CIM Motor Capacitors

[Al Skierkiewicz]

In a few seconds the main breaker would take ~720 amps to trip. The NP18-12 battery is only speced at 500 amps out into a short circuit at which point (at full charge), it is dropping 5.5 volts just across the internal resistance of the battery ignoring any other losses internal to the battery. 500 amps will drop another volt across the #6 wiring ignoring the resistance of the main breaker, Anderson connector, crimps and terminals.

[Ether]

Originally Posted by Al Skierkiewicz

In a few seconds the main breaker would take ~720 amps to trip.

If you have a link to the spec for that could you post it please.

The NP18-12 battery is only speced at 500 amps out into a short circuit

So it is. Interesting. The 2009 battery spec says 720 amps for 5 seconds.

[bobosalad]

What are you running besides your four cims? Did this problem show up during Duluth? If it did, you guys managed it pretty well. After the communication dropped, were you ever able to get it back?

[ProgramLuke]

We are also using 2 of the smallest banebot's, a window motor, and the compressor.

[Al Skierkiewicz]

The main breaker sheet is on CD already. You just have to search to find it. The actual spec is 600% over current for a few seconds and several minutes at 200%.

[Ether]

Originally Posted by Al Skierkiewicz

The main breaker sheet is on CD already. You just have to search to find it. The actual spec is 600% over current for a few seconds and several minutes at 200%.

The Terminal Supply P/N CB3-SM-120 that AndyMark markets as their P/N am-0282 is spec'd by the manufacturer Cooper Bussman at 440 amps nominal for 5 seconds.



[edit] I see Tristan beat me to it. Nominal 440amps, range 352..528 amps for 5 seconds.[/edit]

[kamocat]

Originally Posted by Ether

The Terminal Supply P/N CB3-SM-120 that AndyMark markets as their P/N am-0282 is spec'd by the manufacturer Cooper Bussman at 440 amps nominal for 5 seconds.



[edit] I see Tristan beat me to it. Nominal 440amps, range 352..528 amps for 5 seconds.[/edit]

Does this alarm anyone?

We're using this thing as a switch, not a breaker.

[AlexH]

Originally Posted by kamocat

Does this alarm anyone?

We're using this thing as a switch, not a breaker.

Yep, that explains why our "off switch" has a red reset button. I guess it's just another safety feature built into the system.

[theprgramerdude]

Originally Posted by kamocat

Does this alarm anyone?

We're using this thing as a switch, not a breaker.

It is a breaker - a short circuit breaker. The other breakers down line from the main one are the real ones that do all of the work to prevent component damage. Ever wonder why we end up having like a pound worth for the whole system?

[Daniel_LaFleur]

Originally Posted by kamocat

Does this alarm anyone?

We're using this thing as a switch, not a breaker.

Not really.

The snap action breakers are the real protection circuits while the 120 amp breaker acts as a single point emergency switch for anyone who needs it and as a catastrophic short protection.

In the 9 years I've been in FIRST, I've never seen one trip, not have I seen a need for it to trip (except this years 1519 minibot ... which has no breaker )

[caffel]

Its required by the rules.

What I would like to say here is that in my 11 years with FIRST I have seen three of these fail.

Only one was a complete open and you could feel that it was broken beacuse the lever was floppy.

The other two would fail to 'snap' on, although they looked to be on,
about 2 out of 5 times, which created havoc until we figured it out and replaced it.



Onboard diagnostics ? Voltmeters ? Operators watching the displayed voltage ?

[Al Skierkiewicz]

Guys,
The breaker is rated for switch use, so in our application it is fine. Please remember where it is in the circuit. If there would be a short on the PD, or any wiring feeding it, the main breaker is intended to trip to prevent fire. While I have a had few reports of teams tripping this breaker, I have not personally witnessed any that tripped on the field. I have seen several over the years that were damaged in manufacture and needed replacement.

[Tristan Lall]

Originally Posted by Ether

If you have a link to the spec for that could you post it please.

The main circuit breaker is Terminal Supply's CB3-SM-120, which is actually a Cooper Bussmann 18X series breaker (probably a 185120F). Their characteristics are here (from the manufacturer, see page 32 printed/34 PDF), or here (directly) or here (for an older spec sheet from FIRST).

According to that diagram, some breakers may last for up to 3 seconds before tripping at 720 A.