Abstract: A new and novel system for protecting people and property against electrical shock. It includes a number of preferred and other embodiments which have this as their goal, but which represent a number of distinctive and novel approaches to solving prior art problems. By way of example only, and without limiting the scope of this invention, these approaches include novel immersion detecting circuits, broken wire test circuits, electromechanical circuit breaking means including coil/plunger arrangements, and relay circuit breaking mechanisms cooperative with associated circuitry, all of which are able to be incorporated as a system wholly within the load (appliance) and its associated cord set (including a "plug").

Abstract: A process control instrument receives a DC current from a two wire loop and has overcurrent protection and reverse current protection circuits which pass a portion of the DC current as a device current to a process controlling device. The overcurrent protection circuit includes a current sensing circuit which conducts the device current and generates an output indicative of device current. The overcurrent protection circuit also includes a current diverting circuit coupled across the two wire loop and responsive to the sensor output for diverting loop current in excess of a predetermined upper limit of device current back to the loop when the sensor output indicates the upper limit is reached. The reverse current protection circuit is coupled across the loop and includes a variable impedance which conducts the device current. The variable impedance inhibits the device current from flowing through the device when a loop potential is reversed from a predetermined polarity.

Abstract: Disclosed is a device which includes a Maintenance Termination Unit (MTU) and surge protector in a single 5-pin package. In accordance with one embodiment, a base includes an array of spring contacts, including a grounding element, in which are inserted both a surge protector module and an edge of a circuit board including the MTU.

Abstract: A protection switch with sudden switching on and off, a trip-free release and forced opening is described. A manually movable actuator (10) forms with a U-clip (50) a toggle lever. One leg (51) of the U-clip (50) forming the toggle joint axis is displaceably guided in the actuator (10) in a link (15) with a variable spacing from its rotation axis (11) and against the action of a spring (14) supported on the actuator (10). The other leg (52) of the U-clip (50) is guided in a fixed link (25) and in a ratchet lever (40). The ratchet lever (40) serves to transfer movement to a contact arrangement (21, 22) and cooperates with the release ratchet (60) of an overcurrent and/or undervoltage monitoring device. The fixed link (25) controls the engaging movement of the ratchet lever (40).

Abstract: A remotely controllable circuit breaker and switch for controlling the flow of current from a three phase AC power source to a three phase load, and usable in either wye or delta configurations. A latching relay controls the current for each phase. Current samples in the three phases are scaled and converted to DC values by scalers and RMS to DC converters. The DC values are converted to digital current values by an analog-to-digital converter which sequentially scans the DC values of the currents in the three phases. A central processing unit monitors the digital current values to detect significant phase imbalances and overcurrents which persist for time periods which exceed allowable limits according to a predetermined time-dependent function, and to initiate opening of the relays in response thereto. The central processing unit also opens and/or resets the relays in response to remote control signals.

Abstract: An automatic insulation tester tests the insulation resistance of electrical equipment when the electrical equipment is inoperative. The automatic insulation tester is automatically rendered operative when the electrical equipment is inoperative, and is automatically rendered inoperative when the electrical equipment is operative. The automatic insulation tester applies a voltage on the order of the rated voltage of the electrical equipment to the electrical equipment and measures and displays the insulation resistance of the electrical equipment. When the insulation resistance falls below a predetermined value, an indicator is activated, and remains in an activated state until the insulation resistance of the electrical equipment rises above the predetermined value and the automatic insulation tester is manually reset.

Abstract: A circuit breaker has leakage current detecting functions, that is leakage detection, leakage alarm and disconnection the circuit in the leakage state from the power source side; in order to conduct such functions, the circuit breaker comprises a magnetic release device for disconnecting a circuit in the leakage state, a zero-phase current transformer for detecting a leakage current, a sensitivity selector, an amplifier and a leakage relay for issuing a leakage alarm signal.

Abstract: The gate-source capacitance of a power MOSFET (1) can be protected against positive and negative excess voltages by two integrated Zener diodes (3, 4) the anodes of which are coupled to each other and the cathodes of which are respectively coupled to the gate and source terminals of the power MOSFET. However, when a control voltage is applied, the parasitic bipolar transistor associated with one of the Zener diodes is switched on and prevents the MOSFET from completely switching on. The parasitic bipolar transistor is rendered harmless by the fact that the anode terminal is coupled to a source terminal (S) MOSFET (1) when a gate-source voltage is applied.

Abstract: An overcurrent protection device is provided for one or more phases of a circuit that generates a control signal dependent upon an adjustable trip level setting after a fault has occurred. The device includes a blocking level detector that blocks the generation of the control signal is the current in any of the phases exceeds either a first predetermined blocking level or the adjustable trip level setting. In a preferred arrangement, before control-signal generation, the device also requires that the current in at least one phase is below a predetermined load level.

Abstract: A method and system of transformer protection in which parallel admittance currents indicative of the apparent excitation state of a transformer to be protected are evaluated from the transformer terminal voltages and currents sampled at a proper interval, and discrimination between an internal defect and excitation inrush is made in response to a magnitude of the parallel admittance current, and a breaker opening command is issued in response to a judgement of internal defect. The method and system enables high-accuracy and high-sensitivity fault detection through a simple computation.

Abstract: Error-free, reliable registration of a fault in a power distribution circuit is achieved by a faulted circuit indicator that measures the current in the circuit after a discrete time delay following the detection of an overcurrent condition. A fault is registered only if the measured current is less than a prescribed level, evidencing that the overcurrent has operated a protection device (such as a fuse), upstream from the faulted circuit indicator, to interrupt the circuit and clear the fault. Hence, only actual (true) faults, resulting in circuit interruption and isolation of the fault, will be indicated, thereby precluding false registrations that may otherwise occur from non-faults such as transient currents, momentary overloads, inrush currents, and the like.

Abstract: The present invention teaches a new and novel system for protecting people and property against electrical shock. The invention includes a number of preferred and other embodiments which have this as their goal, but which represent a number of distinctive and novel approaches to solving prior art problems. By way of example only and without limiting the scope of this invention, these approaches include novel immersion detecting circuits, broken wire test circuits, electromechanical circuit breaking means including coil/plunger arrangements, and relay circuit breaking mechanisms cooperative with associated circuitry, all of which are able to be incorporated as a system wholly within the load (appliance) and its associated cord set (including a "plug").

Abstract: An apparatus for protecting against overvoltage includes a semiconductor switching element and a trigger element. The semiconductor switching element is formed of a PNPN junction including a plurality of PN junctions and the trigger element has a characteristic similar to that of a PN junction Zener diode. The apparatus for protecting against overvoltage is normally nonconductive; however, once an overvoltage not lower than a defined level is applied, the trigger element attains a state so as to have a gate current flow from a gate electrode thereof to the semiconductor switching element. In response to this, the semiconductor switching element causes a so-called thyristor phenomenon, thereby protecting a load connected in parallel to the apparatus for protecting against overvoltage, i.e., an object to be protected, from being provided with the overvoltage.

Abstract: The differential tripping threshold of the trip device is a polynomial function of an order greater than or equal to two of the highest phase current flowing in the power system protected by the circuit breaker comprising the trip device.

Abstract: A power supply including a source of AC power, a filter including inductive elements, and rectifying circuitry. Where the AC source comprises a sinewave source, the filter includes inductive and capacitive elements; and where the AC source comprises a square wave source, the filter includes only inductive elements.

Abstract: An improved overcurrent-detection circuit for detecting overcurrent condition of a main current flowing through a semiconductor power device uses a constant-current device to provide a proportionally enhanced potential difference representative of increases in such current. The proportionally enhanced potential difference increases the accuracy of measuring the current flowing between first and second main-current terminals of the semiconductor power device, thereby providing more accurate overcurrent detection, without requiring an increase in the accuracy of a voltage comparator. The power semiconductor device is coupled to a current-mirror element having a shunt-current terminal. The overcurrent-detection circuit incorporates a constant-current device connected between the second main-current terminal and the shunt-current terminal. The constant-current device maintains the shunt current at a substantially constant level, after the shunt current rises to a predetermined level.

Abstract: A sensing conductor and a detection circuit cause a low resistance shorting of an appliance circuit in response to immersion in water or other electrically conductive liquid, and an interrupter device, preferably located in the plug of the cord set, reacts to overcurrent, by opening both sides of the line. The sensing conductor must be strategically placed, within the appliance housing, to pass in proximity to liquid access points and the current carrying parts of the appliance. The detection circuit may be within the appliance or in the plug, with the sensing conductor extended to the appliance as a third conductor in the line cord. When a small current passes between the sensing conductor and the ungrounded or grounded neutral sides of the line or earth ground, current is shunted through the detection circuit from the ungrounded to the grounded neutral conductor, and away from the appliance circuit.

Abstract: An input protection circuit protects MOS semiconductor circuits from electrostatic discharge voltages and from developing circuit latchup. The input protection circuit includes a low resistance input resistor, and two complementary true gated diodes. One true gated diode has a P-doped node coupled to the input node, and a gate and N-doped node coupled to a high voltage power supply node. The other true gated diode has a N-doped node coupled to the input node, and a gate and P-doped node coupled to a second power supply node.

Abstract: A data acquisition system which utilizes a fixed frequency anti-aliasing filter and an analog-to-digital converter which operates at a fixed sample rate and a Fourier transform generator and a transform truncator and an inverse transform generator so as to provide sample data output at rates lower than the analog-to-digital converter sampling rate. By using multiple transform truncators and multiple inverse transform generators which simultaneously operate, multiple sample data outputs can be obtained which are free of aliasing phenomena.

Abstract: An electric motor controller comprises a circuit for selecting between driving and braking an electric motor in accordance with the health or otherwise of a pair of main electric motor control switches (14 and 16). In a preferred embodiment the health of the switch is determined by the voltage (A) between the switches. The controller also comprises apparatus for detecting the sense of movement of the motor. In the event that the motor is moving in a sense opposite to that selected, the apparatus increase field current to reduce the armature current thereby increasing the braking effect of the motor. Also in the controller are apparatus for changing from armature to field current control and vice versa, in response to a given magnitude of control signal. In order to provide an unambiguous change-over, a lockout circuit is provided to inhibit change-over in a transition region. The lockout circuit maintains the mode of control to above/beneath the change-over level when changing from one level to another.