An air-conditioning apparatus includes a refrigerant circuit including a compressor, an indoor-side heat exchanger, and an outdoor-side heat exchanger; a drive circuit configured to drive an electric motor; a connection switching device configured to switch connection of stator windings of the electric motor between a first connection state and a second connection state higher in line-to-line voltage than the first connection state; and a controller configured to perform defrosting operation for removing frost formed on the outdoor-side heat exchanger and cause the connection switching device to switch connection. In performing the defrosting operation with the stator windings being in the second connection state, the controller causes the connection switching device to switch the connection of the stator windings from the second connection state to the first connection state.

Disclosed is a method for controlling a refrigerator including a motor driving a compressor. The method for controlling a refrigerator includes: identifying driving revolutions per minute (RPM) for driving of the motor; performing a control of temperature in the refrigerator based on the identified driving RPM; and storing operation information of the motor associated with the performing of the control of temperature, where the identifying of the driving RPM involves identifying stored operation information of the motor associated with a previous motor driving process.

A synchronous motor control device includes: a DC power supply; an inverter main circuit; a three-phase synchronous motor; and an inverter control unit that outputs a PWM signal used to control the inverter main circuit. The inverter control unit includes: a PWM signal generation unit; a start-up control unit that outputs a start-up voltage command value to the PWM signal generation unit at the time of start-up; a steady state control unit that calculates a steady state voltage command value in a steady state and outputs the value to the PWM signal generation unit; and a steady state control parameter initial value calculation unit that outputs an initial value of a control parameter to the steady state control unit such that an output voltage vector from the inverter main circuit to the three-phase synchronous motor is consistent before and after switching from the start-up to the steady state.

A driving device includes a connection switching unit to switch a connection state of coils between a first connection state and a second connection state in which a line voltage is lower than in the first connection state, a controller to control a motor and the connection switching unit, and a rotation speed detector to detect a rotation speed of the motor. When the connection state of the coils is the first connection state and the rotation speed detected by the rotation speed detector becomes higher than or equal to a first rotation speed, the controller causes the motor to rotate at a second rotation speed higher than the first rotation speed, and then causes the connection switching unit to switch the connection state of the coils from the first connection state to the second connection state.

Embodiments of the present invention provide a method for controlling compressor braking, a frequency converter and a variable speed compressor. The method includes steps of: determining to brake a compressor, wherein a brake circuit includes three switching units and the three switching units are respectively electrically connected to three phases of windings of a motor of the compressor; actuating two of the three switching units to short-circuit two phases of windings of the motor. The two phases of windings of the motor are short-circuited by controlling the three switching units to generate braking torque, such that the compressor is braked without introducing a DC voltage, and thus the braking energy consumption is reduced. Besides, by turning on only two switches at a time, the switching abrasion is reduced, and the overall service life of the three switching units is effectively improved.

An air-conditioning apparatus including a compressor incorporating an electric motor; a temperature sensor configured to detect indoor temperature; a drive circuit configured to drive the electric motor; a connection switching device configured to switch connection of stator windings of the electric motor between a first connection state and a second connection state higher in line-to-line voltage than the first connection state; and a controller configured to enter thermo-off when the indoor temperature reaches a target temperature or a correction temperature set based on the target temperature and cause the connection switching device to switch connection, the thermo-off being entered by stopping the compressor via the drive circuit. When a thermo-off count reaches a reference count with the electric motor being in the first connection state, the controller causes the connection switching device to switch connection from the first connection state to the second connection state.

An air conditioning system of a vehicle having an internal combustion engine includes a condenser configured to receive refrigerant output by an electric compressor and transfer heat from the refrigerant within the condenser to air passing the condenser. A first evaporator is configured to receive refrigerant from the condenser when a first control valve is open and transfer heat from air passing the first evaporator to the refrigerant within the first evaporator. A first blower is configured to blow air across the first evaporator to a first section of a cabin of the vehicle. A second evaporator is configured to receive refrigerant from the condenser when a second control valve is open and transfer heat from air passing the second evaporator to the refrigerant within the second evaporator. A second blower is configured to blow air across the second evaporator to a second section of the cabin of the vehicle.

The present disclosure relates to a heating, ventilation, and/or air conditioning (HVAC) system that includes a mobile air conditioning unit configured to separately dock with each docking station of a plurality of docking stations. The mobile air conditioning unit includes a refrigerant circuit configured to condition an airflow to produce a conditioned airflow and a transportation system configured to autonomously relocate the mobile air conditioning unit.

A variable refrigerant package air conditioner is shown that is easy to install in new construction with a unique base that causes collected mixture that overflows to drain outside the building. A control system is shown that has motors and compressor that are pulse width modulated so the air conditioner is infinitely variable while maintaining the highest possible power factor. Dehumidification of outside air occurs as it is mixed with inside air. By gradually approaching a temperature set point and even reheating after dehumidification, moisture is removed from the room.

A cooling system includes a cooling device, a controller and a defrosting unit. The cooling device has a compressor, a condenser, an expander, an evaporator, a cooling channel and a coolant. The coolant is functioned in the evaporator to thermally exchange with a working fluid in a pipe. The controller is adapted for controlling the temperature of the working fluid by controlling the cooling device. The defrosting unit has a switch disposed on the cooling channel and located between the compressor and the condenser, and a defrosting channel connected with the switch. After passing through the switch, the coolant is optionally fed to anyone of the cooling channel and the defrosting channel. After flowing through the defrosting channel, the coolant passes through the evaporator and then flows back to the compressor. As a result, the cooling system is capable of fast defrosting without using a heater.