30a breaker for 40a spot on pdb

[Racer26]

Literally thousands of teams have been using 4 CIM drivetrains with 40A breakers on each CIM for years. I doubt this is your issue.

Personally, my team has never tripped the 120A main breaker. We've had the 40A's in a 4CIM treaded tank drive stalled and popping, and never popping the main. I would look to something mechanical, or possibly a faulty main breaker.

[Joe Ross]

There was a team at the Los Angeles regional who's circuit breaker would trip when they had a hard impact. After repositioning it and shock mounting it, it still occurred. They were able to reproduce the problem on the practice field by running it into the wall or over a bump hard. They replaced it with a new breaker and it didn't happen again.

What was the position of the black lever on the circuit breaker when you lost power?

[Bruceb]

it was in the tripped....lever sticking out position. Just like it is when you push the red button.
Also for EricH. You say we have Wednesday night to get ready for competition but the rules I have read say uncrating only on Wednesday night. Doesn't even look like they want you setting up the pit or working on the robot at all. What am I missing?
Bruce

[Kris Verdeyen]

The main breaker will run at 2x its rated current for at least ten and up to 40 seconds. That's 240 amps. If it tripped on the field, inspect your big wires and crimps (between the breaker and fuse panel) for shorts, and consider replacing the breaker itself. The big breaker is there to keep stuff from catching fire, it shouldn't trip in regular operation.

[EricH]

Originally Posted by Bruceb

it was in the tripped....lever sticking out position. Just like it is when you push the red button.
Also for EricH. You say we have Wednesday night to get ready for competition but the rules I have read say uncrating only on Wednesday night. Doesn't even look like they want you setting up the pit or working on the robot at all. What am I missing?
Bruce

The FIRST email about the Championship is what you're missing.

They've been monkeying with the Championship schedule and similar things to allow the following on Wednesday night:
--Uncrating
--Pit setup
--Inspection
--work on robots (after all, you want to fix what you found out was illegal at inspection, right?)

They just haven't updated any Manual sections that cover this sort of thing--but all the info comes from Bill Miller and/or the FRC staff, so it's legit.

[Bruceb]

Are they allowing more then 5 people in to do all that stuff Wednesday night?
Bruce

[Al Skierkiewicz]

Bruce,
There was another team in Milwaukee that also tripped the main breaker. They thought is was protected as well but what we found was a small crack in the case. The slight misalignment was enough to cause the breaker to let go. There is another known issue with the breaker. A few over the years have shown up with manufacturing defect. A simple tap on the red button is sufficient to trip the breaker. The test is to tap with your finger and see if it fails. Over the last four years I think I have seen a total of less than ten.

[EricH]

Originally Posted by Bruceb

Are they allowing more then 5 people in to do all that stuff Wednesday night?
Bruce

Nope. 5 is the max, unless you can steal some from another team that's already in there. (All the other teams are probably trying to do the same thing...)

[robself705]

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