Category Archives: Sizing Breakers

Calculating short-circuit currents by hand

You won’t do many short-circuit hand calculations, but it’s useful to go through the exercise to develop an understanding of the fault behavior of typical electrical equipment. There are five you should get to know . . . . Continue reading

Three kinds of protective devices

There are three common types of protective devices you’ll encounter in the nuclear power industry. Here I summarize their functionality . . . .

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Three fault regions of a time-current plot

In a previous article I discussed the importance of coordination curves. Here I provide some home-made examples. Yep, you got it. Fashioned in the fires of Microsoft Powerpoint . . . . Continue reading

Coordination curves

Sometimes you’ll need to use more exact methods for sizing your breakers than the rules given by the NEC . . . . Continue reading

Circuit breaker withstand ratings and overload conditions

These are two elementary characteristics inherent to any circuit breaker. If you get the trip rating right, but neglect one of these, you’ll be all washed up . . . . Continue reading

A breaker’s primary function and electromagnetic forces

There’s a crucial link between circuit breakers and electromagnetics. There is good and bad . . . . Continue reading

Some basic protective-device principles

When you hear “protective device,” think “breakers” and “fuses.” It’s one thing to know how to size them correctly. It’s another thing to know why. But it can be expensive to learn the “why” . . . . Continue reading

Breaker sizing and short-circuits

Breaker sizing is another basic skill required for electrical engineers in the nuclear power industry. Here’s the short of it . . . . Continue reading