ECN Forum Forums General Topics of the Trade General Discussion Area Halogen bulbs trip breaker.

Thanks for the help Guys. This one had me stumped.

I told the customer today, that I didn't know the answer,but I knew a place I could find it.

Thanks again.

Russell

http://members.misty.com/don/bulb1.html#wbs

Why burnout is sometimes so spectacular
When the filament breaks, an arc sometimes forms. Since the current flowing through the arc is also flowing through the filament at this time, there is a voltage gradient across the two pieces of the filament. This voltage gradient often causes this arc to expand until it is across the entire filament.
Now, consider a slightly nasty characteristic of most electric arcs. If you increase the current going through an arc, it gets hotter, which makes it more conductive. Obviously, this could make things a bit unstable, since the more conductive arc would draw even more current. The arc easily becomes conductive enough that it draws a few hundred amps of current. At this point, the arc often melts the parts of the filament that the ends of the arc are on, and the arc glows with a very bright light blue flash. Most household light bulbs have a built-in fuse, consisting of a thin region in one of the internal wires. The extreme current drawn by a burnout arc often blows this built-in fuse. If not for this fuse, people would frequently suffer blown fuses or tripped circuit breakers from light bulbs burning out.
Although the light bulb's internal fuse will generally protect household fuses and circuit breakers, it may fail to protect the more delicate electronics often found in light dimmers and electronic switching devices from the current surges drawn by "burnout arcs".

Around here in areas with low impedance feeders and houses close to the transformer that's a pretty common occurrence even with incandescent bulbs. Ever since they put in new underground wiring in the street we occasionally had tripping breakers when bulbs blew.

The most common reason for a breaker to trip on lamp burn out is that a small section of the filament drops across the lamp bus creating a short and drawing enough current to trip the breaker.
Don

Scott,
Negative resistance would mean that you are creating power. I don't think that is possible.
Don

Scott,
Negative resistance would mean that you are creating power. I don't think that is possible.
Don

Russ!,
Good to see ya posting mate!.
For those of you that don't know, this fella used to be ga56sparky, one of the first people that registered here.

Hi Mike. I still come here and read when I can.

I see ya'll still let Roger and Bob in here.

Ahh yes Roger and Bob.
Good to see they hung around.

In the strictest sense, you would be correct. But a negative resistance region is characteristic of some exotic semiconductor devices, such as a "tunnel diode"
http://en.wikipedia.org/wiki/Tunnel_diode
http://en.wikipedia.org/wiki/Negative_resistance





[This message has been edited by NJwirenut (edited 02-03-2007).]