Abstract: In an apparatus for generating complementary first and second pulse width modulation signals, a signal generating circuit generates a first signal for causing the first pulse width signal to switch from an ON level to an OFF level, a second signal for causing the first pulse width signal to switch from the OFF level to the ON level, a third signal for causing the second pulse width signal to switch from the ON level to the OFF level, and a fourth signal for causing the second pulse width signal to switch from the OFF level to the ON level. A control circuit sets a first dead time between the first and fourth signals and a second time between the third and second signals individually.

Abstract: When finding a current on an AC side of an inverter by observing that on a DC side, a current that is not affected by pulsating components contained in the AC current must be detected. Timing of change of a gate signal for driving a switch element of a phase having an intermediate magnitude among three-phase voltage command signals to ON/OFF is used as a reference time point for DC bus current detection. DC bus currents sampled T1 before and T2 after the reference time point are designated as IDC1 and IDC2, respectively. A detected current value of a maximum voltage phase is computed by using IDC2 and IDC1 respectively in an increase period and a decrease period of a carrier signal alternately. A detected current value of a minimum voltage phase is computed by using IDC1 and IDC2 respectively in an increase period and a decrease period alternately.

Abstract: A motor drive unit includes a controller, a voltage inverter, and a speed estimator. The controller is operable to generate at least one command signal for controlling a motor associated with the motor drive unit. The voltage inverter is operable to generate motor drive signals to be applied to the motor based on the command signal. The speed estimator is operable to estimate a speed of the motor when the voltage inverter is not providing the motor drive signals. The speed estimator is further operable to receive two-axis voltage measurements associated with the motor, determine flux angles for the motor based on the two-axis voltage measurements, and estimate the speed based on the determined flux angles.

Abstract: Amperage control of a power tool motor is provided by pulse width modulation of current from a power supply. The pulse width modulation may be varied according to the determined motor current and measured power supply voltage. The power supply may include a battery such as lithium ion or nickel cadmium.

Abstract: The invention proposes an electrically operated power steering controller for inputting a driving electric current offset value of higher accuracy and being able to make an offset correction of a driving electric current by using this driving electric current offset value of higher accuracy, and an adjusting method of this driving electric current offset. Therefore, an electric motor driving electric current measuring device of accuracy higher than that of an electric motor driving electric current detector assembled into a controller CNT is prepared separately from this electric motor driving electric current detector. The driving electric current offset value of high accuracy is outputted by this electric motor driving electric current measuring device. An input device for receiving the driving electric current offset value of high accuracy from the driving electric current measuring device is arranged in an offset correcting device or an offset signal generator within the controller.

Abstract: A controller for a synchronous machine includes: a power converter; a synchronous machine driven by the power converter; a PWM modulation section for controlling the synchronous machine; a current detection section which detects a current conducted to the synchronous machine; a voltage detection section which detects a voltage applied to the synchronous machine; a current variation operation section which operates a current variation during a time interval between timings synchronized with detection sampling in the current detection section; a voltage integration operation section which operates a voltage integration value during a time interval between the same timings as the timings in the current variation operation section; a current variation operation section for a time interval in which all sets are included, defining, as one set, the current variation and the voltage integration value, and operating a current variation during the time interval in which all the sets are included; a voltage integration

Abstract: A motor drive circuit is provided and includes: a PWM wave generation circuit for generating a PWM (pulse-width-modulated) wave having a high frequency, whose pulse width has been modulated, in response to a rotational frequency control signal used for driving a motor; a switching element (FET) that receives an input of a PWM wave output from the PWM wave generation circuit and performs switching operation; and a current resonance circuit including an inductance and a capacitor. Current resonance is induced in response to power of a battery cell imparted by means of operation of the switching element. A value falling within the range of 60 to 90 KHz, which is 1.1 to 1.7 times as large as a switching frequency 54 KHz of the switching element, may be selected and set for the resonance frequency.

Abstract: A motor controller including an inverter including plural switching elements that are subjected to PWM control to generate sine waves of plural phases, a motor including a stator coil supplied with the sine waves thus generated so that rotational magnetic field is generated in the stator coil, and a rotor that is rotationally driven by the action of the rotational magnetic field generated by the stator coil, a storage unit for detecting the sine waves of the respective phases generated in the inverter and storing a correction amount for each phase that is calculated on the basis of the detection result so that the sine waves of the respective phases are coincident with one another and a correcting unit for correcting a PWM signal for carrying out the PWM control on the switching elements on the basis of the correction amount thus calculated.

Abstract: A controller of a pulse width modulation signal-driven device, includes: an instruction input of operating the pulse width modulation signal-driven device; a control section generating a control clock which operates the pulse width modulation signal-driven device; a frequency modulator frequency-modulating the control clock, to thereby give to the control clock a frequency variation in a predetermined frequency range; a frequency varier generating a modulation signal inputted to the frequency modulator; and a first switching member driving the switching element which flows a predetermined drive current to the pulse width modulation signal-driven device based on the frequency-modulated control clock. The frequency varier includes: a first signal generator setting a range of diffusing a switching noise in a frequency range, and a unit for shifting a frequency band of the switching noise by giving a predetermined offset voltage to an output voltage of the first signal generator.

Abstract: Both the stator core and the rotor core of a switching pattern AC induction motor are fabricated by soft magnetic material laminations or ferrite material, etc., both of which have corresponding frequency characteristic. The rotor is a squirrel cage rotor. Switching pattern excitation is adopted in the stator pole, of which the excitation voltage is sine wave pulse width modulated or sine wave pulse amplitude modulated within the frequency range of voice and ultrasonic. Under the condition of the same power output, the present motor reduces its size and mass to a fraction of or tenth of that of an ordinary one. Meanwhile, it reduces the cost of manufacture. It realizes stepless speed regulating from zero to several thousand rpm while keeping well mechanical characteristic performance.

Abstract: A forklift having a cargo apparatus, the responsiveness of which to the operation by a user is improved. The forklift has: a DSP which generates a frequency instruction f* in response to the operation to a cargo apparatus operation lever, a voltage instruction V* from the frequency instruction f* by using the VVVF control, inverter control signals from the voltage instruction v*; an inverter which generates the three-phase electric power in response to the inverter control signal; a hydraulic pump; an induction motor driving a hydraulic pump by using the three-phase electric power; and a cargo apparatus which is driven by the hydraulic pressure supplied from the hydraulic pump.

Abstract: A linear vibration motor comprises: a stator provided with one of a permanent magnet and an electromagnet including a winding; a vibrator provided with the other of the permanent magnet and the electromagnet and supported to be able to vibrate; a movement detection unit for detecting movement of the vibrator; a control output unit for supplying electric power to the winding of the electromagnet based on an output of the movement detection unit so as to generate vibration of the vibrator; a rechargeable battery for supplying electric power to the control output unit; and a power supply unit for supplying electric power to the control output unit and to the rechargeable battery, wherein the power supply unit supplies electric power in an intermittent mode with synchronized timing such that the timing of the intermittent power supply is synchronized with the timing of the power supply to the winding.

Abstract: A rotary speed limiting device for an electric motor has a current detecting device for detecting a motor current of the electric motor, a nominal value setting for adjusting a torque, a control and/or regulating device which limits the motor current to a maximum value depending on the nominal value setting, a rotary speed detecting device for detecting a rotary speed of the electric motor, the control and/or regulating device determining a maximum value of the motor current depending on the rotary speed determined by the rotary speed detecting device.

Abstract: A DC offset compensation system and method significantly reduce a DC offset voltage in the voltage feedback loop of an AC motor drive control system. A control voltage error signal is demodulated and filtered and applied to the closed loop voltage feedback signals to compensate for DC offset voltages in the closed loop voltage feedback. A frequency discriminator tuned to the fundamental motor frequency improves the precision of the DC offset detection. A startup flux DC offset compensation operates to eliminate initial startup flux DC offset. Motor flux compensation is improved through a variable flux filter time constant.

Abstract: An apparatus for controlling an electric motor provided to drive a movable object such that a detected actual amount of motion of a movable portion of the electric motor or the movable object coincides with a target amount, comprising: a control-condition changing device operable to change at least one of (a) a resolution of detection of the actual amount of motion and (b) a voltage to be applied to the electric motor, depending upon the target amount; and a feedback motor controller operable to control the electric motor by application of the voltage, on the basis of the actual amount of motion detected with the resolution of detection and the target amount, such that the detected actual amount of motion coincides with the target amount. Also disclosed is a motor control method wherein the resolution of detection of the actual amount of motion and/or the voltage of the motor is/are changed depending upon the target amount of motion.

Abstract: The invention is directed to controlling an electric motor by means of a frequency converter. The frequency converter can be connected to one of several different mains voltages. According to the present invention, the maximum output power of the frequency converter, is limited when the actual mains voltage is lower than the maximum nominal mains voltage, for which the frequency converter is designed, and during the limitation the frequency converter controls the speed of the motor within a power range up to a limited maximum output power. This gives a genuine multi-voltage unit, which can be connected to a wide range of mains voltages.

Abstract: The present invention relates to a method for limiting the current output by a speed controller (V) for three-phase asynchronous electric motor (M), said controller (V) operating according to a control law (LC) of pure U/F type. Said method is characterized in that it consists in calculating with the aid of a limitation function a correction value for the frequency of the stator (Wstat) then in applying thereto, so as to obtain, in the voltage control law (LC) of U/F type, a corrected frequency of the stator (Wstatc). According to the voltage control law of U/F type, the method thereafter consists on the basis of this corrected frequency of the stator (Wstatc) in obtaining the control voltage (Vqref) applied to the motor. The invention also relates to a system for limiting the current able to implement said method.

Abstract: A fan motor speed control circuit is disclosed. The circuit includes a digital/analog converting unit and a driving unit. The digital/analog converting unit takes charge of receiving a pulse width modulation (PWM) signal and converting it into a voltage signal. The driving unit is connected with the digital/analog converting unit in series for receiving the voltage signal, while the driving unit provides a first predetermined voltage level and a second predetermined voltage level as references. The fan motor is kept to run with a low constant rotation speed when the voltage signal level is higher than the first predetermined voltage level, with a full constant rotation speed when the voltage signal level is lower than the second predetermined voltage level, and with a variable rotation speed when the voltage signal level is lower than the first predetermined voltage level and higher than the second predetermined voltage level.

Abstract: A rotating electric machine comprises a stator having stator salient poles, three-phase windings wound around said stator salient poles, a rotor rotatable held inside the said stator, and permanent magnets inserted into said rotor and positioned opposite to said stator salient poles. The three-phase windings are concentratively wound around each of the stator salient poles, with windings of each phase wound around more than one stator salient pole. The windings of each phase have a phase difference of voltage between at least one of the windings and the other.

Abstract: A variable speed drive with a boost converter is provided for a chiller system driven by an induction motor. The boost converter can be a diode or thyristor rectifier followed by a boost DC/DC converter or a three-phase pulse width modulated boost converter. The boost converter provides a boosted voltage to the DC link, which results in a boosted voltage being applied to the induction motor by the inverter of the variable speed drive.

Abstract: Under oscillation-reducing control executed while PWM control is performed, an oscillation-reducing torque that is opposite in phase to a varying component of the motor revolution number is generated and, a final torque command value that is the sum of the oscillation-reducing torque and a torque command value is used to drive an AC motor. In a transition state where the PWM control mode is switched to overmodulation control mode, the oscillation-reducing torque that is determined by multiplying an oscillation-reducing torque by a correction coefficient that varies depending on a modulation factor gradually decreases as the correction coefficient decreases and substantially becomes zero when the control mode is switched. Thus, the oscillation-reducing torque has no stepped portion that occurs in the oscillation-reducing torque when the control mode is switched. Thus, oscillations in output torque of the AC motor can be reduced.

Abstract: A motor driving apparatus capable of drivingly controlling a plurality of inverter units with a single motor driving command from a motor control unit, and thereby control a large-capacity motor or the like. The motor control unit sends out a single motor driving command (torque command) S. An intermediary unit obtains motor driving commands S×A1 to S×A4 for the inverter units by multiplying the motor driving command S by each of coefficients A1 to A4 set in advance. The inverter units are fed with the motor driving commands S×A1 to S×A4 individually and drive a single motor. Since the motor is driven by the total current supplied by the inverter units, the motor can generate a large torque. The motor control unit only needs to generate a single motor driving command S, and hence only needs to operate a single processing part. Hence, the motor control unit can generate and send out motor driving commands for other motors to drive them.

Abstract: A multi phase motor includes a switching array for interconnecting a power source to each phase. A current sensor senses current supplied from the power source via the switching array to the winding and a controller generates offset PWM signals for controlling the switching array to supply power to each of the phases of the winding. The offset timing allows the individual phase currents to be determined from a single current sensor.

Abstract: A method for implementing control signal linearization for an electric motor is disclosed. In an exemplary embodiment, the method includes receiving a desired voltage command to be applied to the motor and determining whether the magnitude of the desired voltage command falls between a first value and a second value. If the magnitude of the desired voltage command falls between the first value and the second value, then modulating a voltage command between the first and the second value over a determined sample period, thereby resulting in the application of a modulated voltage command to the motor.

Abstract: A current detecting switching element is connected to an output circuit having switching elements making a bridge connection, current flowing to the switching element is detected by a current detection circuit in response to a torque command signal, a PWM signal generation circuit generates a PWM signal according to the output, a synthesizing circuit synthesizes the output of a power switch circuit for determining an energized phase to a motor coil and the output signal of the PWM signal generation circuit, and PWM operation of a first state and a second state is repeated to control current supply to the motor coil. The first state enables current supply to the motor coil when the switching element on one side is conducting, the switching element on the other side is nonconducting, and the current detecting switching element is conducting.

Abstract: A control device receives a power supply current from a current sensor and a reactor current from a current sensor and detects a maximum value and a minimum value from the reactor current and from the detected maximum and minimum values and the power supply current determines whether the reactor current traverses the zero point, and if so the control device generates and outputs a signal to an up converter which responds to the signal by stopping switching to perform an up or down converting operation.

Abstract: A motor control device selectively turns on or off a drive transistor in-accordance with a PWM control signal Sp, such that a drive current Im supplied to a motor is adjusted. The device also samples and holds a motor current Sm for obtaining a motor current value Ih. With reference to the motor current value Ih, the device protects the motor from an overcurrent. Sampling and holding of the motor current Sm is performed for a sampling and holding time Ts. The sampling and holding time Ts corresponds to a time period between a first point in time when the level of the PWM control signal Sp is switched for turning off the drive transistor and a second point in time that precedes the first point in time by a predetermined period. As a result, the motor current value Ih is detected with high accuracy.

Abstract: In a control apparatus for a motor, which rotates a fan, a semiconductor device is connected to the motor in series to drive the motor. An analog driver circuit drives the semiconductor device with an analog voltage. A PWM control circuit drives the semiconductor device with a PWM signal of a frequency of less than several tens. A switching control circuit selects the analog driver circuit and the PWM control circuit when the motor is to be rotated at speeds lower and higher than a predetermined speed, respectively.

Abstract: An inverter fault detection system of the present invention is provided with: bus voltage monitor means for monitoring the bus voltage of a three-phase inverter; output voltage monitor means for summing the phase output voltages coming from the three-phase PWM inverter, and for outputting the resulting summed output voltage through a filter having a low-pass characteristic of passing through only the cutoff frequency lower than the PWM carrier frequency; and fault determination means for determining that the three-phase PWM inverter is in the faulty state when the output voltage coming from the output voltage monitor means is almost the same as the voltage value corresponding to 3/2 times of the bus voltage monitored by the bus voltage monitor means.

Abstract: A drive method for a brushless motor and a drive control apparatus therefor, in which control parameters are calculated by revolution number control means or motor current control means in accordance with the deviation between a target value and an actual value, a manipulated variable is computed by conduction phase control means on the basis of the calculated control parameters, an advance angle magnitude is computed from the relationship between a manipulated variable and an advance angle magnitude as designed and created beforehand, on the basis of the computed manipulated variable, and the value of a conduction phase angle of a drive circuit as designed on the basis of a rotation position signal or a motor current signal is corrected using the information of the computed advance angle magnitude.

Abstract: Steering apparatus includes at least one motor for generating a steering assisting force in a direction to steer a steerable wheel, two drive circuits having respective switching elements for PWM-controlling the motor, and a controller for differentiating, between the drive circuits, a control frequency at which the switching element is switched on and off. The differentiated PWM switching timing can effectively reduce switching noise and magnetostrictive sound of the motor.

Abstract: The invention provides techniques for reducing or altering the magnetic noise of an AC rotary electric machine. A magnetic noise reducing harmonic current of order n, whose frequency is n times the frequency of the fundamental frequency component of a polyphase AC current fed to an armature of a polyphase AC rotary electric machine, is superimposed on the polyphase AC current, thereby reducing or altering a harmonic component having a frequency (n?1) times the frequency of the fundamental frequency component and occurring due to a radial magnetic excitation force acting radially on an iron core of the AC rotary electric machine.

Abstract: A method and apparatus for controlling a permanent magnet synchronous motor by accurately detecting 3-phase motor currents from a DC input current in a full voltage range are provided. In the motor control apparatus for detecting the 3-phase motor currents on the basis of the value of the current detected at a DC side of a PWM inverter, when a difference width between PWM pulse signals of two of three phases of the 3-phase PWM inverter which cannot detect the motor currents is not larger than a predetermined value or when the output voltage of the 3-phase PWM inverter is low, the apparatus automatically reduce the carrier frequency of the PWM inverter.

Abstract: In the invention, a PWM signal is formed at a frequency of a reference pulse signal, the PWM signal which has a pulse width being changed according to a frequency difference between an FG pulse signal for detecting a speed of a brushless motor and the reference pulse signal of a target speed, an output signal for PWM control is formed by an N-fold frequency of the PWM signal, the output signal for PWM control in which a pulse having the divided pulse width is arranged in each N-divided period, the N-divided period in which each one period of the PWM signal is divided by N, and electric power supply to a coil of each phase of the brushless motor is turned on and off at intervals shorter than that of the output signal control without increasing the frequency of the reference pulse signal.

Abstract: A system and method for controlling a fan is disclosed. In one embodiment, a fan controller is integrated in silicon and uses an embedded microcontroller to implement a digital fan control algorithm. The microcontroller may continually monitor temperature and sample the speed of the controlled fan. The speed of the fan may be compared to RPM values fitted on a desired curve that is representative of the Temperature-versus-RPM function for the given controlled fan. The fan control algorithm may be based on a PID compensator or a Ramp Rate Closed-loop controller (RRCC), which may be operated to drive the fan to the desired speed. The fan may also provide a Fan ID feedback signal to the microcontroller, which may use the Fan ID feedback signal upon system start-up to initialize the PID compensator gain settings or the RRCC parameter settings, and select the appropriate Temperature-versus-RPM function curve based on pre-determined values for the given fan.

Abstract: Amperage control of a power tool motor is provided by pulse width modulation of current from a power supply. The pulse width modulation may be varied according to the determined motor current and measured power supply voltage. The power supply preferably includes a battery, such a lithium ion or nickel cadmium.

Abstract: A fan controlling system applicable in an electronic system having a plurality of fans is disclosed. The fan-controlling system includes a first signal generating module and a second signal generating module for generating a first and a second pulse width modulation (PWM) signals according to control instructions output by the electronic system. The fan-controlling system further includes a phase-inverting module and a delay module. Therefore, PWM signals, which are delayed with a time interval one another, can be generated by the fan controlling system, so as to respectively control a plurality of fans of the electronic system, thereby avoiding the peak value of the total power signals when the fans are run from increasing instantly, and power signal for supplying the electronic system from decreasing instantly, making the electronic system run abnormally, and its stability becomes worse.

Abstract: For providing a controller apparatus for a synchronous motor and a controlling method thereof, enabling to be manufactured, easily and cheaply, and to obtain a lock mechanism, but without necessity of mechanisms, such as, an electromotive lock mechanism, wherein the controller apparatus for the synchronous motor, which has a stator 20 wound with AC windings 21U, 21V and 21W, and a rotor 30 installed within an inside of the stator, rotatably, therein, comprises an inverter 200 for supplying AC voltages having a predetermined voltage/frequency characteristic to the AC windings, which are wound around poles of the stator of the synchronous motor; and further, the inverter is so controlled that the AC voltages, being supplied from the inverter to the AC windings wound around the poles of the stator is changed into DC voltages to be supplied thereto, when rotation of said rotor is zero (0) and also when a lock function signal is ON in condition thereof, thereby obtaining a lock condition of holding a rotating posi

Abstract: A reference signal generation unit 110a generates a reference signal VCA representing a limit indicator. Under the control of a PWM control unit 120a, a bridge rectification circuit 130a controls the current supplied to a coil 19a to the limit indicator, using a current chopper method. Therewith, the circuit 130a implements synchronous rectification where transistors 10 and 12 are brought into conduction when the current supply is stopped, forming a closed circuit with the coil 19a, and a regenerative current circulates in the closed circuit. During a time period when the reference signal is decreasing relatively rapidly, a SR prohibition unit 115a prohibits the transistor 10 or 12 from being brought into conduction when the current supply is stopped, and thereby the decay of regenerative current is accelerated.

Abstract: Windings of each phase in a three-phase AC motor are independent of one another. A motor control unit gives, to windings of each phase (U, V and W-phase), currents (IU, IV, IW) obtained by adding, to a fundamental sine wave current, a current having a frequency which is three times as high as that of the fundamental sine wave current. That is, IU=I·sin ?t+Ia·sin 3?t: IV=I·sin(?t+2/3?)+Ia·sin 3?t: IW=I·sin(?t+4/3?)+Ia·sin 3?t Also, amplitude Ia of a current having a frequency which is three times as high as that of the fundamental sine wave current is set to a predetermined value smaller than amplitude I of the fundamental sine wave current.

Abstract: The electric machine of the present invention comprises a first coil group containing a plurality of coils and a magnet group. The first coil group is classified into M phase sub coil groups, with the coils of the sub coil groups aligned one at a time in sequence at a specified sub coil group interval Dc from the first phase sub coil group to the M-th phase sub coil group. A sub coil group interval Dc is set to a value of K/M times a magnetic pole pitch Pm (K is a positive integer excluding an integral multiple of M) where the distance corresponding to an electrical angle of ? is defined as the magnetic pole pitch Pm. The adjacent sub coil groups are driven at a (K/M)? phase difference. Each coil have substantially no magnetic material core.

Abstract: A microcomputer includes a rotation angular velocity computation section, a feedback gain determination section, and a dead time compensation amount determination section. The rotation angular velocity determination section computes the rotation angular velocity of a brushless motor. Based on the rotation angular velocity, the feedback gain determination section determines feedback gains. The dead time compensation amount determination section determines a dead time compensation amount. The greater the absolute value of the rotation angular velocity, that is, the higher the rotation speed of the brushless motor, the greater the feedback gains determined by the feedback gain determination section become, and the higher the responsivity of the feedback gains becomes. The greater the absolute value of the rotation angular velocity, the smaller the dead time compensation amount determined by the dead time compensation amount determination section becomes.

Abstract: The methods serves for activating an electric motor of a metering pump with which the fluid quantity (Vnom) to be delivered is set by an external impulse trigger, wherein a predetermined delivery quantity (Vnom) is allocated to each impulse (t). The control detects the temporal interval (?t) of the two last-received impulses and activates the electric motor such that the fluid quantity to be delivered, taking the previously evaluated interval as a basis, is distributed over the subsequent impulse interval.

Abstract: A dc motor drive system with a PWM control system permits a high-accuracy rotation drive control while detecting the currents flowing into the coils without using shunt resistors. The system drives output MOS transistors by the PWM control to make the currents flow into the coils, and drives to rotate the dc motor. The system includes current sensing MOS transistors having a predetermined size ratio 1/m (M>1) to the output MOS transistors that make the currents flow into the coils. The current sensing MOS transistors are capable of making flow reduced currents proportional to the currents of the output MOS transistors.

Abstract: A control system for an electric motor. Field Oriented Control, FOC, uses a digital control system, and attempts to maintain the rotating stator magnetic field ninety degrees ahead of the rotor field, in order to maximize torque. However, if a three-phase motor is used, which is very common, large amounts of computation are required, to convert from a three-phase coordinate system to an orthogonal coordinate system. The invention replaces the three-phase motor with a two-phase motor, which has been found to impose certain additional costs, but also provides benefits.

Abstract: Filter network for the reduction of the voltage switching speed between an electrical motor drive and an electrical motor and/or between an electrical distribution network and a motor drive, comprising for each electrical phase a self-damped inductor having a complex impedance determined by a magnitude (Z) and a phase (?), the phase (?) of the complex impedance being comprised between 80 and 90 degrees in the frequency range of the motor's current, and being less than 60 degrees in the frequency range of the overvoltage oscillations. Using the inventive filter network, it is possible to manufacture low cost and small size du/dt-filters generating low voltage overshoot and low losses.

Abstract: A frequency converter for outputting a power to drive a motor, having: an inverter unit for inverting a d.c. power to an a.c. power; a control unit for controlling the inverter unit; and a housing for supporting at least the inverter unit and control unit, wherein a rise time change unit is provided in the housing, the rise time change unit changes a rise time of a waveform of a voltage output from the inverter unit.

Abstract: Methods and apparatus for canceling dead time effects in the form of common mode voltages produced by a three-phase power conversion device in a rectifier/inverter variable frequency drive (VFD) system includes limiting the voltage difference between phase voltages at certain switching transition times to an amount ?, that is a function of the dead time that is specified for the switches and delaying gating signals to the switches to remove unexpected pulses produced by common mode voltages.

Abstract: A technique for reconstructing phase currents based on measurements of a DC bus current. Non-observable regions of DC bus current samples to reconstruct phase currents are reduced in size by using two phase space vector modulation. The non-observable regions can be further reduced by omitting deadtime insertions for switch actuations when output current is higher than a given threshold. Voltage command vectors in non-observable areas can be constructed by two time averaged vectors one of which is constructed to obtain an observable DC bus current reflecting motor phase current. The additive vectors have the same combined time average value as that of the voltage command vector in order to preserve volt-seconds. Current samples may also be averaged to provide a more accurate reconstruction of phase current. Current samples are time delayed to avoid transients for more accurate readings.

Abstract: A microcomputer includes an actual DUTY value detection section that detects an actual DUTY value ?x by measuring the ratio of time in which an output voltage of each phase becomes a power supply voltage in a cycle of a triangular wave. A dead time compensation computation section subtracts the actual DUTY value ?x from a DUTY instruction value ?x before correction, thereby computing a difference value ?x. Subsequently, the dead time compensation computation section adds the difference value ?x to dead time compensation amounts ?xp, ?xm, which have been used for correcting the DUTY instruction value ?x, thereby determining new dead time compensation amounts ?xp? and ?xm?. The dead time compensation amounts ?xp, ?xm stored in a memory are renewed with the new dead time compensation amounts ?xp?, ?xm?.