Abstract: Protective relay apparatus for electric power systems which logically relates the outputs of two algorithms to provide the fastest possible trip for the conditions of the post-fault voltage and current waveforms.

Abstract: An electric vehicle having a separately excited field controlled direct current drive motor powered by a direct current power supply wherein the field currents supplied to the drive motor and the armature currents drawn by the drive motor are responsive to safety control features provided on the electric vehicle. Speed control is provided for preventing overspeed of the drive motor by applying full-field current when the drive motor speed exceeds a selected value. If the motor speed remains above the selected maximum value and armature current remains positive, indicating the drive motor is not providing regenerative braking for the electric vehicle, then the contactor connecting the direct current power supply to the armature of the drive motor is opened. The electric vehicle is also provided with an armature current limiting means which causes full-field current to be applied if the armature current exceeds some maximum value.

Abstract: An automatic self-administered interrogating apparatus that projects a series of film-frame-recorded images onto a rear projection screen. At least many of such images simultaneously present to the viewer both a question and a list of multiple choice answers, any or all of which answers may be selected by actuation of respective response buttons before a new question-answer image is brought into view on the screen. Each question has a serial number that is recorded together with the several answers, and each answer is coded on the basis of branching logic to control the number of film frames to be advanced for presentation of the next question-answer image. A selection device is included for determining which of the several film advancement codes is honored when the choice of answers necessitates such selection.

Abstract: An electric vehicle having a field controlled direct current drive motor powered by batteries which are connectable in a high voltage and a low voltage configuration to change the speed range of the drive motor. Switching of the batteries between the high and low voltage connection is accomplished to provide a relatively smooth transition in both directions and to provide for optimum performance and efficiency. Logic is provided to determine the minimum speed at which high voltage operation is feasible and for initiating switching to the high voltage connection at the determined minimum speed. The minimum speed for operation at the high battery voltage connection is determined as a function of battery open circuit voltage, battery resistance, armature resistance, armature current and field flux. When for the known parameters operation at the high voltage connection is possible, the batteries are switched to the high voltage level. A throttle is provided for controlling the speed of the electric vehicle.

Abstract: A set-reset flip-flop is taught utilizing NAND gate logic elements and an internally connected resistor-capacitor circuit. The time constant of the resistor-capacitor network is such that valid triggering pulses for the input terminal of the flip-flop will not be propagated through the flip-flop to change the output state thereof unless the pulses are of a minimum duration. The duration of such pulses are chosen to be significantly larger than the duration of expected random noise which may appear on the input terminal of the flip-flop. Such being the case, noise signals are not propagated through the flip-flop to change the state thereof. A discharge network is provided for the capacitor to quickly discharge the capacitor at the termination of each input pulse, whether noise or triggering, so that an accummulaton of noise pulses will not cause a shift in the output of the flip-flop.

Abstract: A system incorporating a cathode ray tube display device, a comparator circuit and a data recording media is utilized to continuously display measured parameters and selectively apply signals corresponding to the measured parameters for permanent recording when the measured parameters vary beyond predetermined limits. A delay type circuit is employed to provide permanent recording of signals occurring prior to the excursion of the measured parameter beyond the predetermined limits thus providing a basis for evaluating operating conditions existing prior to an unacceptable variation of a parameter beyond predetermined limits.

Abstract: A control circuit for a static VAR generator measures load current on consecutive half cycles. This information together with voltage information is used to determine the firing angles of the VAR generator thyristors for providing the required compensator currents. The total computation time for determining the firing angles in each succeeding half cycle takes no longer than the length of time of the last complete half cycle immediately preceding the firing of the thyristor.

Abstract: A system for providing a desired energizing current, according to a reference current signal, to a load or group of load elements. Three phase energizing current is rectified by a plurality of controlled switching devices such as thyristors, and apparatus is provided for varying the firing angle of the thyristors in accordance with the reference current signal to regulate the resulting output voltage therefrom and thereby regulate the energizing current through the load.

Abstract: An over current shutdown apparatus for protecting the power circuit of a static VAR generator flicker compensator. The apparatus incorporates a two stage current sensing means and attempts to provide system recovery by limiting the firing angles of thyristors in the flicker compensator for prescribed intervals.

Abstract: An electric vehicle having a separately excited field controlled direct current drive motor powered by a direct current power supply wherein field current is pulse-width modulated in response to operator control and the vehicle operating parameters. An armature current demand signal which is dependent on a throttle setting is compared with an actual armature current signal derived from an armature shunt and the difference is applied to a field current output amplifier which supplies current to the separately excited field to reduce the difference to zero. The armature current demand signal is responsive to the operator's control of the throttle in the electric vehicle. The drive motor of the electric vehicle can be operated in the driving mode for moving the electric vehicle or a regenerative mode for braking the electric vehicle and supplying energy to the power supply. The armature demand signal is also influenced by various operating conditions to improve operation of the electric vehicle.

Abstract: A reference timing generator for a phase locked loop including a phase comparator, a filter, and a VCO. The basic generator utilizes a prefilter in conjunction with a squaring circuit which provides a signal concurrently to a ripple cancelling digital phase detector and a lock-in monitor. The outputs of the last two apparatus are provided to a dual mode amplifier filter. The output of the amplifier filter is provided to a voltage controlled oscillator which provides a signal frequency which is related to the input signal. Reference timing generator signals are provided in one embodiment of the invention to a discretely varying function generator for calculating a thyristor firing angle (.alpha.). The function generator provides an analog signal related to a desired function (.pi./2 - .alpha. - 1/2 sin 2 .alpha.) for utilization in a static VAR generator control circuit. The function generator utilizes switched parallel resistors and a capacitor to generate the required function.

Abstract: Apparatus for significantly reducing the drift and increasing the accuracy of a firing phase angle determination device for the control circuit of a static VAR generator. A phase locked loop is utilized for providing accurate phase information and rapid capture. The phase locked loop utilizes a ripple cancelling digital phase detector and a dual mode amplifier/filter.

Abstract: A digital time indication system for displaying the time to the next racing signal of a yacht race. A quartz crystal oscillator provides time reference signals to a frequency divider chain. The divider chain counts down and provides digital signals representing the number of minutes, tens of seconds and seconds to the next starting signal. The divider chain automatically recycles so as to countdown for the next period of preselected length. Switching means are provided to select the desired period from one of several standard yacht racing signal time intervals. Counter preset means are provided to synchronize the counter to a racing signal. Counter decoding is provided to gate an audio frequency signal to an audio amplifier and electromagnetic sound transducer so as to provide an audible beep at a pre-determined rate during the last several seconds preceding the next racing signal. The digital signals from the divider chain are conditioned by signal drivers to control a digital numerical display.

Abstract: An automatic expansion valve for controlling refrigerant flow from a condenser to an evaporator in which the valve includes an apertured deflectable disc which defines the refrigerant expanson orifice with other structure within the valve, and with the flow passage arrangement in the valve body being such as to subject the upstream face of the disc to the pressure of the liquid refrigerant, and the downstream face of the disc to the pressure of the expanded vaporous refrigerant so that the disc deflects in accordance with the differential pressure on the opposite faces and accordingly effects changes in the effective opening of the expansion orifice.