Abstract: An apparatus for use in the simultaneous deactivation of a set of series-connected switching devices includes gate command control logic to generate a gate command signal for application to a selected switching device of the set of series-connected switching devices. A command compensation circuit processes the gate command signal. The command compensation circuit includes a time differential measurement module that forms a time differential signal indicative of the time from the previous turn-off of the selected switching device and the previous turn-off of the last switching device in the set of series-connected switching devices. A time difference processing module of the command compensation circuit process the time differential signal and creates a delay signal. A delay module of the command compensation circuit delays the gate command signal in response to the delay signal. Each switching device of the set of series-connected switching devices includes a command compensation circuit.

Abstract: The saturation of interphase transformers connected to an inverter is prevented through the use of an inverter switch firing control circuit. The inverter switch firing control circuit includes a control module to execute a standard switch firing scheme to produce a set of inverter pole output signals including a first inverter pole output signal and a second inverter pole output signal, with the first inverter pole output signal having a predetermined phase displacement from the second inverter pole output signal. The circuit also includes a control module to execute a system transient switch firing scheme wherein the inverter reduces the predetermined phase displacement between the first inverter pole output signal and the second inverter pole output signal in the presence of a system transient. This reduction in phase displacement between inverter pole output signals prevents saturation of interphase transformers. Thus, the size, cost, and weight of interphase transformers may be substantially reduced.

Abstract: An apparatus for generating a sensing signal from a generally periodic multi-phase AC signal is set forth. The apparatus utilizes a plurality of integrator circuits, a single integrator circuit being respectively associated with each phase of the AC signal. The integrator circuits each generate an integrated signal from the respective phase of the AC signal by integrating the respective phase during a time period between sloping transitions of the respective phase. A reset circuit is respectively associated with each integrator circuit for resetting each integrator circuit at the sloping transitions of the respective phase. The integrated outputs are summed by a summing circuit to form the sensing signal.

Abstract: A voltage sourced inverter system includes an inverter for coupling to a DC power source and an interphase transformer bank coupled to the inverter. The inverter includes a number of poles for providing discretely displaced voltage waveforms to the interphase transformer bank. A main transformer operably coupled to the interphase transformer bank transforms power therefrom into an AC power output. The interphase transformer bank may be a singular stage or a hierarchial arrangement of plural interphase transformers which combine the discretely displaced voltage waveforms to reduce selected harmonic components therefrom. The inverter may provide notched waveforms to remove additional selected harmonics from the discretely displaced voltage waveforms. A method of inverting DC power into AC power with reduced selected harmonic components is also disclosed.

Abstract: Quasi-harmonic neutralized inverter systems are provided with interphase transformers connected in a waffle tree configuration and each having a pair of inputs for receiving staggered voltage waveforms, wherein the stagger angle of the voltage waveforms reduces a harmonic component of an output voltage on an output terminal of each interphase transformer. Inverters produce voltage waveforms at phase angles necessary to provide the required stagger angles at the inputs of the interphase transformers in a first stage of the waffle tree configuration. A method for quasi-harmonic neutralization of voltages in an inverter system is also provided, in which interphase transformers, each having a pair of inputs for receiving staggered voltage waveforms, are connected in a waffle tree configuration, such that the stagger angle of the voltage waveforms reduces a harmonic component of an output voltage on an output terminal of each interphase transformer.

Abstract: An apparatus and method for reducing certain harmonics in the output of static inverters. Static inverters which employ a switching device arranged in a bridge circuit to convert direct current power to alternating current power produce undesired harmonics in the output of the inverter. Harmonic neutralization techniques are further improved by the invention utilizing selective notching of the inverter pole voltage and a coordinate phase shift between the set of pole voltages produced by the individual inverters. The notch angles in the individual pole voltage outputs are chosen to minimize or eliminate specific undesired harmonics.

Abstract: A multiphased permanent magnet generator (PMG) driven by a rotating shaft, generates a multiphase output which is integrated and applied as the input to a high resolution phase locked loop having a binary counter with an output phase locked to the PMG multiphase output and representing shaft position. As applied to a high performance synchronous drive in which the PMG is driven by the synchronous machine, the digital shaft position signal is used to generate a multiphase current reference signal which is tracked by stator currents generated for the synchronous machine by a power current source. The multiphase current reference signal can be generated by a selected set of multiphase digital sine waveforms stored in a ROM which is part of the phase locked loop or is a separate waveform synthesizer.

Abstract: Apparatus to extend the speed range and maximize torque of an ac drive by optimizing the torque angle as a function of speed. Using the back-emf of the machine, or the voltage from a permanent magnet generator mounted on the mtor shaft for reference, a novel analog biasing arrangement of a fast tracking multi-phase phase locked loop generates a set of stator current reference signals having a phase angle which is programmed to provide the optimum torque angle at any speed.

Abstract: A current fed unrestricted frequency converter (UFC) for supplying power with balanced voltages to a three-phase unbalanced load generates two sets of existence functions for controlling the switching matrices of the UFC to generate positive and negative sequence current components in the load. Existence function generators generating the positive and negative sequence existence functions are phase locked, respectively, to a positive sequence reference signal generated by a clock and a negative sequence reference signal derived by circuits which monitor the negative sequence voltage in the load. Select circuits alternately gate the positive and negative sequence existence functions to the UFC switching matrices in proportion to the detected magnitude of the negative sequence voltage in a sense to drive the negative sequence voltage in the load to zero.

Abstract: A torque angle and peak current detector for a three-phase synchronous motor utilizes a phase-locked loop to generate a digital stator field position signal phase locked to the stator current. The phases of digital -sine and cosine reference signals generated from the field position signal are compared with x and y stator current component signals in multiplying digital to analog converters to generate a phase error signal which is driven to zero with the reference signals in quadrature with the current component signals at phase lock. The reference signals are also multiplied by in-phase current component signals and the products are summed to generate the peak current signal. A digital rotor angle position generated by a resolver and an analog to digital converter is subtracted from the digital field position signal to generate the torque angle signal.

Abstract: Broadband, single and multiphase phase lock loop circuits utilize a sliding window averager to remove the second harmonic and other ac components from a phase error signal which is the product of a sinusoidal or square wave source signal and a corresponding reference signal synthesized from a variable frequency signal produced by a voltage controlled oscillator as a function of the integratal of the phase error signal. The sliding window averager maintains a running average of a number of most recent samples of the phase error signal taken over a selected interval which is preferably one-half cycle of the source signal. Also preferably, the sliding window averager is clocked by the variable frequency signal generated by the voltage controlled oscillator.

Abstract: An ac drive in which the three phase ac current produced by a current controlled inverter is applied to the stator winding of a synchronous or induction motor through an autotransformer equipped with a neutral shorting switch. For starting from zero speed and operation at very low speeds below the speed at which the autotransformer could provide adequate volt-seconds for operation of the motor, the neutral shorting switch is opened so that the current is applied essentially directly to the stator. At normal and high speeds, the neutral shorting switch is closed so that the voltage to the motor stator is increased by the turns ratio of the autotransformer thereby increasing the speed range of the motor. By providing a number of sets of taps on the autotransformer each with a neutral shorting switch, the ac drive mimics the characteristics of a drive with a multi-ratio gear box.

Abstract: A quasi-harmonic neutralized static power converter comprises one or more threephase phase shifting transformers having open primary windings fed at opposite ends by poles in separate ones of an associated pair of six-pulse bridge inverter circuits. The secondary winding of at least one of the phase shifting transformers is a delta winding or a wye winding connected to a neutral line. In order to block zero sequence currents which would be induced in such secondaries, a zero sequence blocking transformer is inserted in either the primary of secondary of any one of the phase shifting transformers. Preferably, the zero sequence blocking transformer has three identical zero sequence blocking windings wound on a common core. Each of the zero sequence windings is connected in series with a separate one of the windings in the selected transformer primary or secondary.

Abstract: An absolute shaft position sensing circuit uses a magnetic sensor and a toothed wheel to produce two pulse trains which are used to determine the absolute position of a shaft which is coupled to the toothed wheel. One pulse train includes regularly spaced pulses which are fed to a phase locked loop to produce an oscillating output signal. A counter counts this signal and produces an output count which is representative of the relative angular position of the shaft. A second pulse train includes an irregularly spaced pulse. Circuitry is provided to detect the occurrence of this irregularly spaced pulse and to reset the counter in response to that occurrence, thereby making the count representative of the absolute angular position of the shaft.

Abstract: A power active filter circuit for an electric power system includes a reference generator for producing a plurality of balanced, constant amplitude, positive sequence, AC reference voltages, each being phase-locked to a corresponding phase voltage of the power system. Error signals are produced by subtracting the reference voltages from their corresponding phase voltages and a plurality of correction signals, which are proportional to the error signals, are combined with the phase voltages to produce a plurality of output voltages having substantially only a fundamental component.

Abstract: The invention is a locally isolated regulated power supply providing a regulated dc power output from an ac current source having a large dynamic range. The power supply comprises an ac-to-dc converter for providing a rectified dc output from an ac current input. The converter includes a current transformer in combination with a rectifier. The current transformer has a saturable magnetic core for receiving primary and secondary windings. The current transfomer produces a reduced secondary output voltage that is a function of the ac system current characterized by the decreased coupling between the core and secondary winding as the core approaches saturation during substantial increases in the ac system current. One or more secondary windings and associated circuitry can be provided. In addition, an electronically controlled switch or shunt having as inputs a predetermined reference voltage and the dc output voltage of the rectifier or a signal equivalent thereto is connected across the converter.

Abstract: A circuit for providing a multiphase digitally synthesized sinusoidal output signal representative of a predetermined symmetrical component set of a multiphase source signal and having a predetermined relationship therewith is taught. The circuit comprises a phase comparator, a phase shifter and a synthesizer. The phase comparator produces an output representative of the phase error in the predetermined phase relationship between the source signal and the output signal. The phase shifter has a variable frequency output for shifting the phase of the synthesized output signal in response to the phase error output signal of the phase comparator. The synthesizer digitally synthesizes at a predetermined amplitude the multiphase sinusoidal output signal. The synthesizer is responsive to the phase shifting output of the phase shifter so as to decrease the phase error between the source signal and output signal.

Abstract: At least two active conditioners are connected in series with a common DC source, and are mounted as a unit between two pairs of AC terminals to act either as a tie-in link between two AC power sources, as a buck/boost regulator between one AC power source and its load, or as VAR compensator as well as active power conditioner between phases of a multiphase AC option.

Abstract: The invention is a method and a circuit for the emergency firing of individual thyristors in a thyristor valve that have a protection circuit for providing an emergency gate control signal for firing the thyristor when the voltage applied thereto equals or exceeds a predetermined initial emergency voltage triggering level. In operation a thyristor is initially fired using the emergency gate control signal produced by the protection circuit when the voltage applied thereto equals or exceeds the emergency voltage triggering level. The emergency voltage triggering level is then reduced. The subsequent firing of the thyristor by the protection circuit occurs when the applied voltage equals or exceeds the reduced emergency voltage triggering level. This allows both economy of operating conditions and protection of the individual thyristor and its associated snubber circuit during prolonged emergency firing conditions.

Abstract: In a power converter switching system, the instantaneous blocking ability of semiconductor switching elements is determined by monitoring the reverse blocking ability of a control junction in each switching device. A gate firing circuit applies negative turn-off drive to the control junction. The control junction impedance is monitored and switch recovery is indicated by a change in the magnitude of the impedance. A switch recovery logic signal is then generated and used to initiate the firing of the next successive switch element. When switches are combined in multipulse groups, the recovery signals may be logically combined to provide proper switching coordination, emergency protection and diagnostic information.