Abstract: The invention relates to a circuit arrangement of a converter (1) for the electrical supply of a multi-phase electric motor (2). The arrangement comprises multiple DC-voltage-supplied (+DC, ?DC) phase intermediate circuits (13) and multiple inverter circuits (5) that are electrically connected to each phase intermediate circuit (13), wherein a respective phase intermediate circuit (13) and inverter circuit (5) are provided for each phase, together forming a commutation cell (14). The invention also relates to an aircraft having a circuit arrangement of this type, and an operating method with a circuit arrangement of this type.

Abstract: Provided is a power conversion controller in which variation in reactive power among power conversion controllers can be inhibited while maintaining the running performance of vehicles. The power conversion controller includes a power factor setter that sets a power factor based on a detection value of an overhead line voltage, and a calculator that calculates a reactive current command value by multiplying an active current command value by a tangent of a power factor angle of the power factor. The power factor setter sets a reference value set in advance as the power factor if the detection value is within a reference range, sets a value smaller than the reference value as the power factor if the detection value is below the reference range, and sets a value larger than the reference value as the power factor if the detection value is beyond the reference range.

Abstract: A motor drive unit for an in-wheel motor includes a housing and one and capacitors and solid state switching devices arranged within the housing. The housing includes: a lower compartment including a bottom plate, sidewalls which extend from the bottom plate, and end sides at the transverse ends of the sidewalls and bottom plate, wherein the bottom plate is provided with cooling channels for receiving a liquid coolant; a separation plate covering the lower compartment, wherein the separation plate is in thermal contact with the sidewalls and with the capacitors. The solid state switching devices are arranged in the lower compartment between the bottom plate and the separation plate and in thermal contact with the bottom plate, wherein the capacitors are connected to DC bus bars and are arranged at a side of the separation plate that faces away from the lower compartment.

Abstract: A traction inverter circuit includes a first energy storage device configured to output a DC voltage, a first bi-directional DC-to-AC voltage inverter coupled to the first energy storage device, and a first electromechanical device. The first electromechanical device includes a first plurality of conductors coupled to the first bi-directional DC-to-AC voltage inverter, a second plurality of conductors coupled together, and a plurality of windings coupled between the first plurality of conductors and the second plurality of conductors. The traction converter circuit also includes a charge bus comprising a first conductor coupled to the second plurality of conductors of the first electromechanical device, the charge bus configured to transmit a charging current to or receive a charging current from the first electromechanical device to charge the first energy storage device via the first electromechanical device and the first bi-directional DC-to-AC voltage inverter.

Abstract: A method of controlling an electric vehicle, wherein the electric vehicle comprises an electric motor, a controller, and an inverter, wherein the controller receives a control signal with an instruction to operate the electric motor. In one embodiment, the method includes collecting an operational data set on a plurality of output signals of the inverter and a rotation angle of the electric motor. In one embodiment, the method includes computing a voltage change of the inverter and a magnetic flux of the electric motor based on a predetermined data set and the operational data set. In one embodiment, the method includes adjusting an output of the inverter to offset the voltage change and the magnetic flux, the output being provided to the electric motor to control the electric motor in accordance with the instruction.

Abstract: A control method includes setting, when a space phase difference of in-phase coils of the respective groups is represented by ?, a time phase difference of electric currents to be supplied to the in-phase coils of the respective groups is represented by ?, and a time phase difference of carrier frequencies with which the three-phase inverters are PWM-controlled, respectively, is represented by ?, values of ? and ? so that any one or both of the following relationships are satisfied: ?=±(?+2?), and ?=±(???)/2, based on a result of comparison between a current amplitude of a primary component and a current amplitude of a secondary component of a carrier harmonic current, to control the dynamoelectric machine.

Abstract: A drive device for use in a vehicle includes a motor, a substrate, and at least one inter-system ground connection capacitor. The motor includes a plurality of motor windings within one housing. Multiple inverters are mounted on the substrate. Each inverter is connected to a different battery and a different ground to form a system, where each of the motor windings is associated with its own system. The inter-system ground connection capacitor is mounted on the substrate, and electrically connects the grounds of the systems together to reduce electrical noise propagated outside the drive device to other parts in the vehicle.

Abstract: Embodiments of the present disclosure relate to a heating, ventilating, air conditioning, and refrigeration (HVAC&R) system that includes a variable speed drive (VSD) configured to supply power to a motor configured to drive a compressor of the HVAC&R system, a rectifier of the VSD configured to receive alternating current (AC) power from an AC power source and convert the AC power to direct current (DC) power, a DC bus of the VSD electrically coupled to the rectifier, an inverter of the VSD electrically coupled to the DC bus, where the inverter is configured to convert the DC power to output AC power, the output AC power has a variable voltage and a variable frequency, and the output AC power is directed to the motor, and a battery electrically coupled to the DC bus, where the battery is configured to provide auxiliary DC power to the VSD.

Abstract: Nonlinear control method for the micro-grid inverter with anti-disturbance. By generating reference currents that satisfy specific active and reactive power command under various working conditions, and introducing a nonlinear control method based on Lyapunov function to control the inverter, fast and accurate tracking of the generated reference signals is realized. The method realizes effective decoupling control of active power and reactive power. The system has high dynamic response and good robustness. Besides, the control structure of the method is simple and easy to implement, and the synchronous control link and the additional voltage and current regulator are omitted. The method realizes fast and accurate power exchange and stable power transmission between the inverter and the grid in the micro-grid under various working conditions, and provides a guarantee for improving the energy management efficiency within the micro-grid.

Abstract: A single-stage three-phase power supply conversion device includes a three-phase rectification and commutation module and a DC/DC conversion module; the three-phase rectification and commutation module has a three-phase AC connection end, a DC source first connection end, a DC source second connection end and a DC source third connection end, and the DC/DC conversion module has a first connection end, a second connection end, a third connection end, a DC source positive connection end and a DC source negative connection end; a three-phase AC source is connected to the three-phase AC connection end of the three-phase rectification and commutation module, the DC source first connection end of the three-phase rectification and commutation module is connected to the first connection end of the DC/DC conversion module, the DC source second connection end is connected to the second connection end of the DC/DC conversion module.

Abstract: Power conversion systems and methods are provided for ride through of abnormal grid conditions or disturbances, in which a system rectifier is operated in a first mode to regulate a DC voltage of an intermediate DC circuit, an inverter is operated in the first mode to convert DC power from the intermediate DC circuit to provide AC output power to drive a load. In response to detecting an abnormal grid condition, the system changes to a second mode in which the rectifier is turned off and the inverter regulates the DC voltage of the intermediate DC circuit using power from the load.

Abstract: This rotating electric machine has a rotor, stator core, field windings for multiple poles, and armature windings for the multiple poles. The rotor is rotatably supported about a shaft. Convex-shaped multiple salient pole sections are formed on the outer circumference of the rotor while arranged in the circumferential direction. The stator core is provided along the outer circumference of the rotor with an air gap from the rotor. Convex-shaped multiple teeth are formed on the inner circumference of the stator core while arranged in the circumferential direction. The field windings for the multiple poles are wound around each of the multiple teeth while insulated from the field windings.

Abstract: A motor drive is provided with integrated frequency response analysis tools for generating drive performance metrics that are independent of motion profile and tuning. The metrics are broadly applicable to a wide range of applications, tunings, and load types, and can be used to fairly compare performance across different drives models and assist in drive selection. The frequency analysis tools include a transformation algorithm that reduces or eliminates spectral leakages, a signal generation component that scales the test input signal as a function of frequency avoid saturation based on defined limits of the controlled system, and a phase unwrapping algorithm that correctly unwraps the phase of open-loop and closed-loop response curves. The frequency response analysis tools yield an open-loop response, a closed-loop response, a tracking error response, and a disturbance rejection response, which are used to derive performance metrics for the drive.

Abstract: The present disclosure provides a voltage-adjusting device applied in a power conversion system including a Vienna rectifier, a direct current (DC) bus, and an inverter. The voltage-adjusting device includes a grid voltage sampling module for sampling a grid voltage, a given bus voltage calculation module, a voltage-adjusting module, a current control module and a pulse width modulation module. The given bus voltage calculation module calculates a given value of the DC bus voltage based on the grid voltage. The current control module receives a three phase AC current from the grid, the active current given signal and the reactive current given signal to output a three phase control voltage. The pulse width modulation module outputs a pulse control signal to the Vienna rectifier.

Abstract: A method is provided for controlling operation of an air conditioning unit. The method comprises supplying line voltage to activate a motor configured to operate the air conditioning unit, and monitoring a supply of control voltage in order to control operation of the air conditioning unit, the supply of control voltage being derived from line voltage. In response to detecting a control voltage below a predetermined threshold and/or by a predetermined percentage, a time delay is initiated. The method further comprises deactivating the motor if a predetermined increase in control voltage is not detected before the time delay expires.

Abstract: A method of diagnosing operating characteristics of a vehicle by a server device includes: obtaining operating characteristics information relative to the operating characteristics of the vehicle; and diagnosing the operating characteristics of the vehicle based upon feature information relative to a feature of a driver of the vehicle registered in advance in the server device and the operating characteristics information obtained from the vehicle.

Abstract: A circuit for controlling a motor of a central vacuum system, the motor being configured to operate using an alternating current is disclosed. The circuit includes an alternating current input for receiving the alternating current; a switched-mode power supply (SMPS) for converting the alternating current to a direct current, the SMPS having an alternating current input terminal and a direct current output terminal; and a control switch coupled to the direct current output terminal, wherein only when the control switch is closed is the alternating current received at the motor.

Abstract: A method of increasing a current sensing range for a vehicle or other polyphase motor system includes measuring phase currents delivered to a motor of the system. A controller calculates an absolute value of each phase current, compares each calculated absolute value to a saturation limit to determine whether only one sensor is saturated, and extrapolates a phase current value of the saturated sensor. The calculated temporary phase current is used as the extrapolated phase current value for the saturated sensor, and a control action is executed using the extrapolated phase current value only when the calculated temporary phase current value exceeds the measured value for the saturated sensor and a sign of the calculated temporary phase current value matches that of the measured value for the saturated sensor. A system includes the motor, a power inverter module, phase current sensors, and a controller which executes the method.

Abstract: A system and method for determining a rotor time constant of an AC induction machine is disclosed. During operation of the induction motor, a flux signal is injected into a rotor flux command so as to generate a time-variant rotor flux. A voltage-current flux observer determines amplitudes of rotor flux variations resulting from the time-variant rotor flux, with the amplitudes of the rotor flux variations comprising an amplitude of a rotor flux variation based on a current model of the voltage-current flux observer and an amplitude of a rotor flux variation based on a combined voltage-current model of the voltage-current flux observer. A rotor time constant of the induction motor is then estimated based on the determined amplitudes of the rotor flux variations.

Abstract: In a system for driving an inverter, a superimposing element superimposes, on an output voltage of the inverter. The high-frequency voltage signal is correlated with a measured high-frequency component value of a current flowing in the rotary machine. A calculating element calculates a rotational angle of the rotary machine based on the measured high-frequency component value. A dead-time compensating element shifts a start edge and an end edge of an on duration for each of first and second switching elements of the inverter by a preset same time to compensate for an error due to dead time. A current manipulating element manipulates a current flowing in the rotary machine to maintain an accuracy of calculation of the rotational angle.

Abstract: To provide a motor control circuit that variably controls the speed of a motor, in which an appropriate control gain corresponding to the speed of the motor that is set can be automatically set. The motor control circuit includes a period error signal output means, a speed error signal output means and a gain correction means.

Abstract: A system and method for controlling an adjustable speed drive (ASD) to decelerate an AC load during a generating mode of operation is disclosed. The ASD includes a capacitor and an inverter coupled to a DC link. A current sensor system is coupled to an output of the inverter. The ASD further includes a control system programmed to calculate an energy of the capacitor, generate a reference power using the calculated capacitor energy, and calculate a feedback power from realtime current signals received from the current sensor system. The control system compares the feedback power to the reference power, defines a frequency offset based on the comparison, generates a speed command using the frequency offset, and outputs the speed command to the inverter to maintain a smooth DC link voltage during deceleration.

Abstract: The invention relates to a method for the open-loop or closed-loop control of an asynchronous machine with or without speed feedback, the asynchronous motor being controlled by a control device (converter or servo converter). First of all, a voltage vector rotating at a rotary field frequency is specified and impressed, both the rotary field frequency and the voltage vector being determined by an open-loop or closed-loop control based on a voltage-frequency characteristic curve configured in any manner and the voltage vector being adapted by a cos ? closed-loop control. Desired values of cos ? are calculated using rating plate data and equivalent circuit diagram data for an optimum-loss or loss-optimized operation of the asynchronous machine for the calculation of cos ?desired value, which results in optimized-loss operation. A value for cos ?actual is then determined using the impressed voltage vector and a current vector or using the real power and apparent power.

Abstract: An apparatus and method for drastically increasing the efficiency of a single phase AC motor. A DC solid state driver is used to pulse a combination of the motor coil and a series capacitor. The coil/capacitor combination allows the motor to run near resonance (or a multiple of resonance). This results in a flywheel effect that only requires pulses at the proper time to keep it going. The solid state driver is powered by pulsed DC at around 150 volts peak and clocked at 60 Hz by a square wave timing circuit.

Abstract: The present disclosure provides a vector control apparatus that operates by a diameter computation-free winder velocity control algorithm with enhanced operational reliability. The vector control apparatus configured to control tension of a motor free from diameter computation includes a tension velocity generator configured to generate command velocity information for constantly maintaining a tension of the motor by adding a PID (Proportional Integral Differential) output value to a value computing a compensation gain value substituting a diameter computation value of a motor to be controlled and a command linear velocity provided from outside, and a vector controller configured to perform a tension control of the motor by receiving a command velocity information provided the tension velocity generator.

Abstract: Provided is a method and controller for controlling a vehicle dc bus voltage. The method includes generating a parameter. The parameter is based on a reference dc bus voltage squared. The method includes controlling the vehicle dc bus voltage based on the parameter and a detected dc bus voltage. The method may also include generating another parameter based on a power demand associated with at least one of a motoring mode operation and a generating mode operation of a traction motor associated with the vehicle. The power demand is indicated in a message received via a dedicated high speed data bus. The method includes controlling the vehicle dc bus voltage based on the another parameter.

Abstract: A motor control method comprises: inputting a PWM signal into a control unit for the control unit to obtain a direction command and a speed command by an identification rule, and generating a control signal according to the direction and speed commands by the control unit; and generating a driving signal according to the control signal by the driving unit for driving a motor to operate according to the direction and speed commands.

Abstract: A conveyor system and a method for driving a conveyor are disclosed. In the method, electric power is supplied to the drive machinery of a conveyor depending on the power requirement with a supply device to be selected from at least two different adjustable supply devices, and the supply device supplying power to the drive machinery is changed on the basis of the power requirement of the conveyor.

Abstract: A motor control system powered by an input power source. The system includes a reactive power reducing input power system in electrical communication with a motor and a constant frequency input power source. The reactive power reducing input power system includes an AC-DC converter and a regulator system, wherein the regulator system is in electrical communication with a DC-AC inverter that is in electrical communication with the motor. The system may include an isolation system to electrically isolate the DC-AC inverter from the motor when the DC-AC inverter is not transmitting power to the motor. The system may accept multiple alternating current voltage sources including both single phase and three phase sources.

Abstract: A method for driving a motor is provided. Pulse width modulation (PWM) signals are generated from a voltage signal and a commanded angle signal, which drives a motor with multiple phases. A motor current from a motor is measured with a single shunt and converted into a digital signal. Based on the digital signal and the commanded angle signal, direct-axis and quadrant-axis currents for the motor can be determined, and the voltage signal and the commanded angle signal can be adjusted based at least in part on the direct-axis and quadrant-axis currents.

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: Power conversion systems with active front end converters for example motor drives and power generation systems for distributed energy sources are presented with adaptive harmonic minimization for grid-tie converters for minimized or reduced total harmonic distortion in the line current spectrum including the source harmonic current, the load harmonics and the PWM harmonics.

Abstract: A motor driving apparatus is disclosed herein and includes a control unit, a soft-start unit and an output unit. When power-up or lock release situation, an external PWM driving signal is inputted to the soft-start unit, the soft-start unit generates an internal PWM driving signal and a power-up initial signal; after the power-up initial signal is generated, the control unit transmitting a motor rotation signal to the soft-start unit; when the soft-start unit counts a plurality of the motor rotation signal, the soft-start unit selects the external PWM driving signal or the internal PWM driving signal to output to the output unit.

Abstract: A system includes a target speed module and a pulse-width modulation (PWM) control module. The target speed module is configured to provide a first waveform based on a first speed setting for a motor. A start of a first cycle of the first waveform corresponds to at least one of a first current or a first voltage. The PWM control module is configured to shift a phase of the first waveform by a torque angle adjustment value to generate a second waveform. A start of a first cycle of the second waveform corresponds to at least one of a second voltage or a second current. The second voltage is greater than the first voltage, and the second current is greater than the first current. The PWM control module is configured to control the motor based on the second waveform.

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 apparatus to control a motor external to the motor control apparatus includes a microcontroller unit (MCU). The MCU includes mixed signal motor control circuitry adapted to perform back electromotive force (EMF) motor control in a first mode of operation. The mixed signal motor control circuitry is further adapted to perform field oriented control (FOC) in a second mode of operation.

Abstract: A method for pulse width modulation control of a multiple phase drive includes identifying at least one phase from the plurality of phases for the drive as eligible for clamping to one of a plurality of extreme power supply voltages, selecting a phase of the eligible phases having a largest magnitude driving current, determining a first offset signal as a difference between a control signal level for the selected phase and an extreme control signal level corresponding to one of the extreme power supply voltages, limiting a rate of change of the first offset signal to form a second offset signal, and determining a modified control signal for each of the phases for the drive including forming for each of a plurality of the phases a combination of the second offset signal and a control signal level for the phase to determine the modified control signal for the phase.

Abstract: A drive system includes an electric machine and a current source inverter (CSI). This integration of an electric machine and an inverter uses the machine's field excitation coil for not only flux generation in the machine but also for the CSI inductor. This integration of the two technologies, namely the U machine motor and the CSI, opens a new chapter for the component function integration instead of the traditional integration by simply placing separate machine and inverter components in the same housing. Elimination of the CSI inductor adds to the CSI volumetric reduction of capacitors and the elimination of PMs for the motor further improve the drive system cost, weight, and volume.

Abstract: A method for pulse width modulation control of a multiple phase drive includes identifying at least one phase from the plurality of phases for the drive as eligible for clamping to one of a plurality of extreme power supply voltages, including excluding from the eligible phases those phases with intermediate control signal levels and excluding phases according to a proximity criterion on the control signal levels. A phase is selected from the eligible phases. An offset signal is determined as a difference between a control signal level for the selected phase and an extreme control signal level associated with one of the plurality of extreme power supply voltages. A modified control signal is determined for each of the phases, by forming a combination of the offset signal and a control signal level for each phase to determine the modified control signal for each phase.

Abstract: An electric drivetrain of a device, such as a gas compression device, includes an electric machine and a system for supplying power to the electric machine, the electric machine including a rotor and a stator. The electric machine is an asynchronous electric machine, and the power supply system is suitable for supplying voltage to the stator of the electric machine, the power supply system making up a source of voltage.

Abstract: A method and system are disclosed for controlling electrical current through an inductive load. The electrical current is supplied by one of at least three selectable dual capacitor bank electrical circuits. The method includes storing electrical energy during a charge operating state in first and second capacitor banks of a first dual capacitor bank circuit. The stored electrical energy is then used to drive the inductive load when operating the first dual capacitor bank circuit in a drive operating state. After depleting the stored electrical energy from the first and second capacitor banks, the first dual capacitor bank transitions to a collection operating state that includes collecting electrical energy from the inductive load. A second and third dual capacitor circuits simultaneously transition among the charge operating state, the drive operating state, and the collection operating state during operation.

Abstract: An object of the present invention is providing permissible values of start currents with sufficiently high start torque ensuring the possibility of the start of a loaded motor, the smoothness of the motor's start, without spikes and fluctuations of the currents, voltages and torques. The other objects of the proposed device are simplicity, reliability and economic efficiency. The proposed method of an induction motor start includes an acquisition of two components of the voltage, feeding the motor. The both components have the different controlled frequencies and root mean square values. The proposed device for an induction motor start comprises two channels forming signals, which create two corresponding components of the motor's feeding voltage.

Abstract: An apparatus and method for drastically increasing the efficiency of a single phase AC motor. A DC solid state driver is used to pulse a combination of the motor coil and a series capacitor. The coil/capacitor combination allows the motor to run near resonance (or a multiple of resonance). This results in a flywheel effect that only requires pulses at the proper time to keep it going. The solid state driver is powered by pulsed DC at around 150 volts peak and clocked at 60 Hz by a square wave timing circuit.

Abstract: An apparatus for improving machine drive performance. The apparatus includes a controller configured to control an impedance of a converter. The converter is configured to be electrically coupled to a plurality of first ends of a plurality of windings of a machine. A plurality of second ends of the plurality of windings of the machine are configured to be electrically coupled to a power source.

Abstract: A method for controlling operation of a multi-phase induction motor may include transmitting a high-speed operation signal by a master computer for high-speed operation of the motor; receiving the signal by a control signal board, and in response to the signal, the control signal board may sense that the master computer is not simultaneously transmitting a low-speed operation signal, and in response to receiving the high-speed operation signal and not simultaneously receiving the low-speed operation signal, closing delta-to-wye contactors and closing contactors in a power section to transmit power to the motor for high-speed operation, whereby the motor is connected to a source of multi-phase power and operates at high-speed; and the control signal board transmitting a first feedback signal to the master computer that the motor is connected to the source of multi-phase power and is running at high speed.

Abstract: A method for determining the angular position of a synchronous machine having a magnetically anisotropic rotor includes an (m) iteration stage and an (n) iteration stage. The (m) iteration stage encompasses: generating an (m) magnetic field of an (m) angular direction and acquiring an (m) peak value of the current pulse generated by the (m) voltage pulse; and providing at least two further (m+i) peak values in different (m+i) angular directions that differ from the (m) angular direction. The (n) iteration stage includes: ascertaining the angular directions (n) and (n+1) in which the two highest or the two lowest peak values from a peak value group occur; and providing an (n) angular direction, which resides between the (n+1) angular direction and the (n+2) angular direction, as an angular position output.

Abstract: A rotation detecting apparatus for detecting a rotational state of a direct-current motor includes a driving device, a control device, an energization detecting device, an alternating-current component detecting device, and a rotational state detecting device. An impedance between brushes of the motor changes periodically in accordance with rotation of the motor. The alternating-current component detecting device detects change of an alternating-current component of electric current that is supplied to the motor based on an electrical quantity. The change of the alternating-current component is caused by change of the impedance caused in accordance with the rotation. The rotational state detecting device detects at least one of a rotation angle, a rotational direction, and a rotational speed of the motor based on a detection result of the alternating-current component detecting device.

Abstract: A motor drive circuit that performs PWM driving of an AC motor includes: rectifying circuit that rectifies power from an AC power supply; a DC intermediate circuit that smoothes an output of the rectifying circuit and holds the smoothed output; an inverter circuit that executes a PWM control of a voltage applied to the AC motor based on DC power held in the DC intermediate circuit; and a filter circuit that is inserted between the AC power supply and the rectifying circuit, wherein the filter circuit includes a noise filter that is inserted between the AC power supply and the rectifying circuit and reduces harmonic noise, and a band elimination filter that is arranged at a posterior stage of the noise filter and reduces harmonic noise having a bandwidth, which can be generated by the PWM control.

Abstract: An electric power tool according to the present invention is provided with a tool main body, an induction motor, a power supply unit, and an inverter. The power supply unit and the inverter are integrally incorporated in the tool main body together with the induction motor.

Abstract: When instructed to switch control modes between overmodulation PWM control and sinusoidal wave PWM control, control device corrects the amplitude of a voltage command signal based on a state of power conversion operation performed by an inverter, so as to suppress a change in an influence of dead time over a voltage applied to an alternating-current motor upon switching the control modes. The state of the power conversion operation performed by the inverter includes at least one of a present value of a carrier frequency in a control mode currently employed, an estimated value of the carrier frequency to be obtained when switching the control modes, the length of the dead time, a power factor of alternating-current power exchanged between the inverter and the alternating-current motor, and a driving state of the alternating-current motor.