Quote:
Originally Posted by Colin P
We think it arced between power out and ground in because the nut holding down the lead was welded to the bolt.
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Colin,
The robot was talking to you but you weren't listening. The only reason for a nut to weld itself to the bolt is because it was loose to begin with. Loose electrical connections cause excessive heat. Since the main breaker (and all of our breakers) is a thermal device, any heat internal or external will cause it to trip. Since your robot caused enough heat to weld the nut, this heat was transmitted to the breaker internals and that tripped the breaker.
Although this device is rated as a breaker, it is also in the switch category. The actuator is designed to act as a switch and the internal structures are designed to act a breaker. Using this switch with high currents flowing can cause damage to the internal contacts but most of the time, very little current is flowing when you turn your robot off.
A dead short somewhere else on the robot would not cause a nut to weld itself if it was tight to begin with. Remember that all robot current flows through this connection and that can be as high as the battery is capable of supplying. That is at least 500 amps for a fully charged battery.