Abstract: A distributed motor drive system includes a power management module and multiple inverter modules integrated with the motors and located on a machine or process remote from the power management module. The power management module distributes DC voltage and command signals to each of the inverters, where the DC voltage is distributed between modules via a DC link cable. The integrated inverters execute switching routines to convert the DC voltage to an AC voltage suitable for controlling the motor. Each of the power management module and the inverters includes a portion of the DC bus. The current on the DC link cable is monitored and general bus utilization as well as overload conditions are reported.

Abstract: A control unit for a stepping motor includes an encoder and a controller. The controller controls the stepping motor based on information sent from an image pickup apparatus configured to capture an object via an image pickup optical system that includes the focus lens. in a case that the image pickup apparatus performs autofocusing in capturing a still image, the controller open-loop-controls the stepping motor in at least one of a drive start period and a drive stop period of the stepping motor, and feedback-controls the stepping motor using an output of the encoder between the drive start period and the drive stop period of the stepping motor. The controller open-loop-controls the stepping motor in a case that the image pickup apparatus performs the autofocusing in capturing a motion image.

Abstract: Certain embodiments provide an angle detector comprising: an AD converter configured to analog-to-digital convert plural-phase signal waves having respective different phases; a corrector configured to delay a phase of an excitation signal by an amount corresponding to a phase difference between the excitation signal and the signal wave; a wave detector configured to perform synchronous detection to an output signal from the AD converter in synchronization with the excitation signal whose phase is corrected; and an angle calculator configured to calculate an estimated rotation angle using an output signal of the wave detector and output the estimated rotation angle to the AD converter.

Abstract: According to the voltage VU that occurs at one end of at least one of multiple coils of a fan motor, a back electromotive force detection circuit generates a detection signal BEMFU asserted in a cyclic manner when a fan motor is stably rotating. A lock protection circuit detects a lock state of the fan motor rotor. A period detection unit measures the detection signal BEMFU period. A synchronization pulse generating circuit generates a synchronization pulse having a period that is 1/N (N represents an integer of 2 or more) of that of the detection signal BEMFU measured in a previous cycle. A lock judgment unit counts the synchronization pulse in increments of cycles of the detection signal BEMFU. When the count value exceeds a predetermined threshold value M (M represents an integer of 2 or more) which is greater than N, the lock mode judgment signal is asserted.

Abstract: A method and apparatus for automatic resonance detection is disclosed for a motor-driven mechanical system such as a voice coil motor (VCM) in which a resonance detector and driver are provided. The automatic resonance detector is implemented on the same integrated circuit as the driver, and dynamically determines the natural resonant frequency of the VCM driven by the driver. The resonant frequency is determined by measuring the back electromotive force (BEMF) of the VCM, detecting the slope of the BEMF signal, and determining the resonant frequency from the slope of the BEMF signal.

Abstract: A method, which is efficient and cost-effective to implement, for controlling, at steady-state, a synchronous electric motor comprising a permanent magnet rotor and a stator provided with windings connected to an electrical grid by means of a switch controlled by a processing unit, said method comprising the following steps: periodically switching on said switch by means of a PWM output of said processing unit; continuously verifying the shift with respect to an ideal operating condition of the motor; and modifying the switched on period of the switch in feedback to approach said ideal operating condition of the motor.

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: The laundry treatment machine includes an inverter to convert direct current (DC) voltage into alternating current (AC) voltage and to output the AC voltage to a motor. The laundry treatment machine includes an inverter controller to control the inverter to supply current corresponding to a direction opposite to back electromotive force generated from the motor to the motor so as to align the motor during a starting operation of the motor. It is feasible to rapidly align a rotor of the motor during the starting operation of the motor.

Abstract: The laundry treatment machine, absent a position sensor to sense the rotor position of a motor, includes a driving unit having an DC/AC inverter, an voltage detection unit to detect output voltage, and an inverter controller to control the inverter. The output voltage detection unit includes a plurality of resistors connected between the inverter and the motor and a comparator to compare voltage detected by some of the resistors with reference voltage and to detect pulse width modulation (PWM)-based output voltage. The voltage detection unit outputs the PWM-based output voltage output from the comparator to the inverter controller in a first mode in which at least one switching device of the inverter is turned on. The voltage detection unit outputs voltage detected by other some of the resistors to the inverter controller in a second mode in which all switching devices of the inverter are turned off.

Abstract: The laundry treatment machine; absent a position sensor to sense a rotor position, includes a driving unit having a DC/AC inverter, an output voltage detection unit to detect output voltage applied to the motor, and an inverter controller to control the inverter to drive the motor based on the output voltage. The output voltage detection unit includes a plurality of resistors electrically connected between the inverter and the motor and a comparator to compare voltage detected by some of the resistors with reference voltage and to detect pulse width modulation (PWM)-based output voltage. Based on the PWM-based output voltage at least one switching device of the inverter is turned on. The output voltage detection unit outputs voltage detected by other some of the resistors to the inverter controller in a second mode in which all switching devices of the inverter are turned off.

Abstract: A laundry treatment machine includes a drum, a motor to rotate the drum, and a driving unit to drive the motor, wherein the driving unit includes an inverter to convert direct current (DC) voltage into alternating current (AC) voltage and to output the AC voltage to the motor and an inverter controller to control the inverter to supply an alignment current to the motor so as to align the motor during a starting operation of the motor and to supply a torque current for rotating the motor to the motor together with the alignment current after the motor is aligned. Such a laundry treatment apparatus prevents a reverse rotation phenomenon of the drum due to load.

Abstract: A microcomputer operates as a positioning part positions a rotor at a control start position, which is a position of the rotor relative to a stator to be able to start controlling driving of a brushless motor, by supplying a current to a winding set a number of times “n” (n is an integer equal to two or more) before starting to control driving of the brushless motor. The microcomputer, operating as the positioning part, controls electric power supplied to the winding set so that the rotor rotates in the same direction at each of “n” times of power supply to the winding set, that is, at each of “n?1” times of switchovers of power supply to the winding set.

Abstract: A drive system for an electrical load such as an electric motor or generator comprises a PWM converter and a controller therefore. A signal indicative of a condition of the converter outpost is used in a controller to drive an optimal value of PWM switching frequency based on a load characteristic that is used to control the pulse switching frequency. The system takes account of the overall system in deriving an efficient PWM switching frequency.

Abstract: A brushless motor drive device switches energization modes for supplying power to two phases of a three-phase brushless motor, based on an induced voltage induced in a non-energized phase. In a case in which a target duty ratio Dt, which is a duty ratio of a PWM signal according to a manipulated variable of the brushless motor becomes less than a detection limit value Dlim, which is the lower limit of a duty ratio capable of detecting an induced voltage, there is set a detection timing (1/N) for detecting an induced voltage according to the cycle of a PWM signal, and a detection time duty ratio D1, which is a duty ratio of the PWM signal at the detection timing, is restricted to Dlim.

Abstract: An engine starting apparatus is provided which can start an engine without inducing malfunctions of various electronic components. The engine starting apparatus comprises a pinion adapted to be brought into meshing engagement with a ring gear linked to an engine, a magnet switch supplied with current from a battery to move the pinion in the direction of the ring gear, a starter motor supplied with the current to rotate the pinion, a control unit for instructing the starter motor to start the engine, and a starter control unit for controlling, on the basis of the instruction, a first semiconductor switch subject to PWM control, wherein the starter motor and the magnet switch are stored in a first housing, the starter control unit is stored in a second housing, and the first housing is integral with the second housing.

Abstract: There is provided a motor driving control device including a state determining unit which determines whether a motor can perform a slow start operation based on a rotating state and a driving state of the motor, a control unit which generates command information corresponding to a speed at which the motor is to be rotated, based on a determination result of the state determining unit, and a motor driving unit which outputs a driving signal corresponding to the command information generated by the control unit to the motor so as to drive the motor. When it is determined that the motor can perform the slow start operation, the control unit generates the command information such that the motor performs the slow start operation.

Abstract: A three-phase synchronous motor drive device includes: a three-phase inverter 3 that drives a motor 4 that is as a three-phase synchronous motor, and that includes switching elements for three phases; a controller 2 that functions as a control unit that selects four switched states from a plurality of switched states that represent on/off states of the switching elements for the three phases, and that sequentially controls the three-phase inverter in the four switched states; a neutral point potential amplifier 13 that functions as a neutral point potential detection unit that detects a neutral point potential Vn0 of stator windings (Lu, Lv, Lw) of the motor 4 in each of the four switched states. It is configured that a rotor position of the three-phase synchronous motor is estimated over a full range of an electrical angle cycle based on at least three of four neutral point potentials detected in the four switched states.

Abstract: Methods and systems for starting an electric motor using a motor controller including a processor are provided. The method includes determining if the electric motor is operating, increasing a failed start counter if the electric motor is determined not to be operating, determining a reverse rotation by comparing a failed start counter to a predetermined threshold, and applying a reverse rotation start routine to the electric motor when a reverse rotation is determined.

Abstract: A method of controlling an electrical machine. The electrical machine includes a stator having a core and a plurality of windings, and a rotor disposed adjacent to the stator to interact with the stator. The method includes configuring an amplitude value and frequency values of a three-phase alternating current (AC) voltage startup signal having an amplitude and a frequency, providing the three-phase alternating current (AC) voltage startup signal to the plurality of windings, and altering the frequency of the three-phase AC voltage startup signal according to a preprogrammed frequency ramp function defined by the frequency values. The method further includes discontinuing the three-phase AC voltage startup signal after the frequency ramp function has completed, and switching to a back electromotive force (BEMF) control mode after discontinuing the three-phase AC voltage startup signal.

Abstract: A driving device of a multi-phase motor having a plurality of coils is provided. The driving device includes a back electromotive force (BEMF) detecting comparator connected to one of the plurality of coils to compare BEMF generated in one end of the one of the plurality of coils with a midpoint voltage of the plurality of coils and generate a BEMF detection signal, when the multi-phase motor starts to be driven; and an initial state detecting unit configured to detect a rotation state of the multi-phase motor based on the BEMF detection signal and a hall detection signal.

Abstract: A circuit includes a processor that analyzes a pulse width modulated (PWM) signal feedback from a brushless DC motor to determine a transition between a mutual inductance zero crossing condition and a Back Electro Motive Force (BEMF) zero crossing condition of the brushless DC motor. A mutual inductance controller is executed by the processor to commutate the brushless DC motor at startup of the motor when the mutual inductance zero crossing condition is detected by the processor. A BEMF controller is executed by the processor to commutate the brushless DC motor after startup of the motor when the BEMF zero crossing condition is detected by the processor.

Abstract: A blower system, including a permanent magnet motor and a wind wheel. The permanent magnet motor includes a stator assembly, a rotor assembly, and a motor controller. The rotor assembly includes a salient pole rotor including a rotor core and magnets embedded in the rotor core. The motor controller includes a microprocessor, a frequency inverter, and a sensor unit. The sensor unit inputs a phase current or phase currents, a phase voltage, and a DC bus voltage into the microprocessor. The microprocessor outputs a signal to control the frequency inverter which is connected to a winding of the stator assembly. The ratio between an air gap of the motor and the thickness of the magnets ranges from 0.03 to 0.065, and the ratio between the length of a pole arc and the length of the magnets ranges from 0.8 to 1.0.

Abstract: A disclosed motor driver control device is configured to control a plurality of switching devices that drive a motor. The motor driver control device includes a duty control unit configured to restrict a duty of a first pulse width modulation signal generated by comparing an oscillator signal generated at a predetermined cycle and a pulse generator signal so as to generate a second pulse width modulation signal, and a switching device control signal generator unit configured to include a logic circuit that operates the second pulse width modulation signal as a clock and configured to generate a switching device control signal controlling the plurality of switching devices based on the clock of the logic circuit of the switching device control signal generator unit.

Abstract: A soft start circuit for a forward/reverse rotation fan includes a forward/reverse switch unit, a soft start activation unit, a soft start control unit, a Hall IC and a driver IC, wherein the soft start activation unit comprises a first signal transmission loop and a second signal transmission loop. The soft start circuit activates the soft start control unit via a first instantaneous signal outputted by the first signal transmission loop or a second instantaneous signal outputted by the second signal transmission loop to make the soft start control unit output a control signal to a speed control terminal. When the rotating direction of fan is switched from one direction into another, the fan starts rotation in a soft start mode owing to high level of the control signal transmitted from the soft start control unit to the speed control terminal during initial rotation of the fan.

Abstract: A method of controlling an electrical machine. The electrical machine includes a stator having a core and a plurality of windings, and a rotor disposed adjacent to the stator to interact with the stator. The method includes detecting a movement of the rotor, generating a three phase alternating current (AC) voltage signal by all phases of the electrical machine, monitoring for a transfer speed of the electrical machine, discontinuing the three phase AC voltage signal when the transfer speed is traversed, and switching to a back electromotive force (BEMF) control mode after discontinuing the three phase AC voltage signal.

Abstract: A motor includes a rotor and a plurality of pairs of electromagnets. The energy needed for alignment of the rotor is used to generate the first movement in forced commutation and may be combined with the initial energy to start the motor. The logic is configured to align the rotor by energizing the three coils of the motor. PWM is applied to the first coil to control current on the coils; when a maximum PWM duty cycle is reached, the coil not required to rotate the correct direction are released, thereby initiating motion in a rotor. A rotation period is determined. One or more pairs of electromagnets are excited at a first excitation level which may be increased, over a second period, to a second level. The second level may be a higher level than the first level. The rotation period may be decreased over the first and second periods.

Abstract: A motor control circuit and associated techniques can drive an electric motor in a start-up mode of operation followed by a normal mode of operation. The motor control circuit and techniques can receive a selection signal provided by a user that can select one of a plurality of sets of parameter values that determine characteristics of drive signals applied to the motor during the start-up mode of operation. The motor control circuit and associated techniques can synchronize operation between the start-up mode of operation and the normal mode of operation.

Abstract: A motor control circuit and associated techniques can drive an electric motor in a start-up mode of operation followed by a normal mode of operation. The motor control circuit and techniques can receive a selection signal provided by a user that can select one of a plurality of sets of parameter values that determine characteristics of drive signals applied to the motor during the start-up mode of operation. The motor control circuit and associated techniques can synchronize operation between the start-up mode of operation and the normal mode of operation.

Abstract: Startup of motor is reliably executed and sonic noise is reduced. A control circuit controls a selector to apply control to output a full-drive waveform at startup and then output a PWM modulation waveform. The full-drive waveform which is an alternating waveform in which positive and negative are inverted at 180° is output. Then, the PWM drive waveform is selected.

Abstract: A command rotation speed is set to an initial rotation speed, and a forced commutation mode is started. In the forced commutation mode, a rotation speed is increased by a predetermined increase amount each time and forced commutation is executed until the rotation speed reaches a set rotation speed. Then, a switchover to the sensorless control mode is made when the rotation speed reaches the set rotation speed (S4) and a rotor position becomes detectable.

Abstract: A position sensorless drive systems for a permanent magnet motors are disclosed. An embodiment includes a square wave voltage source connectable to an input of a permanent magnet motor. At least one current sensor is connectable to the motor, wherein the current sensor is configured to sense the current in at least one power line to the motor in response to the square wave input to the motor. The position of the rotor relative to the stator may be determined based on the current resulting from the square wave voltage.

Abstract: An electric motor driving apparatus having a failure detection circuit includes: a bridge circuit driving an electric motor; a PWM control circuit generating voltage instruction for driving the electric motor; a PWM signal generation circuit generating a PWM signal; a DC current detection circuit detecting DC current of the bridge circuit; a phase current calculation circuit calculating output phase current of the bridge circuit, based on the DC current and PWM signal; and a failure detection circuit detecting failure of the DC current detection circuit. The failure detection circuit determines failure of the DC current detection circuit from the DC current detected values in a zero voltage period in which the high-potential-side arms of the bridge circuit are all ON and in a zero voltage period in which the low-potential-side arms are all ON.

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: Provided is a sensorless BLDC motor apparatus for providing a drive current allowing the rotor of the BLDC motor to be aligned in a predetermined direction during an initial position setting section (or for a first period of time), and providing a drive current allowing a frequency thereof to be varied at predetermined time intervals so as to accelerate the rotational speed of the BLDC motor during an open loop section (or for a second period of time), and a method using the same.

Abstract: There are provided a motor driving control apparatus and method, and a motor using the same. The motor driving control apparatus includes: an inverter unit applying a driving current to a motor apparatus according to a driving control signal; a back-electromotive force detecting unit detecting back-electromotive force generated by driving of the motor apparatus; a driving current change unit reflecting a level of the back-electromotive force to determine a resistance value and reflecting the resistance value in the driving current; and a controlling unit performing a control operation to change the driving control signal using the driving current in which the resistance value is reflected and the back-electromotive force.

Abstract: A control apparatus for an AC rotating machine that can reliably and stably start up an AC rotating machine, particularly a synchronous motor using a permanent magnet, in position-sensorless vector control thereof, includes: a steady speed calculator that calculates, during steady state control of the AC rotating machine, a rotation angular frequency of the AC rotating machine based on an AC current and voltage commands; and a start-up speed calculator that calculates, during start-up control within a predetermined period after the AC rotating machine has been started up, the rotation angular frequency of the AC rotating machine based on the AC current and the voltage commands. The control apparatus corrects during the start-up control current commands so that the AC voltage amplitude of the voltage commands will be a constant value not more than the maximum output voltage of a power converter.

Abstract: A PWM output apparatus includes a calculating circuit configured to calculate an output width of a PWM output signal of a first signal and a second signal, which have phases different from each other, based on a command value of a PWM output. A comparing circuit compares the output width and a reference period which is set longer than a predetermined dead time period. A PWM output signal generating circuit outputs the PWM output signal to a dead time inserting block as a corrected PWM output signal, when a set/clear signal generating circuit outputs the set signal, and carries out a correction of setting the first signal of the PWM output signal to be inactive to output to the dead time inserting block as the corrected PWM output signal, when the set/clear circuit outputs the clear signal. The dead time inserting block corrects the corrected PWM output signal.

Abstract: An electric motor control system includes a power inverter and control circuitry configured to control the power inverter either according to a target voltage in a voltage-based control mode or according to a target current in a current-based control mode. A controller is operable to switch operation of the control circuitry between the voltage-based control mode and the current-based control mode. The controller may be configured to operate the control circuitry in the current-based control mode at lower motor operating speeds where stator current margin is of greater significance, and to operate the control circuitry in the voltage-based control mode at higher motor operating speeds where stator voltage margin is of greater significance.

Abstract: An observer (404), operating during a time when open loop control (402) is being used to drive a synchronous motor (401), the output of the observer (404) being a signal, E_I_angle, related to the angle between a rotational EMF vector and the current excitation vector, the observer (404) determining the angle by an iterative calculation incorporating a summation term, the summation term summing the variation of the quadrature component of a rotational EMF vector relative to an estimated EMF position vector, and using the angle output of the observer to update the estimate of the rotational EMF position vector. In a further aspect of the invention the observer output signal, E_I_angle, can be used to determine the transition to closed loop control (405), when the observer output signal reaches a value indicating conditions close to pull out conditions.

Abstract: A motor drive apparatus comprises: a position signal generation portion that generates a position signal corresponding to a rotor position of a brushless DC motor; and a logic portion that when starting the brushless DC motor, disposes a non-energizing period immediately after starting forced commutation at a phase switchover timing corresponding to a predetermined forced commutation frequency and performs energizing control of the brushless DC motor such that usual commutation is started at a phase switchover timing corresponding to the position signal that is generated during an inertial rotation of the rotor.

Abstract: A motor control unit determines whether a rotor of an electric motor is in rotation or not after the motor control unit is started up but before an initial operation, based on an encoder count value after the start-up of the motor control unit. When the electric motor is stopped, the initial operation is carried out so as to learn a correction value of phase difference between the encoder count value and an actual current-supply phase. When the electric motor is still rotated due to its inertia, a motor-stop control is carried out before the initial operation in order to completely stop the rotation of the rotor. In the motor-stop control, electric power is supplied to windings of two phases at the same time.

Abstract: There are provided a motor driving apparatus and method capable of driving a motor at an optimal driving frequency at which back-electromotive force is generated by sweeping a driving frequency by a preset unit frequency interval during initial driving of the motor, the motor driving apparatus including: a frequency signal generating unit providing a frequency signal of which a frequency is set by a preset unit frequency interval; a driving signal generating unit generating a driving signal based on the frequency signal from the frequency signal generating unit; and a driving unit driving a motor according to the driving signal from the driving signal generating unit.

Abstract: A method of conducting smooth motor startup is provided and includes operating a motor in an open loop control scheme at startup, operating the motor in a closed loop sensorless control scheme at a time after startup and transitioning between the open loop control scheme and the closed loop control scheme by reducing a difference between an estimated rotor angle of the motor and a commanded ramping angle of the motor.

Abstract: There are provided a motor driving control apparatus and method, and a motor using the same. The motor driving control apparatus includes: an inverter unit applying a driving current to a motor apparatus according to a driving control signal; a back-electromotive force detecting unit detecting back-electromotive force generated by driving of the motor apparatus; a driving current change unit reflecting a level of the back-electromotive force to determine a resistance value and reflecting the resistance value in the driving current; and a controlling unit performing a control operation to change the driving control signal using the driving current in which the resistance value is reflected and the back-electromotive force.

Abstract: An electronic circuit and an associated method used to drive an electric motor provide a user selectable relationship between rotational speed of the electric motor and phase advances of signals used to drive the electric motor. By selecting the relationship, efficiency of the electric motor drive can be improved.

Abstract: A BEMF detection circuit generates a rotation detection signal indicating a comparison result between electromotive force voltages VU through VW which occur at a terminal of respective multiple coils and an intermediate-point voltage VCOM. A rotor position detection circuit generates a rotor position detection signal indicating a stopped rotor position An internal start-up synchronization signal generating unit generates a predetermined-frequency forced synchronization signal. Upon receiving a fan motor start-up instruction, a driving signal synthesizing circuit generates a driving control signal based upon the rotor position detection signal. Thus, (1) when back electromotive force voltage occurs, a sensorless driving operation is started based upon the rotation detection signal; (2) when it does not occur, the driving control signal is generated based upon the forced synchronization signal. Subsequently, when it occurs, the sensorless driving operation is started based upon the rotation detection signal.

Abstract: When a forced commutation mode ends, a switchover to a sensorless control mode is made. The sensorless control mode immediately after the switchover to the sensorless control mode is executed with a power source current maximum value set at a value higher than a rated current value of a motor. The sensorless control mode immediately after the switchover is executed only over a predetermined period of time, and, after a lapse of the predetermined period of time, a steady sensorless control mode is executed. In the steady sensorless control mode, the power source current maximum value is set at a value equal to the rated current value of the motor.

Abstract: There are provided an apparatus and method for motor driving control, and a motor using the same. The motor driving control apparatus according to an embodiment of the present invention includes a driving circuit unit providing an initial driving control signal of a motor; a current detection unit detecting initial driving current generated by the initial driving control signal; and a control unit determining that back-electro motive force is generated when the initial driving current decreases to a preset critical value or below and controlling the motor to be normally driven.

Abstract: There is provided an apparatus for generating a motor driving control signal, the apparatus including: an oscillating unit generating an oscillating signal having a preset duty ratio; a selecting unit including a first switch switching a first path connected between the oscillating unit and an output terminal and a second switch complementarily operated with respect to the first switch and switching a second path connected to the first path in parallel; and a duty adjusting unit installed on the second path between the second switch and the output terminal, adjusting a duty ratio of the oscillating signal according to a rotation speed signal of a motor, and outputting the signal having the adjusted duty ratio as a driving control signal through the output terminal.

Abstract: A method for starting an electric motor, the motor having a main machine, exciter, and permanent magnet generator (PMG), each having a stator and a rotor, with each rotor mounted to a common shaft, the method comprising starting the main machine in an asynchronous mode by applying a starting current to the stator of the main machine to induce a damper current in a damper winding of the main rotor to generate a starting torque that initiates the rotation of the common shaft, and then running the main machine in synchronous mode by supplying running current from the exciter rotor to the main machine rotor.