A method for controlling the power-on or power-off of an air conditioner is provided. The method includes the following steps: determining whether a variable capacity compressor of the air conditioner is in a standby single-cylinder operation state before starting the air conditioner, where the variable capacity compressor is configured to be switchable between a single-cylinder operation state and a dual-cylinder operation state; if so, starting the air conditioner; if not, switching the variable capacity compressor to the standby single-cylinder operation state, and then starting the air conditioner. With this control method, regardless of whether the air conditioner is shut down because the power supply of the unit is cut off or because a power-off signal is received, the air conditioner can be started in a single-cylinder operation state in the next startup, so that the operation state of the cylinder is always determined when starting the air conditioner.

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.

A motor driving device that drives a motor and is capable of switching a connection state of stator windings of the motor, includes: relays to switch the connection state of the stator windings by switching positions of contact plates; and a contact control unit to control each of the positions of the contact plates by outputting, to the relays, signals for actuating the contact plates. The contact control unit switches the connection state by sequentially switching output values of the signals such that the output values of the signals are switched at different timings from each other in the relays, and changes a switching order every time the connection state is switched, the switching order being an order in which the output values of the signals are switched.

Systems and methods for monitoring an HVAC&R system employ a monitoring agent that uses observations of evaporator and condenser intake temperatures, evaporator discharge temperature, and a compressor input power parameter to learn operating characteristics of the HVAC&R system in newly maintained condition. Thereafter, the agent continuously or regularly computes a relative coefficient of performance (COP) for the system under subsequent observed ambient conditions, and relates the present instantaneous efficiency of the HVAC&R system under the observed ambient conditions to the instantaneous efficiency when the system was in newly maintained condition. The relative COP can be used to detect system degradation and quantify the energy usage and cost attributable to the degradation. The agent can take appropriate actions to prevent/minimize damage based on the degree of degradation detected, including shutting off power to the HVAC&R system. The monitoring agent can also be extended to other types of systems besides HVAC&R system.

An air conditioning device has: a refrigerant circuit that is formed of a compressor, a switching valve, a cascade heat exchanger, an expansion valve and an outdoor heat exchanger connected to one another by a first pipe through which a refrigerant flows, and capable of performing a defrosting operation in which the refrigerant discharged from the compressor is introduced into the outdoor heat exchanger; a heat-transfer medium circuit that is formed of a pump, the cascade heat exchanger, and the indoor heat exchanger connected to one another by a second pipe through which a heat-transfer medium flows; and a control device that controls the compressor and the pump. When an amount of heat storage of the heat-transfer medium is less than a threshold, the control device reduces the heating capability of the indoor heat exchanger when the air conditioning device transitions from a heating operation to the defrosting operation.

There is provided a starting method for a cryocooler, the cryocooler including a compressor, a cold head, a high pressure line, and a low pressure line, the method including increasing a volume of the high pressure line when the cold head is at a room temperature, cooling the cold head from the room temperature to a cryogenic temperature while controlling an operation frequency of the compressor based on a pressure of the high pressure line or a differential pressure between the high pressure line and the low pressure line, after the volume of the high pressure line has been increased, decreasing the volume of the high pressure line after the cold head has been cooled to the cryogenic temperature, and maintaining the cold head at the cryogenic temperature after the volume of the high pressure line has been decreased.

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 system. The controller obtains a plurality of pulse width modulation (PWM) algorithms. Each PWM algorithm has an associated spectrum of frequencies. The controller further determines one or more resonance frequencies associated with the HVAC system. The controller also selects a first PWM algorithm from the plurality of PWM algorithms wherein the spectrum of frequencies of the first PWM algorithm lacks frequency peaks that overlap with the one or more resonance frequencies associated with the HVAC system. The controller further operates the electronic power converter according to the first PWM algorithm.

A method for operating an appliance motor includes receiving a target speed for the motor, obtaining a power limit for the motor, determining an inverter current limit based at least in part on the target speed and the power limit, determining an inverter output current to achieve the target speed, wherein the inverter output current is limited to the inverter current limit, and supplying the motor with the inverter output current.

A compressor fault diagnostic apparatus including a current sensing unit to sense a current flowing through a motor of the compressor, a fault diagnostic unit to determine whether or not the motor performs a reverse rotation based on the current flowing through the motor, and a cut-off unit to remove power based on a determination of the fault diagnostic unit.

A portable refrigerator includes a main housing, a refrigerator cover, a cooling mechanism, a rechargeable battery pack and a control unit. The cooling mechanism includes heat exchanging tubes, a compressor, an evaporator and a condenser connected to the evaporator and the compressor. The rechargeable battery pack is detachably attached on a power compartment of the main housing. The control unit is supported in the main housing and electrically connected to the rechargeable battery pack and the cooling mechanism for centrally controlling an operation of the cooling mechanism. A predetermined amount of refrigerant is arranged to controllably pass through the heat exchanging tubes, the condenser, the evaporator and the compressor for extracting heat from the accommodating cavity.