A system and method for a compressor includes a compressor connected to a condenser, a discharge line temperature sensor that outputs a discharge line temperature signal corresponding to a discharge line temperature of refrigerant leaving the compressor, and a control module connected to the discharge line temperature sensor. The control module determines a saturated condenser temperature, calculates a discharge superheat temperature based on the saturated condenser temperature and the discharge line temperature, and monitors a flood back condition of the compressor by comparing the discharge superheat temperature with a predetermined threshold. The control module increases a speed of the compressor when the discharge superheat temperature is less than or equal to the predetermined threshold.

A method of operating an electric motor is disclosed. The method includes: starting the electric motor in an open loop control mode; operating an estimator that estimates operating conditions of the electric motor; and, while the electric motor is in the open loop control mode, evaluating a first parameter of the estimator. The method further includes: in response to the evaluation of the first parameter, determining whether the estimator has converged; and in response to a determination that the estimator has not converged within a predetermined period of time after starting the electric motor, signaling a first fault condition.

The invention includes an inverter to convert a direct-current voltage from a direct-current power supply into an alternating-current voltage and apply the alternating-current voltage to a motor that rotationally drives a load, a direct-current-voltage detecting unit to detect a voltage in the direct-current power supply, a shunt resistance that is a current detecting unit to detect an electric current flowing to the inverter, and an inverter control unit to generate PWM signals for driving switching elements of the inverter on the basis of the voltage detected by the direct-current-voltage detecting unit and the electric current detected by the shunt resistance, to set a specific phase difference between a phase of a carrier signal used for generation of the PWM signals and a phase of the alternating-current voltage, and to control the inverter such that a frequency of the PWM signals are synchronized with a frequency of the alternating-current voltage, the frequency of the PWM signals being an integer multiple of three times the frequency of the alternating-current voltage.

A power converting apparatus includes: an inverter converting a direct-current voltage supplied from a power supply unit into an alternating-current voltage and outputting the alternating-current voltage to a motor; and an inverter control unit outputting synchronous PWM (Pulse Width Modulation) signals for driving switching elements of the inverter. A frequency of the synchronous PWM signals is periodically varied when periodic pulsation occurs in a load connected to the motor.

A direct-current power supply device is a direct-current power supply device that converts a three-phase alternating current to a direct current and supplies the direct current to a load, and includes a first capacitor and a second capacitor connected in series between output terminals to the load, a charge unit that selectively charges one or both of the first capacitor and the second capacitor, and a control unit that controls the charge unit. The control unit controls an output voltage of the direct-current power supply device by a charging period of the charge unit, and also controls a power factor and a harmonic current of the direct-current power supply device by a charge timing with respect to a reference phase of the three-phase alternating current of the charge unit as a reference.

There is provided a vehicle air conditioning apparatus that can prevent the amount of the refrigerant discharged from the compressor from reducing when an outside air temperature is low to achieve a heating performance required for a heating operation, and also can dehumidify the vehicle interior without deteriorating the heating performance during a heating and dehumidifying operation. The vehicle air conditioning apparatus includes: 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.

An inverter control device that controls an inverter unit that converts a DC voltage from a converter unit to an AC voltage and supplies the AC voltage to the DC motor includes a storage unit that stores therein information regarding a synchronization-loss limit; a synchronization-loss limit-current calculation unit that calculates the limitation value on the synchronization-loss limit current on the basis of the magnet temperature of the DC motor, the bus voltage to be applied to the inverter unit, and the information regarding a synchronization-loss limit; and a control unit that compares the primary current to be input to the converter unit with the limitation value and that, when the primary current exceeds the limitation value, outputs an adjustment command to adjust the operating frequency of the DC motor such that the primary current becomes equal to or less than the limitation value.

The refrigeration device has an inverter device, an electric compressor, a condenser, an evaporator, a condenser fan, an evaporator fan, and a controller. An AC output from a power generator is supplied to the inverter device. A refrigerant discharge amount of the electric compressor is controlled by the inverter device. The refrigerant from the electric compressor flows in the condenser, and the condenser causes the refrigerant to radiate heat to outside air outside a container. The refrigerant from the condenser flows in the evaporator, and the evaporator cools an interior of the container. The condenser fan is driven by a DC output from a DC power supply device and blows air to the condenser. The evaporator fan is driven by the DC output from the DC power supply device and blows air to the evaporator. The controller controls at least the electric compressor, the inverter device, and the engine.

A motor driving device that drives a motor with an alternating-current power converted from a direct-current power supply, includes an inverter that receives a pulse-width modulation signal and supplies the alternating-current power to the motor, and an inverter control unit that generates the pulse-width modulation signal and supplies the pulse-width modulation signal to the inverter. The inverter control unit reduces the number of pulses of the pulse-width modulation signal generated during a first period within one period of a mechanical angle of the motor to be lower than the number of pulses of the pulse-width modulation signal generated during a second period within the one period of the mechanical angle of the motor. The first period is a period during which a load torque is lower than a load torque during the second period.

A synchronous motor control device includes: a DC power supply; an inverter main circuit; a three-phase synchronous motor; and an inverter control unit that outputs a PWM signal used to control the inverter main circuit. The inverter control unit includes: a PWM signal generation unit; a start-up control unit that outputs a start-up voltage command value to the PWM signal generation unit at the time of start-up; a steady state control unit that calculates a steady state voltage command value in a steady state and outputs the value to the PWM signal generation unit; and a steady state control parameter initial value calculation unit that outputs an initial value of a control parameter to the steady state control unit such that an output voltage vector from the inverter main circuit to the three-phase synchronous motor is consistent before and after switching from the start-up to the steady state.