In one embodiment, a cooling system includes an evaporator, which further includes an evaporator tube, a first mechanical wave emitter, and a control system communicatively coupled to the first mechanical wave emitter. The cooling system is configured to circulate refrigerant through the evaporator tube to facilitate heat exchange between the refrigerant and fluid surrounding the evaporator tube. The first mechanical wave emitter is configured to output first mechanical waves to the evaporator tube, and the control system is configured to instruct the first mechanical wave emitter to output the first mechanical waves to enhance nucleation of the refrigerant in the evaporator tube.

An inverter control device includes an inverter main circuit, a current detector, a voltage detector that detects a DC voltage between DC bus lines, and an inverter control unit that generates PWM signals to perform on/off control of a plurality of semiconductor switching elements respectively with a DC current and a DC voltage. The unit sets a carrier period of PWM signals to be 1/N times a calculation period in which the PWM signals are generated, performs detection of a DC current detected by the current detector in a 1/2 calculation period immediately before a calculation start timing for generating PWM signals, calculates an output voltage vector based on the detected DC current, and reflects PWM signals generated from the output voltage vector in one calculation period from a 1/2 calculation period after the calculation start timing to 3/2 control calculation periods after the same.

A first reactor is provided on the input side of a rectifying circuit that rectifies AC power (on the side of an AC power supply), and on the output side of the rectifying circuit (on the side of a load), first and second capacitors that are connected in series to each other, and first and second switching elements that switch between charging and not charging of the first and second capacitors, respectively, are provided, a second capacitor group in Y-connection, provided with three capacitors, each of which is connected to each phase-terminal of the first reactor on the side of the rectifying circuit, is connected to the midpoint of the first and second switching elements, and the output voltage to the load is boosted, while the on-duty of the first switching element and the on-duty of the second switching element are controlled to be equal to each other.

Provided is an oil level detection device to be mounted on a refrigerating and air-conditioning apparatus, the oil level detection device being configured to detect an oil level of oil accumulated inside a compressor forming the refrigerating and air-conditioning apparatus. The oil level detection device includes an oil level detection unit installed on an outer surface of the compressor and configured to detect a temperature of an installation position, a sensor output unit configured to output, to the refrigerating and air-conditioning apparatus, a signal for changing an operation state of the refrigerating and air-conditioning apparatus, and a determination unit configured to determine depletion of the oil accumulated inside the compressor based on measurement values obtained by the oil level detection unit at least after an output of the signal to be output from the sensor output unit.

The hot and cold water air conditioning system includes a water temperature sensor configured to detect a temperature of water flowing out of the heat pump heat source apparatus by an operation of the water circulation pump, and a controller configured to perform, in a heating operation, on/off normal control that turns on a compressor when the water temperature detected by the water temperature sensor becomes lower than a target water temperature and turns off the compressor when the water temperature becomes higher than a first temperature value higher than the target water temperature, and to switch from the on/off normal control, upon repeating the on/off operation of the compressor at a minimum frequency necessary for an operation of the compressor in the on/off normal control, to on/off restriction control that turns on the compressor when the water temperature becomes lower than a second temperature value lower than the target water temperature and turns off the compressor when the water temperature becomes equal to or higher than a third temperature value higher than the target water temperature.

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 heat pump device includes: a compressor including a compression mechanism compressing a refrigerant and a motor driving the compression mechanism; an inverter unit applying a voltage for driving the motor; an inverter control unit generating a driving signal for driving the inverter unit; and temperature sensors detecting temperatures of the compressor, wherein the inverter control unit includes a normal operation mode in which a refrigerant is compressed by performing a normal operation of the compressor and a heating operation mode in which a heating operation of the compressor is performed by applying, to the motor, a high-frequency voltage, and in the heating operation mode, the inverter control unit determines an amplitude and a phase of a voltage command for generating the high-frequency voltage on a basis of a temperatures detected by the temperature sensors and a necessary amount of heat specified in advance.

A vehicle air conditioning apparatus including a heat released refrigerant expansion valve that decompresses the refrigerant discharged from the radiator during the heating operation and the first heating and dehumidifying operation; a gas-liquid separator that separates the refrigerant decompressed by the heat released refrigerant expansion valve into a gaseous refrigerant and a liquid refrigerant; and a bypass circuit that allows part of at least the gaseous refrigerant separated in the gas-liquid separator to flow into a section of the compressor through which the refrigerant being decompressed passes.

A controller of an inverter control apparatus includes an A/D conversion unit that performs digital conversion of an input signal when a signal for either an A/D converter start trigger or an A/D converter start trigger is input thereinto; a first inverter control unit that generates the A/D converter start trigger which starts the A/D conversion unit, based on A/D converter start timing information and a first carrier signal; a second inverter control unit that generates the A/D converter start trigger which starts the A/D conversion unit, based on A/D converter start timing information and a second carrier signal; and an A/D start factor selection unit that receives either the A/D converter start trigger or the A/D converter start trigger and selects an A/D start factor at a predetermined period timing of an operation period of the first carrier signal and the second carrier signal.

A refrigeration cycle apparatus includes: a refrigerant circuit, a use side heat exchanger, a pressure reducing device, and a heat source side heat exchanger; A fan is provided together with at least one, selected from between, the use side heat exchanger and the heat source side heat exchanger and that has a fan motor; a relay unit connected to a direct-current supply device via the direct-current circuit breaker; a resistor unit connected in parallel to the relay unit; a DC/AC converter configured to convert a direct-current voltage supplied from the direct-current supply device via either the relay unit or the resistor unit into an alternating-current voltage and to supply the alternating-current voltage to at least one, selected from between, the compressor motor and the fan motor; and an opening and closing control unit configured to bring the relay unit into an open state when the direct-current circuit breaker becomes open.