Abstract: A motor control apparatus has a plurality of DC-to-AC inverter circuits which supply respective electric motors, each inverter circuit formed of a plurality of switching circuits, all of the switching circuits being connected in parallel with a smoothing capacitor which smoothes a DC voltage. A charge which remains in the smoothing capacitor, after the source of the DC voltage has become disconnected, is discharged through a single switching circuit in each of the inverter circuits, with all other switching circuits of each inverter circuit being held in a non-conducting state, thereby preventing a flow of discharge current through any of the motors.

Abstract: A motor driving system including command value output means configured to output an analog value according to a rotation speed command; a first power line having first switching means; a drive circuit, to which power is supplied via the first switching means and the first power line, driving a motor supplying rotation based on the analog value; and switching control means configured to make the first switching means nonconductive when the analog value is smaller than a first predetermined value, and independent of the command value output means.

Abstract: A motor controller comprising multiple types of interfaces assigned automatically, including a mother circuit board and a daughter circuit board. The daughter circuit board is plugged into the mother circuit board to form electric connection. The mother circuit board has a power circuit, a microprocessor unit of the mother circuit board, a rotor position sensing unit, a power inverter unit, and an analog sensing unit. The daughter circuit board includes a signal interface circuit. The mother circuit board further has a serial digital communication unit. The signal interface circuit includes a microprocessor of the daughter circuit board, and a serial digital communication unit of the daughter circuit board. The microprocessor unit of the mother circuit board communicates with the microprocessor of the daughter circuit board via the serial digital communication unit of the mother circuit board and the serial digital communication unit of the daughter circuit board.

Abstract: An apparatus for measuring an error in a resolver includes a first calculator that perform an inverse Park transform based on voltages Uq and Ud at an output of PI current regulators, and delivers voltage setpoint signals PWMA, PWMB, PWMC to a power stage via a line on which a DC voltage Ubus-dc is available. The power stage generates a three-phase system of voltages UA, UB, UC for energizing an electric machine. The apparatus also includes a signal processor that provides an angle measurement ?m. Based on currents MesIA, MesIB, MesIC of the three phases, and on a rotor angle ?r, a second calculator of the device delivers values MesId, MesIq used by the first calculator. A PI voltage regulator delivers an angle ?c for correcting the error by regulating a setpoint value for the voltage Ud.

Abstract: A power inverter is provided that can apply to an AC rotary machine three-phase voltages of high amplitudes and low distortion while suppressing ohmic loss attributed to current detection resisters. The power inverter includes a superimposed voltage command computing device which is configured to compute and output a superimposed voltage command depending on the difference between a maximum value and a minimum value of three-phase voltage commands; a voltage command modification device which is configured to add the superimposed voltage command to each of the three-phase voltage commands and outputting modified three-phase voltage commands; and a power output device which is configure to output the three-phase voltages based on the modified three-phase voltage commands.

Abstract: A synchronous machine control apparatus is characterized by including a magnet condition estimation unit (7, 7a) that estimates the temperature or the magnetic flux of a permanent magnet that forms the magnetic field of a synchronous machine (1), and is characterized in that the magnet condition estimation unit (7, 7a) coordinate-converts an armature current into currents on the ?-? axis consisting of the ? axis and the ? axis that is perpendicular to the ? axis, based on the rotor position and the estimated ? axis, and estimates the temperature or the magnetic flux of the permanent magnet, based on the control command for the synchronous machine (1) and the ?-? axis currents.

Abstract: A power supply unit for a press machine having a converter (converter circuit) connected to a commercial AC power supply, and an inverter (inverter circuit) connected to a press motor, includes an electrical energy bank, an inrush prevention circuit, an inrush prevention instruction signal generation section, and a contactor switch section, wherein contactors of the inrush prevention circuit are switched from on ON state to an OFF state and inrush prevention resistors of the inrush prevention circuit are connected to AC phase current paths on condition that the inrush prevention instruction signal generation section has generated and output an inrush prevention instruction signal (Sres) during press operation.

Abstract: A command rotation speed is set to an initial rotation speed, and a forced commutation mode is started. In the forced commutation mode, a rotation speed is increased by a predetermined increase amount each time and forced commutation is executed until the rotation speed reaches a set rotation speed. Then, a switchover to the sensorless control mode is made when the rotation speed reaches the set rotation speed (S4) and a rotor position becomes detectable.

Abstract: The invention relates to power converter circuits which are suitable, in particular, for mobile drive systems with stringent requirements in terms of weight minimization and availability as well as direct attachment to rotating field machines. Inter alia, the strictly modular design of the electronics and the very low expenditure on passive filter elements by virtue of the principle involved are characteristic.

Abstract: A direct current bus management system can include a power management and distribution unit, having a source management section, a bus management section coupled to the source management section, a load management section coupled to the bus management section, a DC bus coupled to the power management and distribution unit, a plurality of DC sources coupled to the source management section and a plurality of loads coupled to the load management section, wherein the bus management section is configured to reconfigure excess DC power on the DC bus from the DC inputs from the plurality of DC sources based on a plurality of priorities, a plurality of feedback signals and a plurality of system parameters.

Abstract: A renewable energy source is converted into a desired DC voltage that is delivered to a DC motor controller of a permanent magnet motor. A micro controller monitors the amount of supplied renewable DC having the desired DC voltage, which is delivered to each phase of the motor by turning on FET switches on demand. If the renewable DC available at a given instant is not adequate to power a particular phase of the motor, then the micro controller turns on backup FET switches that are part of an independent drive circuit that is in parallel with drive circuits of the renewable DC power circuit, to deliver to the motor line DC, which is produced from an AC supply that has gone through an AC to DC converter. Once charged, the renewable DC power will power the next available phase of the motor.

Abstract: In a control apparatus for a rotary electric machine receiving power from a DC power supply, a DC-AC converting circuit is provided with serially connected circuits each having high-potential-side and low-potential-side switching elements. When a short-circuit occurs at the switching elements, all the switching elements are turned OFF for failsafe and a path connecting the machine and the battery is opened. In such a case, a switching element belonging to part of the switching elements is turned ON, with potential at all the terminals of the rotary electric machine being the same. A location of the short-circuit occurs is identified, based on changes in current passing through the machine and being detected in response to turning ON the switching element. The changes are at least one of a reduction change in deviation of the current from a zero point and a reduction change in an absolute value of the current.

Abstract: A power converting apparatus includes a timing signal generator and a phase determination signal generator provided in an ON/OFF signal generating unit as well as a detected current correction unit. On the basis of timing signals ts1, . . . and phase determination signals ph1, . . . , the power converting apparatus determines detected current values and phases of the detected current values fed from a DC bus current sensor at timings set in accordance with the timing signals and corrects the detected current values idc1, . . . for the individual phases obtained at the individual timings during PWM cycles to represent values which would be obtained at reference timing t0 to thereby reduce errors caused by differences in the current detecting timings for the individual phases.

Abstract: A converter circuit capable of being compact and light-weight and capable of reducing switching loss, a motor drive control apparatus, an air-conditioner, a refrigerator, and an induction heating cooker provided with the circuit. The converter circuit including: a step-up converter including a rectifier, a step-up reactor, a switching element, and a reverse current prevention element; a step-up converter having a step-up reactor, a switching element, and a reverse current prevention element and connected in parallel with the step-up converter; switching control unit that controls switching elements; and a smoothing capacitor that is provided at the output of the step-up converters. The switching control unit switches the current mode of the current flowing through the step-up reactors into any of a continuous mode, a critical mode, and a discontinuous mode based on a predetermined condition.

Abstract: For each phase of a controller, semiconductor switches comprise a high side switch and a low side switch. A direct current voltage bus provides electrical energy to the semiconductor switches. A measuring circuit is adapted to measure the collector-emitter voltage or drain-source voltage for each semiconductor switch of the controller. A data processor determines that a short circuit in a particular semiconductor switch is present if the measured collector-emitter voltage or measured source-drain voltage for the particular semiconductor switch is lower than a minimum threshold and if an observed current associated with the particular semiconductor switch has an opposite polarity from a normal operational polarity. A driver simultaneously activates counterpart switches of like direct current input polarity that are coupled to other phase windings of the electric motor, other than the particular semiconductor switch, to protect the electric motor from potential damage associated with asymmetric current flow.

Abstract: An inverter and a control unit that has a command signal processing unit and a PWM frequency control unit and performs pulse width modulation control are provided. If the command signal processing unit has received a first PWM frequency command signal, it outputs a low PWM frequency command signal so that synchronous or asynchronous PWM control is performed at a PWM frequency in a predetermined frequency range. The command signal processing unit outputs a high PWM frequency command signal so that synchronous or asynchronous PWM control is performed at a higher frequency than the above-mentioned frequency if the command signal processing unit has received a second PWM frequency command signal and until a predetermined time period elapses. The command signal processing unit outputs a low PWM frequency command signal if it has received the second PWM frequency command signal and after the predetermined time period elapsed.

Abstract: A sensor-less vector control apparatus for induction motor enhanced in performance of sensor-less vector control by estimating changes in parameters in real time is provided, the apparatus including a current controller, a first phase converting unit, a second phase converting unit, a rotor speed and position estimator configured to measure a rotor speed of a rotor and a rotor flux using an output value of the first phase converting unit and to estimate a rotor position using the output value, and a stator resistance and angle error estimator configured to calculate a stator resistance and an angle error of the induction motor by receiving d, q axis current commands on the synchronous reference frame inputted from the current controller and d, q voltages on the synchronous reference frame outputted from the current controller, and to provide the stator resistance to the rotor speed and position estimator.

Abstract: Systems, methods, and other embodiments associated with back-EMF detection for motor control are described. In an embodiment, an apparatus includes a drive circuit configured to apply excitation signals to respective inputs of a motor, a signal inhibit circuit configured to convey a signal to inhibit application of the excitation signals during an interval, and a measuring circuit configured to measure a back-electromotive force (EMF) signal crossing a reference signal during the interval.

Abstract: A motor can be driven while reducing the power loss of the entire system where a plurality of devices that causes power losses exists. The system is provided with an inverter connected to a motor, a first converter that is connected between a fuel cell and the inverter and sets an output voltage of the fuel cell, a second converter that is connected between a power storage device and the inverter and sets an input voltage Vin of the inverter, and a controller that controls the first converter and the second converter. Under the operating condition (torque, number of revolutions) required for the motor, an input voltage of the inverter which minimizes a power loss of at least one of the motor, the first converter, the second converter and the inverter is determined, and the determined input voltage is output as a necessary voltage for the inverter.

Abstract: A drive circuit for delivering high-level power to a load, and method of stopping a high power load from operating, are disclosed. The drive circuit includes a high power circuit capable of being coupled to the load and delivering the high level power thereto, and a to power circuit that controls the high power circuit. The low power circuit includes a first circuit portion that provides at least one control signal that is at least indirectly communicated to the high power circuit and that controls the delivering of the high level power by the high power circuit, and a second circuit portions coupled to the first circuit portion. The second circuit portion is capable of disabling the first circuit portion so that the at least one control signal avoids taking on values that would result in the high power circuit delivering the high level power to the load.

Abstract: A motor inverter is provided with switching elements for each phase of a 3-phase motor, and driving the motor by turning on and off the switching elements. In an example of a control device of the motor inverter, the control device includes: a stationary phase determination unit for defining a phase in a plurality of phases provided with switching elements for each area as a stationary phase in which a switching operation is not performed, based on current command value of each phase acquired from d-axis current command value and q-axis current command value of the motor, with one rotation in electrical angle of a rotor of the motor divided into a plurality of areas; and a drive unit for performing the switching operation of switching elements of the phases other than the stationary phase determined for each area to perform, and realizing 2-phase modulation control.

Abstract: A method for controlling a specific electric machine includes receiving with a controller a back electromotive force (BEMF) coefficient for the specific electric machine. The controller is configured to control operation of an inverter coupled to the electric machine where the inverter is configured to provide or receive multi-phase electricity to or from the electric machine in motor mode or generator mode, respectively. The method further includes receiving with the controller an input related to a selected torque to be applied by or a selected power to be removed from the electric machine. The method further includes determining a first electrical parameter the inverter is to apply to in motor mode or a second electrical parameter the inverter is to convert power to in generator mode using the BEMF coefficient, and applying the first electrical parameter to the electric machine or converting the received power to the second electrical parameter.

Abstract: A regenerative load electric power management system can include a system bus, an input filter coupled to the system bus, a first bidirectional solid state power controller coupled to the system bus, a motor drive inverter coupled to the input filter, a second bidirectional solid state power controller coupled to the motor drive inverter, a bidirectional direct current DC-DC converter coupled to the second bidirectional solid state power controller and an energy storage bus coupled to the bidirectional DC-DC converter, the energy storage bus providing access to an energy storage device.

Abstract: A control command generator that generates an armature interlinkage flux command and a torque current command by a torque command, a rotation speed, and an operation target command, includes a first flux command generator generating a first flux command by the toque command or the torque current command, a second flux generator generating a second flux command by the torque command or the torque current command and the rotation speed of the synchronous machine, a command allocation setting unit setting an allocation coefficient equivalent to an allocation ratio of the two first and second flux commands by the operation target command, a flux command adjuster outputting an armature interlinkage flux command by the two flux commands and the allocation coefficient, and a torque current command generator generating the torque current command by the torque command and the armature interlinkage flux command.

Abstract: The invention relates to a combined method and device for powering and charging, wherein said device comprises an AC motor (6), a converter (2), storage means (5), and switching means (4) either for enabling the powering of the motor (6) or for enabling the charging of the storage means (5) by the converter (2). The switching means (4) is integrated in the converter (2) and includes at least one H-shaped bridge structure (3) for each phase of the motor (6).

Abstract: A system, method and computer program product for monitoring including detecting internal faults especially inter-turn faults of a synchronous generator and thus protecting the synchronous generator. The synchronous generator includes a winding for each phase of a power network, a terminal for each phase arranged on a terminal side of the synchronous generator, and connected to the respective winding, the terminals on the terminal side are connected to an electrical power network, and the synchronous generator is arranged to input power to the electrical power network by means of the terminals.

Abstract: Provided is a vehicle behavior controller capable of stabilizing a behavior of a vehicle with a high response when an unstable state of the vehicle is judged. The vehicle behavior controller includes: a running state detecting unit for detecting a running state of the vehicle; an unstable state judging unit for judging the unstable state of the vehicle based on the running state; a motor generator connected to an engine of the vehicle, the motor generator operating as a power generator for using an output of a prime mover to generate power and an electric motor for assisting the output of the prime mover; and a control unit for controlling an operation of the motor generator based on r.p.m. of the motor generator, in which the control unit controls the operation of the motor generator to generate braking torque when the unstable state is judged.

Abstract: Motor drive apparatus and methods are presented in which a standby controller uses at least one switching device to power an inverter in a normal mode and to remove power from the inverter and other motor drive components during a standby mode for improved energy efficiency.

Abstract: A method for monitoring input power to an electronically commutated motor (ECM) is described. The method includes determining, with a processing device, an average input current to the motor, the average input current based on a voltage drop across a shunt resistor in series with the motor, measuring an average input voltage applied to the motor utilizing the processing device, multiplying the average input current by the average voltage to determine an approximate input power, and communicating the average input power to an external interface.

Abstract: A motor controller is disclosed. The motor controller includes a current detector that is provided in a direct current side of a power converter and that detects direct current information. A determiner determines a size of an offset voltage contained in the detected current information. The determiner calculates the offset voltage by canceling a positive current component by a negative current component both pertaining to the same one phase and contained in the detected direct current information. A modifier modifies the detected direct current information based on the calculated offset voltage.

Abstract: Example embodiments disclose a drive system including a machine including a plurality of phases and configured to generate power based on a plurality of phase currents, each respectively associated with the plurality of phases and a direct current (DC) bus, operatively connected to the machine. The DC bus includes a high-side line, a low-side line, and an inverter including a plurality of switching systems, operatively connected between the high-side line and the low-side line, the plurality of switching systems, each configured to output a respective one of the plurality of phase currents. The drive system also includes a controller, operatively connected to the DC bus and the machine, the controller configured to determine if a failure exists in the drive system based on the plurality of phase currents and a DC bus voltage, the DC bus voltage being a voltage across the high-side line and the low-side line.

Abstract: A method for driving a brushless motor including a first coil and a second coil for two phases but does not include a coil for one of three phases. A three-phase inverter circuit is connected to the first coil and the second coil. Currents having a phase difference corresponding to an electrical angle of 60 degrees are applied to the first coil and the second coil to generate a circular rotating magnetic field.

Abstract: In a controller for an AC electric train capable of power running and regenerative running, and capable of detecting a power failure in an AC overhead wire for supplying AC electric power, a power failure in the AC overhead wire is swiftly and reliably detected.

Abstract: An AC motor drive control device including: an inverter, having a plurality of switching elements subjected to on-off control, for converting a DC voltage to an AC voltage with a desired frequency to drive an AC motor; a motor opening contactor connected between the inverter and the AC motor; a switching operation beforehand detection unit for detecting a switching operation of the motor opening contactor prior to the contact or detach of main contacts and outputting a switching operation beforehand detection signal; and a control unit having an inverter control unit for performing the on-off control for the plurality of switching elements and switching control for the motor opening contactor, and controlling the inverter based on the switching operation beforehand detection signal.

Abstract: A lower limit value setting unit (52) variably sets a lower limit value (Vth) of a target voltage (Vh*) in a range of a voltage that is higher than the maximum value of voltages (Vb1, Vb2) of power storage devices and is not affected by a dead time provided for converters, based on temperatures (Tb1, Tb2) and required electric powers (Pb1*, Pb2*). A maximum value selection unit (53) sets the maximum value among the voltages (Vb1, Vb2) of the power storage devices and required voltages (Vm1*, Vm2*) of motor-generators, as the target voltage. A target voltage limiting unit (54) compares the target voltage with the lower limit value (Vth), and if the target voltage is lower than the lower limit value (Vth), the target voltage limiting unit (54) sets the lower limit value (Vth) as the target voltage (Vh*).

Abstract: An switch array for use in a motor control circuit with a power source, controller and a motor includes a plurality of bidirectional switches positioned between the power source and the motor, wherein the bidirectional switches are PWM controlled by high speed control signals from the controller to provide power from the power source to the motor as desired, wherein the switch array is positioned substantially adjacent to the motor. The power source may be a three phase AC power source. The switches are preferably bidirectional gallium nitride (GaN) switches.

Abstract: A motor drive PWM rectifier includes a control section which generates the PWM signal in accordance with either a three-phase modulation scheme or a two-phase modulation scheme in which a PWM voltage command for one phase selected from among three phases each constituting the PWM voltage command in the three-phase modulation scheme is set and held at a level equivalent to a maximum value or minimum value of the PWM carrier and in which a PWM voltage command for the other two phases created by also applying an offset, required to achieve the setting, to the other two phases, a detecting section which detects three-phase AC current and outputs a detected current value, and a selecting section which selects the two-phase modulation scheme when the detected current value is larger than a first threshold value but smaller than a second threshold value, and otherwise selects the three-phase modulation scheme.

Abstract: A motor control system for heating, ventilation, and air conditioning (HVAC) applications is described. The motor control system includes a thermostat and an electronically commutated motor (ECM) coupled to the thermostat. The ECM is configured to retrofit an existing non-ECM electric motor included in an HVAC application and to operate in one of a plurality of HVAC modes. The HVAC modes include at least one of a heating mode, a cooling mode, and a continuous fan mode. The HVAC mode is determined based at least partially on outputs provided by the thermostat.

Abstract: Disclosed herein is a motor control apparatus and a method thereof. A phase error of the reference voltage output corresponding to a time delay caused by digital control may be compensated to stably control a motor, thereby improving the stability of a system. The phase compensation unit may be provided therein to convert a reference voltage of the synchronous coordinate system into a reference voltage of the stationary coordinate system when controlling the high-speed operation of the motor, thereby compensating a phase error of the reference voltage output, and allowing the motor to be operated at a high speed while maintaining its efficiency and reducing a volume of the compressor.

Abstract: Described herein is a drive arrangement for the motor-driven adjustment of an adjustable element in a motor vehicle, the drive arrangement having two electrical drives and a control device, the drives, in the fitted state, acting in the same way on the adjustable element and having a substantially identical configuration, apart from tolerance-related discrepancies. The control device has a power controller which, in the fitted state, during the motor-driven adjustment of the adjustable element, subjects the electrical power that is output respectively to the two drives to closed-loop control, for the purpose of compensating for the tolerance-related discrepancies, in such a way that an identical electrical power consumption is established for both drives.

Abstract: To prevent demagnetization of a permanent magnet synchronous rotating machine, a rotating machine control device according to the present invention is a rotating machine control device comprising: a power converter having a switch part on each of a positive side and a negative side for each phase; and short circuit detection unit for detecting a short circuit of the switch part, wherein a command to turn on positive-side switches and negative-side switches of a plurality of phases of the switch part is issued in the case where the short circuit detection unit detects the short circuit.

Abstract: A control apparatus for an electric motor provided with a rotator having a permanent magnet and with a stator for generating a rotating magnetic field by an applied voltage and revolving the rotator includes: a rectangular wave inverter that applies a rectangular wave voltage onto the stator of the electric motor to drive the electric motor; a voltage converting section that raises or lowers an output voltage of a direct-current power supply and applies the voltage onto the rectangular wave inverter; an electrical angle acquiring section that acquires an electrical angle of the rotator of the electric motor; and an output voltage command generating section that generates a command for instructing the voltage converting section to output an electrical-angle synchronized voltage whose amplitude ripples in synchronization with a change of the electrical angle of the rotator acquired by the electrical angle acquiring section.

Abstract: A DC voltage value from a DC voltage detection section is input directly to a voltage correction section without passing through a compensator or a filter. Therefore, even when rapid voltage change occurs, such as short power interruptions, instantaneous voltage drop and return from instantaneous voltage drop, the voltage correction section can quickly perform the correction operation in response to the rapid voltage change. Since the amount of link resonance compensation is limited by the limitation section to a certain range, it is possible to prevent the amount of link resonance compensation from fluctuating excessively upon rapid voltage change. Since the amount of link resonance compensation which is limited by the limitation section to a certain range is input to one compensator that has an appropriate control band, among all control calculation sections, the response does not have to be unnecessarily fast, thus realizing a stable control.

Abstract: An inverter/charger integrated device is provided. The inverter/charger integrated device includes: a three-phase motor; a rectifying unit configured to rectify AC power for charging a battery and output the rectified AC power to a neutral point of the three-phase motor; a rectifier/inverter integrated unit configured to be connected to the rectifying unit and charge the battery; and a control unit configured to control the charging of the battery and an operation of the three-phase motor.

Abstract: The invention relates to an industrial robot having a robotic arm. The robotic arm has several axes (A1-A6) and at least one electric drive, which comprises an electric motor (7-12) and power electronics (16) actuating the electric motor (7-12) and is equipped to move the relevant axis (A1-A6). The industrial robot (1) is equipped to short-circuit the electric motor (7-12) in the event of emergency braking simultaneously by means of two independent electric current paths.

Abstract: The present invention provides a power supply device for an electric vehicle that allows highly efficient operation of a compressor inverter.

Abstract: A power converting apparatus including a power converter that converts a DC voltage into an AC voltage and applies the AC voltage to an AC rotating machine and a control unit that controls the power converter based on an operation command from the outside is provided. The power converting apparatus includes: a first calculating unit that calculates and outputs, from a d-axis current detection value and a q-axis current detection value detected by the AC rotating machine and current command values based on the operation command, first voltage command values to the power converter, magnetic fluxes of the AC rotating machine, and an angular frequency; and a second calculating unit that sets, as an initial value, at least one of the magnetic fluxes and the angular frequency input from the first calculating unit and calculates and outputs second voltage command value to the power converter and an angular frequency.

Abstract: A direct-current to three-phase alternating-current inverter system includes a three-phase motor, a plurality of switching elements, an inverter circuit for the three-phase motor, a capacitor, a direct-current power source and a control circuit. The switching elements arranged in the inverter circuit serve as upper and lower arms for the respective three phases of the three-phase motor, respectively. The capacitor is connected in parallel to the respective pairs of the upper and lower arms. The direct-current power source is arranged between the neutral-point of the three-phase motor and the respective lower arms or the respective upper arms. The control circuit controls the switching elements such that at least the switching frequency of one pair of the switching elements for one phase through which the current having the greatest value flows is lower than the switching frequencies of the other pairs of the switching elements for the other phases.

Abstract: An AC-AC power converter supplies AC power to an AC motor having a plurality of motor windings and a case connected to a ground. The AC-AC power converter architecture includes an asymmetric phase shift autotransformer/rectifier unit (ATRU) that converts an AC input to a DC output, wherein the asymmetric phase shift ATRU generates a common-mode AC voltage across the asymmetric phase shift ATRU. The common mode voltage is diverted to ground through motor case parasitic capacitance via a common-mode voltage pull-down circuit connected between each phase of the ATRU AC input and the ground.

Abstract: A motor drive system includes an inverter that supplies power to a three-phase motor, and a control unit that, when first stopping and then commencing supply of alternating current to three phases of the three-phase motor, switches from first control to third control and then to second control. The first control places switching elements in the inverter in a non-conduction state, the second control is a PWM control of the switching elements, and the third control places and keeps a switching element of each of an upper arm and a lower arm in the conduction state until commencement of the supply of current. The upper arm corresponds to a phase through which current flows in a direction entering the motor upon commencement of the supply, and the lower arm corresponds to a phase through which current flows in a direction exiting the motor upon commencement of the supply.