A screw compressor includes a screw rotor, a gate rotor, and a speed adjuster. The screw rotor has an outer peripheral surface with a plurality of screw grooves. The screw rotor is configured to be rotated. The gate rotor has a plurality of teeth. A ratio T/S of a number T of the teeth to a total number S of the screw grooves is greater than or equal to 2.5. The gate rotor meshes with the screw rotor. The speed adjuster is configured to adjust a rotational speed of the screw rotor. Rotation of the screw rotor at an angle greater than 180° allows the screw compressor to perform a stroke from start of compression to completion of discharge.

Unique apparatuses, methods, and systems of opposing, limiting, and/or preventing undesired or un-commanded compressor rotation are disclosed. One exemplary embodiment is an HVACR system comprising a variable frequency drive configured to drive an electric motor to rotate a screw compressor or scroll compressor. A controller is configured to monitor various aspects of the system and to control the drive. When a condition indicative of potential undesired or un-commanded compressor rotation is identified, the controller commands the variable frequency drive to control the motor to limit and preferably prevent compressor rotation. One technique comprises shorting switches of the drive to a DC bus rail to allow back EMF induced current in the motor windings to be dissipated through winding resistance thus providing a damping force. Another technique comprises controlling the inverter to insert a DC current into the motor to cause the motor to align to and hold a particular position.

A method of controlling an air conditioner including activating a refrigeration cycle by driving an compressor; detecting a high pressure and a low pressure when the refrigeration cycle is activated; adjusting an operating frequency of the compressor based on the detected high pressure or low pressure of the refrigeration cycle; determining a current load of an inside space through a load detecting unit; determining a load level of the inside space by comparing the current load with a reference load; and determining the operating frequency of the compressor based on the determined load level.

A refrigerator and a method for controlling the same are disclosed. The refrigerator may minimize the size and material cost of the control system by controlling the internal temperature and the speed of a compressor using a thermostat used in the conventional low-capacity/low-cost refrigerator without using a system controller equipped with various sensors (internal sensors and/or external sensors) capable of controlling the internal temperature. In addition, since an inverter controller capable of controlling a BLDC compressor estimates the internal/external temperature based on operation information of the compressor, and determines the internal load, it may save energy and reduce vibrations and noise, which are the largest disadvantages of a constant-speed compressor, thereby improving satisfaction of the consumer. In addition, the BLDC compressor may be started and operated stably by applying a differentiated algorithm of the inverter controller.

Embodiments of the present disclosure relate to refrigerators and methods of controlling the refrigerators. The refrigerator comprises a compressor configured to operate at a first rotation speed and a controller configured to calculate a first average of levels of electric signals input to the compressor during a first reference period, and control the compressor to operate at a second rotation speed higher than the first rotation speed when the first average is greater than a first reference value.

A direct current power supply device includes a rectifier circuit that rectifies alternating current power supplied from an alternating current power supply and converts the alternating current power into direct current power, a charge storage unit that includes a function of storing a charge, a charger that charges the charge storage unit, and a heat sink. The charger includes a positive-side switching element, a negative-side switching element, a positive-side backflow prevention diode, and a negative-side backflow prevention diode. The positive-side switching element, the negative-side switching element, the positive-side backflow prevention diode, and the negative-side backflow prevention diode are discrete semiconductor elements. The negative-side backflow prevention diode is a full mold package element. The positive-side switching element, the negative-side switching element, and the positive-side backflow prevention diode are elements that are not full mold packages.

A heat pump device capable of efficiently and reliably preventing a liquid refrigerant from stagnating in a compressor an air conditioner, a heat pump water heater, a refrigerator, and a freezing machine including the heat pump device. The configuration is such that, when the compressor is under operation standby, a high-frequency voltage synchronizing with a carrier signal is supplied to the compressor motor to carry out the locked energization of the compressor motor. From respective inter-phase voltages, respective phase voltages, or respective phase currents of the compressor motor for a plurality of high-frequency energization cycles, the detection values for one high-frequency energization cycle are restored. A power value calculated using the restored detection values for one high-frequency energization cycle is controlled to coincide with a heating power command necessary for discharging the liquid refrigerant stagnated in the compressor to the outside of the compressor.

An air conditioner and a method for controlling an air conditioner are provided. The air conditioner may include at least one indoor device, an electric heat pump (EHP) outdoor device connected to the at least one indoor device and having an EHP compressor driven using an applied current, and a gas heat pump (GHP) outdoor device connected to the at least one indoor device having an engine driven using a combustion of gas and a GHP compressor driven by receiving a driving force from the engine. The EHP compressor may include an inverter that controls a frequency of the current applied to the EHP compressor. The GHP compressor may include a first compressor that receives a driving force from the engine to compress a refrigerant; and a second compressor that is connected to the first compressor in parallel and receives the driving force from the engine to compress the refrigerant.

A power conversion apparatus includes: an inverter to drive a motor, using a first carrier signal; an inverter connected in parallel to the inverter, to drive a motor, using a second carrier signal; respective phase lower arm shunt resistors to detect a first current flowing inside the inverter; respective phase lower arm shunt resistors to detect a second current flowing in the inverter; and a control unit to control the inverters. A phase difference is set between the first carrier signal and the second carrier signal to prevent a detection period for the first current in the first carrier signal and a detection period for the second current in the second carrier signal from overlapping each other when the inverters are controlled.

A heat pump system includes a heat source unit having a variable-capacity compressor and a heat-source-side heat exchanger that functions as an evaporator for a refrigerant, and a plurality of usage units connected to the heat source unit and having usage-side heat exchangers that function as radiators for the refrigerant. The operating capacity of the compressor is controlled to bring the discharge pressure of the compressor, or a state quantity equivalent to the discharge pressure, to a first target value. The first target value is determined based on an equivalent target value equivalent to a usage temperature required in individual usage units.