A heat pump apparatus includes a compressor compressing a refrigerant, a motor driving the compressor, an inverter device, and an inverter control unit controlling the inverter device. The inverter device includes the same number of bridge circuits as those of phases of the motor, and each of the bridge circuits includes plural pairs of series-connected switching elements. The pairs of switching elements are connected in parallel. The inverter device applies to the motor a high-frequency voltage of a frequency at which the motor does not rotate.

A defrosting determination device includes: a condition specifying unit that specifies the air conditioning load condition corresponding to a pair of temperature inside the room and temperature outside the building based on condition information; a slope specifying unit that specifies the slope corresponding to the specified air conditioning load condition based on slope information; a frequency acquiring unit that acquires frequency information specifying the operation frequency of the motor; a calculation unit that calculates a threshold value by multiplying the operation frequency by the slope; a power information acquiring unit that acquires power information specifying power output to the motor; a decision unit that decides whether the power is equal to or less than the threshold value; and a determination unit that determines to start defrosting operation in response to the decision unit deciding that the power is equal to or less than the threshold value.

A control system controls the output capacity of a compressor to avoid surge conditions in the compressor. The control system determines a capacity control output for the compressor and then modifies the capacity control output in view of any output limiters or overrides as determined by system operating parameters and to maintain a minimum frequency of operation for the compressor.

A chiller system includes a compressor, a condenser and an evaporator in fluid communication. A motor drives the compressor. A variable speed drive powers the motor. An oil heater and pump system circulate heated lubricating oil in the compressor. A control panel is arranged to determine whether an input parameter is greater than or equal to a threshold parameter; deactivate the VSD in response to sensing that the input parameter is less than the threshold parameter; determine at least one chiller capacity control parameter at a point when the VSD is deactivated, and maintain the at least one chiller capacity control parameter while the VSD is deactivated; determine that the input parameter has been restored; determine a motor rotation and motor rotational speed; and in response to determining that the input parameter is restored and the motor is rotating in a forward direction, reactivate the VSD.

A climate-control system may include a compressor and a control module. The compressor includes a motor driving a compression mechanism to compress a working fluid. The control module is in communication with the motor and may be configured to determine a balance speed of the motor at which a forward-rotational inertial force of the compression mechanism is equal to a backward-rotational gas force on the compression mechanism. The control module may be configured to adjust a running speed of the motor to the balance speed after receipt of a compressor-shutdown-command and before shutting down the compressor.

A control method for a refrigerator includes driving a refrigerator compartment compressor that is configured to cool a refrigerator compartment; determining whether a temperature in the refrigerator compartment satisfies a first temperature; driving, based on the determination that a temperature in the refrigerator compartment satisfies the first temperature, a freezer compartment compressor that is configured to cool a freezer compartment; stopping the refrigerator compartment compressor; maintaining, after stopping the refrigerator compartment compressor, operation of the freezer compartment compressor; restarting the refrigerator compartment compressor; and varying a driving frequency of the refrigerator compartment compressor.

A drive includes an inverter power circuit that applies power to an electric motor of a compressor from a direct current (DC) voltage bus. A power factor correction (PFC) circuit outputs power to the DC voltage bus based on input alternating current (AC) power. The PFC circuit includes: (i) a switch having a first terminal, a second terminal, and a control terminal; (ii) a driver that switches the switch between open and closed states based on a control signal; (iii) an inductor that charges and discharges based on switching of the switch; and (iv) a circuit that outputs a signal indicating whether the switch is in the open state or the closed state based on a voltage across the first and second terminals of the switch.

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.

The purpose of the present invention is to install an economizer having a sufficient internal volume in a compact turbo refrigeration apparatus specifically using a low-pressure refrigerant, and reduce refrigerant pressure loss and enhance efficiency in the turbo refrigeration apparatus. The turbo refrigeration apparatus according to the present invention comprises: a turbo compressor which compresses a refrigerant; a condenser which condenses the compressed refrigerant; a control valve which causes the condensed refrigerant to expand; an evaporator which causes the expanded refrigerant to evaporate; and an economizer which is installed in such a manner as to be sandwiched between the condenser and the evaporator, and separates the refrigerant expanded by the control valve into gas and liquid. The economizer is installed adjacent to a curved wall, having a drum shell shape, of the condenser and/or the evaporator, the curved wall being shared with the structural wall of the economizer. The economizer has a height (H) greater than the maximum width (W) thereof when viewed in the longitudinal direction thereof.

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.