Mcgraw-edison Company

Cooper Industries, Inc.

Other

Cooper Power Systems, Inc.

Richard J Moran

Ronald A Wainio

Daniel James Schreiber

Norbert J Reis

William N Le Court

A puck deflecting hockey skate covering includes a covering generally has the shape of a hockey skate and including a toe portion, a pair of side walls, a pair of ankle portions and a back wall. The covering has an open top side and an open bottom side. The covering comprises a substantially rigid material. An outer surface of the covering has a plurality of protrusions thereon. A strap has a first end and a second end wherein the first end is attached to a first of the side walls. A fastener removably fastens the second end of the strap to a second of the side walls such that the strap may selectively traverse the bottom side.

Puck deflecting hockey skate covering

An electronic circuit, and corresponding method, for controlling the closing velocity of electrical switchgear, includes an actuator and a current detection circuit that detects whether an optimum amount of current is flowing through the actuator. When the optimum amount of current is detected, a current optimizing resistor is inserted into the path of the current flowing through the actuator, thus limiting the current flowing through the actuator to the optimum amount. This, in turn, limits the closing velocity of the electrical switchgear and minimizes contact bounce.

Current limiting circuit

The sectionalizer control provides a restraint signal responsive to a harmonic current which exceeds a threshold current for less than a preset time.

Sectionalizer control

A distribution line powered switchgear control is provided which reliably initiates switchgear operations with stored energy. Stored energy is preferably maintained in a plurality of devices including a power capacitor. The power capacitor is preferably charged by a fast arming circuit which preferably selects among a plurality of independent power sources. The switchgear control additionally isolates sources of stored energy so that depletion of one does not affect the others. Further the switchgear control will preferably prevent closing of the switchgear unless sufficient energy is stored to allow the control to initiate a subsequent opening of the switchgear.

Distribution line powered switchgear control

A three-phase power supply has a current transformer in each power line. The transformer secondary winding is connected to a load. Generally, the load is a control means responsive to the current being sensed. A triac in parallel with the secondary winding and load has its gate connected by a voltage sensitive circuit to sense the corresponding secondary winding voltage and to conduct and protect the transformer in the event of load loss. The gate circuit includes a metal oxide varistor and a linear resistor in series connected in parallel with the secondary winding. A second linear resistor is connected to the common node of the first linear resistor and metal oxide varistor. The second linear resistor is in series with a diac and connects the gate to the common node of the varistor and first resistor. A trigger capacitor is connected between the common node of the second resistor and diac and the opposite end of the first linear resistor. On load loss, the secondary voltage rises and the varistor conducts, rapidly charging the trigger capacitor. The diac then conducts and the trigger capacitor supplies a large but controlled gate current to drive the triac 'on.' During the opposite half cycle, this cycle repeats until a load draws enough current to keep the secondary voltage within a critical level.

Open circuit current transformer protection circuit

An improvement to fault responsive protective devices, which employ timing capacitors, is provided by controlling the voltage of the timing capacitor by clamping it to a value slightly in excess of the voltage on a master timing capacitor. This allows the master timing capacitor to inhibit the operation of the improved fault responsive device without affecting the input to the timing capacitor. The inherent time constant produced by the timing capacitor is not altered. However, by clamping the voltage level of the timing capacitor only under appropriate conditions, the time current characteristic of the improved fault responsive protective device is altered only when those conditions occur which make it desirable to lengthen the interval before the fault responsive protective device responds to a fault.

Fault responsive protective device

A trip indicator circuit for a circuit interrupter of an electric power system, which includes an electromagnetic status indicator, having an indicator which is movable between an indicating position and a non-indicating position, a pulse-actuated set coil for moving the indicator to the indicating position, and a pulse-actuated reset coil for moving the indicator to the non-indicating position. An indicator set circuit for energizing the set coil is connected across the trip coil by an electronic switching device which is rendered conductive by an overcurrent sensing circuit whenever a particular abnormal condition occurs in the electric power system, so that the set coil will be energized only when the circuit interrupter is tripped during the occurrence of the particular abnormal condition. A reset circuit is connected across the closing coil to energize the reset coil each time the circuit interrupter is closed. The reset circuit includes a capacitor which is connected across the closing coil in series with the reset coil and a first diode which is orientated so that, when the closing coil is energized, a current pulse flows through the first diode, the capacitor, and the reset coil until the capacitor is fully charged. The reset circuit further includes a resistor connected across the first diode, and a second diode connected across the reset coil and orientated to allow the capacitor to discharge through the resistor, the closing coil, and the second diode when the closing coil is deenergized. The resistor prevents two closely-spaced resetting operations of the indicator, which otherwise may occur when the interrupter is tripped immediately after being closed.

Auto resetting switchgear trip indicator circuits

The minimum instantaneous voltage output of a phase resistor connected to receive the rectified phase and neutral currents of three wye-connected current transformers, magnetically coupled to respective phase conductors of a three phase electric power circuit, is proportional to the peak current of the phase conductor carrying the center magnitude phase current. A voltage proportional to this minimum instantaneous voltage is measured and stored by a capacitor each cycle. The peak instantaneous voltage output of a ground resistor connected to receive the full wave rectified output of three, parallel-connected current transformers, also coupled to respective phase conductors of the power circuit, is proportional to the peak ground current of the electric power circuit. A voltage proportional to the voltage output of the ground resistor is applied to the base of a NPN transistor, and the voltage stored by the capacitor is applied to the emitter of this transistor, to turn on this transistor every time the peak ground current exceeds a preselected percentage of the center magnitude phase current. The momentary turnon of this transistor at least once every current cycle activates a timing circuit, which after a predetermined time, initiates tripping of a circuit interrupter.

Proportional ground current relay

An inrush current restraint circuit, for use with a typical overcurrent minimum pickup circuit of a power system switching device, such as a recloser or sectionalizer, for raising the initial overcurrent minimum pickup value upon closure of the switching device to a selected value, then linearly returning this pickup value to normal within a selected period of time. The minimum pickup circuit is actuated by the voltage drop across a current sensing resistor, through which a current signal proportional to current in the power system is passed. The initial pickup overcurrent value is increased by providing another current path in parallel with the current sensing resistor when the switching device is closed. A timing capacitor is discharged each time the switching device is open, then charged from a constant current source each time the switching device is closed. The voltage across this timing capacitor is applied to the input of an amplifier having a unity voltage gain and the output of this amplifier is connected in series with a second resistor across the current sensing resistor. When the timing capacitor is charged to a voltage higher than the voltage produced across the current sensing resistor, the amplifier is back biased to effectively open the additional current path through the second resistor, and return the minimum pickup current to its normal value.

Inrush current restraint circuit for alternating power system switch

A bridge circuit including an eight-leg full wave rectifier bridge connected to rectify the phase and neutral currents produced by three wye-connected current transformers magnetically coupled to respective phases of a three-phase electric power circuit, and used with one or more resistive elements to provide instantaneous D.C. voltage outputs at least once every current cycle, proportional to the highest and/or lowest peak phase current and to the peak neutral or ground current of the power circuit, for operating or preventing the operation of a circuit interrupter in the power circuit being measured.

Bridge circuits for sensing currents in a three-phase A.C. circuit

A protective device includes a circuit breaker with an operating means connected to a fault current sensing control circuit. A small line current and/or a small fault current sensing current transformer means is conductively connected through individual rectifiers and series sensing resistors as a current source to charge a common power supply capacitor. A voltage limiting means across the capacitor maintains the current source. A high impedance signal processing amplifier includes a sensing transistor connected to the sensing resistor which establishes a minimum trip level and driving coupling transistors connected to the capacitor and including voltage sensitive means to positively inhibit full amplifier turn-on before the power supply capacitor is charged to an operating voltage level. In a fault condition, the amplifier rapidly charges a hold-on capacitor which slowly discharges to activate a timing control transistor of a time delay circuit, the output of which triggers a rapid, stabilized switch to operate the circuit breaker. The timing circuit may be driven from the power supply capacitor or a separate timing source capacitor which rapidly charges to the peak value of the sensing resistor and slowly discharges to establish a relatively constant and high average current such that timing is not sensitive to current transformer saturation. Where both line and ground fault sensors are connected to the common amplifier, they share the same timing means and have the same delay curves with a significant reduction in circuit cost and complexity. A clamping network may be connected to the sensing resistor to also minimize transformer core saturation and establish a maximum timing current and allow heavy fault currents of short duration.

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Milwaukee, WI, United States of America

Richard J Moran