Abstract: An induction motor is powered from a DC source through a DC to AC inverter. The inverter frequency and the AC output voltage of the inverter are controlled as a function of motor current to minimize motor starting current and to accommodate a range of DC supply voltages.

Abstract: An electromagnetic energy storage and supply system for supplementing a main power supply to provide D.C. current to a pulsed load by providing that portion of the load current which is above the average load current commanded. The load current is sensed and compared to an average current command to provide a difference signal which is proportional to a desired supplemental current to be provided to the load. An inverter, coupled between the main power supply and a motor, is controlled during the off period of the pulsed load and in response to the difference signal to provide an A.C. signal to the motor which in turn drives an inertia device coupled thereto for storing energy. During the on period of the pulsed load the inertia device decelerates, discharging energy through the motor and inverter to provide the supplemental D.C. current to the load.

Abstract: A variable speed constant frequency generating system for generating constant frequency electrical output power from a variable speed source of motive power includes an exciter for generating excitation current, a main generator for developing the output power, both of the exciter and main generator being driven by a shaft coupled to the motive power source and power converters mounted on the shaft to transfer power between the exciter and the main generator. At shaft speeds below synchronous speed, i.e. that speed which would produce the desired output frequency when DC power is coupled to the main generator field windings, the exciter output is rectified and inverted so that alternating current power of proper frequency is delivered to the field windings of the main generator to maintain the output of the generator at a constant frequency. At synchronous speed, the power converters transfer substantially only DC power to the main generator windings.

Abstract: A multiple output DC power supply having a single closed loop control system for two or more power amplifiers which provide matched DC outputs. The control system is responsive to the sum of the DC signals output from the power supply to derive an average error signal. A switching logic circuit compares signals representing the unregulated AC power driving the power amplifiers to a reference signal in order to generate a set of control signals for each of the amplifiers, the average error signal biasing the reference signal so as to vary the time of occurrence of the control signals and regulate the DC outputs.

Abstract: A bidirectional inverter circuit for evenly distributing energy among two capacitors in a DC power supply of a pulse width modulated inverter which provides an AC output to a load. The bidirectional inverter circuit is responsive to a greater charge on one of the power supply capacitors than on the other to divert regenerative current flowing to the power supply from the load away from the one capacitor and to transfer charge to the other capacitor.

Abstract: A rotor structure for a permanent magnet generator, or PMG, includes a plurality of spaced apart magnets and magnetic circuit elements in series with the magnets on the rotor to act as flux limitation means to thereby limit the output voltage of the permanent magnet generator at low current levels.

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: An excitation system for a brushless synchronous alternator includes an exciter having a stator which includes first and second sets of field coils respectively coupled to a source of DC power and in series with polyphase AC output current developed by the main generator. A base level of exciter field current is provided by the DC current delivered to the first set of field coils while a second variable amount of field current is provided by the AC output current delivered to the second set of field coils. The exciter also includes a rotor structure having first and second sets of armature windings which develop first and second exciter currents in response to movement of the rotor structure within the magnetic fields set up by the first and second sets of exciter field coils. The first and second exciter currents are added, rectified and delivered to a set of main generator field windings.

Abstract: A generator system which is self-excited even during a fault condition includes a main generator having armature windings and a main field winding which is excited by a rotary transformer. The rotary transformer includes a stationary primary winding and a rotating secondary winding, with the primary winding receiving a controlled portion of the main generator armature output. The current through the primary winding of the transformer is controlled by silicon controlled rectifiers which are gated by a voltage regulator circuit. The voltage regulator circuit in turn receives signals from the voltage delivered to the load, the highest phase current delivered to the load and the voltage at the main generator armature output. The voltage regulator controls the current through the primary winding of the transformer in accordance with the voltage delivered to the load if that voltage is greater than a predetermined value.

Abstract: Control systems for controlling load division among plural power sources coupled in parallel and providing power to a common load using feedback techniques. Control systems for various types of plural power sources are disclosed, including DC generators, hydraulic variable displacement pumps and AC generators driven by a constant speed drive. The outputs of the individual power sources are responsive and proportional to individual input control signals. The magnitude of a power component common to all the power sources or frequency, if the power sources are AC generators driven by constant speed drives, is compared to a reference to provide an error signal. Individual sensors sense the magnitude of a variable power component from each power source and provide a signal proportional thereto. Individual signals representing the variable power component are combined with the error signal to provide the individual control signals for each power source.

Abstract: In a synchronous generator-motor, having both its main armature windings and exciter winding located on the stator and both the main field winding and the exciter armature windings including a rectifier for providing DC current to the main field located on the rotor and also including a voltage regulator responsive to the main armature voltage for regulating the current applied to the exciter field; the effects of transient currents in the main field windings resulting from load removal during the generator mode of operation and the voltages induced during motor start-up are substantially reduced by utilizing a resistive circuit operatively controlled by a transistor switching network that is in turn responsive to the exciter voltage and the induced voltage in the main field windings.

Abstract: A transistor switch short-circuits the main field rotor winding of a synchronous machine during start-up. A transistor is connected across the main field rotor winding and is responsive to the polarity of the voltage induced in the main field rotor winding by the main stator winding. When the voltage is of one polarity, the transistor conducts to short-circuit the main field rotor winding. When the voltage across the main rotor winding is of the opposite polarity, diodes limit the voltage buildup. The transistor which shorts the main field rotor winding is rendered inoperative when the machine is operating at or near synchronous speed.

Abstract: A multi-channel generating system wherein each channel is provided with a permanent magnet generator (PMG) coupled directly to the output of a constant speed drive. An overrunning clutch is located between the PMG and the generator. The frequency of the signal from the PMG is proportional to the output speed of the constant speed drive. A circuit provides underspeed information if the speed, as indicated by the PMG, drops below a minimum speed represented by a reference voltage. The underspeed information controls the excitation and de-excitation of the generator exciter voltage and a line contactor switch.

Abstract: An in-line voltage balancing circuit sums a trim voltage with each phase voltage of a polyphase generating system to assure that the voltage between each phase and neutral is equal to the average voltage of all the phases. An individual error signal representative of the difference between each phase voltage and the average voltage is provided to individual phase modulator circuits. The phase modulator circuits develop pulse width modulated signals wherein the pulse width is proportional to the amplitude of the error signal. The outputs of the phase modulator circuits are connected to switching amplifiers which provide trim voltages proportional to the phase modulated signals. Summing transformers are employed to sum the individual trim voltage with appropriate phase voltage so that the voltage for each phase equals the average voltage.

Abstract: An improved rotor assembly for a generator used in a multi-channel parallel electrical generating system. A plurality of laminated sections, each having N outwardly extending poles, are stacked to form a rotor. Field windings are wound around the N poles and damper turns are wound around adjacent pole pairs to reduce the mutual flux coupling between the rotor and the stator, thereby reducing the fundamental component of torque between the rotor and the stator.

Abstract: A DC to AC inverter in which a composite waveform synthesizing a sinusoidal waveform and having three incremental steps for each quarter cycle is formed by summing an alternating stepped waveform having three steps for half cycle, with a square wave in phase therewith and having a frequency three times greater than the alternating stepped waveform. In a three-phase embodiment of the inverter, each of three stages has a coil that is appropriately switched to opposite polarity terminals of a DC voltage source to form beginning and end segments of the alternating waveform, and a single square wave for all three phases is developed by three series-connected windings respectively inductively coupled with the three coils. The single square wave is added to all three alternating stepped waveforms to form the three composite output waveforms of the inverter.

Abstract: An inverter circuit which provides a synthesized sinusoidal output waveform having a low harmonic content. The inverter is light in weight, highly efficient and driven by a fundamental rectangular component having a frequency equal to the desired synthesized sinusoidal output frequency. Single-phase or three-phase output is provided.