Abstract: A drive control apparatus and method drives an AC motor by applying a rectangular wave voltage thereto. The apparatus estimates the torque of a rotor of the AC motor, and detects a torque deviation which is the difference between the estimated torque and a required torque of the motor. A controller controls a state of the rectangular wave voltage applied to the AC motor, through torque feedback control based on the torque deviation, so that the torque approaches the torque command value. The controller detects a current rotation speed of the motor, and switches, in a predetermined order, a plurality of predetermined rectangular wave voltage states corresponding to different phase values of the rectangular wave voltage. The switching timing of the rectangular wave voltage states is set to a timing that deviates from a reference timing determined based on the current rotation speed, by a length of time corresponding to the torque deviation.

Abstract: A motor control system is provided for controlling at least one motor driven mechanical actuator. The control system drives the motor according to a function of the actuator position. The system is further arranged to modify the motor speed to ensure that a predetermined power limit is not exceeded.

Abstract: An electric power steering control device is provided, which comprises a vehicle speed detector, a steering torque detector, a steering shaft reaction torque meter, a motor speed detector, a motor acceleration detector, a steering torque detector for calculating a base target current, a damping compensator for finding a gain of a damping torque based on a steering shaft reaction torque to calculate a damping compensation amount based on the damping torque gain and motor speed, an inertia compensator for finding a gain of an inertia compensation torque based on the steering shaft reaction torque to calculate an inertia compensation amount based on the inertia compensation torque gain and motor acceleration, and an adder for compensating a base target current by a damping compensation amount and an inertia compensation amount to calculate a target current.

Abstract: A disk drive has an arrangement for controlling the spindle motor and driving the disk contained therein as a function of the mode of operation such as a low acoustic noise mode or a low power consumption rate mode. For normal operation of the disk drive, priority is given to the low power consumption rate mode and the spindle motor is controlled and driven by a rectangular wave drive current. On the other hand, priority is given to the low acoustic noise mode according to a command issued from the host system to the disk drive so as to control and drive the spindle motor by a trapezoidal wave drive current.

Abstract: Controlling the torque of a motor by driving a centrifuge rotor connected to the motor; increasing a motor torque of the motor to a specified level; detecting revolutions per minute of the centrifuge rotor; adjusting the motor torque based on detected revolutions per minute; decreasing the motor torque to a constant torque over a range of revolutions per minute; and increasing the motor torque when the detected revolutions per minute are outside of the range.

Abstract: An operation control method of a reciprocating compressor is disclosed in which, in case that a motor is overloaded, an operation frequency is increased to render magnetic fluxes of a magnet and an input current are mutually offset, so that a reciprocating compressor can be stably driven even in case of the overload. For this purpose, while the reciprocating compressor using an inverter is operated at a rated frequency, a current load of the motor is measured and the measured load is compared with a pre-set reference load. Upon comparison, if the measured load is greater than the reference load, it is determined as an overload and the operation frequency is increased by as much as a certain value higher than an oscillation frequency, for performing an overload operation.

Abstract: A safety-guard detective circuit of a fan motor includes a resistor being adapted to limit a large current input into the motor driver circuit, and a discharge member being adapted to perform grounding to discharge the large current limited by the resistor. The resistor and the release member are commonly connected to the third lead of the motor driver circuit.

Abstract: A control unit for an electric power steering apparatus that controls a motor for giving steering assist force to a steering mechanism, based on a current control value calculated from a steering assist command value calculated based on the steering torque generated in the steering shaft, and a current value of the motor, wherein the control unit comprises a current dither signal generating unit for generating a current dither signal when the motor angular velocity is within a predetermined range of angular speed, and for adding the current dither signal to the steering assist command value.

Abstract: A method and apparatus for determining a motor fault in an electric motor (50) determines a calculated rotor position (&thgr;calc) of the electric motor. The calculated rotor position (&thgr;calc) is compared to a measured rotor position (&thgr;meas) of the electric motor (50) to determine a rotor position error (&thgr;err). A motor fault in the electric motor (50) is determined when the rotor position error (&thgr;err) exceeds a predetermined maximum rotor position error (&thgr;err—max).

Abstract: A control system for an electric power steering apparatus detects calculation anomalies in a CPU regardless of the magnitude of a modified control quantity. The CPU has a basic control quantity calculating means for calculating a basic control quantity to drive a motor based on an output from a torque sensor, and a modified control quantity calculating means for calculating a modified control quantity corresponding to the steering conditions (for example, steering speed) of the steering wheel. The CPU-calculation monitoring unit has a first anomaly deciding means for deciding whether the calculation result of the basic control quantity calculating means is normal or anomalous in light of the output from the torque sensor, and a second anomaly deciding means for deciding whether the calculation result of the modified control quantity calculating means is normal or anomalous in light of the steering conditions. The motor is deactivated if anomalies are detected.

Abstract: The present invention is directed to a centrifugal pump wherein voltage and current data are detected from voltage and current sensors in the pump motor. A power signal is then generated from the voltage and current data and spectrally analyzed to determine the low flow or cavitation in the pump. As such, unwanted operational conditions resulting from improper pump operation may be detected and a warning or maintenance flag provided without additional transducers and other instruments on the motor or pump.

Abstract: A microcontroller for controlling operation of a safety clutch of a hand-held electrical power tool and which is arranged in a force transmitting chain of the tool, with the microcontroller including a unit (2,5,4;8) for processing at least one parameter of the power tool and for outputting a resulting parameter in form of a calculated torque (M1), and a control unit (7) for comparing an actually measured torque (M) with the calculated torque (M1), and for outputting a control signal (&thgr;) when a difference between the actually measured and calculated torques exceeds a predetermined threshold.

Abstract: A device includes at least one magnetic field generator placed on a first plane of a right section of a shaft and at least one magnetic field detector placed in a second plane of a right section of the shaft. The detector produces a signal proportional to the torque following the relative angular shift of the field generator in relation to the detector, the magnetic field generator having a magnetic structure supported by support mechanisms connected to the turning shaft. The magnetic field detector is located roughly opposite the magnetic field generator and is supported by support mechanisms connected to the turning shaft.

Abstract: A control apparatus of an electric power steering system has calculating means, controlling means, determining means suppressing means, canceling means. Calculating means calculates an assist current value that corresponds to the assist force based on steering torque of a steering wheel. Controlling means executes assist control of the motor based on the assist current value. Determining means determines an abnormality in the circuit. Suppressing means suppresses the assist control when an abnormality in the circuit is determined. If the determination of an abnormality has continued longer than a predetermined time since the suppression of the assist control, the suppressing means opens relay means that permits electric power to be supplied to the motor. When it is determined that the circuit returns to normal with the assist control suppressed, the canceling means cancels the suppression of the assist control.

Abstract: A momentum-decoupled drive train for a machine, includes a servo motor, a first drive element and a second drive element. The second drive element is movably supported relative to a machine bed in a movement direction of a machine carriage. Reaction forces which are caused by the movement of the machine carriage, are compensated by a corresponding counter movement of the second drive element or a reaction carriage connected thereto, and hence are not transferred to the machine bed. The position of the machine carriage relative to the machine bed is controlled by correcting the position setpoint value with actual position and velocity data for the reaction carriage relative to the machine bed.

Abstract: It is an object of the present invention to overcome various drawbacks of a conventional oil pulse wrench by using an electric motor, to reduce a reaction force and to fasten a screw with high precision. To achieve the object, the invention provides a control method of a screw fastening apparatus using an electric motor as a rotation driving source, the method comprising the steps of; intermittently supplying current pulse DP to the motor, detecting an actual torque at predetermined time intervals, maintaining a current value when a detected torque value does not exceed a maximum value of past detected torques value and increasing the current value by a predetermined amount when the detected torque value exceeds the maximum value of the past detected torque value, and stopping the supply of the current pulse DP when the detected torque value reaches a target value TQJ.

Abstract: A method and an apparatus produce current values dependent on the position of the accelerator pedal controlling the power of one or more electric drives for moving a mobile device that is energised by a fuel cell. The time required by the drive or drives to respond to a change in the desired current value produced as a function of the position of the accelerator pedal is kept as small as possible by producing a current value—convertible into a desired torque value—which is held continuously at a value sufficient to ensure that the output voltage of the fuel cell just avoids undershooting a critical limit.

Abstract: The apparatus comprises a motor, a motor driver, a pulse generator, an MCU incorporating a memory, and an open/close switch. The MCU compares the motor load torque detected at the time of opening or closing the window, with a reference value stored in the memory; when the torque considerably exceeds the reference value, it concludes that there is a foreign object caught in the window and stops or reverses the motor and inactivates the function of foreign object detection until there is no transitional torque fluctuation in the transitional period from a start of the motor. The MCU compares the torque variation per unit time with a permissible variation range stored in the memory; when the number of successive torques which fall within the permissible variation range reaches a maximum permissible number of such successive torques stored in the memory, it activates the function of foreign object detection.

Abstract: In an intelligent electric motor, the rotating speed and performance of a conventional electric motor is changed based on a means controlled by a computer, and the means is installed in the housing of the intelligent electric motor. For example, in the intelligent AC motor, the three-phase power is connected to the three-phase stator winding by three groups of control gates. All of the gates are switched on or off by a signal from the control means. When each of the three groups of control gates is switched on sequentially, the three-phase power is connected to the three-phase stator winding of the three-phase intelligent electric motor at the speed &dgr; in turn, so that the speed of the rotating magnetic field of the intelligent electric motor n0 is increased by a sped &dgr;. Therefore, the actual speed of the motor, n′0, is equal to n0±&dgr;, so the speed and performance of the motor is changed.

Abstract: A method for generating a compensated torque command signal to be applied to an electric power steering motor is disclosed. In an exemplary embodiment, the method includes generating an assist torque command signal responsive to a measured vehicle speed and an input steering torque signal. An assist dependent damping torque signal is generated, the assist dependent damping torque signal responsive to the assist torque command signal, the measured vehicle speed and a compensated motor velocity output value of the electric power steering motor. The assist dependent damping torque signal is then subtracted from the assist torque command signal.

Abstract: In an air conditioner having a control unit receiving a power from a switching power supply, a supplied voltage for the control unit is reduced to a possible lowest voltage for the unit to operate. This arrangement provides the air conditioner with less electromagnetic wave noise of the switching power supply, with a quick check and repair, and with having a motor-driven compressor quick start.

Abstract: A method and an electrical drive assembly 10 which operates in accordance with the method. Particularly, the drive assembly 10 includes a diagnostic portion 18 which compares a voltage signal which is communicated to an electrical machine 28 and a voltage signal which is selected by use of a desired torque command signal 33 and which provides a diagnostic of the electrical drive assembly 10 based upon the comparison, effective to provide a positive indication to a user of the drive assembly.

Abstract: A controller K calculates a command torque by correcting the required torque w1 with a correction based on a motor rotation speed Nm, and controls an electric motor based on the command torque T. The command torque w1 is regarded as one content of an outside input W to the controller K. A difference between the rotation speed of the electric motor outputted by the actual model describing an actual response of the electric motor and another rotation speed of the electric motor outputted by a reference model describing ideal performance and vibration reduction is regarded as one content Z1 of controlled output Z from the controller K. Moreover, a characteristic variation depending on vehicle types and so on, a torque ripple, and a sensor noise are described by weight functions wm1, wm2 and wn. Then a pertubative output w2 and a sensor noise w3 are regarded as the remaining contents of the input W. An output of the weight function wm2 is regarded as the controlled output Z.

Abstract: A fuel gas compression system includes a system which operates on direct current, a system which operates on alternating current and a system which is capable of operating on either direct current or alternating current. In the system that operates on either direct current or alternating current, a jumper is provided which is placed in the circuit when an alternating current is provided. When a direct current is provided, the jumper is removed from the circuit.

Abstract: A method and an apparatus for controlling release of a hoisting motor brake in a hoisting apparatus, where electricity is used as the driving force and a squirrel cage motor as the hoisting motor for hoisting or lowering a load attached to a hoisting member of the hoisting apparatus. Controlling of brake release comprises measuring the current and supply voltage of the hoisting motor after the start-up period of the hoisting motor and determining a variable which describes the load of the hoisting apparatus from the current and supply voltage. The variable describing the load is compared with a pre-determined limit value and hoisting or lowering of the load is interrupted if the variable describing the hoisting apparatus load exceeds the limit value set for the hoisting movement when the load is hoisted or if it exceeds the limit value set for the lowering movement when the load is lowered.

Abstract: A balanced bi-directional current source is provided, which includes first and second current output terminals, a current control circuit, first and second amplifiers and first and second sense impedances. The current control circuit has a reference input, a feedback input, and a control output, which is based on the reference input and the feedback input. The first amplifier has a first amplifier input, which is coupled to the control output, and a first amplified output. The second amplifier has a second amplifier input, which is coupled to the control output, and a second amplified output, which is inverted relative to the first amplified output. The first sense impedance is coupled in series between the first amplified output and the first current output terminal and has a feedback output which is coupled to the feedback input. The second sense impedance is matched with the first impedance and is coupled in series between the second amplified output and the second current output terminal.

Abstract: An electric power steering system is provided which employs an electric motor as a driving source to apply a steering assist force to a steering mechanism. The system includes: an operation degree detecting section for detecting an operation degree of an operation member; a motor current detecting section for detecting an electric current flowing through the electric motor; and a steering angle detecting section for detecting a steering angle of the steering mechanism. A reaction force from a road surface is computed on the basis of outputs of the operation degree detecting section, the motor current detecting section and the steering angle detecting section, and a driving target value of the electric motor is determined on the basis of the reaction force and the operation degree of the operation member.

Abstract: An electric power assisted steering system of the kind in which an electric motor is operatively connected to a steering assembly through a gearbox to apply an assistance torque to the steering assembly and in which the steering assembly includes a steering column coupled at one end to a driver's handwheel and at the other end to steerable wheels, a means being provided for generating a signal representative of the velocity of rotation of the steering column. The system includes a high pass filter which is adapted to generate, for frequencies below a prescribed threshold, a signal at least approximately proportional to steering column acceleration and representative of the inertia of the rotor of the electric motor, the latter signal being arranged to be used to compensate for the motor rotor inertia in an overall assistance torque demand as developed by the system.

Abstract: When air passing through a condenser and a radiator passes through a cooling fan in a state where a driving circuit controls a voltage applied to a motor to be constant in accordance with a motor application voltage instructed by a control signal Sa, a motor current Im decreases. A comparator compares the motor current Im with a reference current set on the basis of a motor voltage Vm. When the motor current Im decreases to a value equal to or lower than the reference current, a switching circuit is switched to select an output signal of an operational amplifier. The operational amplifier performs a feedback control so that the motor voltage Vm coincides with a minimum application voltage VL.

Abstract: A vehicular system includes a controller and an electric motor in signal communication with the controller for receiving current and rotating at speed; while the controller includes a first function responsive to a signal indicative of the speed of the electric motor, a filter responsive to a signal indicative of the heat generation rate of the vehicular system, a second function in signal communication with the first function and the filter, and a limit calculation function in signal communication with the second function for providing a motor current limit responsive to the second function; wherein a method for controlling the vehicular system includes receiving a signal indicative of the heat generation rate of the vehicular system, receiving a signal indicative of a speed of the electric motor, providing a scale factor or an overload value in response to the received signal indicative of speed, filtering the received signal indicative of heat generation rate in correspondence with a time constant, process

Abstract: A power steering system according to the invention includes a running speed detector 1 for detecting the running speed of a vehicle, an operating speed detector 11 for detecting the operating speed of a steering wheel which is the turning speed of the steering wheel, a controller 2 for calculating a target steering speed which is a target turning speed for a steering mechanism 14 based on the operating speed so detected and comparing an actual steering speed which is an actual turning speed by the steering mechanism 14 with the target steering speed for calculation of a deviation and a driving device 15 for driving the steering mechanism 14 in response to the deviation so calculated, the controller being configured to change a set ratio of the target steering speed to the operating speed so as to increase or decrease in response to the running speed of the vehicle.

Abstract: A system and method for improving transient speed response of electric motors includes a comparator that determines a difference between a current reference and an adjusted current reference generated by the electric motor drive system, and an integrator the receives and integrates the difference between the current reference and the adjusted current reference over time to yield total accumulated lost current-seconds, and outputs at least a portion of the integrated difference between the current reference and the adjusted current reference as current-seconds to be added to the current reference. The present invention keeps track of the total accumulated loss-seconds due to current rate limitations, and restores the total accumulated lost current-seconds to the system when current becomes available.

Abstract: A motor control system is provided for controlling at least one motor driven mechanical actuator. The control system drives the motor according to a function of the actuator position. The system is further arranged to modify the motor speed to ensure that a predetermined power limit is not exceeded.

Abstract: The control device carries out a control of the induction machine based upon a flux estimation performed by means of a Luenberger state observer, the estimation error of which can be defined by means of a matrix having a plurality of eigenvalues, the magnitude of each of which is proportional to the magnitude of a respective pole of the induction machine, and the phase of each of which is rotated with respect to the phase of the corresponding pole of the induction machine by a given angle of rotation.

Abstract: An applied force Td is estimated by an observer. A gain A is multiplied by a value obtained by subtracting the estimated applied force Td from commanded force Fe. From this multiplied value, a product of a speed feedback amount and a gain Kv is subtracted to obtain a torque command. With this torque command Tc, a servo motor is driven. Since a feedback control of the applied force is performed, response is fast, and an applied force between welding tips and an object to be welded can be accurately controlled. Feedback control of an applied force, whose vibration is prevented, can be performed by adjusting the gains A and Kv.

Abstract: A rapid increase in motor current (di/dt above a predetermined threshold) causes the motor control system to enter pulse mode operation in-which the motor current is pulsed on and off rapidly to dislodge the workpiece obstruction or binding condition that would otherwise lead to a motor stall. When the workpiece obstruction or binding has been cleared, the motor resumes normal operation.

Abstract: A novel method is proposed for controlling the torque of a PM brushless motor with sinusoidal back-emfs without current sensors by computing the required input phase voltages with measured rotor position and speed and known machine parameters. These voltages are fed to the machine at an angle computed in terms of input parameters and the phase voltage with respect to their back-emfs so that phase currents are aligned with their back-emfs to exactly mimic the performance of the current mode controller.

Abstract: A tan having a fan wheel and an electric motor driving it, and a control unit for controlling the motor output as a function of fan-specific parameters. An actual-value signal corresponding to an actual rotational speed of the fan is measured and compared with a control signal corresponding to a required speed, and the actual speed is adjusted to the required speed by means of the control unit, wherefore the actual speed and the actual motor current or supply current are measured and conducted to a microcontroller as input signal variables, whereby the fan-specific data such as wheel diameter, density of the conveying medium, fan coefficients, motor coefficients, and a preset artificial characteristic curve ps=ƒ({dot over (V)}s ) are stored in the microcontroller as default values.

Abstract: This invention provides a process for determining a desired torque (load) value for a load-dependent current generating system, such as a fuel cell system, in an electric vehicle. The process calculates load based on various driver demands such as accelerator position, brake position, Key on/off, Gear selector position, and system component temperatures. Additionally, the process considers the amount of current available from the load-dependent current generating system and matches that current to the current drawn by the electric motor. The process can be applied to a direct current (DC) electric traction motor or an alternating current (AC) induction motor.

Abstract: The controller possesses a reference torque signal setting unit which generates a reference signal which becomes high when the detected signal becomes high based on at least the signal detected from the steering torque sensor; a correction torque signal setting unit which generates a correction torque signal (DN*RT*RV), which becomes high when the detected signal becomes high based on at least the signals detected from the revolution number sensor for the electric motor and from the vehicle speed sensor; and a target torque signal calculator which subtracts the correction torque signal from the reference torque signal (DN*RT*RV) to output a target torque signal (DT+−DN*RT*RV) to the electric motor; and the controller also making the correction torque signal high when failure of the vehicle speed sensor is detected.

Abstract: In a method for current regulation of permanently excited synchronous motors for guided missiles with an electromechanical actuating drive for the rudder, the commanded current is always guided orthogonally to the magnet-wheel flow. Further: a) from measured current of two voltage phases, a measured magnitude of a current-space pointer is determined and an error value for the current is added to a desired value of the amount via a correction regulator; and b) from measured current of two voltage phases as well as from the angle command of the current-space pointer, a measurement for the angle error is determined and added to the desired angle value via a correction regulator. The method according to the invention can be implemented with little hardware expenditure and in a compact design size, even for high rotational speeds of >10,000 min−1. Current-regulating methods used heretofore, which involve frequency response compensation in polar coordinates, cannot be used with synchronous motors, i.e.

Abstract: An automatic torque-based control system is disclosed which can react to end points and obstructions through a torque sensing arrangement. This torque sensing can be accomplished through use of an electromagnetic interference device so that a change in torque is immediately detected and a modulation in operation of the shade can be effected. Rotating pitched disks elastically connected to each other can be used to act as the torque sensor for drive systems, and in particular and preferred embodiments, for window shade systems. Multiple elastic elements can permit multiple location sensing as well as non-zero, no-load, and fully loaded torque sensing and reaction.

Abstract: Two external rings and an internal ring form an assembly that is connected to a column so it rotates with it, to which column the torque to be measured is applied. Elastically deformable members connect the internal ring to one external ring, and the other external ring remaining essentially unstressed. A measurement device, such as, for example, a probe having at least one with Hall effect device, measures relative displacement of the two external rings to determine the torque applied. The invention also concerns the steering devices equipped with such torque sensors, for example, for power or assisted steering.

Abstract: A pump control system and method employs a variable drive for controlling the speed of an AC electric motor driving a cyclic load. A real-time tuning of the frequency and voltage of the AC input to the motor allows a controlled variation of a cycle speed of the cyclic load. The control system and method adjusts motor speed according to a desired motor speed characteristic for different portions of a complete cycle and over multiple cycles of the cyclic load. The variable drive rectifies a poly-phase AC power input to provide a source of DC power on a DC bus and periodically samples the DC bus current and DC bus voltage across the DC bus to optimize the motor operation.

Abstract: A system and method for providing rotation control stability within a disk drive. In accordance with the system of the present invention, a disk storage medium on which information is recorded is driven to rotate by a multiphase-phase DC servomotor. An actuator is utilized for loading and unloading the head to and from the disk storage medium. A load/unload controller commands the actuator to load or unload said head. In order to effectively compensate for an abrupt change in load on the servomotor caused by loading the head onto the disk storage medium, a slew rate switching unit is utilized to alter a slew rate of current supplied to the three-phase DC servomotor, based on a loading start command issued by the load/unload controller.

Abstract: A control apparatus for an electrical power steering apparatus whereby a high output, small motor can be achieved, variation in the relative magnetization and coil positions and position detection precision requirements can be alleviated, steering feeling is improved, and apparatus cost is reduced. In a control apparatus for an electrical power steering apparatus for controlling a motor applying steering assistance force to a steering mechanism based on a current control value calculated from the current of a dc motor or brushless motor and a steering assistance control value calculated based on steering torque occurring at the steering shaft, torque ripple of the motor is suppressed to 10% or less.

Abstract: An electric power steering system is provided which employs an electric motor as a driving source to apply a steering assist force to a steering mechanism. The system includes: an operation degree detecting section for detecting an operation degree of an operation member; a motor current detecting section for detecting an electric current flowing through the electric motor; and a steering angle detecting section for detecting a steering angle of the steering mechanism. A reaction force from a road surface is computed on the basis of outputs of the operation degree detecting section, the motor current detecting section and the steering angle detecting section, and a driving target value of the electric motor is determined on the basis of the reaction force and the operation degree of the operation member.

Abstract: A motor torque control device of an electric vehicle sets creep torque in accordance with a vehicle speed sensed by a vehicle speed sensor, and sets acceleration torque in accordance with an accelerator control input sensed by an acceleration sensor. Then, the motor torque control device calculates a torque command value by adding the creep torque to the acceleration torque. It is therefore possible to quickly raise the acceleration torque immediately when an accelerator is operated to start the vehicle. It is also possible to prevent a sharp decrease in the torque command value since the torque command value reflects the creep torque even after the start of the vehicle.

Abstract: The present invention provides a motor drive controller for a vehicle having an engine and a motor disposed therein as a vehicle-propulsion system, the motor having both driving and power-generating functions, comprising: an engine controller for controlling a running state of the engine; motor controller for controlling both driving and power-generating states of the motor in a manner independent of control over the engine taken by the engine controller; vehicle velocity-detector for detecting the speed of the vehicle and engine speed-detector for detecting revolutions of the engine; and engine load-detector for detecting an engine load. The motor controller includes a map defined by respective detection signals from the vehicle velocity-detector and the engine speed-detector, enabling gear position to be calculated.

Abstract: A speed controller circuit for a motor including a ramp function generator having a first input connected to a source of a speed demand signal and a second input connected to a ramp step signal. The ramp function generator develops a frequency ramp that has a slope is initiated by the speed demand signal which is adjusted in response to the ramp step signal. The ramp function generator also provides a frequency signal wherein the ramp function increases or decreases the frequency according to the speed demand. A V/F circuit to the ramp function generator and a space vector modulation circuit are connected to the V/F circuit. The output of the space vector modulation circuit is applied through power switching devices to the motor for speed control. A PI controller circuit is connected to a motor current feedback signal and to a maximum current signal, which provides the current limit of the control system.