Abstract: A system for controlling torque ripple in a permanent magnet synchronous machine includes a power converter configured to be coupled to the permanent magnet synchronous machine and to receive converter control signals and a system controller coupled to the power converter. The system controller includes a fundamental current controller configured for providing fundamental voltage commands, a harmonic current controller configured for using harmonic current commands, current feedback signals from the permanent magnet machine, and fundamental current commands in combination with positive and negative sequence regulators to obtain harmonic voltage commands, and summation elements configured for adding the fundamental voltage commands and the harmonic voltage commands to obtain the converter control signals.

Abstract: With the use of three inverter circuits controlled by a single processor, the controller of the motor-driving apparatus provides a rotation drum-driving motor, a compressor-driving motor and a blow fan-driving motor with a simultaneous sinusoidal-wave control. The configuration above offers stable sinusoidal-wave drive, reducing vibration noise of the rotation drum, the compressor and the blow fan.

Abstract: Provided is a motor controller and method of controlling a motor with an improved maximum junction temperature rating. In accordance with one aspect of the present invention, a motor is controlled by varying a common mode voltage duty ratio for a plurality of solid state switching devices in a power inverter, generating drive signals for the solid state switching devices based at least in part upon the common mode voltage duty ratio, and changing states of the solid state switching devices based upon the drive signals.

Abstract: Systems and methods are disclosed to provide torque linearity in the field-weakening region for an IPM machine. The systems and methods adjust the q-axis and the d-axis components of the stator current commands of the IPM machine using a flux weakening and a torque linearity control loop respectively. Thereby, torque linearity is maintained during the field weakening region of operation of the IPM machine.

Abstract: A method for controlling the operation of an electronically commutated motor (ECM) with an ECM control assembly is described. The method includes applying a single pulse width modulated (PWM) signal to a plurality of inputs of a power output module. The method also includes controlling the state of input/output (I/O) circuits to allow the PWM signal to pass through a respective one of the power output module inputs and into a respective winding of the ECM at a desired interval.

Abstract: The present invention is directed to a power converter that can be used to interface a motor 4 that requires variable voltage at variable frequency to a supply network (bus) providing a nominally fixed voltage and nominally fixed frequency. The power converter includes a first active rectifier/inverter 10 electrically connected to the stator of the motor 4 and a second active rectifier/inverter 14. Both the first and second active rectifier/inverters include a plurality of semiconductor power switching devices. A dc link 12 is connected between the first active rectifier/inverter and the second active rectifier/inverter. A filter 16 is connected between the second active rectifier/inverter and the supply network and includes network terminals. The power converter includes a first controller 18 for the first active rectifier/inverter and a second controller 20 for the second active rectifier/inverter.

Abstract: A motor control apparatus which controls an output voltage reference for an inverter driving a permanent magnet synchronous motor based on d-axis and q-axis current references, d-axis and q-axis current detected values, and a computed frequency value. When a torque reference specifying torque greater than maximum torque that the motor can output is input, a limit value for a phase angle that is a deviation between a rotation phase reference of control and a rotation phase value of the motor is varied depending on a quantity of the predetermined state.

Abstract: In an apparatus of controlling a motor in a battery vehicle, a current command generation section has a table, and generates an exciting command current and a torque command current by referring to the table based on a torque command. A converting section generates 3-phase command voltages from the exciting command current and the torque command current. A motor driving section drives a motor in response to the 3-phase command voltages.

Abstract: A power regulator with a bypass and splice capacity includes at least one phase member and a driver. Each one of the at least one phase member includes two cooling fins, two SCR thyristors, a conductive resilient tab and a conductive rigid tab. The cooling fins are conductive and adjacent to each other. The SCR thyristors are mounted on the cooling fins and are inversely connected in parallel to each cooling fin. The conductive resilient tab is mounted on one of the cooling fins and has a moveable contact. The conductive rigid tab is mounted on the other cooling fin and has a stationary contact aligned with the movable contact. When the driver is energized, the driver drives the conductive resilient tab and the moveable contact is contacts the stationary contact and power is bypassed and spliced through the cooling fins.

Abstract: A synchronous machine control apparatus which can produce a torque level as close as possible to a desired torque command level while considering limitations on an output current of a power conversion unit.

Abstract: A field winding synchronous generator-motor includes: a power conversion section that is connected to an electric rotating machine and operating as a generator-motor, and that controls the electric rotating machine; a compensation amount storage section that stores a compensation capable of improving characteristics of the electric rotating machine from a reference position of a rotor; a positional compensation operation section that makes a compensation operation of positional information from a rotor position and a value of the compensation amount storage section; a conducting phase storage section that stores a conducting phase to each armature winding from the reference position; and a rectangular wave application voltage command section that commands a rectangular wave application voltage to each armature winding with respect to the power conversion section from a value of the positional compensation operation section and a value of the conducting phase storage section.

Abstract: Control technique of a synchronous motor capable of suppressing rotation pulsation caused by individual difference without complicating control algorithm is provided. A pulsation generator superimposing a pulsation component anticipated in advance to a current command for the synchronous motor and a correction current generator superimposing a correction signal substantially having an average value of zero to the current command are provided in a synchronous motor control device. By this configuration, the correction signal suppressing a distortion component is superimposed to a value of the current command with a simplified control configuration. Torque pulsation is suppressed by determining the correction signal from difference between a detection current and a command current.

Abstract: An inverter-integrated electric compressor enhances vibration resistance of an inverter apparatus integrated with a housing without degrading cooling performance, reduction in weight, or the ease of assembly of the inverter apparatus. An inverter-integrated electric compressor 1 has an inverter apparatus 22 integrated with an inverter storage box 11 of a housing 3. The inverter apparatus 22 includes a metal plate 23 secured in an inverter storage box 11; a plurality of power semiconductor switching elements 24 mounted on the metal plate 23; a power substrate 25 on which a power-related control circuit for operating the power semiconductor switching elements 24 is mounted; and a busbar assembly 26 formed by integrating a plurality of busbars with an insulator. The metal plate 23 includes a protrusion 33 extending in a width direction perpendicular to a motor shaft direction L of an electric motor.

Abstract: A driving apparatus of a synchronous motor fixes all the switching devices of an inverter at OFF in accordance with a value of an all-OFF control pulse signal outputted by a pulse generator. A motor current keeps flowing through free wheel diodes for a predetermined period even after all the switching devices shift to the OFF state. Therefore, pulse generator changes an induced voltage detection signal to an H (high) level after the passage of the time in which a motor current drops down to zero. A terminal voltage of the motor is taken in to acquire an induced voltage and a rotor position is estimated.

Abstract: The present invention discloses a real-time responsive motor control system comprising a central MCU (Microcontroller Unit) core logic and at least one PWM (Pulse Width Modulation) MCU core logic. The central MCU core logic takes care of all interrupt events. The PWM (Pulse Width Modulation) MCU core logic is dedicated to the transformation of PWM signals so that the PWM signals output to a motor device are highly accurate. Further, the central MCU core logic may directly control the PWM MCU core logics so that the switching timing of the PWM signals is even more accurate. The present invention provides a modularized hardware architecture with flexible software control. The system design is simple and the associated cost is reduced.

Abstract: At first, a plurality of detection modes are applied in sequence to a brushless DC motor, such that with respect to each of the detection modes a composite magnetic field generated by a motor current flowing through motor coils points in a different direction. Then, each of peak values of the motor currents generated by the detection modes is compared with respect to one another so as to select, from the plurality of detection modes, one detection mode which generates a largest one of the peak values of the motor currents. An initial position of a rotor is determined on a basis of a direction of a composite magnetic field generated by the detection mode which generates the largest one of the peak values of the motor currents. Based on the initial position of the rotor, the brushless DC motor is driven to start rotating.

Abstract: A direct current motor controlling method includes a mean for transforming a duty signal to computed value by a microprocessor unit. The microprocessor unit computes the computed value and then produces a target value by executing a dichotomy method, a rotation method and a transformed function, capable of reducing executing time and executing load of the microprocessor unit and saving memory space. The microprocessor unit sends a frequency signal to a driving circuit unit according to the target value. The driving circuit unit receives the frequency signal and then provides a driving voltage to a power switch. The power switch provides a voltage to a direct current motor or not according to the driving voltage for controlling output performance of the direct current motor.

Abstract: A mainframe and power supply arrangement is disclosed to include a mainframe, which has a base frame holding a DC power jack and connector modules, a circuit module, which includes a sliding carrier detachably slidably inserted into the base frame and a circuit board carried on the sliding carrier and having connectors connectable to respective connecting portions of the connector module and a electric power distribution module for distribution of DC power supply received to the DC power jack, and an external power supply unit set outside the mainframe and connectable to the DC power jack for converting AC power supply into DC power supply and providing converted DC power supply to the electric power distribution module.

Abstract: A device to regulate current produced by a permanent magnet machine responsive to a plurality of phase current signals. The motor produces torque for application on a shaft. A processing and drive circuit responsive to a direct current command signal and a quadrature current command signal produces phase current signals for input to the motor. A command circuit responsive to the phase current signals, an angular position of said shaft, and a voltage input command signal to produce a direct current error signal and a quadrature current error signal. A control circuit responsive to the direct and quadrature current error signals produces the direct voltage signal command and the quadrature voltage signal command. The control circuit has a direct and quadrature proportional gain, integrator and clamp circuits. An algorithm produces limited or clamped voltage modulation index signals to obtain maximum efficiency and maximum torque per ampere in the speed range.

Abstract: A DC offset compensation system and method significantly reduce a DC offset voltage in the voltage feedback loop of an AC motor drive control system. A control voltage error signal is demodulated and filtered and applied to the closed loop voltage feedback signals to compensate for DC offset voltages in the closed loop voltage feedback. A frequency discriminator tuned to the fundamental motor frequency improves the precision of the DC offset detection. A startup flux DC offset compensation operates to eliminate initial startup flux DC offset. Motor flux compensation is improved through a variable flux filter time constant.

Abstract: A control apparatus and a semiconductor apparatus of AC motors capable of reducing torque ripple with a comparatively simple circuit corresponding to a high withstand voltage and capable of driving a motor at high efficiency even when the rotational speed or load has changed. The control apparatus detects first phase signals fixed in relative phase to induced voltages of the motor and current polarity signals, recognizes phase differences between them, generates second phase signals so as to make the phase differences approach zero to drive the motor at high efficiency, generates modulation wave signals having quasi-sinusoidal waveforms or trapezoidal waveforms on the basis of the second phase signals, compares the modulation wave signals with a carrier wave signal, and conducts PWM control on an inverter.

Abstract: A method of starting a permanent magnet machine. A machine stator voltage in a stationary reference frame is sensed. An initial speed of a rotor of the machine is estimated based on the sensed voltage, and state variables of control algorithms are initialized based on the estimated initial speed. This method can provide smooth startup and/or restart at any speed.

Abstract: A method of controlling a power converter (258) of a synchronous machine drive system (100) determines position and speed of a rotor (350) of the synchronous machine (300); regulates a current vector relative to a reference frame, having a direct-axis component and a quadrature-axis component, the regulating step selectively causing the current vector to lag a quadrature axis of the machine (300); and outputs a command signal to the power converter (258) as a function of the regulating step. According to one implementation, this process creates higher total torque and maintains supply voltage within a maximum level during a high speed range of the machine.

Abstract: A circuit for controlling a multi-phase machine having a stator with stator windings includes a controller, primary commutation switch pairs, a neutral terminal, and commutation control switches. Each switch pair includes first and second primary commutation switches connected at a node. Each commutation control switch is coupled to a winding so that a stator winding circuit is formed between the neural terminal and a respective one of the nodes. Each commutation control switch includes a first diode connected in parallel with a series switch circuit. Each series switch circuit includes a second diode and a series connected switch element. The controller is coupled to the switch elements and the primary commutation switch pairs to control an on time and an off time of the primary commutation switches relative to a point where a supply voltage is equal to the back emf.

Abstract: An AC servo drive without current sensor includes a PI (proportional integration) controller, at least two first-order controllers (polar point and zero point), a decoupling compensator, a coordinate converter, a pulse width modulator, a counter and a speed estimator. The AC servo drive is connected with a servomotor to form an AC servo module. The servomotor comprises an encoder receiving a current command signal from the servo module to function as input current command signal or the d, q axes PI controller and the decoupling compensator. The voltage command signal generated by the d, q axes PI controller and the signal generated by the decoupling compensator form a control signal and input to the coordinate converter. The signal output from the coordinate converter is processed by PWM controller to control the servomotor. Therefore, the deterioration of servo motor control caused by temperature drift and cost can be solved.

Abstract: An object of the present invention is to provide a motor control apparatus having excellent harmonic current control performance, that can simplify circuit configuration and circuit processing while, at the same time, achieving improved control accuracy. To achieve this object, detected motor currents are converted by coordinate converters 19 and 20 into an nth-order dq-axis signal and an mth-order dq-axis signal, and their DC components are extracted by low-pass filters 22 and 23; then, the differences of the DC components relative to respective command values are converted back into three-phase AC signals to control the motor currents.

Abstract: A field oriented control system for a brushless wound field synchronous machine that determines positioning of a rotor for the machine from exciter stator electrical potentials and current harmonics.

Abstract: The invention concerns a method and an apparatus for field-oriented control of a permanent-magnet-excited synchronous machine. Conversion of an ascertained longitudinal voltage component and an ascertained transverse voltage component into triggering pulses for the synchronous machine is accomplished in a low rotation speed range using a pulse-width-modulated inverter, and in a high rotation speed range using a block switching mechanism or a software program functionally corresponding to a block switching mechanism. The invention reduces output oscillations in the upper rotation speed range that occur in known systems as a result of angular inaccuracies with respect to the target voltage zero transition and the voltage zero transition that is actually implemented.

Abstract: For providing a controller apparatus for a synchronous motor and a controlling method thereof, enabling to be manufactured, easily and cheaply, and to obtain a lock mechanism, but without necessity of mechanisms, such as, an electromotive lock mechanism, wherein the controller apparatus for the synchronous motor, which has a stator 20 wound with AC windings 21U, 21V and 21W, and a rotor 30 installed within an inside of the stator, rotatably, therein, comprises an inverter 200 for supplying AC voltages having a predetermined voltage/frequency characteristic to the AC windings, which are wound around poles of the stator of the synchronous motor; and further, the inverter is so controlled that the AC voltages, being supplied from the inverter to the AC windings wound around the poles of the stator is changed into DC voltages to be supplied thereto, when rotation of said rotor is zero (0) and also when a lock function signal is ON in condition thereof, thereby obtaining a lock condition of holding a rotating posi

Abstract: A motor controller for simultaneously controlling operations of at least two system motors by pulse-width modulation. The motor controller includes a pair of switches, a pair of pulse signal generators, and a phase shifter. The switches are used for supplying driving power to the two system motors. The pulse signal generators are used for generating a pair of pulse signals respectively having predetermined duty ratios at predetermined cycles, and outputting the pulse signals to the pair of switches to turn on or off the pair of switches. The phase shifter is used for inverting, with respect to the phase of one of the two pulse signals that is generated and output by one of the two pulse signal generators, the phase of the other of the two pulse signals, which is generated and output by the other of the two pulse signal generators, by 180 degrees.

Abstract: A sensorless brushless motor controls a rotational speed of a rotor by sequentially energizing a plurality of excitation coils constituting a stator in accordance with a logical product between an energizing timing signal generated on the basis of a back electromotive forces and a pulse width modulation signal to control a pulse width of the pulse width modulation signal, wherein back EMF induced in the plurality of excitation coils are respectively supplied to first and second comparator circuits each having a different reference voltage, respective output signals from the first and the second comparator circuits are sampled simultaneously at a predetermined cycle, and the energizing timing signal is generated at the time of the respective output signals from the first and the second comparator circuits becoming a high-level or a low-level during the sampling. The accuracy of rotor position detection by using a back EMF is improved.

Abstract: The preferred embodiments of the present invention utilize the internal combustion engine of a hybrid vehicle, coupled with an energy storage device and series of inverters to provide electrical power generation capability for an electric power take-off (EPTO) system. Additional embodiments of the present invention utilize an existing on-board AC induction motor to provide filtering capability for the generated AC power.

Abstract: A method is described of regulating the instantaneous electromagnetic torque of a polyphase rotating electrical machine equipped with stator and/or rotor windings supplied by a voltage and a current generated by an inverter formed of switches whose switching is controllable. The method comprises a step of commanding the switching of the switches of the inverter using the fundamental frequency of the voltage generated by the inverter and a form of synchronous pulse width modulation configured as a function of an input set point, and a step of calculating the input set point from an instantaneous torque set point at each regulation time. The method further comprises a step of determining the time interval between two successive regulation times so that the time interval corresponds to an integer multiple of the period of oscillation of the instantaneous torque of the machine.

Abstract: The present invention relates to a method of controlling a power converter (20) of a synchronous machine system (10), the method comprising sampling phase-current values between the power converter (20) and the synchronous machine (30); selecting a reference frame; regulating a current vector to align with the selected reference frame, the selected reference frame having a direct-axis component and a quadrature-axis component; estimating rotor speed and position as a function of instantaneous power; adjusting the selected reference frame, based on estimated rotor position, to synchronize the selected reference frame with a magnetic axis of the rotor, thereby generating a synchronized floating frame; and applying the synchronized floating frame to control the power converter (20). The present invention also related to a power converter controlling apparatus (100) for controlling a power converter (20) of a synchronous machine system (10) without use of a machine position sensor.

Abstract: A motor control apparatus includes an inverter circuit for supplying driving power to a motor, a motor current detector for detecting current flowing through the motor, an inverter controller for controlling the inverter circuit based on the output of the detector. The inverter controller has a setting unit for setting various command values to control motor driving status, and a processing unit for controlling the inverter circuit based on the setting on the setting unit. The setting unit sets command value so that a load angle which is an angle between rotor axis and motor applied voltage is operated on the smaller side of the angle that provides the maximum output torque in the load angle-output torque characteristics.

Abstract: A driving circuit for a brushless motor includes a current sensor for detecting alternating phase-current flowing in one of the phase coils, a switching driver for supplying each phase-coil with prescribed alternating phase-current, a reference value setting circuit which provides a reference value which changes in synchronism with the prescribed phase-current to be larger than the same and an abnormality determining circuit which determines abnormality if the current detected by the current sensor is larger than the reference value.

Abstract: A controller for a wound-rotor induction motor includes a first voltage-type converter connected to a secondary winding of the motor, a capacitor for smoothing DC output thereof, a second voltage-type converter to supply an AC power supply with regenerated secondary power, a speed detector of the motor, a secondary current detector of the motor, a DC voltage detector applied to the capacitor, a speed controller for controlling the speed by the speed detector and outputting a secondary referential current, a first PWM controller to control the secondary current in response to the referential current, and to output a voltage signal by witch switching elements of the first voltage-type converter are controlled by PWM, and a second PWM controller to control a voltage output from the voltage detector in response to a referential voltage, and to control by PWM switching elements of the second voltage-type converter.

Abstract: A motor driving apparatus including a regeneration control function and a power storage device for accumulating a regenerative current and for supplying an inverter section with electric power during acceleration. The inverter section is connected to a converter section by a DC link to which regeneration start detecting means and the power storage device are connected. When the regeneration start detecting means detects that a voltage at the DC link reaches a regeneration control start voltage, a controller controls switching elements and starts regeneration control. The regenerative current is accumulated in the capacitor through a diode. When a motor is in a power running state, the switching elements are turned on to apply the voltage at the power storage device to the DC link, and the charged power is utilized for motor acceleration.

Abstract: A control system for an electric machine includes a flux weakening module, which includes a voltage magnitude calculator that receives d-axis and q-axis command voltages and that generates a voltage magnitude. An error circuit compares the voltage magnitude to a reference voltage and generates an error signal. A controller receives the error signal and generates a feedback flux correction signal. A limiter limits the feedback flux correction signal to a predetermined flux value and generates a limited feedback flux correction signal. A feedforward stator flux generating circuit generates a feedforward stator flux signal. A summing circuit sums the feedforward stator flux signal and the limited feedback flux correction signal to generate a final stator flux command.

Abstract: A stepping motor driver according to the present invention includes a torque component current calculating means for calculating a torque component current from phase currents and a rotor rotation angle, an absolute value converting means for obtaining an absolute value of the torque component current, a high speed-response judging means adapted for outputting a first control signal when a speed deviation between a command speed and a rotor speed is not more than a reference level, and outputting a second control signal when the speed deviation exceeds the reference level, and a current command outputting means adapted for outputting a current command according to the absolute value of the torque component current when the first control signal is outputted, and outputting a maximum current command value as the current command when the second control signal is outputted.

Abstract: In a motor control apparatus of the present invention, a control section which receives an input voltage to an inverter circuit, a motor current flowing to a brushless motor and a motor current command value indicating the value of a current required to flow to the inverter circuit, and controls the inverter circuit by maintaining a phase of the voltage applied to the brushless motor when the value of the input voltage to the inverter circuit is smaller than the value of a voltage required to be applied to the brushless motor.

Abstract: A DC motor drive circuit includes a position detector for producing an output signal that corresponds to a rotational position of the rotor, a current controller for controlling current supply to the winding in accordance with the output signal of the position detector, and a phase advancing portion for the current between the position detecting portion and the current controller, so that the timing for supplying current to the winding is advanced and efficiency of converting the current supplied to the winding into a motor torque is improved.

Abstract: A controller of a rotating electric machine for a vehicle has a magnetic field electric current command arithmetic device for commanding a magnetic field electric current by the command of a torque and electric power command arithmetic device, an electric power converter functioning as a rectifier or an inverter, and a magnetic field electric current command restraining device for restraining a three-phase line electric current by restraining and controlling an output of the magnetic field electric current command arithmetic device when the rotating electric machine functions as an electric generator.

Abstract: A 3-phase AC current flowing to a 3-phase synchronous motor is converted through coordinate conversion to a d-axis current id and a q-axis current iq in a dq-axis coordinate system which rotates in synchronization with the motor rotation and a phase ? of a rectangular wave voltage is calculated based upon the current deviation between a q-axis current command value iq* and the q-axis current iq. A 3-phase rectangular wave voltage is generated from a DC source based upon the calculated phase ? and is applied to the 3-phase synchronous motor.

Abstract: A power module includes a heat radiating member, a power circuit section, a resin layer, and a case. The heat radiating member includes a circuit disposition surface. The power circuit section includes an external connection terminal and is disposed on the circuit disposition surface. The resin layer covers a part of the external connection terminal. The case is attached to the heat radiating member. The external connection terminal stands up from the heat radiating member. The case includes a hood, which has an opening at one end portion thereof. The external connection terminal is inserted into the hood. The resin layer prevents liquid from entering through the hood.

Abstract: An electric power steering apparatus for assisting the steering force of a steering member by an electric motor (18) driven by a driving circuit (13) connected to a power supply (P) by power connecting means (15a). The electric power steering apparatus comprising: means (12) for detecting a short-circuit failure on the driving circuit (13) and on a wiring connecting the driving circuit (13) and the electric motor (18); power off means (15) for turning off the power connecting means (15a) when a short circuit failure is detected; current detecting means (17) for detecting the value of a current flowing between the electric motor (18) and the driving circuit (13) after the power off means (15) turns off the power connecting means (15a); and current cutting means (Fa, Fb) for, when the current detecting means (17) detects a current value exceeding a predetermined value, irreversibly cutting off the current whose current value exceeds the predetermined.

Abstract: A motor controller is provided including a synchronous motor, a feed back detector for detecting the position and velocity of the rotor of the synchronous motor, a detector for detecting a magnetic pole position of the rotor of the synchronous motor, an inverter for controlling an electric power to be supplied to the synchronous motor, an estimator for estimating the magnetic pole position of the rotor of the synchronous motor, and a detector for detecting the abnormality of the feed back detector.

Abstract: A motor control apparatus includes a phase current detecting section for detecting phase currents to a motor, a current phase/current peak value calculating section for calculating a current phase based on the phase currents, a voltage phase setting section for adding a predetermined phase difference to the current phase and setting the resultant sum as a voltage phase, a phase voltage setting section for setting phase voltages to the motor based on the voltage phase and the command voltage. Basically, the motor is operated by maintaining the voltage at constant and always monitoring the current/voltage phases so as to maintain a constant phase difference, without the motor axis position being predicted.

Abstract: A permanent magnet synchronous motor driving system includes: 1) a permanent magnet synchronous motor, and 2) an inverter. The permanent magnet synchronous motor includes three phase terminals. A resonant frequency is generated between an inductance and a ground electrostatic capacitance which are measured between the following: a) one of the three phase terminals of the permanent magnet synchronous motor, and b) a ground. The inverter drives the permanent magnet synchronous motor. The inverter generates a carrier frequency. The resonant frequency of the permanent magnet synchronous motor is free from a conformance with the carrier frequency of the inverter and is free from a proximity of the carrier frequency of the inverter.

Abstract: Limits are imposed on a fundamental voltage command value calculated at a fundamental current control circuit that controls a fundamental component of a 3-phase AC motor current in a dq-axis coordinate system rotating in synchronization with the rotation of the 3-phase AC motor by using predetermined limit values and limits are imposed on a higher harmonic voltage command value calculated in an orthogonal coordinate system (a higher harmonic coordinate system) rotating at a frequency set to an integral multiple of the frequency of the fundamental component in the 3-phase AC motor current by using a predetermined limit values. The voltage command values resulting from the limit processing are added together and a voltage corresponding to the sum is applied to the AC motor for drive control.