A motor driver for driving a motor including three-phase windings includes: an inverter that applies a desired voltage to the motor; and an inverter controller that controls an operation of the inverter. The inverter includes: a current detector that detects a direct current in a first connecting line among three-phase connecting lines connecting the respective three-phase windings and the inverter; and a current detector that detects an alternating current in a second connecting line among the three-phase connecting lines, and a maximum direct current is caused to flow to the first connecting line in a first control mode for positioning a rotor of the motor.

In other features, a refrigeration system is provided and includes a compressor motor, an inverter, a converter and a control module. The inverter is configured to convert a direct current (DC) bus voltage to an alternating current (AC) voltage and supply the AC voltage to the compressor motor. The converter is configured to convert a DC input voltage to the DC bus voltage. The control module is configured to obtain a parameter and in response to the parameter exceeding a predetermined threshold, reduce the DC bus voltage and at least one of (i) reduce a switching frequency, (ii) increase an amount of negative d-axis current of the compressor motor, or (iii) reduce a speed of the compressor motor.

A chiller assembly is provided. The chiller assembly includes a compressor (102), a condenser (106), an expansion device and an evaporator (108) connected in a closed refrigerant circuit. The chiller assembly further includes a motor (104) connected to the compressor to power the compressor, and a variable speed drive (110) connected to the motor to power the motor. The variable speed drive is operable to provide a variable voltage to the motor and a variable frequency to power the motor. The variable speed drive includes multiple sensors and an input current estimator that determines an estimated RMS input current based on sensor data received from the sensors. The chiller assembly further includes a control panel to control operation of the variable speed drive.

An HVAC system includes an unloading device, a centrifugal compressor, a gas foil bearing, a VFD and a controller. The controller is programmed to start the centrifugal compressor from a stopped condition by operating the unloading device to remove a load from the centrifugal compressor, accelerating the motor to a first speed above a liftoff speed of the gas foil bearing and below an operating speed of the centrifugal compressor, running the motor for a period of time, operating the unloading device to apply the load to the centrifugal compressor, and accelerating the motor to the operating speed.

A vector control system is used to control a vapor compression circuit. The vector control system may monitor the vapor compression circuit and adjust the speed of one or more motors to increase efficiency of the system by taking into account the torque forces placed on a compressor motor.

A recreational vehicle air conditioning system supports multiple recreational vehicle air conditioning units having closed air conditioning circuits and a controller that is electronically coupled to each of the recreational vehicle air conditioning units to control each of the closed air conditioning circuits to regulate an overall power consumption of the multiple recreational vehicle air conditioning units. A recreational vehicle air conditioning system may also support multiple recreational vehicle air conditioning units where a refrigerant line set is coupled between the recreational vehicle air conditioning units such that a compressor in one of the recreational vehicle air conditioning units is capable of supplying refrigerant to the evaporators of the multiple recreational vehicle air conditioning units, and such that valves coupled in series with each of the evaporators may be regulated to control cooling by each recreational vehicle air conditioning unit.

In this container refrigerator, the permissible equivalent negative-phase-sequence current of a generator to be connected is calculated in Step S3 based on its capacitance. Next, in Step S4, the power consumption of an inverter device to generate the equivalent negative-phase-sequence current is calculated. Then, in Step S6, the equivalent negative-phase-sequence current generated by the container refrigerator is calculated based on the power consumption of this inverter device. Thereafter, in Step S9, I.sub.t is compared to I.sub.tg. If I.sub.t>I.sub.tg is satisfied, I.sub.t is restricted until I.sub.t≦I.sub.tg is met by lowering the output frequency of the inverter device repeatedly in multiple stages. Consequently, even if the generator connected has small capacitance, the operation may be continued at a number of rotations appropriate for that small capacitance without causing the generator to overheat or be burned out.

A method of cooling a motor coupled to a compressor of a chiller includes adjusting a position of a motor cooling valve located fluidly between the motor and a refrigerant source, using a motor temperature control system coupled to the motor cooling valve to regulate an amount of refrigerant introduced into the motor from the condenser according to a temperature control scheme performed as a function of a monitored temperature in the motor, a first temperature threshold, and a second temperature threshold lower than the first temperature threshold. The temperature control scheme includes a motor cooling control process that adjusts the position of the motor cooling valve based on a stator winding temperature set point relating to stator windings of the motor. A proportionally limited close command override associated with a first temperature range above the second temperature threshold proportionally limits a close command provided to the motor cooling valve.

An ice maker for forming ice during a cooling cycle, the ice maker having a variable-speed compressor, a condenser, and an evaporator, wherein the variable-speed compressor, the condenser, and the evaporator are in fluid communication by one or more refrigerant lines. The ice maker further includes a freeze plate thermally coupled to the evaporator, a water pump, a sensing device for identifying a state of the cooling cycle, and a controller adapted to control the speed of the variable-speed compressor based on the identified state of the cooling cycle. The ice maker may also include a variable-speed condenser fan which may be controlled by the controller based on the identified state of the cooling cycle. Additionally, the water pump may be a variable-speed water pump which may be controlled by the controller based on the identified state of the cooling cycle.

A motor drive device: a power conversion unit; a current detection unit that detects a phase current of the alternating-current motor; a position/speed specifying unit that specifies a magnetic pole position and a rotational speed of the alternating-current motor; a d-axis current pulsation generating unit that generates a d-axis current pulsation command based on q-axis current pulsation or a q-axis current pulsation command, which being in synchronization with the q-axis current pulsation or the q-axis current pulsation command and preventing or reducing an increase or decrease in amplitude of the voltage command; and a dq-axis current control unit that generates the voltage command for controlling the phase current on the dq rotating coordinates, which rotate in synchronization with the magnetic pole position, by using the magnetic pole position, the rotational speed, the phase current, the q-axis current pulsation or the q-axis current pulsation command, and the d-axis current pulsation command.