Abstract: A start circuit for a single-phase AC motor controls the current through the start or auxiliary winding based on time rate of change of voltage or current, or based on the current or voltage dropping or rising some fraction from inrush value, i.e., to 50% of initial start current or to 150% of initial start voltage. The circuit can also include a default timer to time out the start current after some preset period between 300 and 1000 milliseconds.

Abstract: A motor driving system according to the present invention comprises a power converter for supplying a brushless motor having a permanent magnetic rotor with pulse-width modulation controlled driving power; a magnetic-pole position detector for detecting a magnetic-pole position of the motor rotor; a speed detecting means for detecting a rotational speed of the motor according to an output signal of the magnetic-pole position detector; a speed control operation means for outputting a deviation of an output signal of the speed detecting means from a speed instruction; a means for generating a plurality of instruction signals in response to an output signal of the speed control operation means; a means for generating modulated waves by selecting one of the plurality of instruction signals according to the output signal of the speed control operation means; and a means for controlling the power converter by means of pulse width modulation according to the modulated waves.

Abstract: An electric drive apparatus and method for controlling AC motors wherein the motor output is a function of the AC input power to the electric drive. Means are provided for detecting the voltage being supplied by the source of AC power to a drive circuit, and for controlling the output to the multi-phase AC load based on the detected power level. A controller monitors the motor voltage, current, and speed or frequency while also receiving a command for torque or torque-producing current. The method provides for the operation of the drive circuit in the event of either a partial or complete loss of AC input power. During such an occurrence, the controller will cause the circuit to generate sufficient negative torque to cause a power flow from the motor to the drive circuit to substantially equal the inherent losses in the drive and motor to avoid loss of energy from the DC filter of the drive circuit. Motor torque and speed can be quickly restored when the input power is re-established.

Abstract: A method of regulating a rotary machine powered by a voltage inverter receiving, as input a control voltage delivered by a regulator servo-controlling the electromagnetic torque on a reference value, the regulator receiving as inputs the reference value and sat least one sampled signal representative of the torque of the machine, and proceeding at each sampling instant, to predict the torque value at a following sampling instant and to modify the control voltage accordingly.

Abstract: Provided to the motor controller is means which can alter a conversion ratio with which a current value detected by a current detector is converted into a unit (such as voltage) easily usable in motor current control. According to the maximum current value of the motor and the demagnetization limit current of the motor, an optimum conversion ratio is selected and switched over. By making it possible to select and preset a conversion ratio, a plurality of motors can be controlled by one motor controller. Therefore, restrictions imposed on the combination of the motor controller and the motor are lightened.

Abstract: A three-phase a.c. motor for operation with a three-phase mains supply (1), with three single- or multiple-strand windings (2u, 2v, 2w) in a star configuration (2) in which terminals (U2, V2, W2) at the neutral ends of the windings (2u, 2v, 2w) are accessible outside the set of windings (2), with an electronic switch (4) so constructed and so connected by way of switch terminals (U3, V3, W3) to the neutral-end terminals (U2, V2, W2) that the latter can be electrically connected to one another during a process of turning on and disconnected from one another during a process of turning off, and with a control circuit (5) designed to control the electronic switch (4) and connected to the latter. By integration of the electronic switch (4) and the control circuit (5) within the terminal box of the three-phase motor, both the space required and the number of electronic components can be dramatically reduced in comparison to known three-phase motors.

Abstract: A magnetic bearing apparatus for the journalling of a body (3), in particular of a rotor (3), comprises a stator (2) with a control winding (22) having at least three loops (22a, 22b, 22c) for the production of a magnetic control field by means of which the position of the body (3) relative to the stator (2) can be regulated, with each loop (22a, 22b, 22c) belonging to a different electrical phase, and a control device (4) which in a first operating mode supplies each loop (22a, 22b, 22c) with in each case a phase current (Ia, Ib, Ic) or in each case a phase voltage (Ua, Ub, Uc) as a control parameter. Means are provided in order to regulate the control parameter for each loop (22a, 22b, 22c) independently of the control parameter for the other loops (22a, 22b, 22c) as well as a monitoring unit (5) which can switch the bearing apparatus into a second operating mode in which a reduced number of phases, which is at least two, produces the magnetic control field.

Abstract: An apparatus comprised of a processor, a display, and a current measuring device is provided. The current measuring device is adapted to measure the current in a first winding of a first stator of an alternating current motor. The processor causes a first message to be placed on the display if the current in the first winding of the first stator falls outside a first range of values. The first high value and the first low value can be stored in a memory device. The current measuring device may have two input ports, for measuring current in first and second windings of the first stator of the alternating current motor. The processor may cause a second message to be placed on the display if the current in the second winding of the first stator falls within a second range of values. A first relay device for selecting between a first start signal and a first run signal. During a start time period, the processor causes the first start signal to be transmitted to the first winding of the first stator.

Abstract: An apparatus for eliminating variable offset values of current detecting signals and its method having a current detector for detecting feedback current from a three-phase AC motor and for converting the feedback current into voltage detecting signals containing offset elements, differential amplifiers for differentially operating a feedback analog offset signal and the voltage detecting signals, output amplifiers for amplifying the differentially operated voltage detecting signals to fit within the input range for controlling, an analog/digital converter for converting the amplified signals into digital signals, a control part for adding up the digital signals to a digital offset value and for comparing the digital offset value with a predetermined offset command and for applying a proportional plus integral function to the compared result and for outputting a digital offset signal of a pulse-width modulation waveform, and a digital/analog converter for converting the digital offset signal into the analog of

Abstract: A controller for electric vehicles comprising a vector control inverter for controlling motors, which drive wheels of the electric vehicles, by dividing the primary current of the motors into an exciting current component and a torque current component, and controlling respective of the current components based on a respectively designated command, characterized in further comprising a dectector for detecting a wheel velocity (including a rotor frequency of the motor proportional to the wheel velocity), a detector for detecting slipping and skidding of the wheel based on a differential value (a changing rate with time) of the detected wheel velocity, a dectector for detecting re-adhesion of the wheel based on the differential value and a twice differential value of the detected wheel velocity, and an adjuster for adjusting the designated command for the torque current component in response to the detectors.

Abstract: A diagnostic system for electric motors, such as those used in automotive applications. The system comprises a controller for supplying a desired command current to said electric motor, a sensor for measuring the rotational speed of the motor, a sensor for measuring the actual current supplied to the motor by the controller, a diagnostic control unit adapted to receive the measured rotational speed, measured supplied voltage, and a command current level value as inputs. The diagnostic control unit further comprises circuitry to calculate an estimated actual current drawn by the motor and to signal an error condition if the estimated actual current is not within a calculated valid range.

Abstract: An improved force motor current control including feed-forward and feed-back control terms summed to determine a force motor activation for achieving a current command. The feed-forward control term estimates the force motor activation required to achieve the current command, based on the force motor temperature, the system voltage and a model of the force motor circuit. The feed-back control term compares an expected response to the actual response and develops a control term that corrects for modeling errors, providing disturbance rejection and improved command following. The closed-loop feedback error is used to enable adaptive correction of the feed-forward control so that the estimated force motor activation more nearly produces the commanded current.

Abstract: There is provided a controlling device for an AC motor having a structure in which a current of a three phase brushless DC motor is detected and then converted to a rotor coordinate system, to separately control a torque split current (q axis) and an exciting split current (d axis), wherein an offset is estimated with a DC component of a multiplied value of the values corresponding to a d axis voltage command which is an output of an exciting split current controller and an electrical angle, and the detected current is compensated for, so that an offset of a current detector may be estimated and compensated for during its operation without stopping its rotation and the motor can rotate smoothly without a torque ripple, even in the case in which the current detector has an offset error or in the case in which an offset changes due to a temperature drift.

Abstract: A magnetic bearing system includes a rotor shaft 1, stationary electromagnetic pole, a radial displacement sensor 5 for detecting the position of the rotor shaft 1 with respect to the electromagnetic polarity, and a control circuit 220 which supplies a control current in accordance with an output from the radial displacement sensor 5. A permanent magnet 20 is disposed in the magnetic bearing so as to constitute a portion of a magnetic member 10 which forms a magnetic circuit between the rotor shaft 1 and the electromagnetic pole. The position where a balance exists between an attraction force developed in the permanent magnet 20 and static force, which acts on the rotor shaft 1 when no load is imposed on the rotor shaft 1, is set as a target position for the rotor shaft 1.

Abstract: An induction motor control system (10) for electric vehicles having a DC power supply (12), an inverter (14), an induction motor (16), and a clamping unit (26). The clamping unit (26) applies a clamping value iq_clamp to a real torque current command iq*. The clamping value iq_clamp is calculated in a maximum torque current calculation unit 28 and is based on predetermined maximum settings for the motor power Pmax and torque Tmax. The clamping value iq_clamp is applied such that the torque current command iq* cannot exceed the clamping value iq_clamp, whereby the induction motor produces 16 output power Pout and torque Tout that is always less than the predetermined maximum settings, Pmax and Tmax.

Abstract: The invention relates to a regulation system for an asynchroNOus motor by field oriented control, reacting to a torque set value (T) and a flux set value (&phgr;). The flux set value is supplied from the torque set value by an operator carrying out first order low pass filtering (40) and calculating the square root (42) of the result of the filtering.

Abstract: A method and circuit are presented for operating a polyphase dc motor in which substantially sinusoidal drive voltages are applied to the windings of the motor in predetermined phases. Zero crossings of currents flowing in respective windings of the motor are detected, and phases of the drive voltages are adjusted to have zero crossings substantially simultaneously with the detected zero crossings of the currents flowing in respective windings of the motor. The method and circuit results in motor operation with significantly reduced acoustic motor noise.

Abstract: A control algorithm or method for use in controlling a voltage-fed induction machine. The control algorithm includes the following steps. The DC link voltage supplied to an inverter driving the induction machine is monitored. When the DC link voltage is high enough, the algorithm controls the amount of current supplied to the induction machine to provide current controlled operation of the induction machine. When the DC link voltage is not high enough to control the current under transient conditions, the induction machine is controlled by imposing the maximum possible phase voltage and optimal slip angle on the machine to provide maximal torque per ampere operation of the induction machine. The maximal torque per ampere operation is performed when either of the following conditions is met: a) the torque level required by the induction machine is such that efficiency optimization cannot be performed, or b) current regulators approach saturation.

Abstract: This invention relates to a brushless motor driving system for driving an outdoor fan of an air conditioner. The driving system comprises a Hall probe for detecting a position of a rotor of a brushless motor, an inverter circuit consisting of a plurality of switching elements connected in bridge-connection, the inverter circuit supplying ON-OFF electric current to stator coils of the brushless motor, and a control means for switching the switching elements of the inverter circuit based on the output signal of the Hall probe. Before starting the motor, the control means controlls the switching elements to supply DC PWM-controlled current to the stator coils of the motor in synchronization with the output signal of the Hall probe, so that the rotor is braked, stopped and set to home position.

Abstract: An estimated rotation angular velocity □r0 and an estimated secondary resistance Hr0 are processed using a first feedback gain H1 under a condition that a first state deviation E1 is in phase with a quadrature component of an estimated secondary magnetic flux □r01. An estimated primary resistance Rs0 is processed using a second state deviation H2 under a condition that a second state deviation E2 is in phase with an estimated primary current 02. These values are used to control the speed of an induction motor without an angular velocity detector.

Abstract: A prime mover such as a microturbine generator is operated to generate dc power, and an inverter is controlled to convert the dc power to ac power. The ac power is supplied to an electric motor. The frequency of the ac power is ramped up during motor startup to reduce motor inrush current. The frequency or current of the ac power may be varied in response to process requirements during normal operation of the motor.

Abstract: The arrangement has a motor (16) which has an electronic commutator and during operation is supplied from alternating current (AC) mains (L, N) via a rectifier (52) connected thereto, and a direct current (DC) link (22, 58) connected to said rectifier (52) and having a DC voltage (UZK) of greater than 100 V. The motor has an arrangement (25, 27) fed from said alternating current mains (L, N) via a transformer (24) and for supplying electronic components (14, 20, 26) of the motor with a DC voltage, and a user interface (12) provided for transmission of data to or from the motor (16). Said user interface, with which a current supply (24b) electrically isolated from the motor (16) is associated, electrically isolated from the motor (16).

Abstract: A method for controlling the starting, stopping and operation of an AC motor is provided. Each winding of the AC motor is interconnected to an AC source by a thyristor switch and a bypass contactor for providing voltage and current to the AC motor. The method includes a steps of sequently firing a pair of tyristor switches to bring the AC motor to full operating speed. Once at operating speed, the bypass contactors are closed. Upon detection of a voltage drop across a thyristor switch, the thyristor switch is fired immediately to transfer motor current from the bypass contactor to the thyristor switch in order to maintain voltage and current to the AC motor.

Abstract: In an injection molding machine whose movable part is driven by an AC servo motor, d-phase current in a direction of magnetic flux produced by a field system and q-phase current orthogonal to the d-phase current are obtained through d-q conversion on the basis of drive current of the AC servo motor and a phase of a rotor. Control of current is made in DC mode on condition that the d-phase current is set to zero, and the q-phase current is adapted for a current command. Control of current in the DC mode as described above is designed to advance the phase of the q-phase current command, which is an effective component of a current command at the time of the occurrence of magnetic saturation, thereby preventing, the influence of magnetic saturation to lessen the fall of torque.

Abstract: A vector control apparatus having a DC braking function which is insusceptible to trip even upon DC braking and scarcely suffers vibration upon stoppage is provided.The control apparatus includes a DC braking control arithmetic unit 1 and switches S1, S3 and S4 controlled thereby, wherein in a vector control mode, the DC braking control arithmetic unit 1 sets all the switches S1, S3 and S4 to position a for realizing the vector control. When a DC control state is to be validated from the above-mentioned state, phase of voltage vector is calculated to change over the switches S1 and S3 to position b, and the absolute value of the q-axis current is compared with a reference value .alpha.. When the absolute value of the q-axis current is smaller than the reference value .alpha., the switch S4 is changed over to the position b to thereby effectuate only the d-axis current control.According to the present invention, there is provided a vector control apparatus having a tripless DC braking function.

Abstract: A method for detecting a change in motor load and/or motor speed is provided. The method includes the step of measuring the number of transitions (i.e., state changes) of a phase control signal in a motor phase of the motor. The method also includes the step of comparing the number of transitions to a predetermined number that is indicative of a predetermined motor load and/or motor speed. The predetermined number may comprise the number of transitions in a prior phase control signal of the motor. A method for controlling a motor responsive to a change in motor load and/or motor speed is also provided. The method includes the above-described steps for detecting a change in motor load and/or motor speed and further includes the step of selecting one of a plurality of operating modes for the motor responsive to a comparison value obtained by comparing the measured transition number with the predetermined transition number.

Abstract: A drive for controlling the speed of an AC induction motor from an inverter. The inverter applies a voltage to the stator winding of the motor in accordance with the magnitude of a first input signal. The inverter causes the voltage to be applied at a frequency determined by the magnitude of a second input signal to the inverter. The drive includes motor speed sensor and a motor speed reference signal source coupled to a speed regulating amplifier. A slip detector determines the slip of the motor from the speed of the rotor and the energization frequency of the stator winding. A slip regulating amplifier receives the output signal from the speed regulating amplifier and the slip signal and provides an output to a summing amplifier. The summing amplifier also receives a motor speed signal and provides an output. The output comprises the second input signal to the inverter. The output may be supplied through an absolute value circuit as the first input signal to the inverter.

Abstract: Drive circuit for a blower motor employs a microprocessor control element, a controlled rectifier to provide DC power at a controlled rail voltage, and an inverter employing a pair of switching transistors arranged as a bridge inverter or half-bridge inverter. The drive circuit operates over a range of blower speeds and varies both the frequency and amplitude of bipolar pulses that are applied to the blower motor armature.

Abstract: A controller for a starter/generator used with an aircraft engine, includes means for monitoring field return current in a generator field winding; means for monitoring generator voltage; and microprocessor control means for adjusting generator field current as a function of the field current and voltage and field return current. The field return current and output voltage monitoring functions allow for open field, field integrity, over voltage, field weakening and torque limiting functions to be realized in an integrated programmable system configuration.

Abstract: In vector control apparatus and method for a three-phase multiplex winding motor, a plurality of inverters are installed, each inverter operatively driving a corresponding one of multiplex windings of the motor and a plurality of inverter controllers are installed whose number corresponds to that of the inverters. Each controller includes: a decoupling voltage calculator for calculating d-axis and q-axis voltage setting values V.sub.1 d* and V.sub.1 q* on the basis of an excitation instruction value Io*, a torque instruction value I.sub.T *, d-axis-and-q-axis current instruction values i.sub.1 d* and i.sub.1 q* which are quotients of the excitation instruction value Io* and the torque instruction value I.sub.T * divided respectively by the multiplex number N of the windings of the motor, and a power supply frequency .omega. which is an addition of a slip frequency .omega.s to a rotor revolution frequency .omega.

Abstract: A circuit arrangement for feeding a single-phase or multi-phase load from a sinusoidal alternating voltage energy supply mains which carries an at least having a frequency for which the load has a substantially resistive behavior. The circuit arrangement includes a full-wave rectifier stage for deriving a substantially sinusoidal intermediate circuit voltage, a modulation stage, for example, a single-phase or multi-phase inverter, which generates from the intermediate circuit voltage, under the control of a control signal whose frequency is high relative to the frequency of the mains alternating voltage, at least one high-frequency supply voltage which is applied to the load. The supply voltage (voltages) is determined from the product of the control signal and the intermediate circuit voltage. A high-frequency filter stage is coupled to the full-wave rectifier stage so as to suppress interference induced into the energy supply mains in a frequency range which includes the frequency of the control signal.

Abstract: A BEMF detector and method detect the BEMF of a three-phase motor using a fully differential detection system. The motor has a first coil coupled between a first coil tap and a center tap, a second coil coupled between a second coil tap and the center tap, and a third coil coupled between a third coil tap and the center tap. The BEMF detector includes a differential amplifier having first and second inputs and first and second outputs, with the first input being coupled to one of the coil taps and the second input being coupled to the center tap. The BEMF detector also includes a comparator having first and second inputs coupled respectively to the first and second outputs of the differential amplifier and an output at which a BEMF signal is produced that is related to the BEMF of the motor. The differential amplifier may be part of an anti-alias filter structured to fix to a known stable value a common mode at the outputs of the differential amplifier.

Abstract: A voltage vector overmodulation technique considering a counter electromotive force of a motor with respect to a voltage applied to the motor in a transient state during the operation of the motor, selects a voltage having the least logarithmic difference between a counter electromotive force according to the voltage applied to the motor and a command voltage as an application control voltage of the motor. Thus, since a response voltage to correspond to a transient state during the operation of the motor is selected considering the dynamic characteristic of the motor, a voltage most appropriate for the operation of the motor can be selected. Also, the current controller and the speed controller of the motor can stably be operated and maximum use of the available torque of the motor is possible.

Abstract: Converter-powered electric motors are often braked by electrical means. For this purpose the electronic converter that powers the motor is so controlled that the motor, when in generational operation, sends energy by way of the converter into an electrical braking resistor additionally connected to the converter, and this energy is there converted to heat. In order to avoid overloading the electrical braking resistor, an additional electronic or thermo-mechanical protective device is customarily provided. To simplify the arrangement, it is proposed in the present invention to provide as an electric braking resistor one made of a resistive material with a conductance that decreases progressively as the temperature rises through a certain range below the maximal acceptable operating temperature of the braking resistor. As a result, the power that can be accepted by the electrical braking resistor is made self-limiting, so that the braking resistor is protected against overheating.

Abstract: A motor control processor controls motor spin-up in a disk drive by detecting environmental temperature at the spindle motor of the disk drive, controlling commutation phase advance to generate substantially maximum torque if the detected environmental temperature indicates that maximum torque is needed, and adjusts the commutation phase advance for optimal efficiency after the maximum torque is no longer needed. Following motor start and reaching operational speed, the motor is operated in a steady-state maximum operating efficiency mode unless sensed environmental temperature indicates that maximum torque, rather than maximum efficiency, is needed. The system determines that the need for maximum torque has passed either when a predetermined time interval after motor start expires or by repeatedly polling motor temperature information.

Abstract: An object of the present invention is to provide a bearingless rotary machine which is capable of stably controlling the levitated position of a rotor of an induction motor even if the rotor comprises a squirrel-cage type rotor that is simple in structure and can easily be manufactured.A bearingless rotary machine has a rotor having secondary current paths and a stator spaced from the rotor by a gap. The stator has two kinds of windings for imparting a rotating and a levitating and supporting force to the rotor. The rotary machine has a magnetic field command calculator, magnetic flux distribution detecting means and correcting means for adjusting the detected control magnetic flux distribution to coincide with the magnetic field distribution command.

Abstract: The present invention propose a driving apparatus for an image processing system. A DC motor with a feedback controlling system is utilized as the driving apparatus. With the design of the present invention, the accuracy of the position control can be increased and the prior art problem of missing steps and unequalled steps can be eliminated. The driving apparatus of the present invention includes a DC motor, a position detecting device, an error counter, a controlling circuit, and a driving circuit. The position detecting device is employed for detecting positions of the DC motor in order to generate feedback signals. The error counter is responsive to input signals and the feedback signals for generating error signals. The controlling circuit is responsive to the error signals for controlling the DC motor. The driving circuit is responsive to the controlling circuit for driving the DC motor.

Abstract: The invention is an induction motor controller for measuring electrical constants of a polyphase induction motor (102) by supplying test power thereto and controlling driving of the polyphase induction motor with a polyphase inverter (105) by using parameters for controlling driving of a result of the measurement.

Abstract: Latching components of a padlock are driven by a motor between latched and released positions. An encoder element with associated optical elements provides position information to a control circuit. The control circuit correlates the position information with the signal directing power to the motor so that the motor is precisely controlled for moving the latching elements between release and latch. If the motor jams (sensed by overcurrent), it is operated briefly in alternating directions to try and dislodge the grit or ice causing the jam. The padlock shackle is latched into place by balls which are driven into recesses in the shackle legs. The use of plural balls on at least one side helps isolate the drive motor and gears from grit that may enter through the padlock's top shackle holes.

Abstract: Disclosed herein is a monolithic fan controller circuit which provides the following features: a special start-up routine for the fan; a fan fault detector; a thermal fault detector; an automatic speed controller; a minimum speed controller; a routine for attempting to clear temporary fan faults; and a controllable drive signal frequency. A start-up control circuit provides an initial high duty-cycle kick to the fan in order to initiate the rotation of the fan. A temperature sensor, which may be external or internal to the monolithic fan controller, supplies a signal which is proportional to measured temperature. This signal is used to control the output pulse width of a pulse-width modulator (PWM) or control the frequency of a pulse frequency modulator (PFM). The PWM or PFM output signal regulates the speed of the brushless (or brush) DC fan motor. In a preferred embodiment, the monolithic fan controller has 8 pins.

Abstract: A method for driving a servo-motor detects a power voltage of a servo-motor determine a detected value. Through numeric calculation, the detected value is used to control a voltage command to a power converter, where the power converter supplies the proper currents to the servo-motor. The method does not require the use of a feedback loop, and thus, requires fewer components than the traditional method that also requires the use of a current sensor and an A/D converter.

Abstract: A synchronous motor control system which can freely regulate n-phase electric currents in a synchronous motor to control the characteristics of the synchronous motor. The synchronous motor control system can enhance the output torque per unit weight of a synchronous motor (40) simultaneously with reducing torque ripples. The waveform of three phase alternating currents is freely corrected over a range of +30 degrees from a specified electrical angle, at which a target phase current drawing a sine-wave curve reaches its peak value. It is assumed that this range of .+-.30 degrees corresponds to a range of 0 degree to 60 degrees. By way of example, the waveform is controlled to the peak value of the phase current in a range of 0 degree to 28 degrees. The correction of the phase current is carried out for the target phase which produces the primary magnetic flux of a revolving magnetic field.

Abstract: A three-phase generator boost circuit for augmenting the back electromotive force produced by a spindle motor of a disk drive is disclosed. First and second nodes provide normal connection to a source of DC voltage for the spindle motor and a second motor connected between the first and second nodes. A commutator is connected to a sequencer to operate the spindle motor. In the event of catastrophic shutdown, two of the lower commutator switches are operated to short circuit the two stator coils having the highest and lowest voltages to store energy in the coils. The commutator switches are then operated to discharge current through the nodes to a storage capacitor for the second motor.

Abstract: A feedback circuit prevents clipping of the inverter drive signals for a polyphase induction motor. The circuit senses the electromotive force (e.m.f.) of the motor and regulates the slip frequency as a function of the difference between the sensed motor e.m.f. and the DC power supply voltage. When the motor e.m.f. approaches the supply voltage, a voltage controlled oscillator adjusts the slip frequency to reduce the motor e.m.f. and thereby ensure that the motor drive waveforms are not distorted.

Abstract: A motor is reconnected to a motor drive by exciting the motor to induce a back EMF, determining a speed of rotation of the motor based on the induced back EMF induced, and reconnecting the motor drive to the motor based on the speed determined. In order to induce the back EMF, current which flows through the motor is controlled using first and second regulators. The outputs of the first and second current regulators are separated from each other in phase by approximately 90.degree.. A positive feedback loop is established by using the output of one of the first and second regulators to generate an input for the other one of the first and second regulators. The positive feedback loop advantageously causes the back EMF to continually increase as the motor continues to be excited, or at least not decay so rapidly that the speed of the motor cannot be accurately determined.

Abstract: A method and apparatus for starting a motor drive into a rotating motor, the method including determining an initial search frequency and search current wherein the current is less than a rated drive current, providing a d-axis flux generating current to the motor at the search frequency and at a magnitude equal to the search current, monitoring a q-axis flux error, decreasing the search frequency until the d-axis flux error is less than a threshold value, thereafter increasing the search current to the rated drive current and, after a flux-up period, providing both q-axis torque producing current and d-axis flux producing current to the motor.

Abstract: A method for determining the active power (P) of asynchronous electric motors of winning and conveying equipment in underground mining. According to the invention, particularly easy and accurate determination of the instantaneous active power of the motors is obtained by storing the individual motor characteristic (P(n); M(n)) of each motor in a computer, by detecting the instantaneous speed (n, n') of the motor with the aid of a tachometer and by comparing this speed with the characteristic stored in the computer, the active power being derived from the torque value or power value assigned to the detected instantaneous speed, as stored in the computer. This particularly rapid and simple calculation of the power value does not require any readings to be taken at the power supply to the motors.

Abstract: In a motor with permanent magnets and a motor system, the value .alpha. produced by dividing, by the induced voltage constant ke, the product of the inductance Lm of the motor itself or the inductance Ls of the motor system in the d-q coordinate system is selected to meet a predetermined condition. The range of rotational speeds in which the motor can be operated while maintaining a predetermined output under field weakening control can be widened. If a condition is established to determine a ratio by which the rated rotational speed under normal operating conditions is multiplied into a rotational speed under field weakening control, then conditions for a motor or a motor system that can be used can be determined.

Abstract: A control circuit controls the power supply to an electric motor and, comprises a power transistor NM of the NMOS type and a power transistor PM of the PMOS type arranged between two supply terminals VCC and GND, their intermediate node forming an output coupled to a coil Ei of the motor. The well B of the transistor PM is coupled to supply terminal VCC via an isolation diode ID, which has its anode connected to supply terminal VCC and has its cathode connected to the well B. The isolation diode ID ensures that the coil Ei is not short-circuited by the parasitic drain-well diode D of the transistor PM in case of a sudden power failure.

Abstract: A power corresponding to an A/C voltage command id1* is applied in the d-axis direction of rotational coordinates of a stopped synchronous motor via a current control unit, a three-phase converting unit, and a power converter. Further, by using "an amplitude value of a current iq' in the q-axis direction of the rotational coordinates generated in response to the A/C voltage command id1*" which is fed back and detected via a current detector and a dq converting unit, a field pole position estimation value .theta. is converged. The field pole position is estimated by using the converged field pole position estimation value .theta. as a true value of the field pole position .theta. of the synchronous motor.