pic: 3692's PDP after catching on fire at Queen City

[JamesCH95]

Originally Posted by kpie3692

CRE has contacted us and wants us to send them the PDP for analysis. I'm curious to see what they find and I hope they follow up with us on the cause.

It was for sure a massive short but the inline breaker and the main breaker never tripped throughout the fire. We are very careful with our electronics so I'm confident it wasnt a chip, that only leaves manufacturing defects.

...or a faulty termination.
...or a jammed breaker.
...or a motor controller fault.
...or a wire with some nicked strands from stripping.
etc.

My point is that unless you have some very specific and compelling evidence to rule out everything else (or confirm it was a mfg defect) I don't think that you should be so quick to throw CTE under the bus for this!

For example, if a few strands of one wire contacted the terminal of another wire it would take much less than 40A to heat up those strands enough to light some plastic on fire.

[kpie3692]

Originally Posted by JamesCH95

...or a faulty termination.
...or a jammed breaker.
...or a motor controller fault.
...or a wire with some nicked strands from stripping.
etc.

My point is that unless you have some very specific and compelling evidence to rule out everything else (or confirm it was a mfg defect) I don't think that you should be so quick to throw CTE under the bus for this!

For example, if a few strands of one wire contacted the terminal of another wire it would take much less than 40A to heat up those strands enough to light some plastic on fire.

You're right, I shouldn't have been so quick to say it was an mfg defect.

[philso]

It could have been a faulty 40A breaker that was not opening so save the part if you can.

My money would be on a faulty connection in the spring clamp connector in the PDP. Look into the connector with a flashlight to see if there may be some insulation in the connection area or something like that.

A high resistance joint can cause heating leading to a fire. We have had fires in the equipment we build at work when the bus bars are not bolted together tightly and 1000-2000A is put through the connection.

[Michael Hill]

Did anyone at CTRE ever figure out what happened?

[logank013]

One thing I'm noticing is that there is no 40 amp breaker in the circuit. Could that have caused the fire? I'm sort of using my minimal electrical skills to guess so that's why I'm asking. But they probably had a breaker in it and removed all the breakers and excess wire for the photo.

[Darkseer54]

Originally Posted by logank013

One thing I'm noticing is that there is no 40 amp breaker in the circuit. Could that have caused the fire? I'm sort of using my minimal electrical skills to guess so that's why I'm asking. But they probably had a breaker in it and removed all the breakers and excess wire for the photo.

The current must run through the breaker in order to reach the wires, so yes they must have taken the breakers out (along side the rest of the wires). The point of the breakers is to cut off power to the wires in the case that they draw too much current, in which case it opens the circuit. In order to open the circuit the current has to run through the breaker.

https://www.youtube.com/watch?v=GD6qtc2_AQA

[FrankJ]

Originally Posted by Michael Hill

Did anyone at CTRE ever figure out what happened?

I asked one of the CTRE people at the booth in St Louis. He said in effect that it was swarf that had gotten into the board. i forget the exact wording he used. Maybe some one with more direct knowledge will comment.

The current must run through the breaker in order to reach the wires, so yes they must have taken the breakers out (along side the rest of the wires). The point of the breakers is to cut off power to the wires in the case that they draw too much current, in which case it opens the circuit. In order to open the circuit the current has to run through the breaker.

The self reseting breakers used reset so fast that they don't actually cut power, just limit it.

[DonRotolo]

Originally Posted by kpie3692

It was for sure a massive short but the inline breaker and the main breaker never tripped throughout the fire.

Just a comment on circuit protectuion devices (such as fuses and circuit breakers): They are designed to limit the current or open the circuit after a certain current and time has been reached, and they do so quite reliably. However, there are circumstances where they cannot help: An Arc.

An arc is electrical current flowing across a 'space', a gap in the conductor, creating a (relatively) low-resistance plasma which conducts the current. An arc can have a resistance on the order of an ohm, which for 12 volts means maybe a dozen or two Amps - not enough to trip a 40A breaker, but plenty of energy to get real hot, real fast.

I work in the automotive industry, and while this is not my area of expertise, we know that a 30A circuit can form an arc that starts a fire but does not blow the 30A fuse. The arc sustains itself for a 'long' time (more than several seconds, sometimes several minutes).

You likely know what a GFCI (Ground-Fault Circuit Interrupter) is, but look up the term "Arc-Fault Interrupter". The National Electric Code began asking for (or maybe requiring, not certain) AFCIs in all new wiring circuits serving bedrooms back around 2002. They did this because arcs start fires and conventional circuit breakers cannot do anything about it because the arc does not draw enough current to trip one.

All that being said: An arc may have formed (won't speculate why or how, or really even if) that drew less than the circuit breaker's rating, and the resulting plasma arc (several thousand degrees) appears to have started a fire.

[BBray_T1296]

Can I point out that the Head Ref clearly noticed the fire at 2:10 in the video but it was not until 3:07 that the match was halted, with the fire being extinguished a full 70 seconds after being noticed by the field.

Possibly the polar opposite of "quick thinking".