Air Circuit Breakers: An Evolution
The business of circuit breakers began after WWII. Prior to that, the way the world would break a circuit was with fuses. Fuses were effective, but they were not smart. They had to be replaced after an overload.
The First Circuit Breaker
With the war effort, the world saw the first reset-able fuse—the circuit breaker. All the major manufacturers in the war effort had them. The industrial circuit breakers were big and heavy, mounted on large pieces of slate, which was considered the best non-conductive material at the time. The massive contacts would open on overload when two small disks submerged in oil would break apart. The principle of this early tripping mechanism was as the oil in a dashpot would heat up, it would become more viscous, and eventually the two discs submerged in this oil would break apart, as the current would went higher. It was effective, but obviously primitive for our standards today.
Plastics Improves Circuit Breaker
The 1950s saw an era where plastics became a larger part of our everyday lives. Plastic was also a great nonconductive material, and was the greatest change used in the circuit breakers of this generation. The breakers became smaller and lighter. The tripping mechanism, once a dashpot submerged in oil, was now an electro-mechanical unit.
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Remanufactured Industrial Circuit Breakers for Buildings Built Prior to 1955
The other major issue here was that these circuit breakers were in no shape or form interchangeable with their like products made in 1945. All the parts were completely different. All the buildings built prior to this period, 1955, had the first generation of obsolete circuit breakers. They could not get parts, spare breakers or support from the original equipment manufacturers. They had to buy remanufactured circuit breakers to go with their obsolete switchgear.
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Electric Control still stocks in its inventory the first generation of industrial circuit breakers. -This is when Ed Kahn went into business as an electric control equipment company. He supported all those companies who could no longer get parts or complete circuit breakers—rubber companies, airplane manufacturers, gas companies, utilities, universities, sewage plants and any buildings that employed more than 300 people, probably had circuit breakers big enough that were not supported.
In the 1960s, the era of planned obsolescence, the circuit breakers looked the same, but were not interchangeable as the prior generation.
Circuit Breakers with Solid State Trip Units
The 1970s saw the beginning of the solid state era, as diodes transistors played a larger part of our lives. Circuit breakers, though in functionality basically the same, now had solid state trip units. These new trip units would monitor the amperage on a given circuit far more accurately than their predecessors, and they lasted longer and required less maintenance. These circuit breakers were still not interchangeable with any breaker made before this time.
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In the 1990s, there was more refinement of the tripping mechanism. Any building built prior to this period had obsolete equipment and could not get new parts from the original manufacturers.
Contrast these previous years to 2000. Today, I can sit with the head of maintenance at Logan Airport as he closes and trips all his circuit breakers from his PC. He can monitor each circuit breaker in his grid and print out peak running times. In other words, the evolution of that original 600V circuit breaker has come to the point, that his equipment now talks back to him and records data via a central terminal.
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