Abstract: Apparatus for controlling the magnetizing and demagnetizing of the chuck in a machine tool, and the workpieces held thereon. A plurality of individual chucks are incorporated in the machine tool, and they are selectively brought into circuit according to the characteristics of workpieces. The demagnetizing phase is controlled as to length of overall period and the number of reversing steps in that period.

Abstract: An overload detection circuit protects a motor against currents above rated current that persist for certain exposure times. The allowable exposure times are inversely related to the degree of overload current. The circuit has two overload current sensors with two respective overload thresholds. These are both connected to a pulse generating circuit and the pulse rate is accelerated when the second overload threshold is reached. The pulse generating circuit couples pulses to a pair of cascaded counters which generate a fault signal when a predetermined count is reached. The pulse generating circuit includes an integrator with a capacitor that must be discharged, before another pulse can be generated. The pulse generating circuit includes a comparator which operates a switch to discharge the capacitor shortly before coupling each pulse to the counters, to prevent a delay that would otherwise occur between signals from the integrator circuit.

Abstract: A method of isolating a spur line of an electrical power system protected by a multi-shot resetting circuit breaker wherein at least two successive current surges in the spur line which activate the circuit breakers are detected. In response to the detection the spur line is isolated during a subsequent current dead period.A sectionalizer is described for isolating a spur line of an electrical power system protected by a multi-shot resetting circuit breaker. The sectionalizer comprises a metal casing 22 providing a current path across a fuse mounting 10 while the sectionalizer is in a conducting position. An electrical circuit 23 inside the tube detects at least two successive current surges in the casing and during the following dead period actuates a chemical actuator 14 to trip the sectionalizer out of its conducting position.

Abstract: A DC arc furnace has a side wall and an electrically conductive hearth, a roof on top of the side wall and over the hearth, an arcing electrode depending through the roof, a plurality of electrical hearth connections extending from the hearth, a first DC power conductor connecting with the hearth connections to provide current and therefore magnetic field symmetry preventing arc deviations, the first and second conductors are extended from a position horizontally offset from the furnace to a point below the hearth and aligned vertically with the electrode, the first conductor forming at least two branches which extend from the point horizontally in opposite directions to beyond the side wall and upwardly so as to jointly connect with the arcing electrode, the second conductor forming at least two branches which extend horizontally from the point in opposite directions with one branch connecting with one of the hearth connections and the other branch connecting with the other one of the hearth connections.

Abstract: A corona generating device for producing uniform charge along the length of the generating device is described which comprises a plurality of separate parallel coronode wires supported between insulating end block assemblies with the coronode wires being closely spaced relative to the adjacent wire such that when energized, each wire is placed within the electrostatic fringe field of the adjacent wire. In a preferred embodiment the device comprises a pair of parallel coronode wires formed from a single U-shaped wire with a closed end portion wrapped around an arcuate insulating end post in a first end block assembly, and an arcuate insulating end post in the second end block assembly around which the ends of the coronode wire may be wrapped, and insulating block adapters at both ends of the device having wire positioning slits therein, the end post being larger in diameter than the width of said slits in said end block adapters whereby the pair of wires is urged against opposite sides of the slit.

Abstract: A circuit for preventing excessive power dissipation and for avoiding latch-up, in power switching semiconductor devices, monitors the forward conduction drop of the switching semiconductor device and removes the control electrode drive signal provided thereto, if the drive signal is insufficient for supporting the load current flowing through the driven device. The voltage across the controlled-conduction portion of the switching device is monitored and compared to a reference voltage, which may be also related to the load current, to remove switching device drive if the controlled-conduction portion voltage exceeds the reference comparison voltage.

Abstract: A method of protecting a plant for coating objects with charged particles as well as a method and apparatus for coating objects is proposed. The generation of an electric arc having a too high energy which can cause an ignition of the particles to be applied onto the object is prevented by applying a test high voltage between the object to be coated and the respective earth connection. An insulation occurring between the object to be coated and the respective earth connection and having a contact resistance smaller than a permitted maximum value is overcome by an arcthrough of lower energy. The current flowing in the closed circuit is measured for determining the contact resistance of the insulation so that the operation of the plant can be stopped when the actual value of the current is below a minimum value as in this case the insulation cannot be overcome by the arcthrough as its contact resistance is higher than the permitted maximum value.

Abstract: An apparatus for protecting machinery driven by electric motors from operating during over-load and light-load conditions, comprising: a current transformer operatively associated with an electrical supply line for the induction motor; a current-voltage transforming circuit for generating a control signal having a magnitude proportional to current flowing in the supply line; an upper limitation magnitude comparator for generating an over-load signal output whenever the magnitude of the control signal exceeds a predetermined upper safety value; a lower limitation magnitude comparator for generating a light-load signal output whenever the magnitude of the control signal is less than a predetermined lower safety level; an inhibitable protection timer for producing a fault persistence output signal whenever one of the over-load and light-load signal outputs is generated for a period of time longer than a predetermined protection time; a steady state timer for inhibiting an enable output signal for a predetermined

Abstract: A power cable for a submersible motor has a releasable plug-in connector for releasable attachment to the motor. An oil-filled motor has solid conductors to the motor connector part and the flexible conductors to the cable connector part. The cable connector part has a plurality of lead terminals located in a common plane and a plastic molded shell which is flat and rectangular. A shell flange is bolted to the motor. An integrated voltage surge arrestor is located in an opening in the shell which exposes the terminals, and includes a thin arrestor block of silicon carbide or metal oxide varistor secured to a mounting plate which seals the opening. The silicon carbide block is a porous fragile unit supported by the plate and connected to ground by the well liquid, or by a connection to the clamp bolts. The two outer terminals are connected to the 230 voltage lines and the opening is formed with intermediate line insulation separating the chambers of such outer terminals.

Abstract: A pancake induction heating coil for crucible-free zone melting of semiconductor crystal rods, includes a primary winding surrounding a semiconductor rod to be remelted in the form of a ring through which cooling liquid flows, a secondary winding surrounding the primary winding and having a side facing the semiconductor rod, and an energy concentrator lying in the plane of the primary winding and having a circular opening formed substantially in the center thereof for the semiconductor rod, the side of the secondary winding facing the semiconductor rod being electrically conductingly connected to the energy concentrator.

Abstract: An electrical lighting fixture adapted for recessed mounting has structure for mounting and energizing a lamp and has an insulation detecting protector device adapted to interrupt operation of the lamp to prevent overheating of the fixture if thermal insulation is disposed around the fixture in such a way as to excessively block heat dissipation from the fixture. The protector device has structure for mounting the device on the fixture to be subject to representative fixture conditions, has a thermally responsive switch which is actuatable in response to heating to a selected temperature for interrupting operation of the lamp, and has an electrical resistance heater which is thermally coupled to the switch for actuating the switch if thermal insulation excessively blocks dissipation of heat from the protector device.

Abstract: An apparatus and method for detecting a single-phase-to-ground fault on a three-phase electrical power system and for identifying the faulted phase conductor. Each phase conductor is monitored by evaluating three phasor signals associated therewith, i.e., the zero sequence current of the electrical power system, the negative sequence voltage on the phase conductor rotated 90 electrical degrees counterclockwise (or the negative sequence current on the phase conductor), and the quadrature phase voltage for the phase conductor rotated 30 electrical degrees counterclockwise. The coincidence of these three signals for a predetermined time indicates the occurrence of a single-phase-to-ground fault on the monitored phase conductor.

Abstract: Field effect transistors are used in a series current limiter circuit. The field effect transistors are depletion type transistors and are interconnected in a manner to decrease conduction when an overvoltage or overcurrent condition is sensed. Biasing resistors are used to maintain the transistors in a non-conductive state until the overvoltage or overcurrent condition is removed.

Abstract: A protective power foldback circuit which protects a power semiconductor device from damage resulting from variations in load, supply voltage, and input drive power is disclosed. When the supply voltage exceeds a certain value, the drive power to the power device is reduced in an amount greater than that produced by the excess supply voltage thereby protecting the power device from the combined effects of load, supply voltage, and drive power.

Abstract: A current detecting device includes high frequency oscillation detecting circuits which, when a saturable reactor oscillates at a high frequency, detect the high frequency oscillation of the reactor and generate a high level output. Thus, when a large current flows through the reactor and the magnetization characteristic of the reactor is varied to generate a normal detection output, the reactor oscillation due to the large current is detected and an operating circuit for driving an external device is energized.