Abstract: A microprocessor based recloser control has a microcomputer for causing trip and close operations of a recloser in response to the conditions of the power distribution lines being protected and operator commands. The microcomputer may be overridden by a mechanical switch in the recloser control. If power to the recloser control is lost, the microprocessor will continue to function with power storage means for a limited duration. Towards the end of that duration, this microcomputer will power down the microprocessor in an orderly manner allowing automatic return to its functions when power is restored. After the microprocessor is no longer functioning, a secondary overcurrent trip circuit is relied upon to cause a trip operation of the recloser for extended durations of power outage. The secondary overcurrent trip circuit can be disabled by the microprocessor. The microcomputer includes means to normalize the input signals from the power distribution lines and multiple redundancy features to prevent undesired operations of the recloser. The recloser control functions in response to the mean square of the currents in the protected power distribution lines, and includes means for protecting its more sensitive components from input signals normally encountered.

Abstract: An intrinsically safe power supply employing a binary current interrupter connected between the power source and the electrical load. Normally the load is situated in a potentially dangerous environment, like a coal mine, and the intrinsically safe power supply at a safe remote location, e.g., on the earth's surface. The interrupter has a pass and switching transistor, current sensor, gating circuitry, a flip-flop switch, and means to delay the turning on of the transistor--but not its turning off. If an overcurrent or overvoltage condition is sensed between the input and output of the intrinsically safe power supply, load current will cease to flow. In normal operation, only the current interrupter pass transistor will open. A reset signal from an oscillator internal of the interrupter may be used to reset the flip-flop after actuation or upon its initial setting, thereby causing the flow of power into the load.

Abstract: A solid state overload relay protective apparatus for electric motors which includes not only the overload feature, but the additional features of underload and single phase protection. Small current transformers for sensing the current flow in each phase of the motor are utilized, like those found in the ground fault sensing art because a current-to-voltage converter circuit reflects a short circuit back to the secondary of the transformers. The signal from the current transformers which is proportional to the sensed current in the motor is fed through the converter, a scaling and summing amplifier adjustable for a wide range of motor full load currents, an ideal diode peak detector, a time integrator amplifier, to one input of a comparator circuit having a trip reference voltage signal at another input. The comparator provides an output signal to a transistorized trip level circuit that deenergizes a coil of an overload relay opening its contacts and interrupting power to the motor.

Abstract: An overcurrent protection system adaptable for use with power controllers the single or multi-phase ac, or dc types includes a load current sensing element in combination with an overcurrent sensing/inverse time delay circuit, a power switch and a crowbar circuit The system also includes a drive circuit, a drive circuit input current sensor, a trip signal detector and a logic circuit The overcurrent protection system, according to the present invention, uses the drive circuit to power the overcurrent sensing/inverse time delay circuit, to drive the power switch, and to provide a coupling path for an overcurrent fault signal across electrical isolation interface(s) thereof to the logic circuit Thus, the need for a separate isolated power supply for powering the overcurrent sensing/inverse time delay circuit and the need for separate optical and/or electromagnetic isolation interfaces for coupling of the overcurrent fault signal are eliminated

Abstract: This paper presents a novel method for solving the load-flow problem of a general multiterminal dc network in an integrated ac-dc system. The method can handle a great variety of converter controls and operating conditions of the dc system. It has also the ability to handle discrete tap-step and tap limits of the converter transformer, to impose overcurrent limit at the terminal and to represent the combined behavior of the converter control and tap changer during steady-state and transient conditions; all within the iterative procedure. This method iterates directly on the dc voltage equations using a digital current reference balancer to update the dc currents. Since the digital current reference balancer has a simple closed form solution, the computation effort per iteration is extremely small. Numerical examples are presented to demonstrate the various features of the method. The convergence characteristic of the method is good. Storage requirement is only a few percent of that required by other techniques which manipulate with the full Jacobian matrix. Test results showed that the method is considerably faster than previous dc load-flow techniques.

Abstract: A multiple output d.c. to d.c. regulating circuit including an input protection circuit for providing protection against input overcurrent, input transient voltages, sustained input overvoltage and input polarity reversal. The protection circuit powers a d.c. to a.c. inverter which generates high frequency square-wave signals. The square-wave signals are fed to a magnetic saturable reactor regulator which has its controlled windings connected by a rectifying filtering network to a pair of main output terminals and connected by transformer rectifier filter circuits to a plurality of auxiliary output terminals. The d.c. output voltage across the main output terminals is sampled and is compared to a reference voltage of an integrated circuit operational amplifier. The output of the integrated circuit operational amplifier is connected to the control winding of the saturable reactor for controlling the controlled windings so that the square-wave signals are pulse width modulated to regulate the d.c. voltages developed across the pair of main output terminals and the plurality of auxiliary output terminals. A soft starting circuit prevents high in-rushing currents from damaging the d.c. to a.c. inverter. An overload protection circuit senses overloads on the input and main output terminals and causes removal of power from the regulating circuit.

Abstract: A ground fault interrupter type device for protecting an electrical load device such as a range which has conductors supplied from a power source including overcurrent interruption means for interrupting the power source when a predetermined current threshold is exceeded. The electrical load device is subject to a first class of failure characterized by excessive current flow between at least one of the conductors and a ground reference point, with circuit current remaining at or below the predetermined current threshold; and to a second class of failure characterized by current through at least one of the conductors being above the predetermined current threshold. Failures of the second class include ground fault failures. In order to reduce the current interruption capability requirement for the ground fault interrupter device, there is included a means for preventing conductor interruption thereby in the event a failure of the second class occurs. Accordingly, the current-interrupting capability is at least as high as the predetermined current threshold but less than the maximum current which may flow during a failure of the second class. In the illustrated embodiments, the means for preventing conductor interruption in the event a failure of the second class occurs is a time delay which delays the activation of the ground fault interrupter for an interval sufficient to allow the overcurrent interruption means to interrupt the power source in the event a failure of the second class occurs.

Abstract: An electronic drive system for a discharge lamp is disclosed wherein the switching frequency of the chopper is reduced until the lamp striking voltage has reached about 70% of its rated value. The system includes a chopper transistor, a control for varying the transistors duty cycle and a smoothing inductance, freewheeling diode and smoothing inductor to smooth the chopper output. Current limiting is provided to prevent overcurrent within the chopper transistor, smoothing inductor or lamp.

Abstract: An electrical installation device for protection against high excess of voltages has an overvoltage suppressor with an operating element (1), a voltage-dependent resistor (2) and a switchable isolating device with an actuator or optical switch position indicator (6), a locking cam, a contact apparatus with an arc-extinguishing chamber (4) and overcurrent trip devices (7, 8). To simplify the construction, the overvoltage suppressor with the operating element (1) is arranged together with the components forming the switchable isolating device in a common housing (3), of dielectric, in which the connecting terminals (12, 13) for the active lead and for earthing are also accommodated. The overcurrent trip devices (7, 8) can have a bimetallic trip device (7) and an electromagnetic trip device (8), in a known manner.

Abstract: A solid state load protection system whereby the current supplied to a load is monitored enabling a test feature to be used. A current sensing function is utilized so as to produce an output current which is proportional to the current in an electrical circuit. Attached to the current sensing function is a load resistor module which converts the current produced by the current sensing function to a voltage which is also proportional to the current utilized by a load. Attached to the module is an overcurrent and timing function and an output function. The overcurrent and timing function monitors the level of voltage from the load resistor module initiating a timeout sequence when the voltage across the load resistor function, which is proportional to the current utilized by the load exceeds a predetermined level for a predetermined period of time thereby initiating a trip signal to the output function which deenergizes the motor by disconnecting it from its source of power. Upon the removal of the load resistor module and all other modules the input impedance of the overcurrent and timing function becomes very high allowing the test function to simulate an overcurrent condition in a load by causing a higher voltage to appear at the overcurrent and timing function and after a predetermined period of time, initiates a trip signal to the output function. The output function upon receiving a trip signal allows a light emitting diode to conduct and also deenergizes a contactor through which a current source is connected to the load.

Abstract: 1. Tripping system of an automatic circuit breaker for interrupting a current circuit, having at least one thermo-mechanical transducer (21; 31; 41; 51; 61) of an alloy with form memory, a short-circuit trip (12; 22) and a switching mechanism comprising a release gear which, in the event of an overcurrent, is tripped by the thermo-mechanical transducer (21; 31; 41; 51; 61) or short-circuit trip (12; 22) and interrupts the current circuit, characterised in that the thermo-mechanical transducer (21; 31; 41; 51; 61) is in thermal contact with a heat source, which is located in the current path of the automatic circuit breaker, for example the coil or the yoke of a magnetic short-circuit trip (12; 22), the arm of a dynamic tripping loop (17) or the section of a current-conducting path (20).

Abstract: An overcurrent protection device incorporates a microprocessor (42) the ROM of which stores data representing a multiplicity of points on a plurality of different overcurrent margin/trip delay characteristic curves A characteristic selector device (48) is provided to enable a user to select which of the stored characteristic curves is employed The microprocessor is programmed to accept data relating to the current in a circuit to be protected, calculate the required trip delay and actuate a trip relay (46) if the delay expires

Abstract: An overcurrent protection apparatus for a DC motor which can be used with a speed control system of a DC motor to prevent an overcurrent condition arising when the DC motor is run with a heavy load or locked by an overload from burning or overheating windings of the motor. The apparatus is constructed using at least one integrated circuit and includes a current mirror circuit for detecting an overcurrent and for cutting off the supply current of the DC motor. A timing circuit prevents overcurrents lasting only a short time from triggering the apparatus to shut down the motor. Once the apparatus is triggered to shut off the motor, the motor will remain off for an indefinite period of time until the apparatus is reset.

Abstract: A regulator for a blocking oscillator includes overcurrent protection and light-load operation. An error signal derived from sensing output voltages is then summed with an opposite sense ramp voltage at the input of a comparator having a high amount of hysterises. When sufficient ramp voltage is generated to cause the comparator to switch, a pulse is generated to cause the main power switch to turn off. Variations of the error voltage thus causes the ramp time to vary in a way which opposes changes in the voltage at the load.

Abstract: A protected transistor in an electronic circuit receives base drive current and has its collector-emitter path coupled to a source of collector-emitter potential and to a load. Overcurrent protection therefor is provided by a first, complementary conductivity type transistor connected base to emitter and emitter to base with the protected transistor, and thermally coupled thereto, to develop a collector current responsive to the collector-emitter current of the protected transistor. A comparator provides an overcurrent indication whenever the collector current of the first transistor exceeds a predetermined level. The overcurrent indication prevents further increase in the base drive current to the protected transistor. A further feature of the invention reduces the predetermined level in response to increasing collector-emitter potential of the protected transistor.

Abstract: A solid state load protection system having an inverse time delay circuit. A current sensing function is utilized so as to produce an output current which is proportional to the current in an electrical circuit. Attached to the current sensing function is a load resistor which converts the current produced by the current sensing function to a voltage which is proportional to the current utilized by the load. Attached to the load resistor is an inverse time delay circuit which serves as an overcurrent and timing function. The overcurrent and timing function monitors the level of voltage from the load resistor initiating a time-out sequence when the voltage across the load resistor, which is proportional to the current utilized by the load, exceeds a predetermined level for a predetermined period of time. The overcurrent and timing function utilizes two diode paths for prohibiting the charging or discharging of a capacitor during a normal or overcurrent condition, respectively. Encircling the connections to the capacitor is a guardband for minimizing impedances from associated circuitry which affect the timing of the inverse timing circuit. During an overcurrent condition, the capacitor charges up to a specific value initiating a trip signal which is sent to an output function. The output function upon receiving a trip signal causes a light-emitting diode to conduct and also deenergizes a contactor through which a current source is connected to a load.

Abstract: Circuit for detecting a fault current in an installation where the load (RL) varies. Total current (IS) is converted into a voltage (VS). During an initialization cycle, means such as counter (9), digital-to-analog converter (10), comparator (5), resistors (R1, R2) generate a voltage (VS) equal to VS at the end of the initialization cycle, and a threshold voltage VS=kVS. During operation, voltage VS is compared with threshold VD in order to provide a fault detection indication which is transmitted to the protection circuit by a logic circuit, that is, AND gate (17) and OR gate (19). During the initialization cycle, protection is obtained by comparing VS with a reference voltage in a comparator (7). This device is used to protect machines having an expandable configuration.

Abstract: Disclosed herein is a circuit for protecting an inhibitable tristate data driver from damage due to an over current. A logic comparator circuit compares input and output logic levels of the data driver, and inhibits the driver causing the output to go to a tristate if a fault occurs.

Abstract: An energy-saving instant-start series-sequence fluorescent lamp system includes power-reducing capacitor means connected in series circuit arrangement with one or both lamps in a two-lamp system. A protective device is connected in circuit with a first lamp of the system so that in the event the second lamp fails to operate and causes a high current to flow through the first lamp, the protective device reacts to prevent the system from being damaged. A lamp incorporating the power-reducing capacitor and protective device is also disclosed.

Abstract: A current limiting device for use with a circuit breaker in an electric power system utilizes mutual inductance variation between movable windings to limit current to safe levels. In the device, first and second coil windings are electrically connected for current flow therethrough and magnetically linked for mutual inductive coupling. The effective inductance of the connected coil windings is functionally related to the relative physical positioning of the coil windings. The coil windings are movable relative to one another, so as to provide for variation in the effective inductance of the two coils. Structure is provided for disposing the coils in an initial relative positioning, the structure being yieldable to a force produced between the coils due to a predetermined magnitude of current flow through the coils. The force produced between the coils acts to change the relative positioning of the coils, increasing the effective inductance, and thereby limiting the current therethrough. In an alternative arrangement, movement of the coils to designated positions of relative placement due to a predetermined magnitude of current flow therethrough may be utilized to open a set of electrical contacts or to trigger a conventional circuit breaker interrupting the circuit.

Abstract: PURPOSE:To completely prevent the breakage of a frequency converter due to the backward-flow current generated when the motor is operated at a reduced speed by a method wherein a current limiter, having a preset current controlling value, a gate controlling circuit and the like are provided. CONSTITUTION:When an induction motor 5 is operated at an accelerated speed, the degree of increase of the output signal D on an adjustable speed limiting circuit 7 is reduced by an overcurrent Q1 on condition that a preset current controlling value has been exceeded on the motor which will be detected by a current transformer. On the other hand, when the motor is operated at a reduced speed, the backward-flow current of the motor 5 in excess of the preset current controlling value generated by the decceleration, in other words, during the period while the output signal Q2 is maintained, the degree of decrease of the output signal D of the adjustable speed limiting circuit 7 of the overcurrent Q1 is controlled by open-circuiting a gate 21 in such manner that the degree of reduction is maintained in the state which is based on the expected set point. Through these procedures, the decrease of the positive feedback of the output frequency and the output voltage on the frequency converter, generated by the backward-flow current of the motor caused by a powerful inertia of the motor load at the time of decceleration, can be prevented.

Abstract: The present invention discloses an electric safety device in which a fuse element adapted to break a circuit upon passage of an overcurrent and a circuit-breaking conductive member of the heat-sensitive type for preventing overheat are housed in one vessel and are electrically connected to each other, so that the circuit of an electrical appliance can be broken with respect to both overcurrent and overheat.

Abstract: PURPOSE:To prevent the overvoltage for the device, by producing the switch circuit control signal through a comparison between the input voltage and the power supply voltage and then securing a switch action by the control signal. CONSTITUTION:A comparison is given through the comparator 7 between the power supply voltage VDD and the input voltage Vin which is obtained via the input protecting circuit 5 and to be applied to the device 1. And in the case of Vin VDD, the output signal is obtained through the comparator 7. Thus te transistor 31 is turned off, and then the power supply circuit is cut off to the device 1 to given on-control to the device 1. In this way, the device can be protected by cutting off the overcurrent flowing between the VDD of the device can be protected by cutting off the overcurrent flowing between the VDD of the device 1 and the earth VSS.

Abstract: A thermal analysis program has been developed to study the response of a cryostable fusion magnet to abnormal conditions such as a localized heat input, overcurrent, or uncooled length of conductor. It performs a heat balance on each element. Variation of parameters with temperature, pressure, and magnetic field are incorporated. The program has been applied to a conductor with magnetic field variation along its length, carrying a high current as might occur in one toroidal field toil when a neighboring coil discharges rapidly. It is found that a stable normal region can develop, with possibly serious consequences.

Abstract: A high-voltage circuit-interrupting device includes a replaceable container of pressurized arc-extinguishing fluid. A fluid port of the container is closed by a puncturable seal. When an overcurrent occurs in the circuit, the seal is punctured before interrupting contacts of the device open so that the fluid is already flowing when an arc forms between the contacts. Overcurrents are sensed by either a fusible element or a current transformer. Fluid flow before contact opening is achieved by mechanical facilities responsive to the melting of the fusible element or the output of the transformer. The entire device--including the container, the overcurrent sensor and the mechanical facilities--is at the voltage of the circuit.

Abstract: PURPOSE:To prevent the overcurrent flowing to the load and the main switching transistor by a method wherein an auxiliary control loop is provided in addition to the main control loop. CONSTITUTION:When the output level of a detector 3 came up to the reference voltage Vref1 and the amplifier 11 of the main control loop is in operation, an amplifier 12 is in ''OFF'' position and is statically controlled, because the reference voltage Vref2 of the auxiliary control loop is set at a high level. On the other hand, at the time of transient state, when the detecting output becomes larger than the reference voltage Vref2 during the period D of the response delay of the main control loop, the amplifier 12 of the auxiliary control loop, performing low-gain high-speed response, is operated and stabilized. Then, when the main control loop begins to response, the auxiliary control loop is placed in ''OFF'' condition again. Thus, the overcurrent arising from a short-circuit load and the like is controlled and the main switching transistor can be protected.