Abstract: A fan control system and method that maintains the operating temperature of computer and electronic devices or components at about a predetermined control level to minimize power consumption and audible noise. The fan control system is a programmable closed loop system including a temperature sensor, first and second fan controllers, and a fan/motor assembly including a power converter, a motor, and a fan. The first fan controller provides programmable acceleration/deceleration of the fan during an initial fan spin up, and the second fan controller runs the fan only as fast as necessary to keep the sensed temperature level of a computer device as close as possible to the predetermined control level, thereby minimizing the power consumption of the system and the audible noise of the fan.

Abstract: A method is described of regulating the instantaneous electromagnetic torque of a polyphase rotating electrical machine equipped with stator and/or rotor windings supplied by a voltage and a current generated by an inverter formed of switches whose switching is controllable. The method comprises a step of commanding the switching of the switches of the inverter using the fundamental frequency of the voltage generated by the inverter and a form of synchronous pulse width modulation configured as a function of an input set point, and a step of calculating the input set point from an instantaneous torque set point at each regulation time. The method further comprises a step of determining the time interval between two successive regulation times so that the time interval corresponds to an integer multiple of the period of oscillation of the instantaneous torque of the machine.

Abstract: A reactor having a predetermined small capacity is connected to a rectifier, and a capacitor having a predetermined small capacity is connected between DC bus lines of the inverter, so that a small, light and low-cost inverter controller for driving a motor can be implemented, and even when an inverter DC voltage largely fluctuates and it is difficult to drive the motor, the motor can be kept driving by operating the inverter such that a voltage applied to the motor may stay constant by a motor voltage command corrector which generates a motor voltage command correction value of the motor.

Abstract: A power control apparatus includes an inverter giving a rectangular waveform drive signal to an induction motor, an inverter voltage controlling section controlling an output voltage of the inverter, a converter boosting a voltage supplied to the inverter, a converter voltage controlling section controlling an output voltage of the converter, and a control signal generating section that controls the inverter voltage controlling section in a low-rotational speed region and controls the converter voltage controlling section in a high-rotational speed region.

Abstract: A first condenser is connected between output terminals of a rectifier circuit which receives an AC power as an input, and a three phase inverter is connected in parallel with respect to the first condenser, and output of the three phase inverter is supplied to a motor, and a second condenser is connected in parallel to the input side of the three phase inverter, and a current detector is connected between the first condenser and the second condenser, and a third condenser is connected in parallel to the first condenser at a position slightly power side with respect to the current detector, and the capacitance of the second condenser is determined as small as possible within the range in which power devices are not destroyed by surge voltage due to switching, therefore, ringing is suppressed, and taking of current is performed rapidly and with high accuracy.

Abstract: A method of controlling of an induction machine using an inverter is disclosed with output LC filter. The method includes determining an inverter output current vector (iA), determining an inverter output voltage vector (uA), and forming a full-order observer having a system matrix (Â) and gain vector (K). The observer produces an estimated rotor flux linkage vector ({circumflex over (?)}R), an estimated stator current vector (îs), an estimated stator voltage vector (ûs) and an estimated inverter output current vector (îA). An estimation error (iA?îA) of the inverter output current vector is determined, and a speed adaptation law is formed based on the estimation error of the inverter output current vector for determining an estimate for electrical angular speed ({circumflex over (?)}m) of the induction machine. The induction machine is controlled based on the produced estimates and a measured inverter output current.

Abstract: A motor control device that can reduce electrical noise is provided. A motor control device includes an inverter, a current controller, a high frequency wave superpositioner, and a high frequency wave setter. An inverter applies a current to the motor. A current controller outputs a voltage to the inverter according to a current applied to the motor from the inverter. A high frequency wave superpositioner applies a high frequency wave to the voltage from the current controller as a superpositioned wave to infer a position of a rotor in the motor. A high frequency wave setter varies at least one characteristic of the superpositioned wave applied by the high frequency wave superpositioner.

Abstract: A system and method for measuring the speed of a fan in an electrical system is presented. The duty cycle of a pulse width modulated (PWM) signal provided by a signal generator may control the speed of the fan. The fan may generate tachometer pulses that may be used by a tachometer reading-unit to monitor the RPM of the fan. Very low frequency test (VLFT) pulses may be generated and provided through a sampling signal multiplexed with the PWM signal to sample the fan generated tachometer pulses even when the PWM signal is low. The frequency of the sampling signal may be determined based on the duty cycle of the PWM signal and may be dynamically updated when the duty cycle of the PWM signal is updated. The sampling signal may be used as the clock input to a flip-flop with the tachometer pulses as the data input, and the output of the flip-flop providing an input to a pulse counter that counts the number of pulses within a determined period of time, providing as its output the measured RPM of the fan.

Abstract: A method controls a torque of an a. c. motor which does not cause a shortage of torque by using an economical current detection which estimates d- and q-axis currents Idc, Iqc from d. c. current IDC flowing through an input d. c. bus line of a power converter. A value of d- and q-axis motor currents Id, Iq of a rotational coordinate system are estimated from detected input d. c. current IDC flowing through the bus line of the power converter to which power is input from a d. c. power source 21. A output voltages of the power converter 2 are controlled so that the estimated currents Idc, Iqc are equal to respective current instruction values Id*, Iq*. Errors of motor constants are determined from information on the motor currents and the rotational phase errors by an operation.

Abstract: A system and method for controlling a fan is disclosed. A single control signal value for controlling the fan, such as a single PWM duty cycle value for a corresponding PWM generator output powering the fan, may be calculated by combining sensor data from two or more temperature zones. In one embodiment, the single PWM duty cycle value may be determined based on the temperature in a first zone, for example the CPU, with an additional factor based on the temperature in a second zone, for example the ambient temperature of a PC enclosure. In one embodiment, the final single PWM value is determined by adding an offset value to a PWM value calculated based on the current temperature of the first zone, where the offset value is obtained by calculating a first ?PWM factor for the first zone, and using the first ?PWM factor, in conjunction with a scaling factor, to weight a second ?PWM factor calculated for the second zone.

Abstract: A driving circuit of an AC fan motor has an AC to DC converter, a regulated voltage divider, a motor driving unit, two windings each having many coils and a harmonic wave suppression unit. The AC to DC converter converts AC power to high voltage DC power. Since the motor driving unit requires low voltage DC power, the motor driving unit is connected to the AC to DC converter through the regulated voltage divider. The two windings are directly connected to the AC to DC converter to obtain the high voltage DC power. Therefore, when the motor driving unit drives the windings, a large current will pass through the winding to increase rotation ration. Since each winding has many coils, the large current can be held in a suitable range to prevent the winding from being damaged by the large current.

Abstract: A control circuit is described in which a single input terminal receives digital control signals and analog control signals. In accordance with the principles of the invention, the control circuit includes an automatic power down circuit to place the control circuit into a low power draw or “sleep” mode whenever predetermined conditions are present. The automatic power down circuit monitors the single input terminal and when no demand for motor operation occurs for a predetermined period of time, the automatic power down circuit operates to place the control circuit into the low power draw mode.

Abstract: An electrical machine is controlled without using a physical rotor position detector. When the demanded torque output is low, a control method causes the machine to operate on fewer than all the phases, thus increasing the phase current and improving the resolution of the position detection algorithm. The method can include sampling the phase current of the machine, determining whether the phase current is above a predetermined threshold, reducing the number of active phases, and then deriving the value of rotor position from the increased phase current in the remaining phases.

Abstract: A system for controlling the speed of a brushless repulsion motor having a series of switches mounted on a rotating armature for shorting circumferentially spaced armature coils comprising first stationary signaling means and a plurality of rotating detectors for activating said switches; second stationary signaling means for speed control; a plurality of markers on the rotating armature; a speed detector for detecting the speed of the rotating markers and generating a speed feedback signal; means for generating a speed command signal; an error calculator for comparing the speed feedback and speed command signals and generating an error signal; and a controller for controlling the signaling means based on the error signal.

Abstract: An input signal Va is compared with a limitation signal Vlim. When the input signal Va exceeds the limitation signal Vlim, an excess (Va?Vlim) is obtained as an excess signal Vext. In a signal output circuit 60, the excess signal Vext is subtracted from the input signal Va and an output signal Vo is sent.

Abstract: A motor control device is provided with a neutral point shift section. The neutral point shift section shifts a neutral point (command neutral point) of phase voltage commands so that the values of the phase voltage commands after the shifting of the neutral point come within the amplitude of a triangular wave (triangular wave signal), and inputs the phase voltage commands with the neutral point having been shifted, to a control signal output section. Thus, the motor control device is enabled to heighten the output voltage without bringing about increase in manufacturing cost and substantial delay in calculation interval.

Abstract: A current control circuit includes a control current generation circuit that generates a control current in accordance with an external current control signal. A plurality of drive current generation circuits generate drive currents in accordance with the control current that is generated by and supplied from the control current generation circuit.

Abstract: An electric machine assembly having an electric machine. The electric machine can include a first speed circuit and a second speed circuit. In some constructions, both speed circuits can be of a permanent split capacitor design. At least one of the speed circuits can include a switch that is controlled by the controller to limit current through an auxiliary circuit of the unused speed circuit when certain conditions exist.

Abstract: A controller for a wound-rotor induction motor includes a first voltage-type converter connected to a secondary winding of the motor, a capacitor for smoothing DC output thereof, a second voltage-type converter to supply an AC power supply with regenerated secondary power, a speed detector of the motor, a secondary current detector of the motor, a DC voltage detector applied to the capacitor, a speed controller for controlling the speed by the speed detector and outputting a secondary referential current, a first PWM controller to control the secondary current in response to the referential current, and to output a voltage signal by witch switching elements of the first voltage-type converter are controlled by PWM, and a second PWM controller to control a voltage output from the voltage detector in response to a referential voltage, and to control by PWM switching elements of the second voltage-type converter.

Abstract: Methods and apparatus for controlling switching in a DC-to-AC inverter to prevent overvoltages applied to an AC motor by determining the switching order of the phase voltage signals, providing gating signals at switching intervals by modulating a carrier wave with the phase voltage signals, comparing the switching intervals to a predetermined minimum time interval sufficient for reflected wave transients to dissipate, and adjusting the switching intervals to be at least equal to the predetermined minimum time interval.

Abstract: A controller of a steer-by-wire steering apparatus determines whether voltage applied to a steering motor in accordance with a current command value has reached a predetermined voltage. Based on the result, the controller selects one of the value of an actual current through the steering motor and a current command value. Based on the selected current value, an axial force applied to a steering rod is estimated. Based on the estimated axial force, a counter torque motor is controlled. Therefore, An error or oscillation occurring in the estimated steering axial force is prevented, and the driver is suppressed from further turning the steering wheel when the voltage applied to the steering motor is saturated.

Abstract: A three-phase spindle motor has three terminals each driven with pulse width modulated signals. Rotation of the motor is controlled by iteratively measuring an electrical period of the motor, determining a rotational position of the motor, and synchronizing the sinusoidal pulse width modulation of the spindle motor with the measured electrical period. The electrical period of the motor is measured by detecting zero crossings in the a back electromotive force induced at a first terminal of the motor and determining the time between successive zero crossings. The rotation position of the motor is determined based upon the last measured electrical period and a location of last detected zero crossing. The zero crossings are detected by selecting a time window during which the back electromotive force signal is sensed for zero crossings. The time window is selected as a function of the last measured electrical period and the rotational position of the motor.

Abstract: A control circuit is described in which a single input terminal receives digital control signals and analog control signals. A circuit coupled to the single input provides a first output to indicate that a signal at said single input terminal is a digital signal and a second output indicates that a signal at said single input terminal is an analog signal.

Abstract: An electric motor control apparatus of this invention estimates changes in temperature of a semiconductor device to compute temperature change amplitude 108 based on an output current signal 105 computed from a current flowing through the semiconductor device of a switching circuit 5, an operating frequency signal and a carrier frequency signal by a temperature change estimation part 11, and makes conversion into the number of power cycles 110 corresponding to the temperature change amplitude 108 from power cycle curve data stored in a power cycle curve data storage part 14 and computes a thermal stress signal 111 by a thermal stress computation part 13, and does life estimation of the semiconductor device based on the thermal stress signal 111 and produces an output to a display part 16 as a life estimation result signal 112 by a life estimation part 15a.

Abstract: An apparatus for driving a brushless motor and method of controlling the motor, which actively changes an output time of a phase commutation signal depending on variation of a load and stably operating the motor in an overloaded state and improving an operational efficiency of a system. The apparatus for driving a brushless motor includes an inverter, a driver, a counter-electromotive voltage detector and a controller. The inverter switches driving voltages applied to multi-phase stator coils. The driver drives the inverter. The counter-electromotive voltage detector detects a counter-electromotive voltage induced from an unexcited stator coil. The controller calculates a time required to detect a counter-electromotive voltage through the counter-electromotive voltage detector after the driving voltage is turned off, determines a phase commutation point of time based on the determined elapsed time, and controls the driver to perform phase commutation at the determined phase commutation time.

Abstract: A method of controlling the torque of a multiphase induction motor includes the step of energizing the stator windings of the motor from a power converter using thyristors, inserted between a multiphase main supply and the windings producing a stator current set point expressed by its amplitude and its phase, predicting phase coincidences between the stator current and the set point, and commanding the power converteer so that the windings receive current waves substantially when such coincidences occur.

Abstract: A method and apparatus is disclosed for reducing the heat generated by three-phase motors operating under load in cooled chambers such as industrial walk-in refrigerators and freezers. Specific control elements are introduced into the three power conductors connected to a three-phase motor, the elements chosen so as to cause the motor to turn at a speed below a certain critical speed, above which the elements have no control over the motor power used or the motor speed. The results of inserting the control elements into the motor power conductors are (1) the motor turns at a reduced speed and (2) the heat generated by the motor is reduced. In addition, the control elements themselves are specifically chosen and are of such a nature that they generate virtually no heat in the process of reducing the power supplied to the motor.

Abstract: Corresponding to a target torque, the control device calculates a target value of a feature based on at least one of the length of a long axis of a current vector locus and the length of the short axis and further superimposes a superimposed current on a drive current for the motor, the superimposed current having a frequency different from the frequency of the drive current. Further, the control device detects an actual value of the feature based on at least one of the length of a long axis of a current vector locus of the superimposed current and the length of the short axis of the same and finally detects a phase angle of the motor based on the target value and the actual value for the feature. The manipulation of a detecting phase is performed by feedback of a feature obtained by the magnitude of the superimposed current. That is, when the actual feature is more than the target value, the detecting phase is advanced.

Abstract: A system and method for reducing torque ripple in a motor controller includes a step (60) of measuring an output voltage at each phase of the motor controller. A next step (61) includes determining a voltage mismatch between the phases. A next step (62) includes phase grounding one phase of the motor. A next step (63) includes calculating a voltage gain for the phases to compensate for voltage mismatches therebetween. The compensating gain can include a gain and/or offset, which are applied as a function of motor angle and is used to generate a PWM signal for driving the motor with reduced torque ripple.

Abstract: A shutter mechanism includes a drum (2), a stepping motor (5), a driver (20), a microcomputer (10), a memory (16), and a load magnitude detection circuit (30) that detects the magnitude of the load on the stepping motor (5) when an object such as a shutter (3) is either wound or unwound from the drum (2). The microcomputer (10) can set the upper and lower limit stopping positions of the shutter (3) by resetting the number of command pulses stored in the memory (16) when the load magnitude detection circuit (30) detects an increase in the load at the stepping motor (5), and storing the number of command pulses output to that point from the memory (16) when the load magnitude detection circuit (30) next detects an increase in the load at the stepping motor (5) after the outputting of the command pulses is next restarted.

Abstract: A motor drive control apparatus includes a motor, a power supply, a control circuit, a first current detector, a first switching element, and a second switching element. The first current detector generates a first detection voltage indicating a first current flowing through the motor in one direction. The control circuit generates a PWM voltage and generates an ON voltage if the first detection voltage is lower than or equal to a first specified input voltage, and the control circuit generates an OFF voltage and generates the PWM voltage if the first detection voltage is higher than the first specified input voltage to adjust a pulse duty of the PWM voltage in accordance with a difference voltage between the first detection voltage and the first specified input voltage and to control the current flowing through the motor so as to be equal to a target current.

Abstract: In the gaming machine, when the motor drive instruction to drive the motor occurs based on an instruction from an external, a constant voltage is applied to the motor and the motor is driven through the motor drive circuit 39. And when the excitation current value flowing in the motor becomes the first current value based on the constant voltage applied to the motor through the motor drive circuit 39, the voltage with on-time and off time is repeatedly applied to the motor through the motor drive circuit 39. Further, when the rotation speed of the motor becomes constant based on the voltage with on-time and off-time applied through the motor drive circuit 39, the constant voltage is applied to the motor based on the motor stop instruction through the motor drive circuit 39, thereby the motor is stopped.

Abstract: A control system for a polyphase AC motor having a predetermined horsepower rating is provided comprising a plurality of integrated control systems each rated at less than the hoursepower rating for the motor and having a rectifier section, an inverter section, and a controller section, and a parallel controller interfaced to each integrated control system.

Abstract: In a PWM space vector modulation inverter motor drive system, PWM cycles are modified to permit motor phase currents to be reconstructed as observable on the DC bus link. The PWM cycles are modified near sector boundaries so that measurements taken at the DC bus link correspond to actual motor phase currents. With this technique, a single DC bus current measure can be used to reconstruct all motor phase currents, while also providing fault protection.

Abstract: A drive system that is suitable for high bandwidth current control of a three-phase voltage source inverter in the overmodulation region includes a feedback path that has a harmonic decoupling block that subtracts selected harmonic components from signals representative of a corresponding motor phase current signal. The harmonic decoupling block thereby generates corrected feedback signals. The drive system also includes subtractor blocks that subtract the corrected feedback signals from signals representative of open-loop magnetizing reference currents to generate difference signals. Also included is a modulation block that utilizes the difference signals to produce signals to drive a three-phase voltage source inverter in an overmodulated six-step mode.

Abstract: A disk drive is disclosed comprising a spindle motor comprising a plurality of windings for rotating a disk. The spindle motor is rotated by commutating the windings over a plurality of commutation states, wherein audible noise generated by the disk drive is reduced by phase modulating the commutation interval. Further audible noise reduction is achieved by modulating a current applied to the windings which substantially reduces discontinuities in the torque output of the spindle motor caused by phase modulation of the commutation intervals.

Abstract: A carrier wave frequency generating unit 9 modulates a frequency f of a carrier wave in a triangular shape. Occurrence of drawbacks due to the frequency f of the carrier wave can thereby be prevented. Because the frequency f of the carrier wave can be easily computed and estimated, a delay time of control, which is due to time for computing the frequency or an integration constant of PID control, can be kept to a minimum, and motor efficiency can be prevented from deteriorating. Because a control delay time can be estimated easily, it is possible to prevent carrying out of delay compensation by feed forward, and to prevent the motor efficiency from deteriorating.

Abstract: The motor driver having a plurality of output circuits each having two switching elements connected in series includes: a phase switch circuit for putting a switching element on one side of one output circuit among the plurality of output circuits in the ON state during a time period corresponding to a predetermined electrical angle, and performing switching operation for switching elements on the other side of plural output circuits among the remaining output circuits; and a conduction period control section. The conduction period control section generates a signal for controlling the switching operation. Specifically, when the number of times of switching operation performed during the time period corresponding to the predetermined electrical angle is equal to or less than a predetermined value, a switching element corresponding to a phase, for which the magnitude of the current should be decreased, is turned OFF in the time period corresponding to the next predetermined electrical angle.

Abstract: A large domestic appliance has main and auxiliary drives (17, 24) thereof supplied from the same dc voltage intermediate circuit (19) which is provided only once, by way of change-over switch sets (12), by half-bridge circuits (21, 21?). For that purpose a frequency converter (15) with its bridge circuit (21) for the main drive (17) is switched over in single-pole or multiple mode to the rotary field motor (23, 25) of the auxiliary drive (24) by way of a change-over switch set (12) connected in its output-side motor lines (13); or in the frequency converter (15) two half-bridge circuits (21, 211) which are associated with the main and the auxiliary drives (17, 24) are operated in parallel from the dc voltage intermediate circuit (19).

Abstract: A disk drive is disclosed comprising a spindle motor for rotating a disk, wherein the current applied to the spindle motor is controlled by adjusting a duty cycle of a pulse width modulated (PWM) signal. A current sensor generates a current sense signal representing a current flowing from a supply voltage. The current sense signal is integrated to generate an integration signal. The integration signal is compared to a threshold, and the result of the comparison is used to adjust the duty cycle of the PWM signal. In this manner the disk drive draws essentially constant average input current from the supply voltage which decreases the spin up time of the disk.

Abstract: A motor control device includes an electric voltage command value calculation means for inputting an electric current command value every control cycle, calculating an electric current deviation integrated value by integrating an electric current deviation between the electric current command value and an actual electric current value at a coil of a motor, and calculating an electric voltage command value in accordance with the electric current deviation integrated value. The electric voltage command value calculation means controls the electric current deviation integrated value not to exceed a saturation electric voltage value, a value according to the maximum value of the electric voltage outputted from the inverter circuit to the motor.

Abstract: A driving apparatus of a linear motor which reciprocally drives a movable element supported by an elastic member, includes an inverter that converts a direct current power into an alternating-current power with a specified frequency to drive the linear motor, a current detector that detects the output current of the inverter, a voltage detector that detects the output voltage of the inverter, an amplitude detector that detects an amplitude of the movable element of the linear motor, an amplitude controller adjusts the output current or output voltage in a first control cycle so that the amplitude of the movable element is a desired constant value, and a resonant controller that adjusts the output frequency of the inverter in a second control cycle which is larger than the first control cycle so that the output current of the inverter is substantially minimum on condition that the amplitude is substantially constant.

Abstract: A vector control inverter comprises at least one of a set of a torque estimating unit that estimates an output torque of a motor from excitation current and torque current and a pulse transmitting unit that outputs a torque estimation value estimated by the torque estimating unit as positive-negative identifiable pulse stream signals, and a set of a pulse array input unit that receives pulse stream signals input from outside as positive and negative values and a torque instruction converting unit that converts the received pulse stream signals into a torque instruction to be transferred to the motor as a torque.

Abstract: A reactor having a predetermined small capacity is connected to a rectifier, and a capacitor having a predetermined small capacity is connected between DC bus lines of the inverter. A PN voltage corrector calculates a ratio of the DC voltage detection value of the inverter obtained by the PN voltage detector to a predetermined DC voltage reference value of the inverter to thereby generate a PN voltage correction factor. A beat amount corrector calculates a fluctuation amount of the motor current from the motor current detection value obtained by the motor current detector and generates a reverse phase component of the motor current fluctuation amount. Thus, a small, light and low-cost inverter controller can be implemented.

Abstract: The invention relates to a method in connection with an inverter, the inverter comprising a direct voltage intermediate circuit, an optimum switching table and output power switches. The method comprises steps where phase currents (iA, iC) of the inverter are converted to a synchronous dq coordinate system in order to achieve vector components (id, iq), the synchronous current vector components (id, iq) are low pass filtered in order to achieve current vector components (id,jpf, iq,jpf), a current reference (iq,ref) is generated in the direction of the q axis, a current reference (id,ref) is generated, a torque reference (te,ref) is generated, an absolute value reference (|?|ref) of a flux linkage is generated from the currents and switching commands are formed on the basis of the torque reference (te,ref) and the flux reference (|?|ref) using the optimum switching table (5).

Abstract: Improved voltage stiffness in the output voltage of an inverter used for a motor drive is obtained by a minor voltage feedback loop connecting the output of the inverter to a three-phase input in a vector domain.

Abstract: A motor drive circuit and method with frequency setting and correcting functions. The drive circuit includes a speed control device, which simultaneously receives a sense signal and a rotation frequency signal. A pulse width modulation signal capable of modulating a duty ratio may be generated by a pulse width modulation method. The pulse width modulation signal is then transferred to a drive timing controller that generates a timing control signal to control output timing of a power drive signal for the drive circuit. Meanwhile, a sensor is used to detect a motor and to generate a correction sense signal, which is immediately fed back to the speed control device to form a closed loop control, so that the rotation frequency of the motor may be automatically corrected and set.

Abstract: A dynamoelectric machine combining the functions of an exciter, a turning motor, and a starting motor for a turbine. The machine operates in a first mode where the slip between a first stator winding and a first armature winding is positive and thus the magnetic fields interact and operate as a motor to turn the turbine. In a second mode the slip is negative as the turbine turns the shaft and the first stator winding and the first armature operate as an exciter for supplying excitation to the rotating field winding of a main generator.

Abstract: An inverter controller for driving a motor includes a rectifier having a reactor, an inverter, a capacitor, a generator which generates a voltage command value for each phase of the motor, a detector which detects a DC voltage between the DC buses of the inverter, a first corrector which calculates a voltage correction coefficient by comparing the DC voltage with a predetermined DC reference voltage, a second corrector which corrects the voltage command value by multiplying the voltage command value and the voltage correction coefficient, a selector which selects either two-phase modulation or three-phase modulation as a modulation type, a computer that computes a carrier frequency, and a pulse width modulation controller which controls a pulse width modulation so that a value of a voltage to be applied to the motor equals to the corrected voltage command value, by using the selected modulation type and the selected carrier frequency.

Abstract: A current detection method for an electric motor which detects phase currents of the electric motor driven by a power converter that provides ON/OFF control of bridge-connected switching elements, based on a pulse-width modulation excitation pattern, to convert a direct current into poly-phase alternating currents. The method includes connecting a current detecting element which produces a signal corresponding to a current value at the direct current side of the power converter and changing the pulse-width modulation excitation pattern by executing a shift of time of any of the phases of the pulse-width modulation excitation pattern so that a signal directly or indirectly corresponding to the phase currents is produced at the current detecting element. The method also includes detecting the phase currents of the electric motor based on the signal produced at the current detecting element and the excitation pattern which has been changed.