Abstract: A powered screwdriver system includes an electric ratchet. In accordance with one aspect, the powered screwdriver system includes a driver housing and includes a motor disposed within the housing. A working end provides a rotational output and is mechanically coupled to the rotor. A power source provides power to the motor. A controller receives signals representative of a motor condition and, based on the received signals, controls the motor in a manner providing the electric ratchet.

Abstract: An electronically commutated electric motor includes a stator and a rotor formed as a permanent magnet. A control unit is connected to the stator and configured to energize the stator to produce a rotating magnetic field. The electric motor further includes at least one Hall sensor configured to detect at least a magnitude of a sensor magnetic field produced by a sensor magnet connected to the rotor. The electric motor also includes at least one magneto resistive sensor configured to detect an alignment of a total magnetic field during a rotor revolution of the rotor and to generate a rotor position signal representing this alignment. The total magnetic field includes the sensor magnetic field and an interference magnetic field superimposed thereon. The control unit is further configured to determine the rotor position of the rotor at least depending on the alignment of the total magnetic field.

Abstract: A surface motor direct-drive sucker-rod screw pump device is driven by a vertical three-phase permanent magnet brush-less DC motor, and comprises a motor controller (6), a rectifying circuit, an inversion circuit, a CPU and a driving circuit. The motor controller (6) is used to adjust the voltage and frequency of the motor by the rectifying circuit, the inversion circuit, the CPU and the driving circuit. Thus, the speed of the motor can vary from zero to the maximum. The device is easy to operate and has a higher efficiency.

Abstract: A method and a control device operate a three-phase brushless direct current motor with phase windings that are fed by an inverter connected to a voltage source having a high potential and a low potential. The semiconductor switches of the inverter are arranged in a bridge circuit and are controlled such that current always flows through two phase windings during motor operation. The motor is operated with normal commutation when the rotational speed is greater than or equal to a minimum rotational speed, wherein the angles are shifted by 60°. During start-up operation, up to the minimum rotational speed, a high-potential-side commutation angle of a phase winding is shifted toward a low-potential-side commutation angle of the phase winding by an angle greater than 0° and less than or equal to 60° with respect to the normal commutation.

Abstract: A magnetic pole position detecting device includes a calculating unit for correcting a magnetic pole position detected by a magnetic pole position detecting unit. In this magnetic pole position detecting device, an additional phase is added to the magnetic pole position detected by the magnetic pole position detecting unit, in order to move a rotor. In relation to a movement amount before and after this movement, a movement amount detected by the magnetic pole position detecting unit is compared with a movement amount detected by an encoder. When a difference between them is larger than a predetermined threshold, a process of detecting the magnetic pole position is determined as false detection.

Abstract: A surface motor direct-drive sucker-rod screw pump device is driven by a vertical three-phase permanent magnet brush-less DC motor, and comprises a motor controller (6), a rectifying circuit, an inversion circuit, a CPU and a driving circuit. The motor controller (6) is used to adjust the voltage and frequency of the motor by the rectifying circuit, the inversion circuit, the CPU and the driving circuit. Thus, the speed of the motor can vary from zero to the maximum. The device is easy to operate and has a higher efficiency.

Abstract: A controller for a brushless motor that includes an input for receiving an analog signal, an analog-to-digital converter (ADC) for sampling the analog signal, and a processor. The processor starts the ADC during a first electrical half-cycle and reads the ADC during a second electrical half-cycle of the motor. Additionally, a motor system that includes the controller.

Abstract: A ventilating system that can make an air flow rate variable includes a DC motor that drives blades and a control circuit that controls the DC motor. The control circuit includes a first current detecting unit that detects a current flowing in the DC motor, a rotating speed detecting unit that detects a rotating speed of the DC motor, and a control unit that controls the DC motor based on a rotating speed detected by the rotating speed detecting unit and a current detected by the first current detecting unit. The current detecting unit includes a plurality of low-resistance resistors, detects a motor current by using divided voltages of the low-resistance resistors, and calculates a ventilation air flow rate based on the rotating speed detected by the rotating speed detecting unit and the current detected by the first current detecting unit.

Abstract: In a wiper motor including a motor unit having a rotating shaft, and a gear unit having a speed reduction mechanism for reducing and outputting the speed-reduced rotation, a first speed reduction gear forming a speed reduction mechanism is provided to one end side of a rotating shaft, a sensor magnet is fixed to the other end side of the rotating shaft, a control board is provided so as to face the other end side of the rotating shaft from the axial direction of the rotating shaft, a MR sensor for detecting a rotational state of the rotating shaft is provided to a facing portion of the control board to the sensor magnet, and coil end portions of coils configured to generate an electromagnetic force for rotating the rotating shaft on the basis of supply of drive current from the control board is electrically connected to the control board.

Abstract: A motor driving circuit may include a Hall sensor configured to generate a Hall signal according to the position of a rotor of a motor to be driven; a Hall bias circuit; an analog amplifier configured to amplify the Hall signal; an A/D converter configured to convert the Hall signal into a digital signal; an amplitude control circuit configured to adjust the amplitude of the digital signal; a control signal generating unit configured to generate a control signal to be used to drive the motor; and a driver circuit configured to drive the motor according to the control signal. The components may be monolithically integrated on a single semiconductor substrate. The amplitude control circuit may include an amplitude correction circuit; and a target amplitude judgment circuit configured to adjust the gain of the analog amplifier.

Abstract: A drive control signal generating circuit that generates a drive control signal for driving a motor includes an output control circuit that includes a flip-flop in which a state changes by a rotational state signal of the motor crossing a reference value and generates a motor drive control signal according to the state of the flip-flop, a clock generating circuit that generates a clock that defines a time of reading data in the flip-flop of the output control circuit; and a PWM conversion circuit that PWM-converts the drive control signal using the clock as a PWM signal. The clock has a frequency in which the output control circuit operates and has a duty ratio of the PWM signal.

Abstract: The three-phase motor driving apparatus according to an aspect of the present invention comprises a controlling part that estimates a rotational position of the three-phase brushless motor based on a reference pulse signal output by the rotor sensor according to a rotational position of the magnetic pole of the first phase of the rotor when the three-phase brushless motor rotates, and controls the motor driver in driving patterns sequentially prescribed so as to correspond to the estimated rotational position of the three-phase brushless motor.

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 motor control device which can determine a magnetic pole position for a magnetic pole position detector included in a permanent magnet motor in which the reluctance torque proportion is larger than the magnet torque proportion is provided. In a permanent magnet synchronous motor having multi-phase windings of N axes (N?2), the windings of optionally selected K axes (K?N) are DC excited using corresponding independent power supplies.

Abstract: A control method for a sensor-less, brushless, three-phase DC motor. The effects of commutation on the motor may be minimized using a sinusoidal current drive on each electromagnet. The “off” times and/or the “on” times of the drive transistors controlling the electromagnets in a full “H-bridge” configuration drive scheme may be delayed. By overlapping the drive signals to the electromagnets with respect to a commutation command, the effects of switching between electromagnets may be minimized. In addition, the “on” and “off” times may also be adjusted during the overlapping to further ensure that the coils continuously conduct current, and that the current does not change direction during the switching. The delays, and hence the overlap times of the coil drive signals may be dynamically controlled, for example by using digital timers, making the response predictable and easily controlled.

Abstract: A brushless direct current (DC) motor includes a rotor, a stator and a driving unit. The rotor includes a plurality of magnetic poles. The stator includes a plurality of upper pole arms and a plurality of lower pole arms. The driving unit includes at least two coils wound on the upper pole arms and the lower pole arms respectively, and the driving unit generates an alternating magnetic field on the stator for driving the rotor.

Abstract: A driving apparatus has a correction value output unit for outputting correction values ?Ta and ?Tb to correct differences between signals which are output from an A sensor a B sensor when an A-phase coil and a B-phase coil are not energized and signals which are output from the A sensor and the B sensor when the A-phase coil and the B-phase coil are energized. An energization direction of the A-phase coil is switched on the basis of a time A which is measured by a time measurement unit and the correction value ?Ta which is output from the correction value output unit. An energization direction of the B-phase coil is switched on the basis of a time B which is measured by the time measurement unit and the correction value ?Tb which is output from the correction value output unit.

Abstract: A monitoring and control device for an aircraft actuator includes a control module, delivering control signals for the actuator and position signals for the actuator determined according to control messages received from a piloting management system of the aircraft, and at least one first position sensor supplying information concerning the position of the actuator, and a monitoring module, delivering position signals for the actuator and receiving the control signals received from the piloting management system of the aircraft, and information relating to the position of the actuator supplied by at least one second position sensor. The control and monitoring modules are capable of assessing the consistency of the signals processed therein and of controlling accordingly a power supply and disabling module of the actuator.

Abstract: Disclosed herein are a biasing circuit for a hall sensor and a hall amplifier in a motor driving circuit, the biasing circuit including: a regulator installed inside a singled packaged chip, supplied with external power, and regulating the external power in voltage appropriate for a circuit to supply the regulated voltage; the hall amplifier supplied with the voltage regulated from the regulator, receiving an output signal from the hall sensor outside the chip, and amplifying the output signal to output the amplified signal; first and second resistors supplied with the voltage from the regulator to generate an input voltage common mode (VCM) of the hall amplifier; and third and fourth resistors supplied with the voltage from the regulator to generate an input VCM of the hall sensor.

Abstract: A method for aligning Hall sensors location in a brushless DC motor with Hall sensors, the method comprises driving the motor by a sensorless driving system for getting a first commutation phase signal; sending said first commutation phase signal to a sensorless position control unit to be processed thereby for getting an optimal commutation phase point, processing a Hall sensor signal as said motor is running by a Hall sensor circuit unit for getting a second commutation phase signal, and comparing said second commutation phase signal with said optimal commutation phase point by a signal comparing and processing unit to get a phase shifting data for aligning said Hall sensors location.

Abstract: Simple AC circuitry driving a brush-less motor having a rotor consisting of alternate polarity permanent magnet poles, with the rotor journaled in a stator with a like number of wound poles having only two free ends for energizing. The motor is using only two AC electronic switches for starting and accelerating, and an AC switch to run the motor at synchronous speed. It has higher efficiency than previously known circuits, uses less parts and is less costly.

Abstract: Disclosed is an electric motor that includes a stator with a plurality of main poles, each of which includes a coil, and a rotor rotatable about an axis and having a magnet with magnetic poles in which N and S poles are alternating. The motor further includes a first sensor group of a plurality of magnetic sensors fixed relative to the stator, and a second sensor group of a plurality of magnetic sensors fixed relative to the stator. When operating the motor, the first sensor group can be selected so as to rotate the rotor in a first direction. The second sensor group can be selected so as to rotate the rotor in a second direction opposite to the first direction.

Abstract: A motor controller controlling a rotational speed of a motor and including a thermal detector, a capacitor, an operational amplifier (OP), a charging/discharging circuit, a flip-flop and a logic circuit. The thermal detector detects environmental temperature of the motor to set a first reference voltage. The capacitor has one terminal coupled to a second reference voltage while another terminal thereof is charged/discharged by the charging/discharging circuit, controlled by a pulse width modulation (PWM) signal, to provide a third reference voltage. The OP compares the first and third reference voltages and outputs the comparison result to a ‘set’ terminal of the flip-flop. The flip-flop further uses a ‘reset’ terminal to receive a clock signal and the output signal thereof is utilized in generating the PWM signal. The PWM signal is further provided to the logic circuit for setting a duty cycle of a driving current of the motor.

Abstract: A phase difference between an inductive voltage of an armature winding of a rotating electrical machine and an output of a magnetic pole position sensor is detected by a phase difference detection unit. The output of the magnetic pole position sensor is corrected on the basis of the phase difference thus detected and a power conversion unit is controlled on the basis of the corrected output.

Abstract: A motor controlling device is provided that controls a brushless motor having a plurality of phases based on magnetic pole signals output by a plurality of magnetic pole signal output sections each corresponding to one of the phases. The motor controlling device includes an abnormality determining section, a signal generating section, and a motor controlling section. The abnormality determining section determines whether a magnetic pole signal output by each magnetic pole signal output section is an abnormal magnetic pole signal. When the abnormality determining section determines that at least one of the magnetic pole signals is an abnormal magnetic pole signal, the signal generating section generates a simulated signal corresponding to the abnormal magnetic pole signal based on the normal magnetic pole signals other than the abnormal magnetic pole signal and the rotational state of the brushless motor.

Abstract: A motor includes a sensor magnet having a non-circular contour and a magnet cover fixed to an end portion of a shaft to cover the end portion of the shaft. The magnet cover includes a support portion positioned outside the end surface of the end portion of the shaft. In the support portion, a magnet hole having a non-circular cross section as the sensor magnet and extending in the direction of the rotation axis is provided. The sensor magnet is inserted into the magnet hole and fixed to the magnet hole.

Abstract: A rotating electromechanical machine has a rotor having at least one current-carrying winding and at least one rotor-mounted sensor configured to sense a machine property or parameter during machine operation. Rotor-mounted circuitry dynamically modifies at least one property of the current-carrying winding during machine operation in response to the sensed machine property or parameter.

Abstract: A bi-power motor controlling apparatus, which is electrically connected with a motor, includes a driver IC having a first pin and a second pin. The first and second pins are used to receive a first power and a second power, respectively, from outside. The second power is supplied to the driver IC, and the first power is supplied to the motor for controlling the rotational speed of the motor.

Abstract: A brushless motor position detection device has a set of first Hall elements (main Hall ICs 18 for detecting magnetic pole positions) and a set of second Hall elements (sub-Hall ICs 19 for detecting magnetic pole positions) mounted on a plane facing a magnetic pole position detecting magnet 16 for detecting the position of a rotor 12. They are subjected to offset adjustment and are mounted in such a manner that the difference between the maximum value of the magnetic flux density at the mounting positions of the first Hall elements and the maximum value of the magnetic flux density at the mounting positions of the second Hall elements is held within a prescribed limit (mounted in such a manner as to have the offset of a prescribed machine angle in the circumferential direction) to bring the detection accuracy of the plurality of sets of the Hall elements into agreement.

Abstract: During displacement of an actuating element to a target position, a brushless direct-current motor is driven by a driving commutation pattern derived from rotor position signals. After the target position is reached the brushless direct-current motor is transferred to a holding mode in which it is driven by a commutation pattern providing a required holding torque. In the holding mode the holding current necessary for providing the required holding torque is minimized by an iterative holding current reduction method to a holding current value guaranteeing the required holding torque.

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 cycle counter generates a cycle signal which indicates, in the form of a digital value, the cycle of Hall signals H+ and H? that indicate the position of a rotor of a motor to be driven. An up/down counter repeatedly alternates between counting “up” and counting “down” upon detecting phase transitions that occur in the Hall signals, and generates a digital driving waveform signal having a sloping region the slope of which is set according to the cycle signal. A D/A converter receives the driving waveform signal, and converts the driving waveform signal thus received into an analog voltage. A driving unit supplies a driving voltage to the motor according to the analog voltage thus received.

Abstract: A control method for a sensor-less, brushless, three-phase DC motor. A pulse-width modulation (PWM) duty cycle may be calculated. A voltage induced by rotation of a rotor may be sampled at a first expected zero crossing value to produce a first sampled voltage value. An average of a plurality of sampled voltage values, including voltage values sampled at a plurality of prior expected zero crossing values and the first sampled voltage value, may be calculated. The first sampled voltage value may be subtracted from the calculated average to produce a delta zero crossing error (ZCE). The current value of an integral term corresponding to a rotational period may be updated according to the sign of the ZCE. The integral term may be updated periodically and multiple times during each rotational period. The ZCE may be subtracted from the integral term, and the resulting value may be used to generate one or more time values.

Abstract: A servo motor control apparatus has a feedback loop. When an oscillation detection signal indicates no detection of oscillation, a parameter operating section gives an updating section an operational instruction to set a control parameter in accordance with a supplied set value. When the oscillation detection signal indicates detection of oscillation, the parameter operating section gives the updating section an operational instruction to set such a control parameter as to narrow a frequency band width of the feedback loop.

Abstract: A drive device for an adjusting device for adjusting a vehicle component of a vehicle includes an electronically commutated motor and an electronic control device which actuates the electronically commutated motor with an actuating voltage. The electronic control device can adapt the signal form of the actuating voltage on the basis of at least one operating parameter in order to optimize the power output, the acoustics, the electromagnetic irradiation and/or the heating of the drive device.

Abstract: A door operator with an electrical back check feature is disclosed. Embodiments of the present invention are realized by a motorized door operator that electrically creates a back check force for an opening door. The door operator simulates the back check normally created by hydraulic means in convention door closers, but without the use of pistons, springs or hydraulic fluid. The door operator includes a motor disposed to operatively connect to a door so that the door will open when the motor moves, and a position sensor to determine a position of the door. A processor is programmed to exert a closing force on the door in the back check region. In some embodiments, the closing force is exerted by injecting a voltage into the electric motor of the door operator.

Abstract: An image forming apparatus includes an engine unit to perform an image forming job, an engine control unit to control operation of the engine unit, a plurality of brushless direct current (BLDC) motors to operate the engine unit, a communication interface unit to receive a digital control command for the plurality of brushless DC motors from the engine control unit, a sensor unit to sense operation information of the plurality of brushless DC motors, an operation signal unit to generate an operation signal to control the plurality of brushless DC motors, and a speed control unit to control operation of the operation signal unit according to the received digital control command and sensing result of the sensor unit.

Abstract: For the present invention, under various running speeds statuses, the voltage supplied to the DC brushless motor is relatively increased or decreased on the basis of the internal setting of the motor drive control device with the increased or decreased load current, to prevent the shortcoming of too much change of the input impedance caused by the inductive reactance of the winding accordingly changed when the speed of the DC brushless motor is changed with the change of the load, specifically, to prevent the shortcoming of unable to produce required torque resulting from the increased inductive reactance of the winding caused by increasing the rotational speed which makes the current value become too low when input by the original working voltage.

Abstract: There is provided a motor. The motor may include a rotor case including a driving magnet formed on an inner circumferential surface thereof and providing a driving force by interacting with a coil of a stator, a low-speed control magnet formed on an outer circumferential surface of the rotor case and generating a frequency allowing for low-speed rotation enabling label printing as the rotor case rotates at a low speed; and a sensing part sensing an analog signal generated from the low-speed control magnet.

Abstract: An n-phase brushless motor device is provided. The device includes a magnet for magnetic pole position detection having a number of poles twice as many as that of a rotor and fixed to a face perpendicular to a rotation axis of the rotor; n main Hall elements arranged opposite to the magnet, for detecting a magnetic pole position of the rotor; n sub Hall elements arranged in such a way as to have an offset in a direction of a periphery with respect to the main Hall elements, for detecting the magnetic pole position; and a control unit for counting “2” according to a change in an output pattern of the main Hall elements, for counting “1” when the output pattern is the same as that of the sub Hall elements at a predetermined timing, and for controlling a rotation of the rotor according to these counted values.

Abstract: Slow speed operation of a brushless DC (BLDC) motor is enhanced by gating off some of the PWM pulses in each commutation period. By doing so, longer PWM pulse widths may be used at PWM signal frequencies that are inaudible while still allowing desired slow speed operation of the BLDC motor. Centering the non-gated PWM pulses in each commutation period where peak back EMF occurs, further reduces losses and improves delivery of maximum torque from the BLDC motor.

Abstract: A drive apparatus includes a magnet rotor having a plurality of magnetic poles that are magnetized, a stator having a magnetic pole portion that opposes each pole of the magnet rotor, a coil configured to excite the magnetic pole portion, a position detector configured to detect a position of the magnet rotor, 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 position detector, and a controller configured to select the first driver when the output of the position detector is less than a first threshold, and to select the second driver when the output of the position detector is equal to or larger than the first threshold.

Abstract: A low-cost minimal-loss zero-maintenance flywheel battery, to store electric power from a DC power source by conversion to kinetic energy, and regenerate electric power as needed. Its vertical spin-axis rotor assembly is supported axially by repelling annular permanent magnets, and is centered by ceramic ball bearings which have axial preload that prevents vibration and augments axial rotor support. A regenerative multi-pole permanent-magnet motor, controlled by its 2-phase stator current, and connected by power and signal conductors to power interface electronics, is integrated within the flywheel assembly, in a vacuum enclosure supported by a self-leveling structure. Sinusoidal 2-phase stator currents are controlled by high-frequency pulse-width-modulated H-bridge power electronics that draw and regenerate controlled DC current with minimal ripple, responsive to respective 2-phase rotation angle sensors, the DC power voltage, and other settings.

Abstract: A method for determining the position of a rotor in a permanent magnet synchronous motor includes applying voltage pulses to the windings at successive electrical angles while the motor is at a standstill. The resultant current is sampled. The position of a maximum current is determined by identifying an segment of an electrical cycles which includes the maximum current, and using a spline interpolation to model the current flow in this segment. The maximum current is then correlated to the position of the rotor.

Abstract: An apparatus is disclosed for simultaneously measuring the rotational speed and/or direction of a shaft, and providing control power in accordance with the shaft rotation. The apparatus includes a permanent magnet machine (PMM) having a multipole rotor and a stator. The rotor has a plurality of permanent magnet poles and connection to the rotating shaft; the stator includes a winding and electrical connections, so that motion of the rotor with respect to the stator causes a voltage signal at the electrical connections. The apparatus also includes a circuit including a power conversion portion and a speed/direction sensing portion. The circuit receives the voltage signal from the PMM, and simultaneously outputs control power from the power conversion portion and a signal indicating the rotational speed and/or direction of the shaft from the sensing portion.

Abstract: A motor driving circuit capable of outputting a dual FG signal includes a control unit, a first Hall unit, a second Hall unit and a logic unit. The control unit is electrically connected to the first Hall unit and configured to generate a first FG signal based on a Hall signal sent by the first Hall unit. The second Hall unit is configured to detect the change in magnetic fields to generate a second FG signal to the logic unit. The logic unit is electrically connected to the control unit and the second Hall unit. The logic unit is configured to perform a logic operation based on the received first and second FG signals to convert them into a dual FG signal for an external system. With the control unit, the first Hall unit, the second Hall unit and the logic unit being integrated in the motor driving circuit, the convenience in use can be improved greatly. Furthermore, the working hours and the production cost can be reduced.

Abstract: An apparatus for controlling an air distribution system for maintaining a rate of air flow in the system at substantially the target air flow rate, wherein the apparatus detects current speed and torque of said motor and generates said current speed signal and torque signal after detection; receives the current speed signal and torque signal and calculates the current air flow rate in the air distribution system wherein the calculated current air flow rate is compared to the target speed signal of the air flow rate and the current air flow rate is adjusted according to the target speed signal of the air flow by generating a control signal; and controls the motor speed in response to the control signal for maintaining the rate of air flow in the system at substantially the target speed signal of the airflow rate.

Abstract: An electrical brushless motor is described, as well as a ceiling fan utilizing the electrical brushless motor.

Abstract: In a wiper motor including a motor unit having a rotating shaft, and a gear unit having a speed reduction mechanism for reducing and outputting the speed-reduced rotation, a first speed reduction gear forming a speed reduction mechanism is provided to one end side of a rotating shaft, a sensor magnet is fixed to the other end side of the rotating shaft, a control board is provided so as to face the other end side of the rotating shaft from the axial direction of the rotating shaft, a MR sensor for detecting a rotational state of the rotating shaft is provided to a facing portion of the control board to the sensor magnet, and coil end portions of coils configured to generate an electromagnetic force for rotating the rotating shaft on the basis of supply of drive current from the control board is electrically connected to the control board.

Abstract: An inverter controller for driving a brushless DC motor, of which rotor is provided with permanent magnets, includes an inverter circuit, a position sensing circuit, a DC voltage sensor, and a conduction angle controller. The inverter circuit is connected to the brushless DC motor for driving this motor. The position sensing circuit senses a rotor position with respect to a stator from an induction voltage of the brushless DC motor. The DC voltage sensor senses a voltage value of a DC power voltage supplied to the inverter circuit. The conduction angle controller changes a conduction angle of the inverter circuit within a range less than 180 degrees in electric angles in response to a rate of change in the DC power voltage.