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  • Vacuum Circuit Breakers: Features, Operation & Applications

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    John Mulindi
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    In vacuum circuit breakers, vacuum typically at pressures ranging from 10-9 to 10-6 bar is used as the quenching medium. At such pressures, high dielectric strength can be achieved. The contact separation needed at such low pressures is only 0-20 mm and low energy mechanisms may be employed to operate the contacts through expendables bellows.…

  • Air-Blast Circuit Breakers: Features, Operation & Applications

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    John Mulindi
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    Air-blast circuit breakers utilize a blast of compressed air typically at a pressure of 25–75 bar, which is directed across the path to cool and eliminate the ionized gas, in other words the air-blast is employed as the quenching medium. The air-blast cools the arc and sweeps away the arcing products to the atmosphere. This…

  • Air Circuit Breakers: Features, Operation & Applications

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    John Mulindi
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    Air Circuit Breaker Features & Operation An air circuit breaker employs atmospheric air as its interrupting medium. The arc is drawn between its contacts and extended via arc runners on to an arc chute where it is presented with a large cooling surface of arc splitter plates. These break the arc into a number of…

  • SF6 Circuit Breakers: Features, Operation & Applications

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    John Mulindi
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    Introduction Many modern designs of circuit breakers for use at transmission voltages utilize sulphur hexafluoride (SF6) gas both as an arc-interrupting/arc-quenching and a dielectric medium. At distribution voltages SF6 designs of circuit breakers are also used, however vacuum and bulk-oil circuit breakers still find a wide use as alternatives. The SF6 is an electron-negative gas…

  • Miniature Circuit Breakers (MCBs)

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    John Mulindi
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    Miniature circuit breakers (MCBs) are electromechanical devices that protect an electrical circuit from over currents, in other words, MCBs are switches that automatically turns OFF when the current flowing them exceeds the maximum allowable limit. Over currents in an electrical circuit may be caused by short circuits overload or faulty designs. MCBs functions by interrupting…