General Electric Company

Graham A Scott

Roger N Castonguay

Robert Allan Morris

Joseph M Palmieri

Richard A Dziura

Ronald R Russell

Alan Joseph Messerli

Gregory T DiVincenzo

David J Lesslie

Linda Yvonne Jacobs

Donna C DeRosier

Alexander A Krajewski

Eric D Juntwait

A rating plug-metering accessory for molded case circuit breakers of the type employing an electronic trip unit is in the form of a rating plug enclosure that is optionally installed in the circuit breaker cover. Besides setting the ampere rating of the electronic trip unit, the rating plug-metering accessory further provides direct readout of the current in any of the phases of a multi-phase power distribution circuit. The rating plug-metering accessory can be either factory-installed or installed in situ.

Metering accessory for molded case circuit breakers

An electronic circuit interrupter includes an electronic trip circuit contained within a circuit interrupter enclosure along with an externally accessible rating plug for setting the ampere rating. The rating plug includes keying tabs that fit within corresponding keying slots formed on the top surface of the electronic circuit interrupter enclosure. Interlock is provided between the rating plug and the electric panelboard which includes a plurality of electronic circuit interrupters connected within an industrial power system. Tabs formed on the side walls of the rating plug are trapped under the panelboard face plate to prevent removal of the rating plug without first removing the panelboard face plate.

Molded case circuit interrupter rating plug keying and interlock

A compact circuit breaker containing an electronic trip unit for interrupting overcurrent conditions within a protected circuit is made operable over a wide operating current range by means of current transformers having multiple turn primary windings. The primary windings are selected to provide a constant ampere-turns ratio to the current transformers without changing the size of the secondary winding or the volume of the transformer core.

Compact circuit interrupter having multiple ampere ratings

A circuit breaker enclosure consists of a cover and a case designed for robotic assembly of the circuit breaker components. A current transformer assembly and a printed wire board containing the electronic trip unit circuit are precisely positioned within the case and cover by means of a transitory circuit breaker case support platform. The transitory support platform includes four upstanding posts that pass through openings formed in the circuit breaker case and are received within corresponding openings through the circuit breaker cover. Leads extending from the current transformer assembly within the case become automatically positioned within corresponding openings through the printed wire board by means of tapered lead-in openings formed within the circuit breaker cover.

Method of assembling a molded case circuit breaker current transformer

Molded case circuit breaker current transformer assembly

An electronic trip unit within a self-contained circuit interrupter utilizes dual electromagnetic trip actuators. One such actuator responds to overcurrent conditions to interrupt the protected circuit up to a predetermined value. The other such actuator interrupts the protected circuit at all overcurrent conditions in excess of the predetermined value.

Molded case electronic circuit interrupter

An integrated protection unit is a circuit breaker which includes basic overcurrent protection facility along with selective electrical accessories. A molded plastic accessory access cover secured to the integrated protection unit cover protects the accessory components contained within the integrated protection unit cover from the environment. A combined overcurrent trip actuator and multiple accessory unit can be field-installed within the integrated protection unit. The combined actuator-accessory unit includes electronic control circuitry for the accessories along with mechanical trip and reset interface components.

Molded case circuit breaker actuator-accessory unit

An integrated protection unit is a circuit breaker which includes basic overcurrent protection facility along with selective electrical accessories. A molded plastic accessory access cover secured to the integrated protection unit cover protects the accessory components contained within the circuit breaker cover from the environment. A combined overcurrent trip actuator and multiple accessory unit can be field-installed within the integrated protection unit.

Molded case circuit breaker multiple accessory unit

Electronic trip units employed within static trip circuit breakers are individually calibrated and automatically adjusted to ensure that the trip transfer characteristics are within specification requirements. A trimming network within the trip unit circuit contains a plurality of parallel resistors each separately connected within the circuit by means of a fusible link. Test input and output values are compard to idealized values that are binary-weighted within a look-up table in the test equipment computer. The percent correction required is determined and the appropriate links are interrupted to provide ideal trip response.

Static trip circuit breaker with automatic circuit trimming

The overcurrent trip levels of an electronic circuit breaker are selected by means of a variable resistance ladder network comprising binary encoded switches. The binary encoded switches reduce the size and cost of the trip unit, rendering electronic trip facility to a wider range of industrial circuit breakers utilizing both analog as well as digital processing circuits.

Electronic circuit breaker trip function adjusting circuit

Electronic trip units employed within static trip circuit breakers are individually calibrated and automatically adjusted to ensure that the trip transfer characteristics are within specification requirements. A trimming network within the trip unit circuit contains a plurality of parallel resistors each separately connected within the circuit by means of a fusible link. Test input and output values are compared to idealized values that are binary-weighted within a look-up table in the test equipment computer. The percent correction required is determined and the appropriate links are interrupted to provide ideal trip response.

Miniaturized current sensing transformers are electrically and mechanically attached to the printed wiring board carrying the electronic trip unit circuit within molded case circuit breakers. Electrical contacts extending from the current sensing transformers project through openings in the wiring board to springingly engage metal posts extending from the printed wiring board surface. Notched posts mounted on the current sensing transformers, co-extensive with the contacts, snappingly engage the sides of the printed wiring board for good mechanical support and to maintain alignment between the current transformers on the printed wiring board.

Mounting arrangement for circuit breaker current sensing transformers

A removable rating plug connectable with electronic trip molded case circuit breakers allows a common rating plug design to be used over a wide range of industrial rated circuit breakers. The burden resistors carried by the rating plug set the breaker ampere rating in combination with a current transformer tap selection. Electrical connection is made between the rating plug and the trip unit circuit board by a plurality of conductive stabs attached to the plug for insertion within spring connectors arranged on the circuit board. The stabs are keyed to ensure electrical connection with reference ground before, during, and after electrical connection is made with the rating plug burden resistors to protect the current sensing transformers from dangerous overvoltage conditions. Additionally, trip test facility and rating plug integrity indication are provided by test connectors on the rating plug in combination with test circuit implementation on the trip unit circuit board.

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Avon, CT, United States of America

Graham A Scott