Abstract: A control system configured to control a transistor configured to control energy delivery to a load. The control system comprises a system controller to sense an event in the control system and to assert a command signal in response to the sensed event and a switch controller configured to receive the command signal. The switch controller is configured to control the turn on and the turn off of the transistor, wherein the system controller controls the turn on or the turn off, or control both the turn on and the turn off of the transistor with a first drive strength in response to a first command in the command signal and controls the turn on or the turn off, or control both the turn on and the turn off of the transistor with a second drive strength in response to a second command in the command signal.

Abstract: The invention relates to a method for controlling a three-phase inverter (3) using a 120° control arrangement associated with a PWM-type control, the inverter (3) being driven by a controller and configured to power a permanent-magnet synchronous motor (5) of a device on board an aircraft. The motor (5) comprises a stator and a rotor that can be rotated relative to the stator when the motor (5) is powered. The inverter (3) comprises three branches (31, 32, 33), each branch comprising two switches (310, 311, 320, 321 and 330, 331) associated with a motor winding sing a 120° control arrangement of a three-phase inverter. The method is characterised in that when one switch on one branch is controlled such as to switch front the on-state to the off-state, the other switch on said branch is controlled such as to be in the on-state for a sufficient amount of time to allow the magnetic discharge of the motor winding associated with said branch.

Abstract: A motor driving device controls a three-phase motor and a single-phase motor to operate in parallel. The motor driving device includes a dc terminal in which an upper and a lower DC-link capacitor are located. The motor driving device also includes a neutral terminal disposed between the upper and lower DC-link capacitors. The motor driving device includes an inverter that includes three pairs of upper switching elements and lower switching elements. Two pairs of upper switching elements and lower switching elements among three pairs are connected to an a-phase terminal and a b-phase terminal of the three-phase motor, respectively. The other pair of upper switching elements and lower switching elements among three pairs is connected to a first terminal of the single-phase motor. The neutral terminal is connected to a second terminal of the single-phase motor. A c-phase terminal of the three-phase motor is connected to the single-phase motor.

Abstract: A motor system can include a motor, the motor including at least a rotor, and a controller configured to operate the motor. The controller can be configured to perform operations for operating the motor.

Abstract: Technical solutions are described for estimating machine parameters of a permanent magnet synchronous motor (PMSM) drive. An example method includes determining a region for estimating a machine parameter based on a motor velocity value and a motor current value. The method further includes, in response to the motor velocity value and the motor current value being in the region, estimating an error in estimated voltage command, and estimating the machine parameter using the error in estimated voltage command.

Abstract: A battery control apparatus includes: an MCU including a first control terminal, a first sensing terminal connected to a first node, a second control terminal, a third control terminal, a second sensing terminal connected to a second node, and a fourth control terminal; a relay including a switch and a coil connected between the first node and the second node; and a first reduction circuit including a first transistor having a first gate connected to the first control terminal and a first end connected to the first node, and a second transistor having a second gate connected to the second control terminal and the MCU controls the first gate and the second gate to respectively allow the first transistor to be turned on and the second transistor to be turned off when there is no voltage change of the first node.

Abstract: Provided is a motor drive device including a motor having a rotor and a stator, an inverter electrically connected to the motor, and a control device for controlling the inverter. The control device includes: an impedance observer that estimates at least an amount of variation in impedance of the motor on the basis of a voltage command value, a current command value, and an actual current flowing between the inverter and the motor; a comparator that calculates a difference between the current command value and the actual current flowing between the inverter and the motor; and a failure detection unit that outputs a failure flag when the amount of variation in impedance exceeds or falls below a predetermined threshold, or when the difference calculated by the comparator exceeds or falls below a predetermined threshold.

Abstract: A refrigeration system for a temperature-controlled storage device includes a refrigeration circuit, a cooling circuit, and a controller. The refrigeration circuit includes a compressor driven by a brushless DC motor operable at multiple different speeds, a first heat exchanger, an expansion device, and a cooling unit in fluid communication via a first working fluid. The cooling circuit includes a pump and a second heat exchanger in fluid communication with the first heat exchanger via a second working fluid such that the first heat exchanger is liquid-cooled by the second working fluid. The controller operates the brushless DC motor at multiple different speeds to accommodate multiple different thermal loads experienced by the refrigeration system. Each of the speeds corresponds to a different thermal load. The controller modulates the speed of the brushless DC motor to maintain a desired temperature of a temperature-controlled space within the temperature-controlled device.

Abstract: An inverter converts direct-current power to alternating-current power by operations of a plurality of switching elements under a PWM control, and supplies the alternating-current power to an alternating-current electric motor. A feedback control computation unit of an inverter control unit uses current values acquired from current sensors detecting a current flowing to the alternating-current electric motor and a rotation angle of the alternating-current electric motor to perform a control computation in a (N/2) cycle (N is a natural number) of a triangular wave carrier of the PWM control. At the acquisition of the current values detected by the current sensors, an average acquisition unit acquires an average of current values in a carrier half cycle as a period between a peak and a valley of the carrier, or acquires a current value regarded as an average of the current values at an acquirable timing.

Abstract: A 15-level multilevel inverter circuit includes an outer circuit, an inner circuit, a polarity changing circuit and a computing device. The outer circuit and the inner circuit include a plurality of DC voltage supplies. Each DC voltage supply has a positive and a negative terminal. The outer circuit, the inner circuit and the polarity changing circuit include a plurality of unidirectional power switches. Each unidirectional power switch is a transistor with a diode connected in parallel to the transistor. The computing device is configured to provide control signals to the gates of the plurality of the unidirectional power switches of the outer circuit and the inner circuit to add or subtract the voltage of each of inner DC voltage supplies to form square waveforms approximating sinusoidal waveforms, and to the gates of the plurality of the unidirectional power switches of the polarity changing circuit to switch the polarity of the voltage.

Abstract: Switching control of an inverter is performed such that rising and falling of a terminal voltage of U phase including upper and lower arm switching elements are calculated, and the calculated rising of the terminal voltage of U phase and falling of a terminal voltage of V phase or W phase or the calculated falling of the terminal voltage of U phase and rising of the terminal voltage of V phase or W phase are synchronized with each other.

Abstract: The current disclosure provides methods and systems for intelligent load management in off-grid AC systems and provides methods and systems to control and prioritize loads, so that supply and demand can be balanced via an extremely robust and reliable system.

Abstract: A motor driving apparatus for a home appliance includes: a power supply part configured to supply DC power, a DC-Link capacitor connected to the power supply part, an inverter connected to the DC-Link capacitor and comprising a plurality of switching elements, the inverter being configured to convert, by operating the plurality of switching elements, the DC power into AC power and output the converted AC power to a motor, a DC-Link resistor element disposed between the DC-Link capacitor and the inverter, a signal generator connected to the DC-Link resistor element and configured to generate and output a plurality of signals based on an output current flowing through the DC-Link resistor element, and a controller configured to control the inverter based on the plurality of signals received from the signal generator.

Abstract: A charging power supplying system using a motor driving system includes an inverter that is connected to a battery, includes at least one switching device, and is configured to change an on/off state of the switching device and to convert power stored in the battery to output the converted power to an output terminal of the inverter, a motor including a plurality of coils that each receive power provided from the output terminal of the inverter, a charging power output terminal that is connected to a neutral point to which the plurality of coils of the motor is commonly connected and outputs current output from the neutral point to an external charging target, and a controller configured to control the switching device in the inverter based on current of the output terminal of the inverter.

Abstract: For high frequency injection (HFI) transition disturbance elimination, a processor directs an HFI transition for a motor. The processor determines compensation pulse voltages for an HFI compensation pulse. The processor further injects a sum of the HFI compensation pulse and an HFI voltage into a current regulator voltage output signal for a compensation Pulse Width Modulation (PWM) cycle. The HFI compensation pulse settles an HFI current to a steady state.

Abstract: Provided is an AC electric motor control device capable of detecting, in an AC electric motor drive device, abnormal operation of an AC electric motor or abnormal operation due to, for example, a sudden change of a load without an erroneous operation regardless of the operational state of the AC electric motor. When driving a three-phase AC electric motor by an inverter, inside a controller, an electric motor constant is calculated using at least one of the current, voltage, and rotational speed of the electric motor and the variation of the constant value is analyzed, thereby detecting abnormal operation of the electric motor or abnormal operation of a load device connected to the electric motor. In order to analyze the constant, a variation to be determined to be abnormal is preset or an abnormal value is calculated in comparison with the accumulated values of past constant changes. Alternatively, only the variation of the constant calculated in the controller is extracted to detect abnormality.

Abstract: An overcurrent detection reference compensation system of a switching element for an inverter and an overcurrent detection system using the same can correct an overcurrent detection reference used to detect an overcurrent of a switching element according to a temperature of the switching element.

Abstract: A motor control system for selectively controlling power from a power source to a load includes a PCB structure and a power converter affixed to the PCB structure that is operable to provide a controlled output power to the load. The motor control system also includes a standalone protection and control module mounted onto the at least one PCB structure so as to be electrically coupled therewith, the standalone protection and control module further including a front-end switching unit comprising a plurality of switching devices operable to selectively interrupt and control power flow from the power source to the power converter and to a bypass path that bypasses the power converter and a back-end switching unit positioned downstream from the front-end switching unit and comprising a plurality of switching devices operable to selectively interrupt power flow from the power converter and the bypass path to the load.

Abstract: A motor vehicle, particularly a passenger car, contains an onboard electrical system having a number of electrical consumers, a generator and an onboard electrical system rechargeable battery. A bidirectional interface is provided for a rechargeable device battery of a mobile device such that the rechargeable device battery can be coupled to the onboard electrical system by the bidirectional interface and, when coupled, can both be charged by the onboard electrical system and be used as an additional energy source in the onboard electrical system.

Abstract: The invention relates to a method for the closed-loop and open-loop control of two or more EC motors operated using a common converter, wherein for the purpose of setting the operating point of the EC motors, common open-loop or closed-loop control using at least one controller is provided, wherein a combination of at least two control options is provided and in this case a controlled variable regulates the voltage setting at the output of the converter such that the two or more EC motors follow an intended sequence of operating points in a stable manner.

Abstract: The ideal design for a redundant orbitally driven electric ducted fan that can replace a family of current propeller and motor combinations in electric ducted fan designs by meeting air flow and pressure requirements while drawing less electric current to rotate and thus produce the required flow not only would reduce cost of operation over the life of the fan but opens new possibilities for electric powered vertical takeoff and landing vehicles with redundant drives improving safety of operation. The entry of flying machines using propellers and lifting fans such as hover bikes and quadcopters, manned or unmanned is driving a need to re-examine the application of force applied to rotate these fans to achieve a reduction in aircraft weight and increase flying time for a given battery charge or load of fuel.

Abstract: An inverter device includes a motor, a power supply that supplies the motor with electric current, an inverter that, during regenerative operation of the motor, performs switching between a first state in which regenerative current generated in the motor is returned to the motor again and a second state in which the regenerative current is supplied to the power supply, a first detector that detects a first condition electrically acting on the inverter, a second detector that detects a second condition electrically acting on the power supply, and a determiner that performs a first determination to perform switching between the first state and the second state, based on a detection result by the first detector or the second detector.

Abstract: A drive control method and system for controlling an inverter during power disruptions in the operation of an elevator drive includes the steps of predetermining whether a hoist motor of the elevator drive will be operating in a motor mode, a balanced mode or a regenerative mode on commencement of the power disruption, and controlling the inverter in accordance with the predetermined operating mode after commencement of the power disruption.

Abstract: A controller of a motor that drives a driven body includes: an inertia estimating unit that estimates inertia on the basis of feedback information (torque and current) of the motor; a computing unit that computes an acceleration or deceleration time constant of the motor from the estimation inertia estimated by the inertia estimating unit; a storage unit that stores an inertia difference which is a difference between the estimation inertia and at least one known actual inertia and a time constant difference which is a difference between an actual acceleration or deceleration time constant corresponding to the actual inertia and an acceleration or deceleration time constant calculated on the basis of the estimation inertia; and a correction unit that corrects the acceleration or deceleration time constant calculated by the computing unit using the inertia difference and the time constant difference stored in the storage unit.

Abstract: A voltage converter (110, 210) having a first bidirectional voltage line (112, 212), a second bidirectional voltage line (114, 214), a power storage element (L1) arranged between the first bidirectional voltage line and the second bidirectional voltage line, a switch element electronically coupled to the power storage element, a controller (141) for controlling the switch, and the controller configured and arranged to adjust a current flow between the first voltage line and the second voltage line such that a voltage level on the second bidirectional voltage line is substantially maintained at a target DC voltage.

Abstract: A 15-level multilevel inverter circuit includes an outer circuit, an inner circuit, a polarity changing circuit and a computing device. The outer circuit and the inner circuit include a plurality of DC voltage supplies. Each DC voltage supply has a positive and a negative terminal. The outer circuit, the inner circuit and the polarity changing circuit include a plurality of unidirectional power switches. Each unidirectional power switch is a transistor with a diode connected in parallel to the transistor. The computing device is configured to provide control signals to the gates of the plurality of the unidirectional power switches of the outer circuit and the inner circuit to add or subtract the voltage of each of inner DC voltage supplies to form square waveforms approximating sinusoidal waveforms, and to the gates of the plurality of the unidirectional power switches of the polarity changing circuit to switch the polarity of the voltage.

Abstract: Electric drive devices having at least one power electronics module including at least one voltage circuit having power electronics components such as a converter, transformer, frequency inverter, power capacitor, circuit breaker and the like, and at least one fuse for interrupting the voltage circuit in the event of excess currents and/or voltages. The invention also relates to a wind turbine and similar large industrial electrical systems having such a drive device. The device can comprise at least one pyrotechnic fuse with a propellant charge for the irreversible interruption of the voltage circuit, wherein the pyrotechnic fuse is arranged in the voltage circuit of the power electronics module or immediately adjacent to at least one power electronics component such as a converter, frequency inverter, transformer, power capacitor or circuit breaker.

Abstract: Integrated circuitry, such as a microcontroller, for controlling an electric motor includes circuitry for measuring a bi-directional current flowing within a coil of the electric motor. The current is sensed by an externally implemented current sensing element, such as a shunt resistor, to produce a differential voltage that is delivered to input pins of the microcontroller, which are protected by electrostatic discharge protection circuits. Current sources implemented within the microcontroller are coupled to the input pins, and work in concert with external resistors to shift the differential voltage so that it is maintained within an appropriate voltage operating range so that an accurate measurement of the bi-directional current can be made by the microcontroller.

Abstract: An electric tool includes a motor, a drive circuit, a power supply and a controller. The motor includes a rotor and first, second, and third phase windings. The drive circuit is electrically connected to the first, second, and third phase windings and drives the motor to output power. The power supply is electrically connected to the drive circuit and supplies power to the first, second, and third phase windings through the drive circuit. The controller is connected to the drive circuit and outputs a control signal to control the drive circuit. The controller controls the drive circuit according to a rotation position of the rotor when a voltage of the power supply is less than or equal to a preset voltage threshold so that the first, second, and third phase windings are simultaneously connected to the power supply.

Abstract: A system includes a motor operating with an angular velocity and an operational current, a motor controller circuit to issue control signals to the motor, and a stator resistance calculation circuit. The calculation circuit is to introduce a perturbation signal to the motor through the control signals issued by the motor controller circuit, observe operations of the motor in response to the perturbation signal, estimate stator resistance of the motor based upon the observations of the operations of the motor in response to the perturbation signal, adjust operation of the motor based upon a changed stator resistance.

Abstract: A system includes an electronic power converter and a controller. The electronic power converter supplies power to one or more motor drives of an HVAC and/or refrigeration system. The controller obtains a plurality of pulse width modulation (PWM) algorithms. Each PWM algorithm has an associated harmonic signature. The controller further determines one or more resonance frequencies associated with the HVAC and/or refrigeration system. The controller also selects a first PWM algorithm from the plurality of PWM algorithms based at least in part on the harmonic signature associated with the first PWM algorithm mitigating the one or more resonance frequencies associated with the refrigeration system. The controller further operates the electronic power converter according to the first PWM algorithm.

Abstract: A single-phase voltage source inverter including a first stage configured to be connectable to a DC source, and a second stage configured to be connectable to an AC load, the first stage including a bridge leg including first and second decoupling switches, the bridge leg connected through an inductor to a decoupling capacitor, where the decoupling capacitor is in series with the DC source when the inverter is connected to the DC source, and the second stage including a bi-directional H-bridge inverter including first, second, third and fourth switches. The decoupling capacitor can be a small film capacitor. The first and second decoupling switches are the only decoupling switches in the bridge leg. The first controller can use pulse width modulation and the second controller uses sinusoidal pulse width modulation. The first controller can use pulse width modulation and the second controller uses pulse energy modulation.

Abstract: An inverter device includes gate driving circuits for upper and lower arms of a bridge circuit, a first power supply supplying a power supply voltage to each driving circuit, and a second power supply having a reference potential different from that of the first power supply. The inverter device also includes a first fail-safe circuit having a reference potential common to the first power supply and generating driving commands with respect to the upper and lower arms, and a second fail-safe circuit having a reference potential common to the second power supply and generating driving commands with respect to the upper or lower arm. The lower arm gate driving circuit has two driving command input functions having different reference potentials, one function inputs the driving commands from the first fail-safe circuit, and the other function inputs the driving commands from the second fail-safe circuit.

Abstract: The present disclosure may provide a shift range control apparatus that controls on-off operations of switching elements in a driver circuit, drives a motor, and switches a shift range. The shift range control apparatus may be configured to determine an abnormality of a rotation angle sensor detecting a rotation angle of the motor, to control a drive of the motor using a detection value, and to execute a control which switches an energization phase every energization phase switching period without using the detection value of the rotation angle sensor in response to that the rotation angle sensor is abnormal.

Abstract: A power conversion apparatus includes a power converter circuit that outputs an AC power to an electric motor, and circuitry that controls the power converter circuit to add a first change, accompanying a change of a power generated by the electric motor, to a first phase angle, which is a phase angle of a magnetic flux direction of the electric motor corresponding to the AC power, extracts a component generated by the first change from first information indicating the electric power supplied to the electric motor, and estimates the power generated by the electric motor based on the component.

Abstract: A motor system provided with one motor, two batteries, and two inverters further includes a charger which is connected to a first battery and supplies external power; and a control unit which controls drive of the first inverter and the second inverter to drive the motor. When the second battery is charged with the external power, the control unit drives the first inverter and the second inverter to allow power from the first inverter to be transmitted to the second battery through the motor and the second inverter while the motor is in a stationary state.

Abstract: A motor driving circuit including a first and a second driving signal output circuit is configured to selectively output a six-step square wave driving signal from the first driving signal output circuit, or a space-vector driving signal from the second driving signal output circuit to an inverter to drive a motor according to whether an operating power exceeds a power threshold. The first driving signal output circuit is configured to generate the six-step square wave driving signal. The second driving signal output circuit is configured to generate the space-vector driving signal.

Abstract: A locus of integrals, in terms of time, of unit voltage vectors forms a loop within a period shorter than a reciprocal of a maximum value of an operating frequency, in terms of electrical angle, of a compressor motor, the unit voltage vectors being voltage vectors that are units composing an instantaneous space vector indicating voltage which an inverter for driving the compressor motor outputs except in a dead time period.

Abstract: Disclosed herein is a wireless power receiving device that includes a power receiving coil that takes in AC power via a magnetic field, and a rectifier that converts the AC power to DC power and outputs the DC power to a load. The rectifier includes a plurality of diodes bridge-connected to each other, the plurality of diodes including a first diode whose anode is connected to one input terminal of the rectifier and a second diode whose cathode is connected to the one input terminal of the rectifier; a first capacitor connected in parallel with the first diode; and a second capacitor connected in parallel with the second diode. Capacitances C1 and C2 of the first and second capacitor satisfy C1<1/(2fRLmax) and C2<1/(2fRLmax) where a frequency of the AC power is denoted by f, and a maximum resistance value of the load is denoted by RLmax.

Abstract: A permanent-magnet three-phase duplex motor is provided with two systems, namely a system that includes a first three-phase winding and a first inverter circuit, and a system that includes a second three-phase winding and a second inverter circuit, and a controlling apparatus is configured such that when one system fails, the controlling apparatus stops operation of the inverter circuit of the failed system, and controls operation of the inverter circuit of the normal system to increase the driving current that is supplied from the inverter circuit of the normal system, and the first three-phase winding and the second three-phase winding are configured such that magnetic fields that act on the permanent magnets in a demagnetizing direction when the increased driving current is supplied from the inverter circuit of the normal system are equal to magnetic fields that normally act on the permanent magnets in the demagnetizing direction.

Abstract: A cascaded inverter system is described and includes an electric machine that is electrically connected in series between first and second inverters. A controller is in communication with the first and second inverters, and includes an executable instruction set. A first dead-time compensation term and a first voltage compensation term are determined based upon an initial phase current and a switching frequency for the first inverter, and a final first duty cycle is determined based thereon. Simultaneously, a second dead-time compensation term and a second voltage compensation term are determined based upon the inverted initial phase current and a switching frequency for the second inverter, and a final second duty cycle is determined based thereon. Operation of the first and second inverters are dynamically controlled based upon the final first duty cycle and the final second duty cycle, respectively.

Abstract: Disclosed is a driving circuit for an electric vehicle having a battery pack and an inverter, and a control method thereof. The driving circuit includes a first contactor connected between a first terminal of the battery pack and a first terminal of a capacitor included in the inverter, a second contactor and a current limiting circuit connected to the first contactor in parallel, and a control unit configured to control operations of the first contactor and the second contactor. The second contactor and the current limiting circuit are connected to each other in series. The current limiting circuit includes at least one resistor, wherein the control unit outputs a first control signal when the first contactor is normally operating and outputs a second control signal when the first contactor is abnormally operating. The first control signal induces the first contactor to turn on, and the second control signal induces the second contactor to turn on.

Abstract: A method for operating at least one electric machine that is designed to drive a vehicle, in which a value is determined for at least one operating parameter of the vehicle, wherein a change is predicted for the torque of the at least one electric machine at a target time point from the value of the at least one operating parameter, wherein a current for a magnetization of the at least one electric machine prior to the target time point is set at a value, wherein the value of the current for the magnetization at the target time point is changed and adapted.

Abstract: Disclosed is a driving circuit for an electric vehicle having a battery pack and an inverter, and a control method thereof. The driving circuit includes a first contactor connected between a first terminal of the battery pack and a first terminal of a capacitor included in the inverter, a second contactor and a current limiting circuit connected to the first contactor in parallel, and a control unit configured to control operations of the first contactor and the second contactor. The second contactor and the current limiting circuit are connected to each other in series. The current limiting circuit includes at least one resistor, wherein the control unit outputs a first control signal when the first contactor is normally operating and outputs a second control signal when the first contactor is abnormally operating. The first control signal induces the first contactor to turn on, and the second control signal induces the second contactor to turn on.

Abstract: An ohmic-inductive electrical load, such as an electric motor, for example, for a hard-disk drive, is driven by supplying thereto a load current via a switching power stage supplied with a source current delivered by a supply source. The driving action may include sensing the load current; estimating the source current starting from the load current sensed; generating a feedback signal that assumes different values as a function of the result of the comparison between the source current estimated and a source-current threshold value; and driving the switching power stage via the feedback signal, increasing or decreasing, respectively, as a function of the different values assumed by the feedback signal, the load current, thereby controlling the source current.

Abstract: A welding or cutting device includes a first transistor coupled between a first node and a second node. The first transistor controls current and voltage provided to an inductor during a welding or cutting operation. The welding or cutting device also includes a first diode coupled in series with the first transistor between the second node and a third node, and a second diode coupled in parallel with the first transistor and the first diode between the first node and a fourth node. Additionally, the welding or cutting device includes a second transistor coupled in series with the second diode and in parallel with the first transistor and the first diode between the fourth node and the third node. The second transistor controls a voltage applied to a transistor during a freewheeling operation of the inductor.

Abstract: Provided are a motor control device and a method for controlling a motor control device. A switching frequency is varied with respect to a control sampling for controlling an inverter, whereby controlling is performed by securing a required control sampling according to a motor speed.

Abstract: A method estimating position and speed of a rotor of an alternating current machine for a motor vehicle.

Abstract: A DC machine for connection to an electrical system may include a stator configured as a portion of the DC machine; a rotor configured as a portion of the DC machine being rotatable with respect to the stator; and a control circuit to control the rotor to allow the rotor to continuously slip with respect to the stator.

Abstract: Provided is a control device of an AC motor, including: an inverter including a switching element; switching control means for controlling the switching element; and phase detection means for detecting a rotor phase of an AC motor, wherein the switching control means controls the switching element so that a voltage waveform of the inverter has half-wave symmetry in an interval of a width centering on a fundamental voltage phase of 180 deg±180 deg, the switching control means controls the switching element so that a harmonic voltage phase of the inverter becomes variable on the basis of a fundamental voltage-rotor phase difference which is a difference between a fundamental voltage phase and the rotor phase of the AC motor, and the switching control means controls the switching element so that a harmonic voltage amplitude of each order of the inverter is inversely proportional to the order.