Abstract: A power train for a transport vehicle is provided. The power train includes an electric motor comprising a shaft, a stator and a rotor, a power supply system receiving direct input voltage and delivering a polyphase voltage to the motor. The system has a modulation factor equal to the voltage amplitude of each phase of the motor divided by the direct input voltage, and includes a sensor for the rotational speed of the rotor.

Abstract: A control device of a synchronous machine is disclosed. The control device includes an inverter configured to provide an output current to a synchronous machine. A controller configured to control the output current and to estimate a voltage command, at least in part, by using pulse width modulation to choose a non-zero vector at a time when the inverter is not driving the synchronous machine with the output current. The estimating the voltage command is performed without using a zero vector. A phase angle and angular velocity estimating section configured to estimate a phase angle and an angular velocity of a rotor of the synchronous machine based, at least in part, on an inductance value, an induction voltage value, the voltage command, and the output current. The controller is further configured to control the output current based, at least in part, on the phase angle and the angular velocity.

Abstract: Provided is a technique to suppress hunting in a range of a minimum resolution of a pulse encoder when a servo motor has reached a target position and stopped, thereby maintaining a stable stop state. A servo motor position control device uses a cascade configuration having a position control loop as a main loop and a velocity and current control loop as a minor loop. A proportion control is performed for a position control while a proportion integration control is performed for a velocity control and a current control. When the servo motor position has reached the target position and stopped (S201), a current instruction value for the current control is maintained at a value upon stop (S202) and the current control is switched to the proportion control (S204).

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

Abstract: An active rectifier controller controls operation of an active rectifier employed in a power conversion system that supplies a direct current (DC) output to an inverter that converts the DC output to an AC output supplied to an AC motor. The active rectifier controller includes a field-oriented control (FOC) controller that monitors an alternating current (AC) input currents provided to the active rectifier, the DC output provided to the inverter, and speed of the AC motor. The FOC controller selects a reference DC output value based on the speed of the AC motor and compares the monitored DC output to the reference DC output as part of the FOC control algorithm used to generate control signals. A PWM signal generator generates PWM signals for controlling the active rectifier based on the control signals.

Abstract: A method for determining the position of a component, that is able to be moved into at least two end positions with the aid of a drive, especially of a flap for controlling fluid flows in an internal combustion engine, includes the following steps: providing an electric signal that indicates the speed of motion of an element of the drive, determining a change in position of the component by the integration of the electric signal, and determining the absolute position of the component from the change in position.

Abstract: The present invention provides an electronic commutator circuit for use with a stator winding of an electrical machine. The stator winding of the electrical machine includes a number of coils linked by the same number of points of common coupling. The electronic commutator circuit comprising the same number of switching stages, each switching stage being connected between a respective one of the points of common coupling and first and second dc terminals. Each switching stage further includes a first reverse blocking semiconductor power device (such as a Reverse Blocking Gate Turn Off Thyristor (RB-GTO 1) capable of being turned on and off by gate control having its anode connected to the first dc terminal, and a second reverse blocking semiconductor power device (RB-GTO 2) capable of being turned on and off by gate control having its cathode connected to the second dc terminal.

Abstract: A power conversion device in which an inverter for controlling a load is connected to an alternating current power system, and arranged to perform an electric power assist by connecting a direct-current power assist device having a chopper and a charge device to a direct-current circuit of the inverter. The device including a setting section to set charge and discharge target values in accordance with a sensed value of the direct-current voltage of the inverter; a charge control section to perform a charge control based on the charge target value; a discharge control section to perform a discharge control based on the discharge target value; and an instantaneous-low high-speed-compensation section to estimate an electric power corresponding to a direct-current sensed voltage of the inverter, and to output a value to the discharge control section which is obtained by dividing the estimated value by the direct-current sensed voltage.

Abstract: An electric power converter includes a control unit outputting a PWM signal, a bridge circuit producing AC electric power supplied to a motor by turning semiconductor switching devices in the bridge on and off in response to PWM signals, a cut off unit cutting the PWM signals off from the bridge circuit in response to a gate signal, and a monitoring unit generating a test signal for checking the cut off unit. The cut off unit includes a switching circuit switching between the test signal and an external cut off signal, and a delay circuit that delays the output of the switching circuit. The arrangement enables the electric power converter to monitor as to whether the cut off unit is abnormal without stopping the operation of the electric power converter.

Abstract: There are provided a motor controlling circuit, a motor driving device, and a motor controlling method. The motor controlling circuit includes: a frequency detecting unit detecting a frequency of an internal clock signal of a motor driving circuit; a sampling unit sampling an input pulse width modulation (PWM) signal using the frequency of the internal clock signal; and a calculating unit sensing a change in a speed of the internal clock signal from a sampling result of the sampling unit and calculating a revolution per minute (RPM) of a motor from the sensed change in the speed.

Abstract: A motion control system including components such as an accelerometer for detecting zero force positions and for self-calibrating the motion control system. The motion control system may be implemented in an active seat suspension.

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

Abstract: A rotary electric machine control device includes a positive/negative determination section that determines whether an output torque of the rotary electric machine is positive or negative; a correction parameter setting section that sets as a correction parameter a phase difference of a sinusoidal ripple correction wave for reducing torque ripple of the rotary electric machine with respect to a magnetic pole position of the rotary electric machine depending on whether the output torque is positive or negative; and a correction wave generation section that generates the ripple correction wave on the basis of the correction parameter.

Abstract: An inverter circuit for a motor outputs three-phase AC currents, which are outputted from common connection points to stator coils, based on output voltage of a DC power source and a power supply capacitor by a switching operation of transistors. An inverter control circuit determines that a system main relay is turned off, upon receiving a main relay-off signal from an electronic control unit. The inverter control circuit turns on the low-side transistors, while turning off the high-side transistors. A discharge current flows from the positive electrode to the negative electrode of the power supply capacitor through the stator coil and the low-side transistors, so that electric charge stored in the power supply capacitor is discharged.

Abstract: The machine in accordance with the present disclosure is an AC machine whose pole numbers can be switched (from pole p1 to pole p2), and whose number of series turns per phase N can be switched say from N0=Nrated to N1=N0/2. Furthermore, it employs an inverter so that the frequency can be changed from a low value (e.g., 5 Hz) to a high value (e.g., 200 Hz). Due to the combination of pole number and number of series turns switching/reconfiguration, a high torque at low speed (e.g., 0 rpm) and a high torque at high speed (e.g., 5,000 rpm) can be achieved, making mechanical gears obsolete. In addition, the output power of the motor can be increased at high speed in direct proportion to the speed increase.

Abstract: A motor controlling device includes an encoder to output pulse signals with a predetermined angle interval as a rotor of a motor is rotated. An energized phase of the motor is sequentially switched by detecting a rotation position of the rotor based on a value of counting the signals. An initial drive controlling portion executes an initial drive to switch the energized phase with a predetermined pattern after the device is activated so as to learn a relationship among the count value, the rotation position and the energized phase. An initial drive prohibiting portion prohibits the execution of the initial drive until a predetermined time is elapsed after the initial drive is finished.

Abstract: An apparatus and method for use with a PMSM detect the fall time or the rise time and the fall time of a motor current in the PMSM under different voltage vectors when the PMSM is in start-up to determine an initial rotor position for the PMSM at standstill.

Abstract: A motor control device that has a high-frequency component, and a DC bias component that has a magnitude which causes a motor to be magnetically saturated and take on a certain value over a predetermined period, and is positively and negatively symmetrical are impressed as an observation command on a d-axis current command. The polarity of the magnetic pole of a permanent magnet is identified based on a relationship of large and small magnitudes between a first amplitude, which is attained during a period during which a DC bias component takes on a positive certain value, among amplitudes of a high-frequency component contained in a d-axis response voltage computed based on a feedback current respondent to the observation command, and a second amplitude attained during a period during which the DC bias component takes on a negative certain value.

Abstract: In sequentially selecting and driving two phases of the three-phase stator windings of a synchronous motor, detect a speed electromotive voltage of a de-energized phase, relate the speed electromotive voltage to rotor position information beforehand, then count rotor position information backward based on the detected the speed electromotive voltage to estimate rotor position; and then detect rotation speed from the change rate of the rotor position information so as to achieve highly accurate position and speed control.

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

Abstract: A multiphase alternating current permanent magnet synchronous electric motor is coupled to an actuator. A sensorless electric motor drive control system controls operation of the electric motor. An initial phase angle and a rotational speed of a rotor of the electric motor are estimated. Operation of the sensorless electric motor drive control system and the electric motor are monitored using the estimated initial phase angle and the estimated rotational speed of the rotor of the electric motor. A fault in one of the sensorless electric motor drive control system and the electric motor is detected based upon the monitored operation.

Abstract: Methods and devices are presented herein for estimating induction motor inductance parameters based on instantaneous reactive power. The induction motor inductance parameters, e.g., the stator inductance and the total leakage factor, can be estimated from motor nameplate data and instantaneous reactive power without involving speed sensors or electronic injection circuits.

Abstract: The present invention provides a position sensorless control method of a high performance permanent magnet synchronous motor during emergency operation, which can accurately detect a magnetic pole position of the synchronous motor based on a position sensorless vector control using an adaptive observer configured based on a permanent magnet synchronous motor model.

Abstract: A method for starting a permanent magnet single-phase synchronous electric motor which includes a permanent magnet rotor and a stator with windings, and which is connected to an electrical grid by a switch. The method includes: a first starting attempt in which the windings are fed in current with first starting impulses generated only during the half-periods of a first polarity of the voltage of the electrical grid; a first control step which detects whether a starting condition has been obtained in the first starting attempt; and, if the first control step does not detect that the starting condition has been obtained within the term of the first starting attempt, a second starting attempt in which the windings are fed in current with second starting impulses generated only during the half-periods of a second polarity that is opposite to the first polarity of the voltage of the electrical grid.

Abstract: A device and a method for determining the current position of a rotor, particularly the angle of rotation of the rotor, of an electric motor, wherein said device determines the current position of the rotor using the fluctuations of the armature current or the armature voltage of the electric motor. The fluctuations of the armature current or the armature voltage are separated from the fluctuations of the motor current or the motor voltage with the help of an amplifier unit dependent on a controllable offset value. The offset value is changed according to the motor current or the motor voltage. By virtue of the device and the method, the fluctuations of the armature current or the armature voltage can be separated from the fluctuations of the motor current or the motor voltage over the full measurement range of the motor current or the motor voltage.

Abstract: The synchronous motors are controlled by a three-phase AC power controller. According to an embodiment of the invention, firing points for the AC power controller are determined. A pair of two or three phases is determined from the angular position of the rotor, for which the firing points can be present for the respective A.C power controller. Actual firing points are determined from the mains voltage phase position of the phases so that only positive torque is produced.

Abstract: A ventilation apparatus with a two-section feedback compensation control and a method for operating the same are disclosed. The ventilation apparatus includes a power conversion trait (10), a driven circuit (20), a DC motor (30), a current-sensing unit (40), a voltage compensation unit (60), and a control unit (50). The power conversion unit (10) receives and converts an AC power voltage (Vac) into a DC power voltage (Vo). The driven circuit (20) receives the DC power voltage (Vo) and outputs a driven voltage. The DC motor (30) is driven through the driven voltage. The current-sensing unit (40) senses an output current of the DC motor (30). The control unit (50) receives the output current to compare to a threshold current value, thus controlling the voltage compensation unit (60). Accordingly, the DC power voltage (Vo) is adjusted to adjust the speed of the DC motor (30).

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

Abstract: A storage section stores three-phase detection currents and outputs them as three-phase storage detection currents and also stores three-phase voltage commands and outputs them as three-phase storage voltage commands. A second voltage command calculating section outputs three-phase voltage commands on the basis of the three-phase storage detection currents and the three-phase storage voltage commands, which are acquired from the storage section, and the three-phase detection currents acquired from a current detecting means. A voltage command output means outputs, to a voltage application means, three-phase voltage commands acquired on the basis of the three-phase voltage commands from the storage section and the three-phase voltage commands from the second voltage command calculating section. The voltage application means applies a voltage to an AC rotary machine on the basis of the three-phase voltage commands from the voltage command output means.

Abstract: A motor controller comprises a processor selectively outputting an on-signal to either one of an upper arm switching element and a lower arm switching element based upon a detected position by the position sensor, gate drivers inputting a driving voltage to the gates of the switching elements by shifting a level of the on-signal from the processor to the upper arm switching element and a bootstrap capacitor configured to be charged while the upper arm switching element is turned off and to behave as a voltage supply for the gate driver while the upper arm switching element is turned on. The processor is configured to reduce a set duty ratio when the set duty ratio is equal to or larger than a predetermined value (e.g. 80 percents) and a rotational position of the motor does not change for a first predetermined time. This motor controller can prevent the switching element from a burnout even if the motor is locked.

Abstract: To prevent a step-out of a permanent magnet synchronous type motor (1), a motor control device (3a) is provided to include a flux control unit (16) for deriving an excitation current command value (i?*) according to the rotation speed (?e) of the motor, and a voltage shortage determination unit (30) for determining whether or not the supply voltage to the motor is running short based on the excitation current command value (i?*). When a negative excitation current command value (i?*) is smaller than a negative determination threshold value, the motor control device determines that the supply voltage is running short and prohibits an increase of the rotation speed or decreases the rotation speed.

Abstract: A motor controller is provided with a first PWM circuit that repeatedly outputs an on-signal at a first carrier frequency, a second PWM circuit that repeatedly outputs an on-signal at a second carrier frequency that is lower than the first carrier frequency, an AND circuit that receives both the on-signal outputted from the first PWM circuit and the on-signal outputted from the second PWM circuit and outputs a third on-signal which is a logical product of the received on-signals, and a voltage apply circuit that applies a voltage to the motor intermittently in synchronization with the third on-signal outputted from the AND circuit. At least one of the first carrier frequency and the second carrier frequency is equal to or lower than 1 kHz or equal to or higher than 3 kHz. As a result, generation of an unpleasant noise by a motor controller using two PWM circuits may be suppressed.

Abstract: Embodiments of the present invention permit the optimization of torque control of a permanent magnet machine including obtaining instantaneous terminal voltages of the machine, transforming the instantaneous terminal voltages to a zero direct axis voltage and a non-zero quadrature axis voltage, using a mathematical transformation, regulating the electrical frequency of the permanent-magnet machine such that the zero direct-axis voltage is adjusted to have a value of zero, determining a non-final electrical angle of the permanent-magnet machine by applying an integrator to the regulated electrical frequency of the machine, determining a final electrical angle of the of the machine by integrating the non-final electrical angle and an electrical angle from a previous calculation cycle, and regulating the current vector of the machine such that the current vector is perpendicular to the final electrical angle of the machine, thereby optimizing the torque of the machine.

Abstract: One embodiment relates to modernizing a technical system, in particular a producing system with the aim of obtaining economic and technical advantages. The technical system comprises at least one drive mechanism provided with at least one drive motor powered by a power element, a torque controller controlling the power element and a speed controller prescribing the nominal value of the torque (Msoll) for the torque controller. When the determination of the nominal value of the torque (Msoll) for the torque controller by the speed controller is deactivated, a standard drive element is available. The drive element comprises at least one speed controller, a torque controller and a power element. The nominal value of the torque (Msoll) of the torque controller of the drive motor is determined by a speed controller of the standard drive element.

Abstract: A system is used to measure a fan rotational speed. The system includes a main controller, a first socket coupled to the linear fan, a second socket connected to the main controller, and an optical fiber amplifier connected to the main controller. A PWM (pulse width module) fan is coupled to the second socket, the PWM fan sends a first rotational speed signal, which represent a rotation speed of the PWM fan, to the main controller via the second socket. The optical fiber amplifier is capable of radiating light on fan blades of the linear fan, and sensing light reflected by the fan blades to count a rotational speed of the linear fan, and generating a second rotational speed signal which represents a rotational speed of the linear fan. The optical fiber amplifier sends the second rotational speed signal to the main controller.

Abstract: The command signal processing unit outputs, when a first PWM frequency command signal is received, a high-PWM frequency command signal such that an asynchronous PWM control is performed at a PWM frequency of a predetermined constant frequency. The command signal processing unit outputs, when a second PWM frequency command signal is received, a low-PWM frequency command signal such that an asynchronous or synchronous PWM control is performed at a frequency lower than the above-described frequency. The PWM frequency control unit controls the PWM frequency such that an asynchronous PWM control is performed if a motor has a rotational speed less than a predetermined rotational speed and that a synchronous PWM control is performed if the motor has a rotational speed greater than or equal to the predetermined rotational speed, when a low-PWM frequency command signal is input.

Abstract: A method and apparatus for determining electrical parameters for commissioning a sensor-less permanent magnet synchronous machine uses knowledge of the rotor position to apply balanced pulses along the rotor magnet axis and perpendicular to the rotor magnet axis allowing measurement of q- and d-inductance at multiple current levels without substantial rotor movement.

Abstract: A control system for a motor, including a first detector providing signals indicative of the sign and zero-crossings of a supply voltage, and a second detector providing signals indicative of the sign and the zero-crossings of BEMF developed in the stator winding. A switch is driven to cause a first current pulse through the winding at a first delay relative to the zero-crossing of the supply voltage. The system checks if the BEMF has a first zero-crossing within a predetermined period of time preceding a third zero-crossing of the voltage, and if so, causes an opposite second current pulse through the winding with a second delay relative to the third zero-crossing of the supply. If not, the first current pulse is repeated, reducing or increasing the duration of the first delay if the first zero-crossing of the BEMF took place after or before the predetermined period of time.

Abstract: a method and a device for detecting the rotation of a brush-operated d.c. motor comprising a number of winding branches which are electrically connected between brushes, during the operation of the motor, by means of plates, according to the rotational angle. According to the invention, an alternating voltage signal is modulated on the basis of a supply direct voltage for the brushes, by which means the course of the complex resistance of the direct current motor is determined and used for the detection of rotation. In this way, the invention enables a cost-effective rotation detection that can be used in motor vehicle technology without requiring additional mechanical components.

Abstract: A method (100) is provided for controlling torque of an electric motor (12) including the step (106) of supplying drive current to drive the electric motor. The speed of the electric motor is monitored (108) and from the monitored speed, it is determined (110) when the motor has reached a steady state condition. The supply current is turned off (118) if the monitored torque of the electric motor exceeds a predetermined value (114) after the electric motor has reached the steady state condition.

Abstract: A synchronous-machine starting device includes an electric power conversion unit for converting supplied electric power into AC power for supply to the armature of the synchronous machine, a rotor position detection unit for detecting a position of the rotor of the synchronous machine based on an AC voltage in the armature of the synchronous machine detected by an AC voltage detection unit, an electric power conversion control unit for controlling the electric power conversion unit based on the position of the rotor detected by the rotor position detection unit, and an abnormality detection unit detecting a rotation abnormality of the synchronous machine based on the AC voltage detected by the AC voltage detection unit after supply of the field current to the rotor of the synchronous machine is started.

Abstract: A control device has a unit for preparing a pattern having first and second periods by comparing a triangular wave and a sine wave having an amplitude ratio set at each value of a modulation factor, and selecting one pattern corresponding to an instructed modulation factor, and a unit for applying a controlled voltage, set at low and high levels in response to first and second periods of the selected pattern, to a generator. The triangular wave has a cycle duration obtained by dividing the cycle duration of the generator by product of 3 and odd number, a crest having a level higher than the sine wave at a timing of each first period, and a trough having a level lower than the sine wave at a timing of each second period.

Abstract: An apparatus and a method for driving a sensorless motor are described and shown in the specification and drawings, where the method includes steps as follows. First, a control signal is acquired, where the control signal has information of a predetermined rotational speed. Next, energy is supplied and progressively increased to the sensorless motor, so as to rotate a rotor of the sensorless motor. Then, a position of the rotor is detected. Finally, the energy is gradually regulated so that the sensorless motor is maintained at the predetermined rotational speed.

Abstract: A hybrid drive device includes a first motor; an operative mechanism that drivingly connects the first motor to an engine of a vehicle; a second motor that is drivingly connected to a drive wheel; an engine rotation speed sensor that detects a rotation speed of the engine; a magnetic pole position sensor that detects a magnetic pole position of the second motor; a current sensor that detects a current flowing to the first motor; a sensorless motor control device that estimates a magnetic pole position of the first motor based on the current detected by the current sensor, and drivingly controls the first motor; and a second motor control device that drivingly controls the second motor based on the magnetic pole position detected by the magnetic pole position sensor.

Abstract: The machine in accordance with the present disclosure is an AC machine whose pole numbers can be switched (from pole p1 to pole p2), and whose number of series turns per phase N can be switched say from N0=Nrated to N1=N0/2. Furthermore, it employs an inverter so that the frequency can be changed from a low value (e.g., 5 Hz) to a high value (e.g., 200 Hz). Due to the combination of pole number and number of series turns switching/reconfiguration, a high torque at low speed (e.g., 0 rpm) and a high torque at high speed (e.g., 5,000 rpm) can be achieved, making mechanical gears obsolete. In addition, the output power of the motor can be increased at high speed in direct proportion to the speed increase.

Abstract: A motor driving integrated circuit comprising: a speed control circuit configured to control a rotation speed of a motor according to a speed control signal; a detecting circuit configured to detect whether the speed control signal indicates stop of rotation of the motor; and a shut-off circuit configured to shut off power supply to a circuit included in the motor driving integrated circuit when the detecting circuit detects that the speed control signal indicates stop of rotation of the motor.

Abstract: A method of controlling an electrical machine that includes exciting a phase winding with a supply voltage, and freewheeling the phase winding when current in the phase winding exceeds a threshold. The threshold is then adjusted in response to changes in the supply voltage and/or the speed of the electrical machine. Additionally, a control system that implements the method and an electrical machine comprising the control system are described.

Abstract: Disclosed is a method for detecting the current position of a rotor, in particular the angle of rotation of the rotor, an electromotor and a method for detecting the speed and/or the angle of rotation of an electromotor. The speed of the electromotor is hereby implied inter alia from the number of zero crossings of a comparison signal of the armature resistances or respectively conductances determined continuously in time and the average values of the armature resistances or respectively conductances determined continuously in time.

Abstract: In an apparatus for controlling a sensorless electric motor that drives an electric oil pump, in a case where a rotational speed of the motor deviates from a first range defined between a first upper limit value and a first lower limit value, a rotational speed limiting section generates a current command signal acting for controlling the rotational speed of the motor to suppress deviation of the rotational speed of the motor from the first range, and in a case where deviation of the rotational speed of the motor from the first range is continued for a predetermined time or more, the rotational speed limiting section sets a second range defined between a second upper limit value and a second lower limit value which are respectively displaced from the first upper limit value and the first lower limit value in a direction in which the deviation is continued.

Abstract: A power train for a transport vehicle is provided. The power train includes an electric motor comprising a shaft, a stator and a rotor, a power supply system receiving direct input voltage and delivering a polyphase voltage to the motor. The system has a modulation factor equal to the voltage amplitude of each phase of the motor divided by the direct input voltage, and includes a sensor for the rotational speed of the rotor.