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Unread 24-03-2002, 10:46
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 10,811
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On the subject of the 60 amp breakers, I do not believe that any team can trip this breaker on current overload. The breaker has been tested and has predictable trips when run at 120 volts AC and 45 volts DC. Even though the battery at full charge is capable of delivering 450 amps, the terminal voltage at that current would be low enough to reset the robot controller before the circuit breaker would have a chance to react. These circuit breakers are very susceptible to impact trips, however. (try it yourself by tapping on the circuit breaker on either side the wires enter, you will be surprised at how little it takes.)They are especially sensitive to shocks from the sides, where the the wires are attached. For this reason, circuit breakers should not be firmly mounted in the robot such that any shock to the robot is transmitted directly to the circuit breaker. Teams have been successful in adding a few inches of extra #6 wire when installing the breaker. This allows the wire to absorb most of the shock and keeps the breaker from shock tripping.
We add a small block of plastic to the breaker that is wider than the body by 1 inch on both sides. (This allows us to tywrap the #6 wires to prevent flex failures in the wire at the breaker.) Then we bend the wires back so that there is several inches before they are attched to a frame member. That extra wire then absords the impacts to the frame.
I saw several impact trips at Great Lakes this weekend.
Hope this helps,

P.S. The clips on circuit breakers (in a distribution panel) are to prevent someone from turning them off accidently. They do not prevent the breaker from tripping on either current overload or impact.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
 


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