Abstract: An AC exciter and a main AC generator are mounted on a common rotating shaft of an engine, and a power rectifier and a power inverter are connected in series to the output of the main AC generator. In starter mode, an external AC power source is connected by a switch to the input of the power rectifier, and the output of the power inverter is applied to an armature winding of the main AC generator to drive it as a nocommutator motor to start the engine. A permanent magnet AC generator is also mounted on the common shaft of the engine to provide DC excitation to the AC exciter after converting the output of the permanent magnet AC generator into DC current, and the output of the permanent magnet AC generator is further utilized to detect the rotational speed of the engine to control the switch.

Abstract: The output frequency of an electric power generator is kept constant with variable rotor speed by automatic adjustment of the excitation slip frequency. The invention features a digital slip frequency generator which provides sine and cosine waveforms from a look-up table, which are combined with real and reactive power output of the power generator.

Abstract: An output frequency control circuit is mounted on the rotating shaft connecting a motor and generator. The motor-generator system includes exciter circuits, an input power factor control and an output voltage regulator. The input power factor control ensures that the motor input power factor is unity, which is desirable for motor control. The frequency control circuit responds to variations in the AC power source frequency by generating low frequency excitation to boost or buck the operational speed of the machine, causing the generator output frequency to remain constant at a selected frequency output irrespective of input power source frequency variation. The output frequency may be selected over a given range from a control panel adjustment pot.The major innovation is that the entire frequency control circuit is shaft-mounted and requires no slip-rings or magnetic transformers for signal transfer, thus reducing the possibilities of mechanical failure.

Abstract: The converter described comprises a generator (2) having a rotor (3) driven by a spring (1) via a gear-train (4), and means (11) for electrically braking the rotor (3). In one form of embodiment of the converter, the mean rotational speed of the rotor (3) is adjusted to a predetermined set speed by a control circuit (12) which periodically cuts out the braking means (11) in response to a reference signal having a period equal to the ratio between a predetermined rotational angle of the rotor (3) and the set speed. The control circuit (12) cuts the braking means (11) in again after a length of time which varies in response to a signal generated by a circuit (26, 27) for comparing the real angular position of the rotor (3) at the beginning of each period of the refernce signal with the angular position it should be in when running at the set speed.The converter may for instance be used in a timepiece having hands (9) that are also driven by the spring (1).

Abstract: A plurality of permanent magnets mounted at equally spaced angular intervals on a drive shaft are rotated past a plurality of electromagnets at equally spaced fixed angular intervals about the axis of the shaft on a plate supported by a frame. An electric motor drives the drive shaft. The electromagnets are connected across each its own capacitance. At the appropriate speed of rotation the frequency of electrical energy generated by the permanent magnets as they pass the electromagnets causes resonance to occur. This action controls the drive shaft speed. A plurality of capacitors is attached to the base plate and the cross bars of the frame supporting the plate.

Abstract: The present invention provides an improved alternator system in which the magnetic flux modulating sleeve is carried by the rotor and rotates with the rotor. The position of the sleeve on the rotor is adapted to be adjusted during operation of the alternator while the rotor and sleeve are rotating. The repositioning of the sleeve on the rotor during rotation beneficially provides a more constant voltage output during load and speed variations. Concurrent rotor and sleeve rotation reduces eddy current losses in the magnetic circuit and increases alternator efficiency. The alternator of the invention is estimated to provide a constant voltage for a 10:1 variation in either electrical load (in OHMS) or rotor angular velocity (revolutions per minute, RPM), or a combined 10:1 variation of electrical load and rotor angular velocity.

Abstract: A dual voltage motor vehicle electrical system wherein a pair of batteries are connected in series across the direct voltage output terminals of a bridge rectifier that is connected to a polyphase output winding of an alternating current generator. First and second groups of controlled rectifiers are connected between a junction of the batteries and the generator output winding. In low speed operation of the generator the groups of controlled rectifiers are alternately biased conductive. The time period of conduction of the groups of controlled rectifiers is controlled as a function of the difference in the voltages across the respective batteries. The phase voltages of the output winding are summed by a summing amplifier to provide a control signal. The system includes means responsive to the control signal for preventing simultaneous conduction of the groups of controlled rectifiers.

Abstract: A starter generator system is provided with a dynamoelectric machine having a stator and a rotor which is mounted for rotation with respect to the stator. The rotor carries a main field winding, an exciter armature winding and means for rectifying the output of the exciter armature winding to provide DC excitation for the main rotating field winding. A main armature winding is mounted on the stator and magnetically coupled to the main field winding. An exciter portion of the stator supports both a multiple phase AC exciter field winding and a distributed DC exciter field winding, both of which are mounted to be magnetically coupled to the exciter armature winding. A variable voltage, variable frequency power converter is capable of being alternatively connected to drive the dynamoelectric machine as a starting motor or to receive power from the machine during generator operation.

Abstract: The output current and drive torque characteristics of a vehicle generator during cold, startup periods are approximated to those of a warmed up generator by sensing the field winding current, and interrupting it for a time period prolonged by a feedback/charging capacitor (904) whenever it exceeds a reference level. The field winding current never exceeds the reference level when the generator is warmed up, whereupon the interrupting circuitry has no effect.

Abstract: A control device for a vehicle generator includes an acceleration detector (9) whose output disables the generator during periods of acceleration to attendantly reduce the engine load. A phase voltage regulator (11) responds to a voltage at one phase (P) of an armature winding of the generator to override the acceleration detector output and increase the generator voltage to a limited, detection level when such voltage is reduced below a predetermined level.

Abstract: A speed control unit for an aircraft generator includes a continuously variable gear ratio drive device through which the generator is driven by a shaft of the engine and which is responsive to an error signal indicative of a difference between desired and sensed generator speeds. A control circuit prevents the error signal from being applied to the drive device until a predetermined speed of the generator is reached and a ramp generating circuit increases the rise time of the error signal after the generator has reached the predetermined speed.

Abstract: A control apparatus for a vehicular generator for use in an automobile, etc., in which the temperature of the generator is detected so as to control switching of the field current of the generator when the temperature of the generator is below a predetermined value, so that the cold output current and cold drive torque of the generator are substantially the same as the hot output current and hot drive torque of the generator.

Abstract: An arrangement for recovering power loss of an internal combustion engine including a turbine, the driving power of which stems from a power loss of the internal combustion engine. The turbine is coupled to a generator, a winding of which feeds a d-c motor relieving the internal combustion engine. Power matching between the generator and the d-c motor is made possible without a separate control device because the generator or its excitation circuit is designed in such a manner that the voltage induced in the generator winding exhibits a steep dependence within a narrow operational speed range.

Abstract: An electronic voltage regulator for an ac electric generator precisely controls the generator output voltage and enhances motor starting ability. A filtered dc representation of the output voltage of the generator is produced by circuitry sensing the output voltage of the generator and rectifying to dc and filtering the voltage sense to obtain a relatively smooth dc voltage which is directly proportional to the output voltage of the generator and has on it a small amount of ripple voltage. A dc voltage which is proportional to the frequency of the generator is also produced by circuitry means which senses the frequency of the generator and produces a dc voltage proportional to the frequency of the generator up to a predetermined maximum frequency, not increasing above that maximum, and for amplifying the voltage produced. A comparator circuit compares the dc voltages.

Abstract: A balance vehicle speed at which mean charging current and mean discharging current are balanced is obtained. A charge stop vehicle speed corresponding to the balance vehicle speed is decided as a reference value. An actual vehicle speed is compared with the charge stop vehicle speed to produce a charge stop signal, when the actual vehicle speed is lower than the charge stop vehicle speed. A charging regulator is responsive to the charge stop signal for disabling the regulator so as to stop the charging of a battery.

Abstract: The inventive control system introduces the current (.DELTA.I) and voltage (.DELTA.C) deviations simultaneously with the injection set point (C) to define a new injection set point (C') that is utilized in conjunction with the measurement of diesel engine speed (V.sub.rD) to adjust the injection and with the measurement of the injection flow rate C.sub.r to adjust the generator excitation current.

Abstract: An emergency power generating system according to the present invention includes an emergency power converter which is selectively coupled to the output of a permanent magnet machine forming a part of a constant speed drive in the event of a failure of a main generator so that the permanent magnet machine and the emergency power converter provide emergency power to one or more loads.

Abstract: A permanent magnet rotary electric machine has two permanent magnet rotors rotatable within respective stator windings, and drivingly connected to an input shaft. The driving connection to one of the rotors is provided by an epicyclic gear train to which the input shaft is coupled. A second input to the gear train is provided by a gear carrier which is angularly movable about the input shaft axis by an actuator which is responsive to a difference between a desired and sensed operating condition of the machine, as for example desired and sensed values of output voltage when the machine is a generator.

Abstract: A generating apparatus for charging the battery of an automobile or the like is disclosed. A charging generator has an input shaft on which is mounted a driven pulley which is belt-driven by the drive pulley of an automobile engine. An adjustable speed change mechanism in the form of a planetary cone reduction gear is housed inside the driven pulley. The reduction gear transmits drive force from the driven pulley to the input shaft of the charging generator. A reduction ratio adjustment mechanism automatically decreases the ratio of the rotational speed of the input shaft to the rotational speed of the driven pulley as the rotational speed of the driven pulley increases so as to maintain the rotational speed of the input shaft substantially constant. In a preferred embodiment, the reduction ratio adjustment mechanism comprises a centrifugal governor.

Abstract: A control apparatus for a vehicular charging generator utilizing various sensors which detect an unstable rotation during the starting of an engine, the acceleration/deceleration condition of the engine, an overload condition of the engine etc. to regulate the output voltage of the generator by a micro-computer, whereby the rotation of the engine is stabilized and the acceleration performance is enhanced due to a reduction of the load of the generator while and over-discharge of the battery is effectively compensated. Also, various abnormal conditions are detected by the sensors and indicated.

Abstract: A primary and at least one backup alternating voltage source are coupled to a common load to provide interrupt free electric current to the load through a simplified interconnecting network. Phase control of all but one of the sources is accomplished by monitoring the phase difference across choke coils coupling the sources to the load.

Abstract: A voltage regulator for regulating the output voltage of a diode-rectified alternating current generator that supplies the electrical loads on a motor vehicle including the storage battery. The voltage regulator has an up-down counter which is incremented when the output voltage of the generator is below a desired regulated value and is decremented when the output voltage of the generator is above the desired regulating value. The magnitude of the count in the counter is repeatedly sampled and used to determine the on time of a semiconductor switch that is connected in series with the field winding to thereby control the duty cycle of the field voltage pulses. The counter is incremented at a lower rate when the speed of the engine that drives the generator is below a predetermined speed than it is when the speed of the engine is above the predetermined speed. When the generator is not rotating, the up-count of the counter is limited to a predetermined value that provides a minimum field voltage duty cycle.

Abstract: A voltage regulating system for an automotive vehicle having a switching transistor connected to a field winding of an alternating current generator and a regulator for comparing a battery voltage with a reference value and for driving the transistor into a conductive state when the battery voltage is lower than the reference value. A current limiting circuit is provided for limiting the field current when the switching transistor is going to be driven into the conductive state over a predetermined interval, so that a maximum charging current can be obtained and an unfavorable heating of the switching transistor can be avoided.

Abstract: A load control system for controlling the field current of an alternating current generator and the idle speed control system for the engine that drives the generator. A voltage regulator senses the output voltage of the generator and controls field current by causing a semiconductor switch connected in series with the field winding to switch on and off in accordance with the magnitude of the sensed voltage. The voltage regulator is controlled to operate in a conventional manner when engine speed is higher than engine idle speed. When engine speed is in an idle speed range the duty cycle or on time of the semiconductor is controlled such that consecutive occurring on times are gradually increased to gradually increase field current when the output voltage of the generator is below a desired regulated value.

Abstract: An electronic circuit is disclosed for detecting a non-operating or fault condition in an alternator. The disclosed embodiment senses the alternator's unrectified output voltage and generates a control signal when the alternator's output voltage fails to exceed a threshold. That threshold is selected to be outside the range of any static voltage the alternator might generate as a result of leakage currents therein. Further circuitry preferably responds to the control signal by generating an indication of a non-operating condition in the alternator.

Abstract: Subsynchronous resonance is detected in an electric a.c. power supply system by determining changes in wave parameters of substantially successive half cycles and applying said changes as a relationship of said subsynchronous resonance. The parameter change measured is the wave period, and changes in the ratio of the difference of the period of positive and period of negative half cycles over the sum of the period positive and the period of negative half cycles is related to detection of subsynchronous resonance.

Abstract: A D.C. charging and starter circuit for a vehicle includes a microcomputer which monitors the state of battery switch units, a pair of charging generators and a starter switch, and operates to control various switching elements and the like to prevent accidental discharge of the batteries, and to prevent damage to either the electrical load or the generator rectifier circuits.

Abstract: Methods and apparatus are disclosed for synchronizing multiple AC motor driven synchronous generators to the voltage on a common output bus. In one method, the rotating motor is disconnected from its AC power source, the generator voltage is phase synchronized to the output bus voltage, and then the generator rotor is caused to slip one generator pole at a time until the motor generated voltage is phase synchronized to the AC power source voltage. At that point, the motor is reconnected to the AC power source. Other methods are disclosed in which magnetic position sensors are employed to provide an indication of when the rotors on multiple motor driven generators are mechanically phase synchronized.

Abstract: A DC-link, variable speed constant frequency power system is provided with an auxiliary DC output. The system includes a variable speed generator for producing a DC voltage on a pair of DC-link conductors. When the generator is operated in its normal speed range, an inverter converts the DC voltage to a constant frequency AC voltage. When the generator is operated at a speed which is below its normal speed range or when an external auxiliary output command signal is received, the DC-link conductors are switched to an auxiliary output line and the DC-link voltage is regulated to maintain the desired auxiliary output voltage level.

Abstract: A battery charging control system for automobile, wherein a voltage regulator for regulating the output voltage of an AC generator for charging the automobile battery is controlled by detecting changes of the output voltage. When the output voltage of the generator changing with ripples is reduced with an increase of load current, the minimum value of the output voltage is detected, while when the output voltage increases with an increase of the generator rotational speed, an average value of the output voltage is detected. In accordance with these values, the voltage regulator is controlled to compensate for the changes of the output voltage of the generator.

Abstract: A supervisory unit for detecting abnormalities in shaft voltage of rotary electrical machinery and apparatus such as brushless synchronous machines. The supervisory unit includes a first detector for detecting the voltage across at least two points of the rotor shaft, a second detector for detecting the voltage between the rotor shaft and ground, and a third detector for detecting an electrical condition of an AC exciter which constitutes part of the field system of the apparatus. The third detector may detect electrical signals indicative of the field system voltage or the field system current. The supervisory unit includes a voltage comparator and a frequency comparator which receive detection signals from the three detectors to provide a signal indicating abnormality when an abnormal condition occurs, such as contact failure of a grounding brush or a failure in coil insulation.

Abstract: An electrical power system has a variable speed multi-phase alternator. A multi-phase full wave rectifier with controlled rectifier elements converts the electrical power to DC. The DC voltage is regulated by a control circuit which determines the angle of conduction of the rectifier elements. If the alternator frequency is excessive, the controlled rectifier elements are not reliably commutated. The control circuit compares the alternator frequency with a reference. When the frequency is above a selected value, rectifier operation is modified either for half wave rectification or for full wave rectification of less than all of the phases from the alternator. Additional switching time is provided, improving reliability.

Abstract: A power conversion system for converting between electric and motive power may be utilized either in a generating mode to generate electric power from motive power supplied by a prime mover or in a starting mode wherein motive power is developed by the power conversion system from electrical power and is supplied through a torque converter to the prime mover to start same. The power conversion system includes a main generator, an exciter and a permanent magnet generator, or PMG, which together comprise a brushless alternator. When operated in the starting mode, power is supplied to the PMG to cause it to act as a motor and thereby drive a rotor which is common to the PMG, exciter and main generator. Once a predetermined operating condition of the generator is attained, the main generator is supplied power from a motor control to cause the generator to act as a synchronous motor and the power supply to the PMG is disconnected.

Abstract: A coupling system for an induction motor type generator (10) to an A.C. power line (18) wherein an electronic switch means (28) which is controlled by a control system (30) is regulated to turn "on" at a relatively late point in each half cycle of its operation whereby the energizing power supplied by the line (18) to the induction motor type generator (10) is decreased and the net power delivered to the line is increased.

Abstract: In a motor-generator set, the frequency of the AC generator outputted voltage is automatically adjusted by field winding regulation of the DC motor, through a closed loop in which a dual-slope converter is charged during a clock-defined time interval in accordance with a potentiometer setpoint, and the charging plus discharging period of the dual slope converter encompasses the period of the outputted voltage.

Abstract: The alternator comprises an induction winding sub-divided into two half-windings (1, 2) each connected to the input terminals of a respective double half-wave rectifier circuit (3, 4). It further includes thyristors (14) each of which connects a terminal (A, B, C) of one half winding (1) to a non-homologous terminal (C',A',B') of the other half-winding (2) such that, when the thyristors (14) are triggered, the electromotive forces generated in the two said half-windings (1, 2) are added in phase with each other. When the speed of rotation of the engine of the motor vehicle is less than a predetermined value, the said thyristors (14) are triggered and hence the two half-windings (1, 2) are connected in series with each other. If the speed of rotation of the engine surpasses this predetermined value, the thyristors (14) are not triggered, and the two half-windings (1, 2) are connected in parallel with each other.

Abstract: A control unit is disclosed for controlling the driving torque of a generator driven by an engine in accordance with the number of cylinders to be operated, thereby to achieve stabilized operation. A voltage regulator is provided for varying the field current through the field coil of the generator so as to regulate the output of the generator. A circuit component including a pair of NC contacts in parallel with a resistor is connected in series between the field coil of the generator and a power source. Depending on the number of cylinders to be operated, the NC contacts are either closed to provide a low resistance path for current to the field coil or are opened to provide a high resistance path through the resistor.

Abstract: The present invention relates to a charging generator control system comprising a generator which includes a field winding, and an armature winding being in three-phase connection to generate an A.C. output; a rectifier which rectifies the A.C. output from said armature winding of said generator; a battery which is charged with a D.C. output from said rectifier and which can supply an exciting current to said field winding; a separately-exciting power source which generates a D.C.

Abstract: A circuit for use with an induction generator. The circuit is arranged to initiate operation of the induction generator as a motor to bring the system up to operating speed and subsequently to rearrange the system automatically to cause the induction generator to operate in a generating mode. The automatic reconnection is effected as an incident of the motor reaching a preselected speed. Determination of the preselected speed may be effected by voltage responsive means in one form of the invention, and by centrifugal switch in another form of the invention. The control is effected by suitably selectively connecting the phase winding of the generator. In the illustrated embodiment, a starting capacitor and a power factor correction capacitor are automatically connected at proper times in the operation.

Abstract: To provide for effective cooling of an automotive-type alternator and/or other equipment within an automobile, for example the radiator or other heat exchanger, even under external high-temperature conditions and low engine speed (n.sub.E), for example under idling conditions, the alternator phase windings (6, 7, 8) are connected to respective phase windings (16, 17, 18) of a three-phase squirrel-cage motor which is connected to a blower (2), preferably a radial-type fan, directing forced air circulation towards the alternator and/or the vehicle radiator, the alternator then being placed within the airstream of the radiator as well. A temperature and/or speed-responsive switch can be interposed between the alternator and the motor to energize the motor only if the temperature of the alternator and/or the engine, or other component, rises above a predetermined level, or if the alternator speed drops below a predetermined level.

Abstract: A variable frequency drive for a motor-generator/alternator set which is used to supply electrical power to computer or data processing equipment. Power failures in commercially supplied power results in aberrations and erroneous computations in computers and data processing equipment. An induction motor is used to drive a generator/alternator. The induction motor is driven below the synchronous speed of the generator/alternator and a variable speed drive increases the velocity supplied to the generator/alternator, preferably to a point above its synchronous speed. Therefore, when there is a commercial power failure, the generator/alternator remains within a desired frequency range for a longer period of time than a comparable generator/alternator driven at synchronous speed.

Abstract: The variation of the load on a wind-driven A.C. generator (16) in accordance with a predetermined law which relates the load to the speed of rotation, is achieved by detecting the period of each half cycle with the aid of a timing unit (10), calculating the percentage conduction required in each half cycle in accordance with the predetermined mathematical law, and using the calculated result to gate a pair of thyristors (12, 14) to conduct for said calculated percentage in alternate half cycles so as to pass a unidirectional current to said load. By variation of conduction during each half cycle the effective resistance of the load can be matched to the voltage output of the A.C. generator over a wide range of speeds. Not only can the efficiency of the system be increased, but the windmill is prevented from being stalled in light breezes.

Abstract: To utilize the full power capacity of alternators 1, the alternator phases are connected through a transformer 9 to the rectifier 4 which provides rectified output to a battery 8. The transformer 9 has tapped windings, the taps being placed in circuit with the alternator-rectifier network in dependence on a speed control signal, for example derived from the frequency of the alternator, to effect tap changing and matching of the internal impedance of the alternator 1 to the battery 8/load L combination. In accordance with one feature (FIGS. 2, 3), the taps are on the primary, and a-c switches such as triacs 15 are selectively energized as the speed of the generator changes; in accordance with another embodiment (FIGS. 4, 5), the taps are on the secondary of the transformer, and unilaterally conductive switches, such as thyristors or SCRs 48, can be used, in parallel with the rectifier diodes 47 of the rectifying array, and selectively fired as a function of speed.

Abstract: An electric power generator system including a switched capacitor controlled induction generator adapted to provide power at a regulated voltage and frequency. The system is adapted for autonomous operation for delivery of power with unity power factor to an external power grid.

Abstract: A substantially constant frequency self-regulated generator produces in one embodiment 120 volts or the like single phase output or in another embodiment 120 or 240 volts or the like single phase output. The generator employs an exciter stator and a stationary rectifier assembly with the former being a six pole exciter stator alternately wound with three shunt poles and three series poles with two separate windings on each series pole. The three shunt poles of the exciter stator are connected in series making, in effect, one shunt winding. The series circuit consists of two separate windings on each series pole, which are respectively parallel connected and wound on all three series poles. Each series pole then has two separate isolated coils. With the exciter stator there is employed a stationary diode assembly utilizing three diodes as rectifiers for the shunt and isolated series windings.

Abstract: The invention is an aircraft power generation system which utilizes an induction-machine (G.sub.1) as a primary generator of variable-voltage/variable-frequency power. The induction-machine (G.sub.1) is directly driven by the engine (14) and is excited by an excitation-generator (G.sub.2) such that the induction-machine (G.sub.1) operates in a generating mode. A variable-speed drive (20), shown as a toroidal drive (30), controls the excitation frequency of the induction-machine (G.sub.1) such that the negative slip-frequency is controlled as a function of the input speeds (N.sub.1), (N.sub.2) and the electric load on the generator. Control of the toroidal drive (30) and thus speed (N.sub.2) is accomplished by a negative-slip control circuit which includes a drive control logic circuit (36), a proportional actuator (34), a control-start panel (48), and a steering mechanism (32).In another aspect of the invention, the induction-machine (G.sub.1) operates in a start-mode to start the engine (14).

Abstract: A digital electronic governor controls and stabilizes the electrical power output delivered to an output circuit by an AC alternator having a rotating shaft driven by a source. The governor provides a first relatively fast acting governing function operatively responsive to phase shift of the electrical power output relative to the rotating shaft corresponding to changes in load at the output circuit. The first governor stabilizes the phase shift of the electrical power output at a specified phase lag interval relative to the shaft rotation. The electronic governor also provides a second governing function operatively responsive to relatively slower inertial changes in the speed of rotation of the shaft, corresponding to changes in the power level of the AC alternator. This second governor stabilizes the rotating shaft at a specified speed of rotation, e.g., 60 cycles per second. The first governor generates load signals in response to the measured phase shift deviation from a standard phase lag interval.

Abstract: A circuit for damping hunting oscillations of controlled electric machines. The circuit is provided with a measuring circuit for determining the hunting oscillations and an identifier circuit for determining the angle components of such hunting oscillations. A phase shifter circuit is provided for receiving the angle components produced by the identifier circuit and forming a hunting oscillation correction signal which is shifted in phase from the hunting oscillations by a predetermined phase angle. The hunting oscillation correction signal is conducted to a control unit of the electric machine. The invention is particularly useful in damping hunting by the rotors of voltage controlled synchronous generators.

Abstract: A power generating system for adjustably coupling an induction motor, as a generator, to an A.C. power line wherein the motor and power line are connected through a triac. The triac is regulated to normally turn "on" at a relatively late point in each half cycle of its operation, whereby at less than operating speed, and thus when the induction motor functions as a motor rather than as a generator, power consumption from the line is substantially reduced.

Abstract: A voltage source is connected in series with the neutral secondary winding on a generator step-up transformer through an electrical reactance. A control circuit and a pair of thyristor banks are employed to apply the voltage source to the transformer winding to dampen sybsynchronous resonance currents and to prevent torsional mode vibrations from occurring within the generator.