to compress a refrigerant, a condenser fluidly connected to the dynamic compressor, a first expansion device fluidly connected to the condenser, and an evaporator fluidly connected to the first expansion device and the dynamic compressor. The dynamic compressor includes a housing, a shaft supported in the housing by a bearing, an impeller connected to the shaft, a motor operably connected to the shaft to drive rotation thereof, and a drive operable to control the motor. The secondary loop includes a second expansion device fluidly connected to the condenser, a heat exchanger fluidly connected to the second expansion device, the condenser, and the dynamic compressor, and a supply duct fluidly connected between the heat exchanger and the dynamic compressor to provide a flow of refrigerant to the bearing.

Methods are directed towards dynamically determining refrigerant film thickness at the rolling-element bearing and for dynamically controlling refrigerant film thickness at the rolling-element bearing. Further, an oil free chiller system is configured for dynamically determining refrigerant film thickness at the rolling-element bearing of the oil free chiller system, wherein the oil free chiller system is also configured for dynamically controlling refrigerant film thickness at the rolling-element bearing of the oil free chiller system.

A system may include first and second compressors, first and second heat exchangers, a flash tank, and first, second and third fluid paths. The first compressor may include first and second inlets. The second compressor may receive fluid from an outlet of the first compressor. The first heat exchanger may receive fluid from the second compressor. The flash tank may receive fluid from the first heat exchanger and includes a vapor outlet and a liquid outlet. The second heat exchanger may be in fluid communication with the flash tank and may receive fluid from the liquid outlet. The first fluid path extends from an outlet of the second heat exchanger to an inlet of the second compressor. The second fluid path extends from the vapor outlet to the first fluid path. The third fluid path may transmit fluid from the vapor outlet to the second inlet.

A method and apparatus for controlling temperature of a compressor motor (170) having a motor cooling circuit in a refrigeration system (1014) is provided. The motor cooling circuit includes a second expansion valve (1043) providing fluid communication between the condenser and the compressor motor. The compressor motor (170) is in fluid communication with the refrigeration circuit (1014) between downstream of the first expansion valve (1040) and a compressor inlet. Refrigerant is provided as a cooling fluid to the motor cooling circuit. A primary PID loop (402) and a secondary PID loop (414) are used to control the temperature and the flow of refrigerant to the motor (170).