Our 20A and 30A and 40A breakers . . .

[Frank(Aflak)]

are they breakers or fuses?

I mean, they don't have a switch but everyone calls them breakers . . . .. are they self resetting? how long does it take for one to reset?

or are they fuses, and where can we grab more of em?

[Adam Shapiro]

They are self-resetting breakers. I actually got into the habit of calling them fuses and I'm trying to break it.

On another note, why do you have AFLAC in your name (plus you spelled it wrong)? I don't mean any offense but our team uses AFLAC because of a long story, I was wondering if you had one too... (it seems that a few "AFLAC"s have popped up recently after our team began to post with it)

[Andy A.]

The breakers are thermal, meaning that they sense current by how much they heat up. The more current you pull, the quicker they heat up.

Don't take the 30 amp rating at face value. In reality, you can pull much more for 2 minutes and never trip the breaker once. Exaclty how much for how long is a little subjective, but I belive the curves are avalible. When you do trip one, depending on the circumstances, it should reset within 5 seconds. However, when it resets, it will still be hot, and even currents less then its rating will cause it to trip.

Some teams have reported that spraying the breakers with cool-in-a-can just before a match slows their tripping. This makes sense, since if they start cold they have that much more heat to build up. This is a bit of legal gray area, since it circumvents the point of the breakers (30 amp breakers become 60 amp breakers). But, since the breakers let so much current by anyways...

Its up to you, since there is no rule against it, but it isn't completly legal, or illegal.

-Andy A.

[Adam Shapiro]

I think that that may be the reason for the 40's this year. Last year a lot of teams (including mine) reported a bunch of tripping with the 30's and the CIM's... It may be due to improper gearing (we didn't have much help) but I can't be sure...

[Al Skierkiewicz]

These breakers are a thermal reset type. As they have current flowing through them above the trip point, the current flow through the internal resistance causes heat.(Ohm's Law for power(heat) P(watts)=I^2 * R) The switch mechanism is a bimetallic design. The two metals which form the switch expand at different rates when heated and cause the internal parts to deform opening the breaker. When the current flow stops, the metals return to normal shape and the switch closes. However, once the breaker is near to trip temperature, only a little additional current is needed to send it over the edge. So...the breaker is more likely to trip again if it has tripped already in a match. The subsequent trips will occur at lower currents than the initial one. In sustained, high current situations, the reset occurs rapidly sometimes resulting in a buzzing sound from the breaker. Also, breakers that are operating at sustained high temperatures due to high currents, can raise the temperature of nearby breakers as well. The maxi block should help a little with that problem this year. It will be something I am interested in getting feedback on. If any team experiences 40 amp breaker trip during your build time will you post here and let us know the conditions you encountered.
Thanks,

[Frank(Aflak)]

we did bimettalic stips earlier this year in physics. As soon as 'heat' was mentioned I figured it was those, or something along the same lines.

[jburstein]

We tripped our 40 amp breakers today. We finally got our robot driving (latest ever, i think, for us) and using a 12:1 reduction fromt the chalupa motors (yes i know that's not what they're called), we tripped breakers while turning.

[DougHogg]

Anyone know where the thread is on how long the 30 amp breakers will hold at different amps of current?

I know I saw it last year, but I couldn't find it.

[Lloyd Burns]

The curves for fuses and circuit breakers are similar - I did a lot of searching when we started this 200% for 2 minutes thing.

A source for such curves is the pdf here:

http-www.1firsttech.com-ft-pdfs-ext200.pdf