Circuit breaker protection against "arc short circuit" hazards

An electric service installation comprising,

• A. a circuit breaker box,
• B. an incoming electrical service connection extending into said circuit breaker box, and comprising
• two energized conductors of opposite phase and
• a neutral conductor with respect to which the energized conductors have a potential that is half the potential between the two energized conductors,
• C. a pair of main circuit breakers, mounted in said circuit breaker box, to which the energized conductors are, respectively, connected,
• D. a pair of main buses, respectively connected to the output of each of the main circuit breakers,
• E. a neutral bus,
• mounted in said circuit breaker box, to which the third, neutral conductor is connected,
• F. a plurality of branch circuit breakers connected to each of said main buses, each branch circuit breaker having
• a current rating which has a relatively low magnitude, and
• a magnetic trip mode which is actuated by current flow exceeding a threshold value that is a several treats multiple of the current rating for the circuit breaker,
• G. a plurality of branch circuit cables extending into the circuit breaker box, each branch circuit cable comprising
• a first conductor connected to the neutral bus and
• a second conductor energized from one of the branch circuit breakers, whereby separate branch circuit loads may be, respectively, energized from said cable,
• said electric service installation being characterized by
• H. acceleration means for enhancing operation of the branch circuit breakers to provide protection against the hazards of "arc short circuits" having a current flow which randomly varies in magnitude pursuant to a bell shaped frequency distribution curve, upwardly from a minimum threshold value,
• said acceleration means being actuated in response to overcurrent flow, in any branch circuit cable, exceeding the threshold value for an "arc short circuit",
• said acceleration means including
• means, responsive to such overcurrent flow, for substantially instantaneously increasing current flow through the branch, circuit breaker that is connected to the branch circuit cable in which such overcurrent has occurred,
• whereby the circuit breaker will be magnetically tripped by branch circuit current flows substantially less than are otherwise required for magnetic tripping,
• wherein
• the branch circuit breakers require a current flow for magnetic tripping that is greater than the current flow that occurs in 40% of the occurrences of an "arc short circuit", and
• further characterized in that
• the acceleration means is actuated in response to current flow occurring in at least 90% of the occasions of an "arc short circuit".

An electric service installation comprising,

• A. a circuit breaker box,
• B. an incoming electrical service connection extending into said circuit breaker box, and comprising
• two energized conductors of opposite phase and
• a neutral conductor with respect to which the energized conductors have a potential that is half the potential between the two energized conductors,
• C. a pair of main circuit breakers, mounted in said circuit breaker box, to which the energized conductors are, respectively, connected,
• D. a pair of main buses, respectively connected to the output of each of the main circuit breakers,
• E. a neutral bus,
• mounted in said circuit breaker box, to which the neutral conductor is connected,
• F. a plurality of branch circuit breakers connected to each of said main buses, each branch circuit breaker having
• a current rating which has a relatively low magnitude, and
• a magnetic trip mode which is actuated by current flow exceeding a threshold value that is a several times multiple of the current rating for the circuit breaker,
• G. a plurality of branch circuit cables extending into the circuit breaker box, each branch circuit cable comprising
• a first conductor connected to the neutral bus and
• a second conductor energized from one of the branch circuit breakers,
• whereby separate branch circuit loads may be, respectively, energized from said cable,
• said electric service installation being characterized by
• H. acceleration means for enhancing operation of the branch, circuit breakers to provide protection against the hazards of "arc short circuits" having a current flow which randomly varies in magnitude pursuant to a bell shaped frequency distribution curve, upwardly from a minimum threshold value,
• said acceleration means being actuated in response to overcurrent flow, in any branch circuit cable, exceeding the threshold value for an "arc short circuit",
• said acceleration means including
• means, responsive to such overcurrent flow, for substantially instantaneously increasing current flow through the branch circuit breaker that is connected to the branch circuit cable in which such overcurrent has occurred,
• whereby the circuit breaker will be magnetically tripped by branch circuit current flows substantially less than are otherwise required for magnetic tripping;
• wherein
• the energized conductors of the incoming electrical service have an alternating current potential of 120 volts with respect to the neutral conductor, and
• the branch circuit breakers have a current rating of 15-20 amperes, and
• further characterized in that
• the acceleration means comprise
• an acceleration bypass circuit extending from the output of each branch circuit breaker to the neutral bus,
• a normally non-conductive SCR
• disposed in series with each acceleration bypass circuit,
• triggered to a conductive state by a predetermined potential between its cathode and gate,
• with a cathode connection to the output of the associated branch circuit breaker;
• sensing resistor means connected, respectively, with the output of each branch circuit breaker and in series with the second cable conductor energized therefrom, said sensing resistor means being connected across the cathode and gate of the SCR for the associated branch circuit,
• whereby the potential between the SCR cathode and gate is proportional to the magnitude of current flow through the associated branch circuit cable, and the SCR is triggered to a conductive state to thereby actuate the acceleration means,
• further characterized in that
• the SCR's are triggered by a cathode/gate potential of no more than approximately 0.75 volts, and
• further characterized by
• means for limiting acceleration bypass circuit current flow to no more than about 140 amperes.

An acceleration unit to accelerate the magnetic tripping of a circuit breaker, said unit mounted in a circuit breaker box, said unit comprising

• an SCR having
• an anode,
• a cathode, and
• a gate,
• sensing resistor means,
• a gate limit resistor, and housing means on which the SCR, sensing resistor and gate limit resistor are mounted,
• a first conductor connected between the output of a circuit breaker and the SCR cathode,
• a second conductor connected to a branch circuit conductor,
• means connecting the sensing resistor means in series with said first and second conductors and across the SCR cathode and gate, and
• a third conductor extending from the SCR anode and connected to an acceleration bypass circuit.