Included are: a compressor including a compression mechanism that compresses refrigerant, and a motor that drives the compression mechanism; an inverter that applies desired voltage to the motor; an inverter controller that controls the inverter; a high-pressure switch that operates when a discharge pressure of the compressor becomes a preset pressure or higher; and a thermal protector that operates when the temperature of the compressor becomes a preset temperature or higher, wherein the high-pressure switch and the thermal protector are installed on a power supply line for supplying power to the inverter, and the high-pressure switch is opened when the discharge pressure of the compressor becomes the preset pressure or higher, or the thermal protector is opened when the temperature of the compressor becomes the preset temperature or higher, to interrupt power supply to the inverter.

A direct-current power supply includes: a rectifier circuit in which switching elements are bridge-connected; a reactor; a gate circuitry that drives the switching elements; and a gate circuitry that drives the switching elements. A connection point between the switching element and the switching element is connected to an alternating-current power supply via the reactor, and a connection point between the switching element and the switching element is connected to the alternating-current power supply without via the reactor. A time during which the gate circuitry turns on the switching elements is longer than a time during which the gate circuitry turns on the switching elements.

An air conditioning apparatus includes an indoor unit and an outdoor unit. The outdoor unit includes a compressor that compresses a refrigerant and a motor drive apparatus that drives the compressor. The motor drive apparatus includes an inverter that converts a direct-current voltage into an alternating-current voltage and a motor that operates on the alternating-current voltage from the inverter. The motor includes six stator windings that are each openable at both ends. The motor drive apparatus further includes a connection state switching unit that includes a function of switching a connection state of the six stator windings of the motor among at least four types of connection states.

Provided is a controller, an air conditioner, and a high-pressure protection circuit. The controller includes a first rectifier unit, a power conversion unit, a high pressure switch (HPS) wiring terminal, a low-voltage control unit, and a high-voltage operating unit. An input end of the first rectifier unit is capable of being electrically connected to an input power supply. An output end of the first rectifier unit is electrically connected to an input end of the power conversion unit. An output end of the power conversion unit is electrically connected to a power supply end of the low-voltage control unit. The HPS wiring terminal is connected to the front end of the power supply end of the low-voltage control. The controller has a function of high-pressure protection.

A motor driving device is a device for driving a motor including stator windings, includes: a connection switching unit that is connected to the stator windings, includes circuits including semiconductor switches, and switches connection condition of the stator windings to either of first connection condition and second connection condition different from the first connection condition by setting the semiconductor switches to ON or OFF; and an inverter that supplies AC drive voltages to the stator windings.

A free cooling outdoor unit includes: a refrigerant circuit through which refrigerant circulates; a brine circuit through which brine circulates; a water circuit through which water circulates; a fan configured to send air to the second heat exchanger; a flow control valve configured to control a circulation amount of the brine in the brine circuit; a water temperature detection sensor configured to detect a water temperature in the water circuit; an outside air temperature sensor; and a controller configured to control, where the outside air temperature is equal to or lower than a freezing temperature of the brine, the circulation amount of the brine based on the water temperature such that a brine temperature is prevented from reaching a temperature equal to or lower than the freezing temperature of the brine.

A refrigerating cycle device includes a compressor, a motor, and a wiring switch part. The compressor compresses a refrigerant. The motor generates power for compressing the refrigerant by rotating a rotor with voltage applied to a plurality of wirings. The motor is disposed in the compressor. The wiring switch part switches between a plurality of wiring states by changing connection between the plurality of wirings. When a rotational speed of the rotor exceeds a predetermined value, the wiring switch part switches to a first wiring state of the plurality of wiring states. The first wiring state differs from a second wiring state of the plurality of wiring state. Efficiency of the second wiring state is highest at the rotational speed.

A gas compressor includes inverters, a plurality of compressor units and a control device for controlling each of the inverters. The control device increases the number of compressor bodies to be operated after confirming that the rotational speed of the operational motors will reach a steady value immediately after causing the number of the compressor bodies to be operated to increase.

A compressor for a heat transfer circuit includes a variable frequency drive (VFD), an electric motor that rotates a driveshaft, bearing(s) for supporting the driveshaft, a backup gas supply, and a power supply. During a utility power interruption, the backup gas supply operates utilizing DC electrical power generated by a back electromotive force of the electric motor. A method of operating an electric power supply system for a compressor includes operating in a utility power mode and operating in a backup power mode during a utility power interruption. In the utility power mode, AC electrical power is supplied from the VFD to the motor. In the backup power mode, DC electrical power generated in the VFD by a back electromotive force of the motor it used to operate a backup gas supply to supply compressed working fluid to gas bearing(s) of the compressor.

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.