Westinghouse Electric Corporation

Donal E Baker

David A Fox

Mirza A Beg

Eric J Stacey

Kenneth C Shuey

Charles L Doughman

Ralph D Jessee

Roger D Thornton

Jack W Ogden

William J Shilling

A variable speed, constant frequency starter generator system is provided with a dynamoelectric machine, electrically connected to a multiple-phase bus and pair of multiple-phase rectifiers for producing a DC voltage on a pair of link conductors. An inverter converts the DC voltage to floating AC voltage which is further converted to a ground-referenced AC voltage by a transformer. During generator operation, the output voltage of the machine is rectified by at least one of the rectifiers to produce a DC voltage on the link conductors which is converted to a constant frequency AC voltage by the inverter. During starter operation, an externally supplied AC voltage is applied to the transformer. The transformer converts the externally applied AC voltage to a pair of phase-displaced AC voltages which are rectified by the pair of multiple phase rectifiers to produce twelve-pulse rectified DC voltage on the link conductors. This reduces the harmonic content of the current supplied by the external power source. In another embodiment, a third multiple phase rectifier performs the function of rectifying the output voltage of the machine to produce a six pulse DC voltage on the link conductors for generator operation.

VSCF starter/generator systems

Voltage regulation of a DC electrical power source having a generator with an exciter field coil for producing an AC output voltage which is rectified to produce a DC output voltage, is accomplished by producing voltage signals proportional to the AC output voltage of the generator and the current in the generator exciter field winding, and combining these signals to produce a control signal. An additional voltage signal proportional to the DC output voltage of the power source is compared to a DC reference voltage signal to produce a trim error voltage signal. The trim error voltage signal is combined with an AC reference signal to produce an additional control signal. These control signals are compared and the result of that comparison is used to control the current in the generator exciter field winding.

Method and circuit for voltage regulation of DC power sources

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. During motor operation, the AC exciter field winding receives power from an external power source, usually of constant voltage and constant frequency. During generator operation, DC power is supplied to the DC exciter field winding.

Starter generator system with two stator exciter windings

A method for sensing real load unbalance in an electrical power system having at least two clock based power sources which are connected for parallel operation combines a real load difference current signal, proportional to the difference in real load currents in corresponding phases of the power sources, with a phase angle signal which is proportional to the phase difference between an external clock signal and an internal clock signal of one of the power sources, to produce an error signal. When this error signal exceeds a predetermined threshold level, a trip signal is produced to indicate that an excessive real load unbalance situation exists.

Real load unbalance protection system for parallel variable speed

A parallel power system includes at least two DC link variable speed constant frequency power sources each having a plurality of output phases connected to a common bus. The total real error current flowing in the output phases of each of the power sources is monitored and the relative phase angle of the Thevenin voltage of the power sources is controlled in response to the monitored total real error current to reduce the magnitude of this real error current. The reactive error current flowing in at least one of the output phases of each of the power sources is monitored and the relative magnitude of the Thevenin voltage of the power sources is controlled in response to the monitored reactive error current to reduce the magnitude of the reactive error current. For operation at no load, the phase angle control loop is sensitive to both real and reactive error currents.

DC link variable speed constant frequency power source paralleling

A clock control system for a multiple channel electric power system includes a master clock circuit and control circuitry in each parallel connected channel. The channel control circuits are intially phase-locked to a master clock signal. If the master clock signal is out of a preselected frequency range, the individual channel control circuits are decoupled from the master clock signal and one of those circuits produces a backup clock signal. The control circuits in the remaining channels are then phase-locked with the backup clock signal to provide continued parallel system operation.

Master clock system for a parallel variable speed constant frequency

An electromechanical constant speed drive generating system is provided with a mechanical differential having first, second and third rotatable shafts, wherein the speed of the second shaft is equal to the speed of the first shaft multiplied by the first contant plus the speed of the third shaft multiplied by a second constant. The first shaft is coupled to an external engine and is driven at a variable speed ranging between predetermined lower and upper limits. A constant speed generator is connected to the second shaft for producing a constant frequency output. A power converter is electrically connected between the output of the constant speed generator and a variable speed dynamoelectric machine which is coupled to the third shaft, to transfer power between the output of the constant speed generator and the variable speed dynamoelectric machine, thereby controlling the speed of the dynamoelectric machine such that the speed of the second shaft remains substantially constant when the speed of the first shaft varies between the defined upper and lower speeds. The system can also be used to start the engine by operating the constant speed generator as a motor. Thus both start and generate modes of operation are possible.

Electromechanical constant speed drive generating system

A current limiting circuit for a DC to AC inverter is provided with means for sensing the current in the inverter output phases and means for switching all of the power poles to the polarity of the minority power pole when an overcurrent condition occurs. This reduces the switching current levels of the inverter power pole switches to reduce switching stresses and improve reliability. A current sensing scheme is illustrated in which self-excited transductors are used to sense the current in two of the three inverter output phases and the current in the remaining output phase is derived from these two sensed currents.

Electrical inverter with minority pole current limiting

A multiple phase electronic inverter circuit includes a transistor bridge output circuit having a pair of series connected transistors in each output phase leg connected between a pair of conductors for supplying direct current to opposite ends of the phase leg with a connection point between the transistors of each phase leg serving as an output power pole. A waveform pattern generator generates a transistor switching pattern which causes the transistors to alternate between two complementary operating modes such that one transistor in each phase leg functions in a communication mode and the other transistor in that phase leg functions in a non-commutation mode. By switching between the two operating modes, saturation of controlled current feedback transformers in the base drive circuit of each transistor is prevented.

Inverter with constant voltage to frequency ratio output capability

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.

Variable speed constant frequency power system with auxiliary DC output

A phase detecting circuit for use in a phase-locked loop is provided with a pair of bistable circuits such as type D flip-flops. One of the circuits is clocked by a controlled output signal from a voltage controlled oscillator, and reset by an input reference signal. The other of the bistable circuits is clocked by an inverted input reference signal and reset by an inverted output signal from the voltage controlled oscillator. The Q and NOT Q outputs of these bistable circuits are fed to a voltage divider and shifted in magnitude by a fixed amount such that the phase error detection signal is a constant zero when the input reference signal and output signals are in phase.

Electronic phase detector having an output which is proportional to the

A demodulator circuit utilizes a switching demodulation technique to detect the real and reactive components of load current unbalance in a parallel source alternating current power system. A signal representing load current unbalance is selectively switched to a pair of output terminals in response to a series of pulse wave control signals which bear a phase relationship with the Thevenin equivalent voltage of one of the power sources such that the signal appearing at one of the output terminals represents the real load current component while the signal at the other output terminal represents the reactive load current component. The signals at these terminals are fed back to control the frequency and voltage magnitude of one of the power system sources to eliminate load current unbalance.

Demodulator circuit for parallel AC power systems

A toroidal transformer is provided with an inner winding electrostatic shield formed by bringing together two conductive annular cups having a generally U-shaped radial cross section. The widths and radii of the sidewalls of these cups are dimensioned such that one of the sidewalls of the first cup forms a conductive interference fit with the corresponding sidewall of the second cup, while the other sidewall of the first cup is separated from the corresponding sidewall of the second cup by a gap, which prevents the shield from becoming a shorted turn. The shield formed by these two cups is placed around a wound core and a second winding is wound over the shield to form a transformer.

Toroidal transformer with electrostatic shield

An alternating current power controller is provided that employs DC transistor switching for subcycle switching capability and to eliminate problems associated with SCRs and furthermore provides internal elements for generating the required DC control power from the AC source whether the AC load is on or off.

Alternating current power controller with DC transistor switching and an

The firing pulses to the nonload carrying bank only of the naturally commutated thyristor power circuit of a static power converter are retarded to reduce or eliminate the interbank circulating current. In one form of the invention, half wave rectified load current signals are summed with the output waveform reference signal applied to the positive and negative bank firing pulse generators in a sense to retard the pulses in the nonload carrying bank. In another form of the invention, the inversion end stops are used to generate the retarded firing pulses in the nonload carrying bank.

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American, OH, United States of America

Donal E Baker