Abstract: An electrical overcurrent circuit provides both digital based modeling and analog based modeling of the temperature of an electrical conductor to simulate the conductor temperature during all expected operating conditions including a condition when electrical power is unavailable to the electrical overcurrent circuitry. When electrical power is available to the circuitry, the conductor temperature is calculated from the sensed load currents to form the digital based model. During such a condition, the analog based model is forced to track the digital based model. Once the temperature of the electrical conductor exceeds its maximum safe operating temperature, the electrical overcurrent circuitry initiates a trip of the circuit breaker. Since the overcurrent circuitry is powered either by the sensed load currents or derived from the circuit breaker output, the circuit breaker trip will result in a loss of electrical power to the electrical overcurrent circuitry.

Abstract: A PC computer monitors the energy consumed at a plurality of local stations placed behind the electrical meter of the utility company for individual billing of the local users, a bidirectional communication line being used therebetween. A command from the PC computer causes at each station the totalized energy to be stored, and thereafter the PC computer derives individually the results for separate estimations and central billing.

Abstract: Process and apparatus for calibrating an electrical device such as a circuit breaker, motor controller or monitor is taught. A precision power supply device is interconnected by way of appropriate input channels to the device to be calibrated for supplying a precise accurate calibration variable as an input. A personal computer PC is interlinked by way of a communications network with the apparatus to be calibrated and is also interlinked with the precision supply device so that the personal computer PC has available the exact value of input variable utilized. Gain adjustment calibration is made by supplying the predetermined value of circuit variables, for instance 10 amperes or 120V to the input terminals of the device being calibrated. Upon command, the personal computer PC instructs the device being calibrated to deliver to the personal computer PC those values of input variable which the device being calibrated interprets as the input variable value.

Abstract: A PC computer monitors the energy, power, voltage, and current consumed at a plurality of local stations placed behind the electrical meter of the utility company for individual billing of the local users, a bidirectional communication line being used therebetween. A command from the PC computer causes at each station the power, voltage, current and totalized energy to be stored, and thereafter the PC computer derives individually the results for separate estimations and central billing.

Abstract: A hybrid monolithic IC that is standardized for controlling various types of electrical equipment, such as circuit breakers, motor controllers and the like. The IC is a hybrid monolithic IC, fabricated in CMOS technology, The shortcomings of utilizing CMOS technology for linear or analog circuitry is overcome by the implementation of the IC to provide a monolithic IC that is relatively less expensive than using multiple ICs or a single IC fabricated from biCMOS technology.

Abstract: A circuit breaker bandwidth limits a sensed rate of change of current, di/dt, in the neutral conductor of a protected electrical system and fullwave rectifies the bandwidth limited di/dt signal for comparison with an instantaneous trip reference signal. The bandwidth is selected to provide a selected relative sensitivity of the instantaneous trip to sinusoidal currents associated with overcurrent faults and step currents associated with sputtering arc faults. The rectified bandwidth limited di/dt signal is also filtered and delayed for comparison with a delayed trip reference signal. The time constant for the filter is selected to provide a selected relative sensitivity of the delayed trip to overcurrent faults and sputtering arc faults. A low mu sensing coil used to generate the di/dt signal can also serve as the neutral current sensing coil of a dormant oscillator ground fault protection system.

Abstract: A method and apparatus for rapidly analyzing ac waveforms containing dc offset by generating digitized samples of the waveform to be analyzed with alternate samples separated by ninety electrical degrees. Alternate samples are paired for calculation of the magnitude and phase of the waveform. A suitable microcomputer performs a calculation using pairs of the most recently generated samples. Using the pairs of samples, the microcomputer calculates the dc offset, and the peak magnitude of the waveform which may be voltage or current. The phase angle of the waveform can also be calculated if required. The method and apparatus are particularly useful with protective systems where the calculation is necessary to determine whether there is a fault on an electric power transmission line. In addition, the effects of dc offset are eliminated and thereby false trips are avoided. A reliable system having a fast response time at relatively modest cost is provided.

Abstract: The first capacitor of a capacitive divider adapted for measuring the voltage on a bus bar utilizes the bus bar as one plate, the normal insulation provided on the bus bar as the dielectric and a first conductive layer applied over the insulation as the second plate. While a separate capacitor can be used for the second capacitor of the capacitive divider, preferably the first conductive layer serves as a common plate for both capacitors, with a second insulation layer applied over the first conductive layer forming the dielectric of the second capacitor, and a second conductive layer applied over the second insulation layer serving as the second plate which is grounded. The voltage on the common plate formed by the first conductive layer is applied to a voltmeter to provide a voltage reading proportional to the voltage on the bus bar.

Abstract: A motor controller or contactor is disclosed which utilizes a non-saturating current transformer for sensing the amount of current flowing in the electrical conductor connected to the contactor. The current sensor is made of homogeneous sintered powdered metal having evenly distributed microscopic air gaps therein which increase the reluctance of the magnetic circuit but resist the influence of stray magnetic flux. This increased reluctance prevents magnetic saturation over a wide range of input current and allows the secondary of the transducer to produce a voltage which is proportional to the derivative of the primary current, that is the current being sensed by the transducer. The aforementioned voltage is linearly proportional to the derivative of the current over a wide range of primary current values. This voltage is integrated to produce an output signal which is directly proportional to the aforementioned primary current over the wide range of current values.

Abstract: A contactor includes two DC sensors within the housing which are isolated from the tripping unit, from the power supply and from each other by the combination of a transformer and photoelectric coupling, the sensed signals being pulse width modulated and demodulated on the respective sides of the photoelectric coupling barrier.

Abstract: A light driven remote system and power supply therefor that includes a laser diode that provides pulses of light to a fiber optic cable. The pulses of light are detected by a remote photodiode that is connected in parallel with a step-up transformer. The output of the step-up transformer is filtered to provide power for a remote system. Data transmission from the remote system is synchronized with transmission of light to the photodiode.

Abstract: An AC electric energy meter is coupled to a source of AC electrical energy and to an AC load. A sensing circuit senses the amount of AC electric energy consumed by the AC electric load. An AC electric energy measuring circuit generates a pulse signal representative of the amount of AC electric energy consumed by the AC electric load. A switching circuit receives the pulse signal from the AC electrical energy measuring circuit and controls current flow from the AC electrical energy source to a stepper motor to drive an output shaft of the stepper motor in a unidirectional manner based on the pulse signal. A register is coupled to the output shaft of the stepper motor for registering the amount of electrical energy consumed by the AC electric load based on the amount of rotation of the output shaft of the stepper motor.

Abstract: An automatic transfer switch with microprocessor and a display which includes clusters or combinations of display cells. There may, for example, be sixteen display cells for a 16-word display. The display cells are driven by two serially connected shift registers, the input of the first of which is interconnected with the microprocessor. Sixteen digital words are supplied in sequence to the shift registers. One portion of the digital word is then provided in parallel to each of the display cells simultaneously but another portion of the word is supplied to an encoding device which tells which of the sixteen display cells will display that word. One 16 word message requires sixteen reiterations performed at high speed so that it appears that all sixteen display devices are actuated simultaneously to display one multi-word message.

Abstract: An electromagnetic contactor or controller is taught in which the voltage which is impressed across the electromagnetic armature winding is controlled with an algorithm to enhance the closing operation. A microprocessor is utilized to implement the algorithm.

Abstract: A motor controller system is taught in which an overload relay board utilizes a current monitor which produces an output signal which is related to the current being sensed thereby over a wide range of currents which may vary for instance between 1 and 1,000 amperes. This indicative signal is converted to a DC voltage level which is then provided to the analog-to-digital portion of a microprocessor for being converted to a digital number for being processed by the microprocessor for causing the contacts of the motor controller to open at appropriate current values. The system utilizes an integrating capacitor which samples the output current from the sensor 32 times in succession providing a voltage which is proportional to the line current. This voltage which may exceed the input voltage level of the analog-to-digital converter is nevertheless supplied to the analog-to-digital converter and sampled internally by the microprocessor at double the line cycle time period until the 32 samplings have expired.

Abstract: An electrical motor contactor or controller is taught in which control signals from remotely located pushbuttons are supplied to the logic portion of the controller for the purpose of initiating or stopping a predetermined contactor or controller actions. The controller or contactor is of a universal nature adapted for the acceptance of relatively high voltage AC control signals or relatively low voltage DC control levels. For instance, a 120-volt AC signal may be provided or a 5-volt DC level may be provided. Because an AC signal may be provided to the controller, capacitive filter elements are utilized in the control circuit for filtering transients or AC components above a predetermined frequency which may be 60 Hz for example. Furthermore, voltage regulator elements within the control circuit and the microprocessor input terminals within the control circuit represent relatively high impedance in the discharge path for the aforementioned capacitors.

Abstract: An automatic transfer switch is taught which includes as part thereof a voltage sensing device which is interconnected with one of the lines to be monitored and controlled by the automatic transfer switch and neutral. This voltage may vary over a wide range and it is desired to provide a universal transfer switch control for operation over the wide range. The output analog voltage is provided to an analog-to-digital converter which has a maximum number of output bits. In order to keep the resolution of the output digital signal from the analog converter as high as possible, it is necessary to range the input voltage according to a menu of potential ranging values which are stored in the memory of a microprocessor. A programming device is utilized to input the line voltage and the microprocessor determines the maximum value for the ranging constant as a function thereof. The output analog voltage is reduced by this factor then provided to the analog-to-digital converter.

Abstract: A master metering module is taught which utilizes a programmed microprocessor and externally operated switches to alert the module as to what kind of system is being monitored thereby. For example, is the system being monitored a .DELTA.-connected electrical system or a Y-connected electrical system. This is useful in providing output indications of line-to-line voltage or line-to-neutral voltage, for example. When measuring voltages whether line-to-line or line-to-neutral one voltage value is substituted from another. A differential amplifier is utilized to do this. In one case the differential amplifier subtracts one line voltage from another line voltage, but in another case it subtracts neutral or zero ground potential from a line voltage. A switching arrangement is provided which interconnects one terminal of the differential amplifier with the neutral input terminal and with a line input terminal through appropriate conditioning of the microprocessor.

Abstract: Long conductors in a common cable which interconnect control pushbuttons to the basic control circuit for an electromagnetic contactor often have distributed capacitance between them. This distributed capacitance may conduct capacitive current from the power supply line to a parallel control line. This current interacts with high impedance in the control circuit for producing a voltage, or False signal, which may be of a magnitude which would otherwise be supplied by an ON pushbutton. In order to discriminate between a TRUE signal and a False signal the first capacitor is connected between the power supply conductor in system common and a second capacitor, larger than the first capacitor, is connected between a signal conductor and system common so that under normal circumstances the alternating voltage on the second conductor lags the alternating voltage on the first conductor by an amount .DELTA.

Abstract: Programmed overcurrent protection control apparatus with selectable time-overcurrent operation to govern the interruption of current through at least one power line associated with either a ground phase or a power phase of a power system network is disclosed. A programmed processor is included to derive an overcurrent time-to-trip in accordance with sampled measurement current values of the power line and selected derivation constants stored in a memory look-up table. The derivation constants are selected from the look-up table based on derivation parameters which may be set and read by the programmed processor from time to time. The programmed processor utilizes the selected derivation constants to derive the time-to-trip over a number of predetermined time intervals during which the overcurrent condition persists.