04-04-2015 12:19

coolhandluke811

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

Could you share more info on this?

-What likely caused it
-How long it took you to fix.

04-04-2015 12:37

Michael Hill

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

Wasn't our team so I can't comment on it.

04-04-2015 12:44

Racer26

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

Making an educated guess based on the photo?

Looks to me like the positive lead of those wire stubs pulled too much current through the board (possibly by shorting to ground somewhere in the wiring between the PDP+(Speed controller of choice)), overheating it and ultimately igniting the plastic chassis of the PDP.

04-04-2015 12:53

Michael Hill

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

I will say looking at the bottom of the PDP, there was a distinct burn mark (Unfortunately I don't have a picture) between the 40-Amp breaker slot and the smaller ones. I don't know enough about the situation to say much more.

05-04-2015 11:45

Jaxom

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

I do have a picture, which I will post as soon as I can figure out how to make CD allow me to. One theory was some kind of internal arcing. I'm not on their team either, but I think they've already contacted CrossTheRoads. The "good" news is that they only missed one match while repairing their bot.

It definitely was on fire - not just smoke. In addition to the PDP there was a bundle of CAN wire right next to the PDP that was crisped.

06-04-2015 09:32

kpie3692

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

We are still not sure why it happened but it was definitely not something that we caused. It took us under an hour to replace the pdp, 2 talons and test everything.

06-04-2015 10:28

techhelpbb

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

So did the field's fire extinguisher get some use?

06-04-2015 10:48

Tungrus

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

Are you or CRE doing any analysis as to why this happened? If it was a short, the inline circuit breaker or the main breaker should have tripped (it auto resets and finally the main breaker trips), I think.

Curious to know if it the heating started on the PDP PCB (internal circuit board) somehow (possibly a metal chip that got under the cover of PDP), so the bypassed inline circuit breaker did not trip and before the main breaker (120A), tripped it melted the plastic.

06-04-2015 10:58

Robby Unruh

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

Yes it did. Here's a video of the incident straight from the stream. (we're working on uploading the other match days- watch them on our website!)

06-04-2015 11:17

kpie3692

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

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.

06-04-2015 11:25

Tungrus

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

Please share your/CRE findings, we all can learn from your experience.

Thanks in advance.

06-04-2015 11:44

ayeckley

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

Good thinking on somebody's part to have a CO2 extinguisher available rather than just standard Class ABC. That would have made a real mess.

06-04-2015 12:01

FrankJ

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

The trouble with the self resetting breakers is that they will set there self resetting, passing enough current to feed a fire. It probably limits the current enough so the main breaker would not trip. Even 40 amps @ 12V will burn things if concentrated enough. Think car cigarette lighter for those of you with cars old enough to have them.

06-04-2015 12:33

kpie3692

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

This was no small fire. With a 3 to 4 inch flame visible from the stands I'm worried about how the whole situation was handled. They let the fire go for just under a minute. Isn't the main priority of first safety? Letting a fire go that long does not seem safe to me.

06-04-2015 12:35

JamesCH95

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

...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.

06-04-2015 12:40

kpie3692

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

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

06-04-2015 13:03

philso

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

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.

14-07-2015 19:42

Michael Hill

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

Did anyone at CTRE ever figure out what happened?

14-07-2015 20:25

logank013

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

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.

14-07-2015 21:17

Darkseer54

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

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

15-07-2015 08:59

FrankJ

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

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

17-07-2015 21:46

DonRotolo

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

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.

18-07-2015 22:30

BBray_T1296

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

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".