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Unread 31-03-2010, 17:09
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Team Leader / Mechanical
AKA: Rob Self
FRC #0706 (Cyberhawks)
Team Role: Mechanical
 
Join Date: Nov 2008
Rookie Year: 2009
Location: Arrowhead High School Wisconsin
Posts: 72
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Re: 30a breaker for 40a spot on pdb

Ok, I know what everyone is saying that the breakers should last well above their rated amperage but this is not true and it is not the issue or the question. I physically tested all of the breakers yesterday because we are adding a programmed throttling device that limits the cim motor power under high loads. We have an external ammeter that measures the amperage draw to 2 amps. Yesterday I WAS ACTUALLY STALLING A CIM and tripping the 40 amp breaker, the problem is each 40 amp breaker will let you pull 50 amps for about 2 seconds before it trips. They let you spike up to 80 amps for a fraction of a second. We can draw 180 + amps for over 30 seconds JUST FROM OUR CIMS. We also have a vacuum that draws up to 30 amps continuously. WE ACTUALLY TRIPPED OUR BREAKER IN A MATCH. So its not a question of whether or not it can happen, it did. Switching to 30 amp breakers would partially solve the issue. I tested them and they allow about 35 amps draw for a second before they trip. This would mean MAX from the cims we could draw 140 amps for just second. This would partially solve our issue, it would just be a lot easier to swap them they have to re wire. We are counting more on our current draw feedback to keep this issue from happening again. But it does happen, the main can be tripped.

However we might try swapping out our main breaker to see if that is the issue. I was looking at charts previously posted and it should last for 20 seconds with 200% draw. We didn't have low enough ohm resistors to test the main breaker.

I'm am not yelling so don't get the wrong impression I just want to make it clear what the issue is. Thanks for everyone's valuable input
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Rob Self-
Cyberhawks Team 706
Hartland, WI

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Last edited by robself705 : 31-03-2010 at 19:50.