Abstract: A converter for synchronous motor starting rectifies the input voltage from a polyphase input power source to develop a starting current having a substantial DC component. The starting current is then sequentially applied to each of the phase windings in the synchronous motor, with the sequential rate of application occurring at a continuously increasing frequency. The angular velocity of the motor synchronously increases with the increasing frequency of the sequential rate of application of the starting current to the phase windings. By application of the starting current at an increasing frequency, the synchronous motor operates in a forced commutation mode. The starting current is removed when the angular velocity of the motor is synchronous with the constant frequency of the polyphase input power source. When the starting current is removed, and the motor is synchronous with the input power, the input power may then be applied directly to the motor in a natural commutation mode.

Abstract: An inverter apparatus for a battery-powered vehicle drive which is selectively operable in either a normal drive mode or an alternative battery-charging mode. In the drive mode, the inverter functions to invert DC from the vehicle's on-board storage batteries to a polyphase AC to power the vehicle drive motor. In the battery-charging mode, the inverter draws charging current from an external energy supply source and supplies it to the battery as a DC charging current. The apparatus is usable with external energy supply sources varying widely in voltage and frequency.

Abstract: An a-c drive having a plurality of parallel connected polyphase d-c link power converters is operated in currents and with the alternating output currents contributed by the respective power converters phase shifted by an amount which reduces selected harmonics in the composite output current.

Abstract: A load commutated inverter (LCI) a-c drive system includes a synchronous motor with two 30 degree angularly displaced sets of three-phase windings. Each set of motor windings is powered by a three-phase inverter fed by a three-phase rectifier in a separate d-c loop. The three-phase rectifiers are fed by either a generator with two angularly displaced sets of three-phase windings or by a transformer with a three-phase primary winding, and delta and wye secondary windings separately supplying the two rectifiers. Twelve-pulse operation in the line commutated mode with substantially constant d-c link currents significantly reduces torque pulsations. At low speeds, sinusoidal segment pulsed d-c currents in the d-c links are gated to pairs of windings in the two sets of motor windings which generate component MMFs either 90 degrees or 150 degrees displaced to produce a resultant rotating motor MMF of constant magnitude to completely eliminate torque pulsations.

Abstract: In a voltage-source inverter system, wherein the commutation between static switches in the AC/DC converter in the regenerative mode is forced by a GTO or transistor device in series with an auxiliary thyristor in order to bring the current path to zero, a reactor of large inductance is inserted for improved operation in the forward and regenerative mode, but an additional thyristor is converted in unparallel to such reactor in order to neutralize the inductance when bringing the current to zero in the regenerative mode, and such additional thyristor is turned OFF by natural commutation when the next converter static switch is coming ON.

Abstract: In an AC motor drive, a voltage-source inverter is provided in the DC-link thereof with a GTO switching arrangement which upon braking allows matching the voltage, current domains for the forward power and regeneration modes, the GTO devices being interrupted with a duty cycle selected in response to the voltage difference between the inverter DC input voltage and a constant reference voltage.

Abstract: Three terminal, six and twelve pulse unrestricted frequency changing circuits are provided by inserting controllable bidirectional switching circuits between open star configured coils in multiple phase windings of isolation transformers. Where the switched winding are secondaries of the isolation transformer, interphase transformers are provided between each pair of three pulse circuit groups and additional interphase transformers are required between six pulse circuit groups to provide a three terminal output. Where the switched windings are primary windings of the isolation transformer, the secondary windings are electrically connected in series with each other to provide the three terminal output.

Abstract: A constant voltage voltage-source inverter of a motor drive includes in its DC-link the combination of diode means, a GTO device and an auxiliary thyristor, the GTO device and the auxiliary thyristor upon transferring to the regenerating mode being cyclically controlled for conduction concurrently with the thyristor of the AC/DC converter so as to match the (voltage-current) domains converter and input of the inverter. Conduction of the GTO device is interrupted before each cyclical control thereof to allow recovery.Initiation of GTO and auxiliary thyristor conduction upon mode transfer is retarded to allow settling of the system before firing the thyristors of the AC/DC converter with a different firing angle.

Abstract: A sensor coil characterized by an elongated insulating substrate, which substrate is folded and formed into a cylindrical toroidal core having adjacent substrate sections disposed at acute angles to each other forming a star-like cross-section, a winding on at least one side of the substrate which winding includes transverse and longitudinal portions on each substrate section which transverse portions are parallel to the axis of a current conductor on which the coil is mounted.

Abstract: An improved circuit is provided for a solid state electrical energy meter having a pair of mutual inductance current transducers, a pulse width modulation circuit, an analog switch, and a voltage-to-frequency converter. The pulse width modulation circuit includes an integrator having a first operational amplifier with a feedback circuit providing a constant DC gain and a variable gain at the power frequency. The pulse width modulation circuit also includes a second operational amplifier configured as a comparator and connected to the first operational amplifier such that the reference level of the comparator is proportional to the average DC output of the first operational amplifier. The summing resistors connected to the input of the integrator are of like value and are formed in a common array.

Abstract: A pulse width modulator for an electronic kilowatt-hour meter includes an integrator having its inputs connected to a square wave clock signal and a sine wave signal proportional to the time derivative of current on the metered circuit. A plurality of series-connected inverters are connected to the output of the integrator to function as a comparator which generates a pulse width modulated signal having a duty cycle proportional to metered current. A negative feedback path including a low pass filter is connected between the output of the last inverter and an input to the integrator to compensate for errors produced by the integrator and inverters, thus permitting the use of low cost inverters fabricated on an integrated circuit.

Abstract: In a pulse-width modulated unrestricted frequency changer (UFC) the harmonic contents of the input current are minimized by splitting the active time intervals within the fundamental time frame into at least two pulses which are located within such time frame and controlled in width as if individual PWM single-pulse UFC's were controlled having a phase shift between each other so as to eliminate or reduce undesired frequency components. Such elimination or minimization of selected frequency components is used to reduce the size of the lowpass filter at the input of the UFC, namely by allowing a higher cut-off resonance limit.

Abstract: In a static frequency changer controlled by adjusting the time of conduction of the bilateral switching units forming static converters, the time of conduction is split into n time intervals of respective subdurations adding up to be equivalent to the effective time of conduction of the controlled switching unit, and such subdurations are spread and distributed throughout the time period of control of the switching unit both within the original switching pattern of each converter and between the effective times of conduction of the respective converters, thereby to minimize harmonic distortion of the input supply current of the frequency changer.

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: A low cost, small rating AC motor drive includes an inverter in which static controlled switches are in two sets associated with opposite poles and controlled in such a way that current continuously fed is sensed relative to one set for feedback current sensing and that the switch current is modulated in the other set in order to regulate the motor current. When starting, or overloaded, the motor drive speed is automatically reduced under air gap motor sensing.

Abstract: An electronic AC electric energy measuring circuit converts a di/dt analog input signal into a pulse width modulated signal responsive to the amplitude of a current component of an alternating current energy quantity to be measured. The pulse width modulated signal is produced by a first modulator circuit including an integrator circuit deriving both a modulating frequency signal and a current analog signal proportional to the current component. A multiplying circuit receives a voltage analog input signal and applies it to a reference input of a second modulator circuit. The modulating control of the second modulator circuit receives the pulse width modulated signal so that the multiplying circuit produces a variable amplitude and pulse width modulated signal having an average value equal to an average power measurement.

Abstract: The coupling and decoupling of one or more of a plurality of differential transformers comprising a digital position probe assembly develops a phase encoded signal indicative of the position or level of a magnetically permeable element such as liquid metal or a lead screw in a nuclear reactor assembly. The phase encoded signal, which is developed as a Gray code, is processed in a phase decoder and digitally converted into a binary coded decimal to provide a digital representation of the level or position of the magnetically permeable material.

Abstract: A system for the emergency deenergization of a multibranch power circuit includes a ground fault circuit interrupter having capability to trip under both ground fault and grounded neutral conditions. A plurality of receptacles are provided on the circuit to receive connecting plugs of electrical devices to be powered. A removable plug adapted for insertion into any of the receptacles includes the series combination of a normally open pushbutton switch and resistor connected between plug pins which are in contact with the neutral and ground conductors of the circuit so that actuation of the switch when the plug is inserted in a receptacle establishes a low-impedance path from neutral to ground which is detected by the ground fault circuit interrupter. This causes the interrupter to trip and deenergize the circuit.

Abstract: An apparatus for inductively heating cooking utensils comprising four induction cooking coils excited by a central power oscillator providing an alternating sinusoidal excitation voltage at about 25 kilohertz which is 100% amplitude modulated at 120 hertz. Power to the four induction coils is duty cycle controlled by four 60 hertz triacs each series inserted between the power oscillator and a respective one of the induction coils. The triacs switch to excite their respective induction coils only at the zero point of the excitation voltage modulation envelope. Line power fluctuations are minimized by sequential switching of the triacs in a manner that results in an effective power switching frequency of approximately 46 hertz when all four induction cooking coils are excited. The central power oscillator is inherently protected from high Q load conditions without the provision of feedback loops.

Abstract: The invention relates to induction heating for cooking. Solid state reciprocal power switches are used to excite a resonant power output circuit including an induction coil to be inductively coupled to a cooking utensil. A first control signal which is a function of the Q of the coil, the direct current voltage applied to the power switches and the frequency of operation of the power switches is used to offset the power circuit from oscillating at resonance in order to control the power output. A solid state differential circuit is used responsive to a second control signal establishing the level of power desired and to the first control signal for regulation about the selected power level. The same differential circuit is responsive to a third control signal to insure low starting power or in case of a failure of the power line. Minimum power output is provided at the lower end of the ultrasonic frequency spectrum without entering the audible frequency range.