Abstract: A power semiconductor module includes a half-bridge circuit having a first power semiconductor element and a second power semiconductor element that are connected in series with each other. The power semiconductor module also includes first to third external terminals, a first wiring member that connects a high-potential-side main electrode of the first power semiconductor element to the first external terminal, a second wiring member that connects a low-potential-side main electrode of the second power semiconductor element to the second external terminal, a third wiring member that connects an output of the half-bridge circuit to a third external terminal, and at least one of a first corrosion sensor disposed in an installation environment of the first wiring member, a second corrosion sensor disposed in an installation environment of the second wiring member, or a third corrosion sensor disposed in an installation environment of the third wiring member.

Abstract: A device for assessing remaining life of a rotating electrical machine includes: a data acquisition unit configured to acquire actual running performance data and electrical data about the rotating electrical machine to be assessed; an index value calculation unit configured to calculate a first index value to a third index value based on the acquired data, and to calculate, as a fourth index value, an estimation value of a residual withstand voltage value of the rotating electrical machine by performing analysis that uses an MT method on each piece of the electrical data; and an insulation deterioration estimation unit configured to assess the remaining life of the rotating electrical machine by estimating the remaining life of the rotating electrical machine with use of four index values from the first index value to the fourth index value.

Abstract: A circuit for controlling a motor that includes control circuitry configured to generate, for a phase of the motor, a switching signal indicating to couple the phase to a first terminal of a supply for an entire portion of each switching cycle of a first plurality of switching cycles corresponding to a first range of electrical angles for the rotor and to couple the phase to a second terminal of the supply for a portion of each switching cycle of a second plurality of switching cycles corresponding to a second range of electrical angles for the rotor. The control circuitry is further configured to control the motor based on the switching signal.

Abstract: A control device for controlling a rotary electric machine, the control device includes a current command unit, a voltage conversion device, a current conversion device, a signal demodulation device, an error compensation unit, an adding device and a position estimation device. The current command unit provides a d-axis current command and a q-axis current command. The current conversion device converts a current of the rotary electric machine to a synchronous reference coordinate current. The signal demodulation device computes a current variation of a high-frequency synchronous reference coordinate current. The error compensation device outputs a first correction value. The adding device adds the current variation of the high-frequency synchronous reference coordinate current and the first correction value to generate a second correction value.

Abstract: A method of controlling a refrigerator is disclosed. The method includes: operating a cool air supply means with a predetermined output; a controller determining the output of the cool air supply means based on a current temperature of a storage compartment sensed by a temperature sensor while the cool air supply means operates with the predetermined output; and the controller operating the cool air supply means with the determined output.

Abstract: A power tool is provided including a housing, an electric motor disposed within the housing, a power switch circuit disposed between a power supply and the electric motor, a main controller, and a secondary controller. The main controller is arranged to control a switching operation of the power switch circuit to regulate a speed of the motor, and is configured to monitor at least one of a speed or a rotational direction of the electric motor and deactivate the power switch circuit upon detection of fault condition associated the speed or the rotational direction of the electric motor. The secondary controller is configured to monitor at least one of the speed or the rotational direction of the electric motor independently from the main controller and deactivate the power switch circuit upon detection of fault condition associated the speed or the rotational direction of the electric motor.

Abstract: A motor control apparatus includes a motor, a motor driver to drive the motor, a motor current detection unit, a motor state estimation unit, a motor control unit, and first and second abnormality detection units. The motor current detection unit detects a current value of the motor. The motor state estimation unit estimates a state of the motor based on a voltage applied to the motor and the detected current value. The motor control unit applies a driving voltage of first driving corresponding to the estimated state of the motor or apply a driving voltage of second driving, which does not use the estimated motor state, to the motor driver. The first abnormality detection unit detects a rotation abnormality of the motor based on the estimated motor state. The second abnormality detection unit detects the rotation abnormality of the motor based on the detected current value of the motor.

Abstract: The present invention relates to a precise predictive maintenance method of a driver and the configuration includes: collecting slope information for a peak value between drive periods by connecting the peak value in a respective drive period in a driving state of the driver before a failure of the driver occurs; setting an alarm slope value for the peak value between the drive periods based on the collected slope information; and detecting, in a case where an average slope value for the peak value between the drive periods measured at a unit time interval set in a real-time driving state of the driver is more than the alarm slope value, the case as an abnormal state of the driver.

Abstract: A motor controller includes: a rotation speed estimating unit that estimates a rotation speed of a motor based on current information and primary frequency information of the motor; a proximity switch that outputs an ON signal when a portion of a rotating body of the motor is in proximity and that outputs an OFF signal when a portion of the rotating body of the motor is not in proximity; a rotation speed calculating unit that calculates a rotation speed of the motor based on the ON signal and the OFF signal output from the proximity switch; a speed command compensating unit that compensates a speed command value such that an error between the speed command value and a rotation speed calculation value becomes smaller; and a speed control system that perform the speed control on the motor based on the compensated speed command value and the rotation speed estimation value.

Abstract: Provided is a motor control device generating a torque command such that a detection speed of a motor matches a command speed, and controlling the motor. The motor control device includes: a torque command differential component taking a differential of the torque command and obtaining a torque command differential value; a motor actual speed second order differential component taking a second order differential of the detection speed of the motor and obtaining a motor jerk; and a runaway detection component determining that the motor is in a runaway state in a case where an abnormal state in which a sign of the motor jerk and a sign of the torque command differential value do not match continues for a predetermined time or more. Accordingly, the runaway of the motor can be detected in a short time while the erroneous detection can be suppressed.

Abstract: There is provided a numerical controller that automatically acquires detailed information on a wired device prior to connection setting. The numerical controller is connectable to a plurality of devices, and includes a connection information acquisition unit that acquires connection information on each of the devices, including information indicating a connection order and a kind of each of the devices by communicating with each of the devices in a hardware level, a connecting data creation unit that creates connecting data using the connection information, a connection processing execution unit that executes connection processing with each of the devices in a software level using the connecting data, and a detailed information acquisition unit that acquires detailed information from each of the devices subjected to the connection processing.

Abstract: The present invention relates to a precise predictive maintenance method of a driver and the configuration includes: collecting slope information for a constant speed value between drive periods by connecting the constant speed value in a respective drive period and the constant speed value in a driving state of a driver before a failure of the driver occurs; setting an alarm slope value for the constant speed value between the drive periods based on the collected slope information; and detecting, in a case where an average slope value for the constant speed value between the drive periods measured at a unit time interval set in a real-time driving state of the driver is more than the alarm slope value, the case as an abnormal state of the driver.

Abstract: A pump includes a piezoelectric element that deforms when a drive voltage is applied to it, and a reservoir that has a capacity to store lubricating oil and that is at least partially deformed elastically to change in the capacity when the piezoelectric element deforms. The pump discharges the lubricating oil when the reservoir decreases in the capacity. A drive circuit unit is switchable between an application state where the drive circuit unit applies the drive voltage to the piezoelectric element, and a release state where the drive circuit unit releases the drive voltage applied to the piezoelectric element. A controller controllably switches the drive circuit unit between the application state and the release state. An electric power storage unit stores electric power that is output from the piezoelectric element when the drive voltage applied to the piezoelectric element is released.

Abstract: A control device of a power conversion device for driving a motor includes a current detector and an angle detector. The control devices also includes a motor controller that acquires an electric current and an angle from the respective detectors in a first cycle and drives the motor via the power conversion device, and a toque monitor that acquires the electric current and the angle from the respective detectors in a second cycle and estimates an output torque for determining abnormalities in the motor control. The control device prioritizes acquisition requests for the current and angle from the motor controller and the torque monitor. The torque monitor acquires the current and angle at least twice in the second cycle to acquire a current and angle that are detected at the same time by the detectors.

Abstract: A sheet conveyance apparatus includes a connection member to connect or separate a motor to drive a conveyance roller, where a motor rotor has a rotation phase and a motor winding includes a driving current controlled by a controller. Per control by the controller, a value of a torque current component of a detected driving current becomes a target value of the torque current component and a value of an exciting current component of the detected driving current becomes a target value of the exciting current component. The controller can cause a deviation between a rotor target phase and a determined rotation phase to decrease, cause magnetic flux passing through the winding to be weaker than a magnetic flux of the rotor, and cause the magnetic flux to be stronger than that passing through the winding in a first period.

Abstract: A power electronics switching system has a power converter including switching elements respectively disposed in parallel paths. The system also has a controller that outputs switching commands for the switching elements derived from carrier waveforms and reference waveforms corresponding to the switching elements, and generates a shape for one of the carrier waveforms according to a difference in magnitudes between the reference waveforms such that the shape is of a first type responsive to the difference being greater than a first threshold and is of a second type different than the first type responsive to the difference being less than a second threshold.

Abstract: A motor controller includes: a primary frequency control unit that generates a primary frequency command value based on current information of an induction motor and limits the primary frequency command value based on a maximum primary frequency; a rotation speed estimating unit that estimates a slip frequency based on the current information of the induction motor and estimates a rotation speed based on the estimated slip frequency estimation value and the primary frequency command value; a proximity switch that outputs an ON signal or OFF signal when a portion of a rotating body of the induction motor is in proximity or not in proximity; a rotation speed computing unit that computes a rotation speed based on the ON signal and the OFF signal; and a maximum primary frequency computing unit that computes the maximum primary frequency based on the rotation speed computation value.

Abstract: A motion control system provides optimized communications within and between an amplifier and a profile generation subsystem. In particular, the communications can provide data streams between components of the motion control that are derived from observed variables of the motion system. An amplifier subsystem drives a motor and output motor data indicating status of the motor. The profile generation subsystem issues motor control commands to the amplifier subsystem and generates motor summary data based on the motor data. The profile generation subsystem selectively output an error signal based on at least one of the motor data and motor summary data.

Abstract: A motor driving circuit and a motor component are provided.

Abstract: A torque estimating system for a synchronous electric motor having a permanent magnet includes: a superimposing unit configured to superimpose a voltage or current of a frequency different from a frequency of a fundamental wave driving the synchronous electric motor on at least a d-axis of the synchronous electric motor; a magnet temperature estimating unit configured to estimate a temperature of the permanent magnet from the superimposed voltage or current and a current or voltage obtained by the superimposing; and a torque estimating unit configured to estimate a torque of the synchronous electric motor from the estimated temperature of the permanent magnet.

Abstract: A method and apparatus for controlling commutation of a motor. A voltage is measured at each of a plurality of windings of a motor using an electric circuit. A controller computes an overall back electromotive force for the motor using the voltage measured at each winding in the plurality of windings. The controller generates a result having either a first value or a second value based on the overall back electromotive force. The controller adjusts the commutation phase and the commutation period of the motor using the result.

Abstract: A training apparatus including a training element for a user performing exercises, an AC motor and a frequency converter being arranged to control the AC motor, wherein the frequency converter comprises measuring means being arranged to measure a voltage and a current of the AC motor and calculation means being arranged to calculate a magnetic state of the AC motor using the measured voltage, the measured current, a reference torque and a reference flux in order to generate a torque of the AC motor. The training apparatus further comprises a control unit having a machine control module being arranged to calculate the reference flux and the reference torque using an intended overall torque, wherein the machine control module is connected to the frequency converter and arranged to transmit the reference flux and the reference torque to the frequency converter.

Abstract: A method for driving an AC motor is disclosed. The method comprises generating two phases of currents to drive the motor coils to generate one magnetic field sum, and each positive and negative half output cycle of each phase of current has a positive or negative curved-triangle current. A method for generating electric power with an AC motor generator is also disclosed.

Abstract: A rotating electric machine control device includes: a q-axis PI controller calculating a pre-restriction q-axis voltage instruction value based on a q-axis voltage detection value and a q-axis current instruction value; a first q-axis restricter calculating a post-restriction q-axis voltage instruction value by restricting the pre-restriction q-axis voltage instruction value, for an excess of output exceeding a maximum outputtable voltage V_max; a correction value calculator calculating a q-axis correction value that has a reverse phase of a ripple current of a q-axis current; and a corrector correcting the post-restriction q-axis voltage instruction value with the q-axis correction value. In such manner, even when the pre-restriction q-axis voltage instruction value is saturated, a ripple current is reduced, thereby reducing a sound and/or a vibration caused by the ripple current.

Abstract: The method is for making an electric motor more efficient by iteratively changing when a processor sends activation signals to transistors to minimize a current required to rotate a rotor at a constant rotational speed. The method is also for changing a rotational direction of the rotor by switching the order in which activation signals are sent to the transistors.

Abstract: An electric machine assembly includes an electric machine having a stator configured to have a stator current and a controller configured to receive a torque command (T). The controller has a processor and tangible, non-transitory memory on which is recorded instructions for executing a method of modifying the stator current for enhanced flux weakening. The controller is programmed to obtain a base stator current [IdLU, IqLU] from a look-up table based at least partially on the torque command (T). The controller is programmed to obtain a characteristic angle (?i, i=1, 2, 3) based at least partially on a value of the torque command (T) and the base stator current [IdLU, IqLU]. A stator current modifier [?Id, ?Iq] is obtained based at least partially on the characteristic angle (?i, i=1, 2, 3) and a flux weakening factor (?IS) such that: ?Id=(?IS*cosine (?i)) and ?Iq=(?IS*sine (?i)).

Abstract: A method and a device for operating a closed-loop or open-loop speed-controlled electric motor of a fan drive, which motor is connected to an on-board system voltage of a motor vehicle and the motor speed of which is set to a defined first desired speed, wherein, if the on-board system voltage fluctuates, the motor speed is set to a desired speed that is lower compared with the first desired speed.

Abstract: A system and method for dynamically optimizing flux levels in electric motors based on estimated torque. Motor parameters and motor equations are used to estimate operating characteristics and to set current and voltage limits which define an optimal flux operating range for a given speed and torque of the motor. A slope of a linear flux gain is determined within the defined operating range at different speeds of the motor. The determined slopes for the different speeds are saved in a memory element. A control element determines and achieves an optimal flux level for the motor by accessing the table to identify a specific slope which corresponds to an actual speed of the motor, multiplying the slope by the estimated torque and adding an offset value to determine a phase current component value associated with the optimal flux level, and applying the determined phase current component value to the motor.

Abstract: A drive unit includes: an electric motor; a flux estimator circuit configured to estimate at least a flux angle; a synchronous frame generator coupled to a rotor of the AC induction motor and configured to detect a rotor mechanical angle; and a switch configured to selectively provide either the flux angle or the rotor mechanical angle for controlling the motor.

Abstract: An electric motor controller includes a first coordinate conversion unit that converts a three-phase current into a current in a ?c-?c rotating coordinate system, a first calculation unit that obtains a first term, a second calculation unit that obtains a voltage command value in the ?c-?c rotating coordinate system as a sum of the first term and a second term, a second coordinate conversion unit that coordinate-converts the voltage command value into a voltage command value of a voltage to be applied to a rotary electric motor in another coordinate system.

Abstract: A method controlling a powertrain fitted in an automobile and including an electric motor including a rotor and stator, the method including: regulation of currents of the rotor and the stator via control signals from the electric motor, wherein the currents and control signals are expressed in a rotating coordinate system and include a plurality of axes, the control signals resulting from a first transformation including a change of variable that enables dynamic decoupling between the control signals, along each of the axes of the plurality of axes; saturation of the control signals resulting from the first transformation to satisfy constraints of a battery fitted in the automobile and connected to the electric motor; and blockage of at least some of the current reference values of the regulation if the control signals are saturated.

Abstract: A power interruption circuit for use in a power distribution module is provided. The power interruption circuit is configured to provide power to a load and includes a shunt resistor, a plurality of switches, and microprocessor. The microprocessor is configured to determine a digitized value of a current flowing through the shunt resistor, determine a digitized value of an output voltage of the power interruption circuit, calculate, from the digitized current value and the digitized output voltage value, a power provided by the power interruption circuit to the load, compare the calculated power to a threshold power level, and control the plurality of switches based on the comparison.

Abstract: A power converter that includes: a power conversion unit; and a control unit configured to control the power conversion unit such that the power conversion unit operates as a virtual synchronous generator. The control unit includes: an AVR model unit; a governor and driving source model unit; a power generation torque arithmetic operation unit; a rotation angle arithmetic operation unit; a voltage d-q conversion unit; and a generator model unit configured to perform arithmetic operation.

Abstract: An inverter is provided. The inverter includes a current providing unit providing a first axis current and a second axis current to an induction motor; a revolutions per minute (RPM) measuring unit measuring the RPM of the induction motor; and a control unit changing the second axis current according to the measured RPM.

Abstract: The invention relates to a method (40) for monitoring a torque of an electric motor (10), in particular for application in a motor vehicle, wherein the electric motor (10) is supplied with electric current (IS1, IS2, IS3) in multiple phases. A first torque value (M2) of the torque generated by the electric motor (10) is determined (58) on the basis of the electric output of the electric motor (10) and a detected rotational speed (n) of a rotor of the electric motor (10). A second torque value (M1) is determined on the basis of at least one measured phase current (IS1, IS2, IS3) and a rotational position of the rotor, and the two determined torque values (M1, M2) are compared (60) to one another for plausibility checking.

Abstract: In a device in which the rotation angle of the rotor is detected with a resolver, the rotation angle of the rotor with less error can be obtained while reducing burden of the operator. The measured angle value acquisition unit acquires the measured-rotation angle value of a motor shaft. The error calculation unit calculates the error included in each of measured-rotation angle values. The frequency component acquisition unit determines the phase and the amplitude of a frequency component of the error based on the errors. Thus, by using the error frequency component acquisition device, the phase and amplitude of the frequency component of the error included in the measured-rotation angle value can be automatically calculated and the correction with respect to the measure-rotation angle value can be performed using the acquired phase and amplitude. Therefore, the rotation angle of the rotor with less error can be obtained, while reducing the burden of the operator.

Abstract: A motor driving device includes a microcomputer, a command voltage adjusting circuit, and a driving IC. The command voltage adjusting circuit converts a first command voltage signal from the microcomputer to a second command voltage signal. The driving IC generates a drive pulse based on the second command voltage signal. An upper and a lower limit of an input voltage range of the driving IC are larger than an upper and a lower limit of a voltage range of the first command voltage signal, respectively.

Abstract: A rotation-angle detection device includes: an amplitude adjustment unit that performs correction to match amplitude values of multiple detection signals output from multiple rotation detection units to output corrected signals, the rotation detection units changing outputs in accordance with a rotation angle of a rotor and being provided such that the rotation detection units output the detection signals having different phases; a vector generation unit that performs addition and subtraction on two signals out of the corrected signals to generate two vector component signals that are perpendicular to each other; an amplitude correction unit that performs correction to match amplitudes of the two vector component signals to output corrected vector component signals; and a rotation-angle searching unit that searches for the rotation angle of the rotor on basis of a vector that is represented by the two corrected vector component signals to output a detection angle.

Abstract: A system and method are described for conserving energy by decoupling a supply voltage to an electric motor operating under periodic load variations. A time segment value corresponding to a duration of periodic load variations is obtained and the supply voltage is adjusted to maintain an observed phase angle for a supply voltage and current at a value corresponding to a target phase angle. At least one off-time period is identified during the time segment value that corresponds to when the adjusted supply voltage is applied to the motor. During a remainder of the time segment value, at least one turn-on time period is provided when the supply voltage is coupled to the motor. The system may enter to a closed-loop control process after a predetermined period of time to adjust to any changes in the periodic load variations.

Abstract: A motor control device includes an inverter, a power device temperature obtaining unit, a motor temperature obtaining unit, a power device temperature determination level storage unit, a motor temperature determination level storage unit, a PWM frequency storage unit that stores at least two PWM frequencies including a high PWM frequency a low PWM frequency, a power device temperature determining unit that determines whether or not a temperature of a power device is equal to or higher than a power device temperature determination level, a motor temperature determining unit that determines whether or not a temperature of a motor is equal to or higher than the motor temperature determination level, and a PWM frequency selecting unit that selects a PWM frequency to be given as a command to the inverter.

Abstract: An angle estimation control system of a permanent magnet motor is provided. The angle estimation control system includes a Clarke transform module, a Park transform module, and an angle estimation module. The Clarke transform module generates orthogonal current signals in accordance with motor phase currents. The Park transform module generates a current signal in response to the orthogonal current signals and an angle signal. The angle estimation module generates the angle signal in response to the current signal. The angle signal is related to a commutation angle of the permanent magnet motor. The current signal is controlled to be approximately equal to zero. The angle signal is further coupled to generate three phase motor voltage signals.

Abstract: A fan control circuit includes a hardware controller, a rectifier circuit, first to third electronic switches, and a fan. When the hardware controller outputs a pulse width modulation (PWM) signal to the rectifier circuit and the fan, the rectifier circuit transforms the PWM signal into a direct current (DC) voltage and outputs the DC voltage to the first electronic switch. The first electronic switch is turned on, and the second and third electronic switches are turned off. A rotation speed of the fan is controlled by the PWM signal received from the hardware controller. When the hardware controller does not output the PWM signal, the first electronic switch is turned off, the second and third electronic switches are turned on, a DC power supply supplies power to the fan through the third electronic switch, and the fan rotates at full speed.

Abstract: A sensorless brushless motor control device includes a first amplification module common to all motor phases and generating an intermediary voltage signal, a voltage divider between each motor phase and a node on which the intermediary voltage signal is generated, and a computation unit. Each voltage divider generates a first corrected electromotive force with a predetermined average value. The computation unit controls the motor on the basis of the first corrected electromotive forces. By using only hardware components, the control device maintains the average of the corrected electromotive forces at the center of the analog acquisition zone of the computation unit.

Abstract: There is provided a motor controlling circuit including: a hall signal level detecting unit detecting a hall signal from a hall sensor; and a signal generating unit sensing a change in a level of the hall signal to generate a motor controlling signal according to the change in the level of the hall signal, wherein the signal generating unit determines that the hall signal is maintained at a high level in a case in which a high level maintaining time of the hall signal is equal to or shorter than a preset time.

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: A pitch drive circuit that operates in an emergency mode, for a wind or water power plant. The circuit has at least one rectifier unit, at least one DC intermediate circuit, two inverter units and a pitch rotary current motor with motor trains that can be contacted on both sides. A first contact side of the motor trains is connected to a first inverter unit and a second contact side of the motor trains is connected to a second inverter unit. At least one switching element is connected to at least one contact side of the motor trains. In a normal operating mode of a first switching state of the switching element the motor trains can be energized via both inverter units, and in an emergency operating mode of a second switching state of the switching element, the motor trains can be energized via a single inverter unit.

Abstract: A motor control device has an overcurrent test unit to send a first test voltage Vt1 lower than a reference voltage Vref for overcurrent determination and a second test voltage Vt2 not lower than the reference voltage Vref to an overcurrent determination unit when a synchronous motor is not rotated. The motor control device determines that an abnormality occurs in the overcurrent detection unit when the overcurrent determination unit determines that the first test voltage Vt1 causes an overcurrent on the basis of a comparison result, or the second test voltage Vt2 causes no overcurrent on the basis of the comparison result.

Abstract: When a current sensor fails, instead of a normal-time motor control section, an abnormal-time motor control section drives and controls a motor. The abnormal-time motor control section detects a timing at which motor current I becomes zero in a state in which all the switching devices are turned off (S11 to S13). Every time the motor current I becomes zero, the abnormal-time motor control section sets an ON time T0 corresponding to steering torque |tr| (S14 to S15), and turns on the switching devices corresponding to the direction of the steering torque for the ON time T0 (S17 to S20). With this operation, an average current Iavg corresponding to the steering torque |tr| flows through the motor 20, whereby deterioration of the followability of steering assist is suppressed.

Abstract: A controller for an AC electric motor, includes a Feed Forward Torque Controller and a load model. The Torque controller directly derives a torque related component of applied motor voltages from a signal representing a torque command input T* and at least one motor parameter. The load model derives a motor speed value including a model of motor speed behavior of the AC electric motor to provide an output signal which represents the motor speed of the AC electric motor. This motor speed output signal is used in determining a frequency of rotation of an applied motor voltage vector. Where an input to the load model is the signal representing the torque command input T*, the load model uses the signal representing the torque command T*, at least over a part of an operating speed range of the AC motor which includes zero speed, to determine the motor speed output signal.

Abstract: A motor control apparatus according to the embodiment includes a rotational position estimating unit, a change amount estimating unit, and an inductance estimating unit. The rotational position estimating unit estimates a rotational position of a rotor from a motor parameter including a q-axis inductance of a motor on a basis of an output current to the motor and a voltage reference. The change amount estimating unit estimates a change amount of an output torque with respect to a current phase change of the motor corresponding to a high frequency signal whose frequency is higher than a drive frequency of the motor. The inductance estimating unit estimates an inductance value that obtains a maximum torque on a basis of the change amount as the q-axis inductance.