A system includes an electronic power converter and a controller. The electronic power converter supplies power to one or more motor drives of an HVAC and/or refrigeration system. The controller obtains a plurality of pulse width modulation (PWM) algorithms. Each PWM algorithm has an associated harmonic signature. The controller further determines one or more resonance frequencies associated with the HVAC and/or refrigeration system. The controller also selects a first PWM algorithm from the plurality of PWM algorithms based at least in part on the harmonic signature associated with the first PWM algorithm mitigating the one or more resonance frequencies associated with the refrigeration system. The controller further operates the electronic power converter according to the first PWM algorithm.

A power converting apparatus includes: a rectifying unit configured to rectify an input AC power, a buck converter that is configured to step down a voltage of the rectified power and that is configured to output DC power having the step down voltage, a first inverter that is connected to an output terminal of the buck converter and that is configured to convert the DC power into AC power to drive a first motor, a second inverter that is connected to the output terminal of the buck converter, that is disposed in parallel to the first inverter, and that is configured to convert the DC power into AC power to drive a second motor, and a converter controller configured to control an output voltage of the DC power of the buck converter.

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.

A motor drive device includes a reactor, a converter circuit, a capacitor, an inverter circuit, and overcurrent determination units. The converter circuit converts a first AC voltage output from an AC power supply into a DC voltage. The capacitor smooths a second voltage on the DC side of the converter circuit. The inverter circuit converts DC power stored in the capacitor into AC power. One of the overcurrent determination units determines overcurrent based on a detected value of the first AC current, flowing between the AC power supply and the converter circuit. Another overcurrent determination unit determines overcurrent based on a detected value of the second DC current, flowing between the converter circuit and the capacitor. The converter and inverter circuits stop operating when the determination result of one of the overcurrent determination units indicates an overcurrent.

The present application concerns a climate control unit for controlling air temperature and/or humidity. Moreover, the present application concerns a system comprising such a climate control unit.

The climate control unit according to the invention makes uses of two refrigerant paths that share a common part in which a compressor and evaporator are arranged, and that each have a non-shared part. A reheat coil is provided in one of the non-shared parts. According to the invention, a respective expansion device is provided in both non-shared parts.

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 dehumidifier for operation within the 5° C. to 20° C. temperature range and 50 to 100 percent relative humidity range of air includes an evaporator, a condenser, a fan that draws humid air through the evaporator and condenser, and a compressor for pumping refrigerant fluid through both the evaporator and condenser. The evaporation temperature is maintained in the evaporator at least at −4° C., resulting in a temperature within the evaporator and at the outlet thereof being greater than 0° C., thereby preventing the formation of ice in the evaporator and allowing the operation of the evaporator to its full power all the time.

Disclosed herein are a compressor driving apparatus and a refrigerator including the same. A compressor driving apparatus includes: a plurality of switching elements; an inverter for converting direct current (DC) power into alternating current (AC) power according to a switching operation to output the converted AC power to the motor; an output current detector for detecting an output current flowing through the motor; and an inverter controller for controlling the inverter based on the output current, wherein the inverter controller controls the piston so that one end of the piston is fixed at a first position spaced apart from the discharge unit at stroke of the piston during a first period, controls the piston to collide with the discharge unit when a change rate in an operation rate or a position error of the compressor is equal to or greater than a predetermined value, and controls the piston so that the one end of the piston is fixed at a second position spaced apart from the discharge unit at stroke of the piston during a second period after the collision of the piston. Accordingly, control accuracy may be improved and a noise may be reduced upon piston position based operation control.

This method for controlling asynchronous electrical motors of a compressor system, comprises: —receiving an order to start a first asynchronous electrical motor and a second asynchronous electrical motor of a compressor system; —unloading said first and second motors, by operating respectively a first load control unit of the first motor and a second load control unit of the second motor, in order to reduce the mechanical load associated to said motors; —starting the first motor and, only once the first motor is running at nominal speed, starting the second motor, —loading both the first and second electrical motor only once the second motor has started and is running at nominal speed, by operating the first load control unit and the second load control unit, in order to increase the mechanical load associated to said motors.

A compressor retrofit assembly for replacing a D/C compressor with an A/C compressor includes a control unit that is installable in a refrigerator when the compressor in the refrigerator has failed. The control unit is electrically coupled with an existing power supply in the refrigerator, a compressor relay of a replacement compressor for the refrigerator, an existing power input of a fan in the refrigerator and a coil of the compressor relay of the replacement compressor. The control unit supplies electrical power to the coil of the compressor relay thereby facilitating the compressor relay to be closed. In this way the control unit supplies operational voltage to the replacement compressor.