Abstract: A power conversion scheme for transferring power between a DC current source and an AC voltage source employs a polyphase bridge and a thyristor to short circuit the DC current source to interrupt AC current. Comutation of the thyristor is achieved by scheduling firing switch devices of the bridge as a function of phase voltages of the AC voltage source.

Abstract: A method and apparatus for enabling the continuous monitoring of the operational state of circuit components includes a scheme for generating a plurality of voltage signals representing neutral-to-line voltages of the system and adding to each of those signals a second signal, each second signal being identical. This addition is done vectorially to yield a modified signal. A representation of the modified signal as acted upon by the circuit to be monitored is compared with a representation of the neutral-to-line voltage signal to yield an output signal representative of the operational state of the circuit components.

Abstract: A power conversion scheme employing a group of parallel connected, individually controlled converter circuits each providing output currents employs a scheme of distributed notches in the output currents to facilitate connection between common DC current and AC voltage sources. By the parallel connection of a pair of groups, time phase displaced group to group, additional power capability and harmonic reduction is achieved.

Abstract: A power switching system for controlling the conductivity of a plurality of thyristors of the gate turn-off type (GTOs) which are connected in parallel between two power sources by gradually introducing a time compensation to force the times of turn-off of each of the thyristors toward matched values by determining the turn-off time during each conduction cycle and thereafter advancing or retarding the turn-off signal for the following conduction cycle to correct for the difference in turn-off times. A difference signal is generated between time of turn-off of an average current of the thyristors and the time of turn-off of an individual current in one of the thyristors from which a time advance or delay signal is added to the thyristor turn-off signal in response to the current flowing in a capacitor type integrator. This allows the turn-off times to reach a perfect match during periods in which the current is the same for several cycles.

Abstract: An electrical power converter including both DC and AC power terminals which are respectively connected to a DC current source and an AC voltage source, the latter comprising the grid of an AC power utility. A capacitor is coupled to the AC terminals along with a load. A control and gating circuit is coupled to the converter for supplying control signals for the thyristors of a converter bridge included in the polyphase converter. When disconnected from the utility grid, a relatively fast acting control loop is coupled to the control and gating circuit and is responsive to the current flowing in the capacitor and an AC reference voltage to accommodate the current source characteristics of the converter for maintaining an output voltage of substantially constant amplitude across the AC terminals.

Abstract: A method for operating a multi-phase switched reluctance motor is a generator mode includes gating switches connected in series with selected ones of the phase windings of the motor into conduction to establish current flow in a selected one of the windings. The switches are thereafter disabled and current is forced to commutate into flyback diodes whereby the current is returned to an associated DC bus. The instant at which the conducting switches are gated out of conduction is selected or measured in angular displacement between an associated stator pole and a corresponding rotor pole by establishing a preselected magnitude of current such that when the current in the winding reaches that magnitude, the switches are disabled. The voltage at the DC bus is regulated during generator mode operation by adjusting the phase angle measured between a stator pole and a corresponding rotor pole at which the switches are gated into conduction.

Abstract: A method of controlling a switched reluctance motor during high speed operation in an operational range when the counter electromotive force exceeds the available DC source voltage and, therefore, the maximum desired converter current cannot be obtained, establishes torque control in a feedforward manner by controlling current pulse position.

Abstract: In a system for stabilizing the operation of an electrical generator connected to a power distribution network, which system includes a power system stabilizer operating through a modulator circuit to control generator oscillations, there is included a scheme for testing the integrity of the power system stabilizer and modulator circuit which involves the application of a test signal having known values to the power system stabilizer. This test signal propagates through the circuitry and the resultant output is demodulated to be compared with a stored representation of the test signal to thus yield outputs representing the gain and phase shift of the power system stabilizer and modulator circuit in combination.

Abstract: A method and apparatus for enabling the continuous monitoring of the operational state of circuit components includes a scheme for generating a plurality of voltage signals representing neutral-to-line voltages of the system and adding to each of those signals a second signal, each second signal being identical. This addition is done vectorially to yield a modified signal. A representation of the modified signal as acted upon by the circuit to be monitored is compared with a representation of the neutral-to-line voltage signal to yield an output signal representative of the operational state of the circuit components.

Abstract: A method and apparatus for improving the operation of a switched reluctance motor at low speed incorporates an advance angle regulator which regulates the firing angle of current pulses to the switched reluctance motor so that over a wide range of speeds and levels for direct current source voltages, the winding current reaches a commanded set point at a commanded angle. The advance angle regulator may comprise a closed loop regulator which includes apparatus for detecting the actual angular position at which motor current reaches a commanded level and adjusts the turn-on angle to shift the angle at which current reaches its desired level to a desired angle. The regulator incorporates a feedforward portion and an integral portion. The feedforward portion is utilized primarily to accommodate situations in which there is no current feedback. The integral portion provides the primary regulation when current is regulated to its desired value.

Abstract: A system for controlling a polyphase electric motor, particularly at low speeds, using a load commutated inverter includes the generation of half sine wave signals within a range of desired frequencies which are subsequently converted to single phase alternating current power for application to selected windings of the motor. In a single channel polyphase embodiment, motor starting is achieved using zero current commutation and normal phase control. A two channel embodiment results in what amounts to two phase operation of the motor.

Abstract: A scheme for stabilizing a synchronous alternating current generator through the excitation control to dampen generator oscillations includes a power system stabilizer responsive to signals representing the generator output voltage and output current to provide an oscillation signal which represents the instantaneous magnitude of the generator oscillations. A modulator means is included which develops a signal, representing the generator voltage with respect to neutral, and this latter signal is multiplied by the oscillation signal to provide a control signal which controls the excitation of the generator.

Abstract: A scheme for detecting reduced source of voltage of a controlled switching power supply including a transformer employs the inherent insolation characteristics of the transformer to yield an isolated alarm signal indicative of a failed or inadequate source voltage.

Abstract: An induction motor drive having source and load side converters with individual control channels for the respective converters includes a cross tie arrangement between the channels for increased system stability.

Abstract: An insulated coil assembly for use in electrical apparatus includes a coil of conductive wire formed in a predetermined configuration around selected portions of which is disposed an insulating layer comprised of a cured resin impregnated, close woven, heat-cleaned glass fiber tape.

Abstract: A digital filter for a power system stabilizer in a generator power system. The filter comprises a multi-stage filter having a low DC gain, a phase lead in the region of power oscillations (approximately 0.1 to 2 hertz) of the power system, a torsional reject characteristics (approximately 13.5 to 45 hertz) associated with mechanical resonances of the system, and high attenuation at the fundamental power frequency (e.g. 60 hertz). The filter is comprised of four digital filter sections, the first providing a lead and lag characteristics, the second and third providing a torsional reject characteristic, and the fourth providing a substantially zero DC gain characteristic for the elimination of any DC signal offset as well as a line freqeuncy notch, which tracks the fundamental line frequency.

Abstract: An induction motor drive including a current source inverter system having controlled turn on and turn off semiconductors in a load side inverter selectively places notches in the waveshape of the current supplied to the parallel combination of the motor and a capacitor bank for the minimization of harmonics.

Abstract: A brush wear indicator for a dynamoelectric machine, such as a direct current motor, comprises a fiber optic conductor coupling an emitter and a detector. The fiber optic conductor is fed into a brush holder where it is supported by a spring holder to which is attached a coiled biasing spring. The fiber optic conductor includes a region of separation where an element actuated by the biasing spring operates to complete or interrupt a light path between the exposed ends of the conductor at the separation. In one embodiment, an angulated tab secured to the spring operates as a shutter to move in and out of the spring holder to complete or interrupt the light path, while in a second embodiment, a rubber flexible diaphragm having an inwardly projecting body portion is actuated by the spring, by moving in and out of said region of separation to complete or interrupt the light path.

Abstract: A method and apparatus for performing a complete functional test of a power system stabilizer connected to the excitation system of an electrical power generator is disclosed. Two tests are performed, one an on-line modulation test, and the second a system response test. In the on-line modulation test, an internal 0.5 hertz sine wave is generated by a microprocessor which is applied as a frequency modulating input to the continuous wave frequency transducer included in the power system stabilizer. Such a signal acts to stimulate intertie mode oscillations and provide a means of determining the gain and phase shift characteristic of the power system stabilizer. In the second test, a voltage step type of signal is generated and applied to the output of the power system stabilizer where it is then coupled to the excitation system of the generator. This has the effect of stimulating local mode oscillations. The generator response to the local mode oscillation is sensed to determine system damping.