Circuit Breakers

[Teammax]

I have helped wire the robot most years and I am pretty sure I know which ckt bkrs are for what motors. The problem is that I cannot find the actual requirements in the rule book. I did find rule (R45) which states what wire size is needed for components powered by various ckt bkrs. But which rule lists the motors and their appropriate corresponding breaker?

The 2009 Power Distribution Diagram does not list motors by name either.

I am sure it is in the rules somehwere but I am not finding it

Thanks in advance

[Trent B]

In the past im pretty sure it is that CIMs need 40AMP and the others are fine with 30AMP, then for the rest of the electronics 20AMP.

[RyanN]

Look through R38 to R45.
http://usfirst.org/uploadedFiles/8%2...%20Rev%20G.pdf

Doesn't say for the motors, but it gives the wire size. Generally, the CIMs are put on a 40A. FP motors can be put at any amperage, but I like 20A as they are less likely to burn out. Go by wire size and not motor though.

[Teammax]

I follow what you are both saying and I agree that the CIMs are 40amps. But is there a clear cut rule written down that matches motors to the appropriate ckt bkr? Is every team just going by past experience?

How would you go by wire size? Do we know what size wire is required for each motor?

[Tristan Lall]

Originally Posted by Teammax

I follow what you are both saying and I agree that the CIMs are 40amps. But is there a clear cut rule written down that matches motors to the appropriate ckt bkr? Is every team just going by past experience?

How would you go by wire size? Do we know what size wire is required for each motor?

Years ago, the rules required certain breakers for different motors. Nowadays, FIRST considers the function of the circuit breaker to be protection of the wiring. Teams supply excessive current to the motors at their own risk. Therefore, for general robot wiring, circuit breakers correspond to wire gauges only.

To protect the motor, which is optional, you've got to figure out how much current the motor can draw, and for how long, before failure. The motor's specification sheet is a good starting point for this, because it will tell you what the maximum (stall) current of a motor is. The actual time to failure is not specified—so make an educated guess. Then, you consult the circuit breaker's specification sheet, and determine if it will trip before the motor fails.

[Teammax]

If this is the official stand then it makes sense. We are planning on using a 20amp breaker with 18gauge wire for the RS545 motor but I did not want to fail inspection because of this. I do think both are adequate.

Thanks for your help