A discharge duty that is a duty at which a switch is conductive takes a value obtained by dividing a product of a crest value of a single-phase AC voltage and a square of a cosine value of a phase of the single-phase AC voltage by a both-end voltage across a capacitor. A sum of a product of a rectifying duty that is a duty at which a converter is conductive and a rectified voltage output from the converter and a product of the both-end voltage and the discharge duty varies in a period that is a half of the period of the single-phase AC voltage.

A converter performs full-wave rectification on a single-phase voltage, thus outputting a rectified voltage across DC power supply lines. An inverter receives the rectified voltage and then supplies a three-phase AC current to an inductive load. Between the DC power supply lines is connected a charge and discharge circuit. The charge and discharge circuit includes a buffer circuit and a boost circuit. The buffer circuit includes a series connection between a capacitor and a switch. The boost circuit, which may be configured by a boost chopper, includes a switch, a reactor and a diode. The charge and discharge circuit provides and receives part of pulsations of the power input to the converter between the DC power supply lines.

An apparatus and method for extending component life in a motor drive having a stator heating mode is disclosed. The current supplied to stator windings is cycled through a set of primary stator power transistors to increase the overall lifespan of the drive, thus preventing premature failure of the stator power transistors by splitting the workload between them, rather than having a single transistor supply the bulk of the stator heating current.

A motor control system includes: a converter; two inverters; two alternating-current motors; and a control unit. The control unit is configured to control the system voltage by feedback of a current phase of a current vector of motor current of each of the motors on a d-q coordinate plane so that rectangular wave control of at least one of the first and second motors is performed in a state where the current phase is an optimal current phase, wherein the control unit selects, as a subject of the feedback, the current phase of one of the motors that is larger than the other motor in system voltage deviation obtained based on the current vector.

Provided is a drive device for a rotating electric machine, including: a power conversion unit configured to convert DC power supplied from a storage battery into AC power, and to supply the AC power to a rotating electric machine; and a control unit output a switching signal to the power conversion unit. The control unit is configured to set, when the storage battery is to be charged, in a case in which a temperature of the storage battery input from an outside is lower than a set temperature suitable for charging, the switching signal for the power conversion unit so as to be different from the switching signal in a normal drive state of the rotating electric machine.

The first square wave control mode using the square wave pulse pattern is used when the voltage acting on the inverter is equal to or higher than the threshold voltage. On the other hand, when the voltage acting on the inverter is lower than the threshold voltage, a square wave pulse pattern is used when the rotation speed of the motor is equal to or higher than the first predetermined rotation speed that is higher than the first resonance region, and the second square wave control mode using the first switching pattern for suppressing the LC resonance in the first resonance region is used when the rotation speed of the motor is lower than the first predetermined rotation speed.

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 a motor driving apparatus including a DC power supply circuit of variable output voltage value, an inverter of variable frequency, and a connection switching device for selecting connection, switching of the connection switching device is performed in a state where an output voltage of the DC power supply circuit is increased, a rotational speed of a motor is increased, and a current flowing through the motor is made not greater than a predetermined threshold. For example, the switching of the connection switching device is performed in a state where the current through the motor is made zero. For example, the switching is performed in a state where the output voltage of the DC power supply circuit is set at a value corresponding to the rotational speed of the motor during the switching. It is possible to prevent increase in apparatus size and switch the connection of windings while the motor is rotating.

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.

A filter unit is intended to be connected between an inverter and an electric motor. The filter unit includes: a number of phase connections for connecting to corresponding phase connections of the inverter; a first DC link connection for connecting to a first DC link connection on the inverter and a second DC link connection for connecting to a second DC link connection on the inverter; a number of motor connections for connecting to corresponding connections on the electric motor; a number of filter elements for reducing a rate of voltage rise at the motor connections of the filter unit, filter element is connected between corresponding phase connections of the filter unit and corresponding motor connections of the filter unit; and a coupling unit, which couples the filter elements capacitively with the first DC link connection and the second DC link connection of the filter unit.