A heating, ventilation, and/or air conditioning (HVAC) system includes a compressor, a fan, an inverter configured to drive operation of the compressor, and a controller communicatively coupled to the fan and the inverter. The controller includes a tangible, non-transitory, computer-readable medium with computer-executable instructions that, when executed by processor circuitry, are configured to cause the processor circuitry to determine an operating parameter of the fan in response to an interruption in receiving communication signals from the inverter and operate the fan based on the operating parameter during the interruption.

A heating, ventilation, and air-conditioning (“HVAC”) system for use with a refrigerant. The HVAC system may include a compressor, a condenser, an expansion device, an evaporator, a variable speed inverter, and a fixed inverter. The compressor may be operable to compress the refrigerant. The condenser may be positioned downstream of the compressor and operable to condense the refrigerant. The expansion device may be positioned downstream of the condenser and operable to reduce a pressure of the refrigerant flowing therethrough. The evaporator may be positioned downstream of the expansion device and upstream of the compressor. The evaporator may be operable to vaporize the refrigerant from the expansion device. The variable speed inverter may be operable to deliver DC power to the compressor. The fixed inverter may be operable to deliver DC power to the compressor.

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.

There are provided an inverter connected to n (n being as integer not less than 2) motors each including a rotor having a permanent magnet and capable of driving the n motors, and a connection switching device to switch a connection state of at least one motor of the n motors and the inverter between connection and disconnection. While the n motors are connected to the inverter and driven by the inverter, when an abnormality is detected in the at least one motor, the connection switching device switches the connection state to the disconnection and the inverter drives the n motors except the at least one motor.

A water heater may operate according to different modes. The water heater may include a storage tank configured to store water, at least one sensor configured to sense a temperature of the water and a temperature related to an outside of the water heater, a first heater assembly (comprising a heating element) configured to heat the water, a first controller configured to control the first heater assembly, a second heater assembly (comprising a heat pump system) configured to heat the water, an inverter connected with the heat pump system, and a second controller configured to control the heat pump system by adjusting an output frequency of the inverter.

The motor-driven compressor includes an electric motor, a housing, a compression portion, and an inverter device. The inverter device includes an inverter circuit, a current sensor, a coordinate converter, a speed controller, a current controller, a PWM controller, and a rotation angle estimator. The speed controller generates a d-axis current command value and a q-axis current command value such that a necessary torque to drive the electric motor occurs. The inverter device includes a heat-generating current command section that increases a temperature of the electric motor by changing the d-axis current command value and the q-axis current command value. The heat-generating current command section changes the d-axis current command value and the q-axis current command value so as to shift them in a direction in which a d-axis current value increases along a constant torque curve in a d-q coordinate system.

A motor driving apparatus includes: an inverter that includes a plurality of switching elements and that is configured to output AC power to a motor by a switching operation of the plurality of switching elements, a switching unit that includes a relay and that is configured to switch a connection mode of the motor by an operation of the relay, and an inverter controller configured to control the inverter and the switching unit. The inverter controller is configured to, based on the relay being turned off, apply a reverse voltage to the relay.

Embodiments of a variable frequency drive (VFD) apparatus are disclosed. In an embodiment, the VFD apparatus includes an enclosure and one or more internal components housed in a first portion of the enclosure. Further, the VFD apparatus includes a compartment housed in a second portion of the enclosure. In an embodiment, the compartment includes an ingress for facilitating entry of air into the compartment and an egress for facilitating an exit of the entered air from the compartment. The first portion of the enclosure is isolated from the second portion of the enclosure.

A variable capacity screw compressor comprises a suction port, at least two screw rotors and a discharge port being configured in relation to a selected rotational speed that operates at least one screw rotor at an optimum peripheral velocity that is independent of a peripheral velocity of the at least one screw rotor at a synchronous motor rotational speed for a rated screw compressor capacity. A motor is configured to drive the at least one screw rotor at a rotational speed at a full-load capacity that is substantially greater than the synchronous motor rotational speed at the rated screw compressor capacity. A variable speed drive receives a command signal from a controller and generates a control signal that drives the motor at the selected rotational speed.

A current estimating device that estimates a capacitor current of a high-voltage circuit for driving a motor, wherein the current estimating device calculates a voltage utilization rate using the input voltage of an inverter included in the high-voltage circuit and the speed of the motor, calculates a first constant by applying the voltage utilization rate to a predetermined first arithmetic expression, and calculates the capacitor current of an electrical condenser included in the high-voltage circuit by multiplying the first constant by a motor current effective value.