A circuit system and a circuit control method applied to a motor drive are disclosed. The circuit control method includes the steps of providing a phase-locked circuit unit and providing a PWM control unit. The phase-locked circuit unit enables a first carrier signal and a second carrier signal to have identical amplitudes and starting points. The PWM control unit compares the first carrier signal with a reference signal for controlling a switch. When a load current is independently supplied by at least one DC capacitor, a SVPWM control unit controls an inverter unit for the load current to be zero, thereby reducing DC voltage ripple, operation loss and transient voltage surge.

In other features, a refrigeration system is provided and includes a compressor motor, an inverter, a converter and a control module. The inverter is configured to convert a direct current (DC) bus voltage to an alternating current (AC) voltage and supply the AC voltage to the compressor motor. The converter is configured to convert a DC input voltage to the DC bus voltage. The control module is configured to obtain a parameter and in response to the parameter exceeding a predetermined threshold, reduce the DC bus voltage and at least one of (i) reduce a switching frequency, (ii) increase an amount of negative d-axis current of the compressor motor, or (iii) reduce a speed of the compressor motor.

Apparatus and methods are provided for operating an electric motor, comprising selectively energising the coils of a stator having a plurality of stator teeth, each stator tooth having a said coil mounted thereon. The stator coils of a subset of the stator teeth are energised during a given time period to attract a corresponding rotor tooth into alignment with each of the stator teeth in the subset over the given time period. The stator coil of at least one stator tooth in the subset is energised during a portion of the given time period before the at least one stator tooth overlaps the corresponding rotor tooth.

A vehicle powertrain includes a DC-DC converter and a controller. The DC-DC converter is coupled between a traction battery and an inverter for an electric machine. The controller is configured to, in response to a rotational speed of the electric machine dropping below a back EMF threshold speed, transition to a current control based six step inverter mode and operate the DC-DC converter to output a voltage less than an open circuit voltage of the traction battery.

An interleaved bridgeless power factor correction (PFC) converter-based motor drive system is provided. The system includes a first inductor coupled to a second inductor. The coupled first and second inductors are coupled to a first input configured to be coupled to a first line of an alternating current (AC) power supply. The system also includes a third inductor coupled to a fourth inductor. The coupled third and fourth inductors are coupled to a second input configured to be coupled to a second line of the AC power supply. The system further includes a digital active power factor correction (PFC) controller configured to cause current in at least one of the coupled first and second inductors and the coupled third and fourth inductors to be interleaved.

In a boost chopper circuit, a backflow prevention diode circuit has a withstand voltage equal to or more than a withstand voltage of a capacitor circuit connected in series to the backflow prevention diode circuit between opposite ends of a switching device circuit.

There is provided an electric-power conversion system controller in which even when the temperatures of a switching device and a diode included in the driving circuit for a converter become high, the performances of the devices are prevented from being deteriorated and the lifetimes thereof are prevented from being shortened. In the case where even when determining that direct-coupling control is to be performed, a positive-polarity-side device temperature is higher than a determination temperature, the electric-power conversion system controller performs voltage-boosting control in which the positive-polarity-side switching device and the negative-polarity-side switching device are on/off-controlled in an on/off period; in the case where the positive-polarity-side device temperature is the same as or lower than the determination temperature, the electric-power conversion system controller performs direct-coupling control in which the positive-polarity-side switching device is turned on and the negative-polarity-side switching device is turned off.

A circuit that increases input voltage to higher output voltage connected to a variable frequency drive in an appliance. Several switching arrangements, timing, and safety mechanisms are in place to assist. When the circuit experiences high draw, high voltage output values of circuit decrease over time, but different aspects of the circuit can be constructed so that the amount of time required at a higher voltage does not exceed the amount of time in which the high voltage output is provided.

The DC power-supply device includes a rectifier circuit rectifying an alternating current, a reactor connected to an input or output side of the rectifier circuit, a first capacitor and a second capacitor serially connected between output terminals to a load, and a charging unit that selectively charges one or both of the first capacitor and the second capacitor. A ratio, to a period obtained by combining a charging period and a non-charging period of a pair of the first capacitor and the second capacitor, of the non-charging period, is controlled according to an operating condition of the load, to change a charging frequency of the first capacitor and the second capacitor based on the ratio, at the time of controlling an output voltage to the load.

According to one embodiment, the controller configured to, when an operation of the boosting circuit is in the boosting mode, and if an instantaneous value Ia of a current flowing through the reactor lowers to a value smaller than or equal to a set value Ias, switch the operation of the boosting circuit from the boosting mode to the non-boosting mode.