Abstract: When it is determined that a rotor is initially in a stationary state, a current vector is applied to a coil by a vector control method so as to rotate the rotor in a forward direction from a present position of the rotor regardless of a predetermined start position of the rotor. Therefore, a motor can be stably started with less power consumption and noise/vibration.

Abstract: A control technology for a synchronous motor for suppressing rotational pulsation caused by variation in individuals without making a control algorithm complex is provided. In a motor drive system which is a control device for a synchronous motor, in order to suppress the pulsation component of N times as high as the AC frequency for driving the synchronous motor, a controller in which the phase property of the disturbance response of the controller with respect to the pulsation frequency is within ±45° is arranged. Therefore, the torque pulsation component generated from distortion in induction voltage or variation between phases is suppressed.

Abstract: A converter for an electrical machine having a plurality of phase lines for connecting the electrical machine. For each phase line the converter has a half-bridge with a first first semiconductor switch is configured to electrically connect at least one of the phase lines intermittently to a first supply line of the converter, and a second semiconductor switch configured to electrically connect the phase line intermittently to a second supply line of the converter. The converter is configured for operation in a first energy recovery limiting mode in which at least two of the first semiconductor switches are at least intermittently on simultaneously.

Abstract: An electronic circuit and an associated method used to drive an electric motor provide a user selectable relationship between rotational speed of the electric motor and phase advances of signals used to drive the electric motor. By selecting the relationship, efficiency of the electric motor drive can be improved.

Abstract: A control system for an electric machine, the control system including a position sensor and a drive controller. The drive controller generates one or more control signals for exciting a winding of the electric machine in response to edges of a signal output by the position sensor. The times at which the control signals are generated by the drive controller are corrected by a position-sensor offset that is fixed over an operating speed range of the electric machine.

Abstract: An electrically commuted reversible synchronous motor is activated in a calibration journey using an externally forced rotating field, during which an electrical angle of a rotating field and a mechanical angle of the rotor are measured simultaneously at a reference position by an external sensor. These items are stored associated with one another as a measurement series of value pairs. The electrical angle of the rotating field and the mechanical angle of the rotor are also detected simultaneously after direction reversal of the rotating field. These are stored as a second measurement series of value pairs. The angle difference between the electrical angle and the mechanical angle are calculated from value pairs of both measurement series. The correction value for taking the actual incorrect angle into consideration is calculated from the two angle differences by averaging.

Abstract: A motor control apparatus includes a sensing module, a phase modulating module, a duty cycle modulating module and a driving module. The sensing module detects a motor to generate a sensing signal. The phase modulating module receives the sensing signal and generates a phase modulation signal in accordance with the sensing signal. The duty cycle modulating module receives the phase modulation signal and generates a duty cycle modulation signal in accordance with the phase modulation signal. The driving module receives the duty cycle modulation signal and generates a motor control signal for controlling the motor in accordance with the duty cycle modulation signal.

Abstract: To achieve peak acoustic and power performance, the coil or applied current should be in phase or substantially aligned with the back electromotive force (back-EMF) voltage. However, there are generally phase differences between the applied current and back-EMF voltage that are induced by the impedance of the brushless DC motor (which can vary based on conditions, such as temperature and motor speed). Traditionally, compensation for these phase differences was provided manually and on an as-needed basis. Here, however, a system and method are provided that automatically perform a commutation advance by incrementally adjusting a drive signal over successive commutation cycles when the applied current and back-EMF voltage are misaligned.

Abstract: An apparatus and a method for detecting a lock error in a sensorless motor are disclosed, where the apparatus includes a multiplexer, a negative booster, a comparator and a timer. The multiplexer can receive a coil voltage from the sensorless motor. The negative booster can receive a neutralizing voltage from the sensorless motor and drop the neutralizing voltage. The comparator can compare the coil voltage with the dropped neutralizing voltage for outputting a zero-crossing signal. The timer can count time duration during the zero-crossing signal maintained at the a logic level and determine the lock error in the sensorless motor when the time duration exceeds a predetermined period.

Abstract: A compact field programmable gate array (FPGA)-based digital motor controller (102), a method, and a design structure are provided. The compact FPGA-based digital motor controller (102) includes a sensor interface (206) configured to receive sensor data from one or more sensors (104) and generate conditioned sensor data. The one or more sensors (104) provide position information for a DC brushless motor (108). The compact FPGA-based digital motor controller (102) also includes a commutation control (210) configured to create switching commands to control commutation for the DC brushless motor (108). The commutation control (210) generates commutation pulses from the conditioned sensor data of the sensor interface (206). The compact FPGA-based digital motor controller (102) also includes a time inverter (208) configured to receive the commutation pulses.

Abstract: A rotation speed detection circuit includes an internal clock generation portion which receives an input of a period signal whose period varies in accordance with rotation speed of a motor and generates an internal clock signal having a predetermined number of pulses in one period of the period signal, and an internal clock counter portion which counts the number of pulses of the internal clock signal for a predetermined period every one period of the period signal and delivers a count value thereof as a digital data signal.

Abstract: A motor control apparatus includes a current control unit which is configured to calculate dq-axis voltage commands to match d-axis and q-axis current commands with d-axis and q-axis currents of a motor current, respectively. A power conversion circuit is configured to drive the motor. A modulation factor command unit is configured to determine a modulation factor command. A modulation wave command unit is configured to determine modulation wave commands. A pulse width modulation generating unit is configured to generate a pulse width modulation pattern. A modulation factor saturation level calculating unit is configured to determine a modulation factor saturation level. A field-weakening control unit is configured to correct the d-axis current command.

Abstract: A motor control system includes a power control module and a detection module. The power control module controls power applied to first and second stator coils of a motor to rotate a rotor. The rotor induces voltages in the first and second stator coils when the rotor is rotating. The detection module determines a first time when a first voltage is induced in the first stator coil and determines a second time when a second voltage is induced in the second stator coil after the first voltage is induced. The detection module determines a speed of the rotor based on a difference between the first and second time. The power control module applies current through the second stator coil a predetermined period after the second time. The power control module determines the predetermined period based on the speed of the rotor.

Abstract: The invention concerns a rotary single-phase electromagnetic servo actuator consisting of a rotary actuator designed to move a mobile member along a limited travel, including a 2N pole stator structure, N being equal to 1 or 2, and at least one field coil, said stator structure being made of a material with high magnetic permeability, and a rotor having a ferromagnetic yoke and a thin magnetized portion consisting of 2N pairs of axially magnetized poles, in alternate directions and a rotor angular position sensor. The invention is characterized in that the position sensor has a magnetic field emitter integral with the yoke and a receiver for the magnetic field stationary relative to the stator structure.

Abstract: A three-phase AC motor drive control device has a phase command calculation unit. When driving a three-phase AC motor by a three-phase alternating square-wave voltage that is converted in power according to a switching command corresponding to one cycle of the electrical angle obtained from a rotational position of the rotor of the three-phase AC motor, the phase command calculation unit performs a torque feedback calculation based on a torque deviation, obtains, based on this calculation result, a phase command that is the lead or lag angle amount of a phase to be corrected, and stores and updates this obtained phase command. To generate the switching command, the three-phase AC motor drive control device outputs a pulse pattern to an inverter, the pulse pattern being shifted in phase by the amount of the phase command with respect to the basic phase of the three-phase alternating square-wave voltage uniquely determined with respect to the one cycle of the electrical angle.

Abstract: A motor driving apparatus has a loss-of-synchronism monitoring circuit that monitors the rotation of a rotary machine such as a brushless DC motor to detect a sign of transition to a state of loss of synchronism. When the sign is detected, an energization control circuit temporarily stops driving of the rotary machine to bring it into a free running state, and thereafter carries out control so as to resume driving of the rotary machine. Further, the motor driving apparatus has an inverter and a drive control circuit that controls switching operation of the inverter based on rotation of the rotary machine.

Abstract: The invention relates methods and devices for compensating for load factors in permanently excited motors, wherein the rotor position is determined from the inductivities of the phases. The methods and devices are characterized by a stabilization of the inductivity-based signals for the determination of the position of the rotor in permanently excited motors against load factors. To this end, advantageously current-dependent faults of the angular values determined during the operation of the motor are corrected. For this purpose, in order to correct the inductivity-based determination of the position of the rotor, in a measuring device either the phase currents are measured or the intermediate circuit current is captured.

Abstract: An apparatus for controlling an operation of a reciprocating compressor, includes: a control unit for detecting a current pushed amount of a piston when a TDC is detected as an inflection point of a phase difference between stroke and current, comparing the current pushed amount with a pushed amount reference value, and applying a DC voltage applied to a linear motor based on the comparison result. An AC voltage and a DC voltage are applied to the linear motor to increase the stroke, and when the TDC is detected, the current pushed amount is calculated and compared with the pushed amount reference value, and then, the DC voltage or a DC current applied to the linear motor is varied based on the comparison result, thereby obtaining a maximum compression volume without collision of the piston.

Abstract: The invention relates to an electric motor having at least two stators disposed coaxially to each other and a rotor, wherein each stator has 2*n poles, with n=1, 2, 3, . . . , wherein each stator has at least one common coil or winding for all poles, wherein each stator has a first and second partial shell, wherein each partial shell has a shell bottom and n poles, wherein each pole is formed as a tooth extending in axial direction or substantially in axial direction and beginning on the shell bottom, wherein with assembled partial shells of a stator the tooth or the teeth of the first partial shell is or are disposed in alternating manner in circumferential direction with the tooth or the teeth of the second partial shell, and wherein with assembled partial shells or a stator, the at least one coil) or winding is received between the partial shells.

Abstract: A control method of a current limit of a DC motor includes generating a reference voltage according to a preset current limit value of a DC motor; comparing the reference voltage with the voltage drop of a power control switch which drives the DC motor to generate a compare result; and controlling the power delivered to the DC motor according to the compare result in order to limit the current of the DC motor.

Abstract: A drive apparatus includes a magnet rotor, a stator having a coil, a position detector configured to detect a position of the magnet rotor, a lead angle circuit configured to output a signal having a lead angle relative to an output of the position detector, a first driver configured to switch an electrification state of the coil in accordance with a preset time interval, a second driver configured to switch an electrification state of the coil in accordance with an output of the lead angle circuit, and a controller configured to adjust a lead angle amount of the signal output from the lead angle circuit within a range that does not cause step out in the driving by the first driver, prior to changing the driving by the second driver to the driving by the first driver.

Abstract: In application of a square wave voltage to a motor MG2 to make the motor MG2 output a torque equivalent to a torque command Tm2*, the procedure of square wave control corrects reference phases ?b and ??b as phases for maximizing an absolute value of the output torque of the motor MG2 with a rotational position detection error ?err and sets the results of the correction to an upper limit phase ?ul and a lower limit phase ?ll of the square wave voltage (step S110). A target voltage phase ?* is set within a phase range defined by the upper limit phase ?ul and the lower limit phase ?ll, in order to reduce a torque difference between the torque command Tm2* and a torque estimate Tm2est (steps S120 and S130). An inverter 42 is controlled based on the target voltage phase ?* and a rotational angle ? of the motor MG2.

Abstract: A variable-delay-time control system for a motor is provided. The system includes a control unit, a driving unit, and a motor. The control unit is used to output at least one control signal according to at least one predetermined signal, and the control signal has a variable delay time. The driving unit is connected to the control unit, and is used to receive the control signal and generate a driving signal. The motor is connected to the driving unit, and conduction time of the motor is controlled according to the driving signal and the variable delay time. With the variable-delay-time control system of the present invention, the delay time of the control signal is variable, so the motor can operate at a high efficiency (for example, at a reduced current). Moreover, as the variable-delay time can be adjusted according to the predetermined signal, the motor can operate at a high efficiency in different operating states, thus improving the overall efficiency of the motor.

Abstract: A method of controlling an electrical machine that includes commutating a phase winding of the electrical machine at a time T_COM(1) after a first edge and at a time T_COM(2) after a second edge of a rotor-position signal. T_COM(2) is defined by the equation: T_COM(2)=T_COM(1)+T_AVE?T_PD, where T_AVE is an average period between edges of the rotor-position signal, and T_PD is the period between the first and second edges. Additionally, a controller and control system that implement the method.

Abstract: A brushless D.C. disk motor has one or more disk rotor assemblies and pairs of stator assemblies for each rotor assembly. Each disk rotor assembly has a disk and a plurality of permanent magnets distributed along two or more circular paths in the disk inboard of the peripheral edge of the rotor. Each stator assembly has a plurality of pole pieces and coils distributed along a mounting plate in corresponding circular paths. The disk is rotatably mounted to a support member; while the stator sub-assemblies are fixed to the support member. The coils are selectively activated by commutated power control signals generated in response to a vehicle condition parameter, such as vehicle speed or disk motor load, to optimize power drain from the source of electrical power in accordance with the value of the vehicle condition parameter.

Abstract: An electric machine is disclosed comprising a first energy source, a second energy source, and a stator which comprises a first set of windings and a second set of windings. The electric machine has a rotor and a controller, the controller configured to control the first energy source to supply a first current to the first set of windings and control the second energy source to supply a second current to the second set of windings. The controller also detects an angular position of the rotor, detects the first current, detects the second current, and determines an optimum phase shift angle of the first current based on the angular position of the rotor, the first current, and the second current. The controller controls the first energy source based on the optimum phase shift angle to modify the first current supplied to the first set of windings.

Abstract: The drive control circuit for an electric motor is provided. The drive control circuit includes: an original drive signal generator that generates an original drive signal; an excitation interval setter that is able, for each half cycle of respective length ? in each 2? excitation cycle of the original drive signal, to arbitrarily set excitation intervals during which to excite coils of the electric motor to any one of a plurality of intervals which include at least either one of a symmetrical interval centered on a center of each half-cycle and an unsymmetrical interval; and a drive signal shaping circuit that generates a drive signal for driving the electric motor, by validating the original drive signal during the excitation intervals and invalidating the original drive signal during non-excitation intervals other than the excitation interval.

Abstract: A driving method for a motor includes sensing variation of magnetic pole of a rotator of the motor, to generate a magnetic pole sensing signal, determining dead zone of the motor according to the magnetic pole sensing signal, to generate a determination result, and adjusting voltage outputted to a coil of the rotator according to the determination result.

Abstract: An electrically commutated actuator and control system has a stator and a shaft that is movable with respect to the stator. A plurality of magnets movable with the shaft provide a first magnetic flux, and an electric current in at least one coil defined on the stator provides a second magnetic flux. The second magnetic flux is controlled in response to the first input so that the second magnetic flux has a predetermined phase with respect to the first magnetic flux. The second magnetic flux is controlled in response to the second input so that the phase of the second magnetic flux with respect to the first magnetic flux varies from the predetermined phase.

Abstract: A method wherein the signals (SW1, Sw2, Sw3) controlling the power supply (10) of the phase windings (4) of the motor consist of signals (So1, So2, So3) that are out-of-phase by a phase angle (f) which is continuously variable in relation to synchronization signals (Si1, Si2, Si3) generated by sensors (1) detecting the position of the rotor. According to the method, a processing unit (5) comprises inlets (8) for receiving the synchronization signals and outlets (6, 7) for transmitting the out-of-phase signals. The synchronization signals are binary signals presenting synchronization fronts and the rising and falling fronts of the out-of-phase signals are generated, following a level switching time depending at least on the phase angle, from at least one reference front selected from the synchronization fronts such that the switching time is minimum.

Abstract: An electromechanical device includes: a magnet coil; a PWM driving circuit; and a control unit, wherein the control unit performs a first control of setting an excitation interval which is an interval in which a PWM drive signal is supplied to the magnet coil and a second control of changing a duty ratio of the PWM drive signal, and wherein the control unit performs an advance angle control of putting the phase of the center of the excitation interval earlier than the phase in which a counter-electromotive force generated in the magnet coil has the maximum value in the first control, and increases the duty ratio of the PWM drive signal in the second control so that a gain is greater than 100% when the gain is 100% at the time of generating the PWM drive signal so as to have a sinusoidal shape.

Abstract: An electric machine is disclosed comprising a first energy source, a second energy source, and a stator which comprises a first set of windings and a second set of windings. The electric machine has a rotor and a controller, the controller configured to control the first energy source to supply a first current to the first set of windings and control the second energy source to supply a second current to the second set of windings. The controller also detects an angular position of the rotor, detects the first current, detects the second current, and determines an optimum phase shift angle of the first current based on the angular position of the rotor, the first current, and the second current. The controller controls the first energy source based on the optimum phase shift angle to modify the first current supplied to the first set of windings.

Abstract: A motor drive unit includes a position detection section configured to detect a rotor position by detecting a zero cross of a counter electromotive voltage during a de-energizing period to output a position detection signal, a current waveform generation section configured to generate, based on a torque command signal and the position detection signal, a current waveform which is to flow through the motor and includes the de-energizing period, an energizing control section configured to generate a control signal for controlling energizing of each of motor coils, and perform switching of an energizing phase of the motor based on the position detection signal, and a drive section configured to supply a current to each of the motor coils according to the control by the energizing control section, and the current waveform generation section changes a start timing of the de-energizing period according to a given control signal.

Abstract: A motor control device includes a dq-axis current control unit for generating a dq-axis voltage reference based on a dq-axis current reference and a dq-axis current signal, an initial magnetic pole position estimation unit for estimating a magnetic pole position of the motor upon power-on to generate a magnetic pole position signal, and a magnetic pole position estimation precision confirming unit for supplying a current in a d-axis direction after generation of the magnetic pole position signal with the initial magnetic pole position estimation unit, and checking an error of the magnetic pole position signal based on an angle of movement of the motor.

Abstract: A motor drive circuit comprises positive and negative input terminals for connection of the motor circuit to a DC supply, a DC link filter connected between the input terminals: an electric motor having at least two phases, a plurality of motor drive sub-circuits, each connected to a respective phase of the electric motor and which each control the flow of current into or out of the respective phase of the motor that has been drawn from the supply through the DC link filter, and a switching means provided in the electrical path between the DC link filter and the electric motor drive sub-circuits, the switching means being movable between a closed position in which it connects the DC link filter to the motor drive sub-circuits, and an open position which isolates the DC link filter from the motor drive sub-circuits.

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

Abstract: A method of preventing concurrent or quasi-concurrent commutations of a pair of phase shift modulation (PSM) drive signals of an output bridge stage driving an electrical load includes establishing a threshold level of a programmed current level to be transmitted though the electrical load. The method also includes, if the programmed current level is lower than the threshold level, enhancing a time offset between commutation edges of the pair of PSM drive signals by a minimum time.

Abstract: A method of controlling a brushless permanent-magnet motor that includes rectifying an alternating voltage to provide a rectified voltage having a ripple of at least 50%, and exciting a winding of the motor with the rectified voltage. The winding is excited in advance of zero-crossings of back EMF by an advance period and is excited for a conduction period over each electrical half-cycle of the motor. The advance period and/or the conduction period are then adjusted in response to changes in the speed of the motor and/or the RMS value of the alternating voltage so as to maintain constant average power. Additionally, a control system that implements the method, and a motor system that incorporates the control system.

Abstract: A method of controlling a brushless motor that includes exciting a winding of the motor in advance of predetermined rotor positions by an advance period. The length of the advance period is defined by a waveform that varies periodically with time. Additionally, a control system that implements the method, and a motor system that incorporates the control system.

Abstract: A method of controlling a brushless motor that includes rectifying an alternating voltage to provide a rectified voltage, and exciting a winding of the motor with the rectified voltage. The winding is excited in advance of predetermined rotor positions by an advance period and is excited for a conduction period over each electrical half-cycle of the motor. The length the advance period and/or the conduction period is defined by a waveform that varies periodically with time. The method then includes adjusting the phase of the waveform relative to the alternating voltage in response to a change in one of motor speed and RMS value of the alternating voltage. Additionally, a control system that implements the method, and a motor system that incorporates the control system.

Abstract: A method of controlling a brushless motor that includes exciting a winding of the motor until current in the winding exceeds a threshold, and then continuing to excite the winding for an overrun period. The length of the overrun period is adjusted in response to a change in one of time, motor speed and excitation voltage. Additionally, a control system that implements the method, and a motor system that incorporates the control system.

Abstract: A method of controlling a brushless motor that includes exciting a winding of the motor for a conduction period over each electrical half-cycle of the motor. The length of the conduction period is defined by a waveform that varies periodically with time. Additionally, a control system that implements the method, and a motor system that incorporates the control system.

Abstract: A brushless motor controller that controls a brushless motor by determining an energizing timing of a three-phase stator coil based on the rotational position and speed of a rotor. The controller includes a normal timing generation unit, an advancing timing generation unit, and a control switching unit. The normal timing generation unit generates a normal energizing timing. The advancing angle timing generation unit generates an advancing angle energizing timing advanced by a predetermined amount from the normal energizing timing and a final advancing angle energizing timing delayed by a delay amount from the advancing angle energizing timing. The control switching unit switches rotation control of the motor between a first rotation control executed in accordance with the normal energizing timing and a second rotation control executed in accordance with the final advancing angle energizing timing.

Abstract: A motor drive device has a drive circuit for driving a motor, and a control section for controlling the drive circuit. The control section has a current command value calculating portion for calculating a current command value, a rotation calculating portion for calculating a rotation angle and an angular speed of the motor, a current command value correcting portion for correcting the current command value based on the rotation angle, a voltage command value calculating portion for calculating a voltage command value based on the current command value, a voltage command value correcting portion for correcting the voltage command value based on the current command value and the rotation angle and the angular speed, and a drive signal generating portion for generating a drive signal based on the voltage command value.

Abstract: The synchronous motor driving apparatus including position sensors provided in the synchronous motor, a current polarity detection circuit for detecting the polarities of the currents in the respective phase windings of the synchronous motor, an inverter driving the synchronous motor, a motor speed calculation unit calculating the rotational speed of the synchronous motor depending on the output signals from the position sensors, a speed control unit outputting a first voltage adjusting component (q-axis current command value Iq*) to cause the rotational speed of the synchronous motor to approach a speed command value and a phase control unit outputting a second voltage adjusting component (d-axis current command value Id*) to cause the phase differences between the phases of the position sensor signals and of the currents in the respective phase windings of the synchronous motor to become a predetermined value.

Abstract: A brushless DC motor configured to drive a driven member includes a rotor having a magnet, a stator having a coil configured to provide a rotational force to the magnet, a position detector configured to output a first signal that is periodic, in accordance with a rotating position of the rotor, a signal generator configured to generate a second signal by adding a lead angle to a phase of the first signal output from the position detector, an excitation switch configured to select an excitation to the coil in accordance with the second signal, and a phase change part configured to change the lead angle in accordance with at least one of a position and a moving direction of the driven member.

Abstract: Methods and systems of accelerating a brushless, DC electric motor based on torque may include determining a slope based on a maximum torque of the BLDC motor at a lower operating load and a maximum torque of the motor at a higher operating load, determining a period of the rotor based on sensor signals, and determining and applying a phase advance to a PWM pulse for a subsequent revolution of the rotor based on the period and the slope. In some embodiments, the amount of the phase advance is further based on maximum load optimum advance and/or maximum load speed. In some embodiments, a phase dwell is determined based on a positive torque zone and applied to the PWM pulse. In some embodiments, when the motor is operating below a given threshold, fixed-width PWM pulses are applied to subsequent revolutions of the rotor instead of phase-advanced PWM pulses.

Abstract: A brushless motor controller is disclosed. The brushless motor controller includes a control unit and a drive timing generation unit. The control unit detects a load state of the motor. The drive timing generation unit generates a normal energizing timing determined by the rotational position of the rotor. Also, the drive timing generation unit generates an advancing angle energizing timing determined by the rotational position of the rotor and advanced by a predetermined amount from the normal energizing timing, generates a delay amount that changes in correspondence with the detected load state of the motor and the rotational speed of the rotor, and generates a final advancing angle energizing timing delayed by the delay amount from the advancing angle energizing timing.

Abstract: Information indicative of the placement of spindle motor components may be obtained and used to provide a correction to one or more BEMF-derived attributes used to control the spindle speed. In some implementations, first and second signals indicative of BEMF of different stator windings may be used to determine a speed-related characteristic. The speed related characteristic may be used to determine an error amount, which may be used to determine a correction factor to control the speed of the spindle motor.

Abstract: Phase correction unit (25) for outputting a commutation signal for switching a winding that allows a current to flow to brushless DC motor (4) and drive unit (16) for outputting a drive signal indicating supplying timing of electric power supplied to brushless DC motor (4) by inverter (3) based on the commutation signal output from phase correction unit (25) are provided so as to maintain a predetermined relation between a phase of a current flowing to a predetermined winding of brushless DC motor (4) and a phase of a voltage. Since brushless DC motor (4) is driven by a signal for holding the predetermined relation between the phase of the current and the phase of the voltage, the stability of drive under high-speed and high-load conditions is enhanced and a drive range is extended.