sim motor wires?

[Dragon Princess]

we noticed that our Sim motors have size 14 wires, but r47 a and b say that you can't have a wire above 12 gauge,the 40 amp fuse requires 12 gauge wire but since the Sim motors have 14 gauge so the Sim motors have been unqualified for it, and so the robots should have been disqualified for the past 4 years.

Can anyone help with this problem?
I"m really confused.
thanks!

[EricH]

The rule applies to PDB branch circuits. I'm not sure that a motor-Jag/Victor connection is counted as part of PDB branch circuit. I do remember somebody asking about it in the past; it wouldn't hurt to ask Q&A this year and get the official response again. (And, a note to any GDC member reading this--it probably wouldn't hurt to include a specific explanation about this in the rules next year.)

[Al Skierkiewicz]

The wire size minimums were written with the short length of CIM motor wires taken into account. The wire used in the CIM motor has a higher temperature insulation that wire generally available.

However, Gold Star for having been the first to notice this discrepancy in quite a while.

[Bigcheese]

I think most of the teams noticed it, but we just ignore it as it's been that way for the past few years. Anyway, no one that showed up would be able to play if they didn't allow it . As fixing the leads requires disassembling and modifying the CIM, which is against the rules also.

[Bill_B]

Originally Posted by Al Skierkiewicz

The wire size minimums were written with the short length of CIM motor wires taken into account. The wire used in the CIM motor has a higher temperature insulation that wire generally available.

However, Gold Star for having been the first to notice this discrepancy in quite a while.

I noticed the "problem" when the team was trying to put the wrong size connectors onto the motor leads. If you use 12 wire from the controller, you need to use a yellow connector, with the blue connector for #14 wire from the motor. The alternative is a terminal board and spade connectors of the correct wire size. I do not think the thermal characteristics of the insulation is (or should be) a factor in determining the size of the circuit protector.

[Joe Ross]

Originally Posted by Bill_B

I do not think the thermal characteristics of the insulation is (or should be) a factor in determining the size of the circuit protector.

The circuit breaker is sized to protect the wiring. If the wiring can has a higher ampacity, a larger circuit breaker may be used. Ampacity is calculated based on the temperature rise of the wire among other things. If a higher quality insulation is used which has a higher temperature rating, the wire can handle higher current. Therefore, a larger circuit breaker may be used.

FIRST must be conservative when choosing wire sizes that teams must use, but that's why a smaller wire could be used based on the insulation.

[Al Skierkiewicz]

There is a little fudge factor in there as well. The temperature rise and voltage drop are used to generate wire tables. As the voltage drop for a few inches of the CIM motor wire is small and temperature of the wire in air is different (lower) than the wire in conduit, there can be a little derating when comparing to standard wire tables. Add to that the series resistance of the speed controller and the final current will be lower at the motor wiring.