Circuit Breakers: Tripping

[Al Skierkiewicz]

I thought this was important enough to start a new thread so here goes...
Over the last two weekends I have had the opportunity to inspect many robots that have been tripping circuit breakers. In all cases I was informed by the team members that they were tripping due to current overload. When questioned though most reports were that the breakers tripped when in shoving matches or when grabbing a goal. With a few when just running all by themselves. Additionally most teams reported never having tripped in practice, only in competition.
So this is what I observed...
1. The majority of robots that tripped had their breaker hard mounted to the robot frame.
2. If a team used the #6 wire to cushion the breaker, the breaker was mounted vertically (i.e. wires out the top and bottom.)or the wires were not flexible.
3. The teams had aggressive tread design or tank treads that caused a lot of vibration when running.
4. The team play strategy was to "bang" a goal out of position.
5. The robot had a high center of gravity or short wheelbase causing some bouncing while running.
Of the robots I observed, vibration or impact were involved in some form or another in every case. Some robots tripped just running from one side to the other on the second day. (This I am guessing is in relation to the carpet getting beat up over the course of a competition and causes an irregular surface.)
I still cannot point to current tripping as a possibility. It may be a contibuting factor in some robot designs made worse by vibration. One team who suspected they were tripping on overloads and were replacing breakers every few matches graciously opened one for inspection. No major defects were noted, but the design of the breaker would suggest that heat, vibration, and current could all contribute to a trip condition and very likely multiple vibrations or impacts would make tripping more likely.
One final note, in the case of one team, the wire clamp on the circuit breaker was loose. Loose connections on high current wires cause heat and the heat from that connection was transmitted to the thermal cutout in the breaker and tripped it off. Tight wires and no more trips.
Hope this helps. If you have had problems tripping breakers and are going to nationals, I'd like to see your robot. I am usually in our pit, just stop by.
Good Luck All