electrical dudes, circuit breaker question for ya

jrlouie

I was hoping someone more educated in this type of stuff could give me their opinion. I'm wondering how instantaneous a circuit breaker on a surge protector/conditioner is. For example, the surge protector has a breaker on it stating that it will open if its power draw exceeds 15 amps. Does that essentially include a brief peak type of situation too? In other words, if that puppy never opened, could I say I have never drawn 15 amps from the wall through that conditioner?
Please see pic for reference.

disneyjoe7

Not a circuit breaker 15 amps constant or more like 10 amps constant for a blink of an eye maybe something around 100 amps before it would trip. The same is true with Slo-Blow fuses acting like a CB, but fast act fuses don't like in rush current so would blow where a Slo-Blow fuse wouldn't.

I-SIG

DJ7 is right. You could have peaks well over the rated 15 amps but are of such short duration that it never gets near the time-current curve of the breaker.

On a larger scale, the fuses that the power companies use can handle thousands of amps, but only instantaneously, usually in either an in-rush situation that dj7 mentions, i.e. the power has been out for a couple of hours and everyone's A/C kicks on or in a fault situation that is of such short duration the fuse never has time to melt. Don't get into ground fault detection on distribution systems....:o

Wes

shadowofnight

I have replaced more circuit breakers then I care to remember ( In the manufacturing area I support we use a LOT of robots moving large assy's...one particular tool set uses these robots in a water enviroment ...those I usually find melted ) As mentioned above, the breakers can take a much higher instantaneous current for low millisecond pulses...but a tiny bit longer in duration and they trip. Also, the more cycles they are tripped...they tend to trip at a lower current level the next cycle...and so on. Here is a quick link to show how the common ones actually work . http://electronics.howstuffworks.com/circuit-breaker2.htm

jimmyzen

In general, anything that has a transformer or winding like an electric motor is called an inductive load. When voltage is first applied to an inductive load the wire in the windings acts like a straight piece of wire, or for illustrative purposes a short, so it draws a bunch of current. As the current starts to flow it creates a magnetic field that radiates out from around the wires at a 90 degree angle. As the magnetic field passes through adjacent windings it induces a current in opposition the the initial flow of current in the winding of the coil. This opposition to current flow reduces the initial inrush current and eventually limits the amount of current that passes through the winding. If you have ever seen lights dim in a garage when an air compressor kicks on or in the house when a washing machine starts its cycle you have seen this phenonmenon in action. Consequently circuit protection devices have this condition accounted for and designed into them. In some industrial applications there are circuit breakers used that have a time delay adjustment. Again, this is a very simplistic explanation.

(If you hold a pencil in your hand to represent a conductor with your fingers wrapping around it and your thumb pointing down its length, your thumb indicates direction of current flow and your encircled fingers indicate the magnetic lines of force radiating out of the conductor. The magnetic lines passing through a conductor next to the first one would have a current induced in it that flows in the opposite direction.)