Using CIMs at 30 amps?
 

Hello,
In our team's current design we plan on using 6 CIMs in our shooting mechanism and 4 mini-CIMs for mechanum drive, but we only have slots for 8 40A breakers. We need to use four of the breakers for our mini-CIM drive motors and that only lets us use the remaining 40A breakers for 4 of our 6 CIMs. We figured that we could use 30 amps on 2 of our CIMs but the rules are iffy on this. It says that we need a circuit breaker value of "up to 40A" for the motor controllers (in the Branch circuit protection table 4-2). Does this mean we can legally use 30A for 2 of our motor controllers? Also, if CIMs don't run well off of 30 amps, could the mini-CIMs run fine on only 30A?

Re: Using CIMs at 30 amps?
 

What part of "up to" precludes the use of 30A breakers?


The other question you should be asking is, why not use the 4 mini-CIMs on the shooter and 4 CIMs in the drivetrain, with 2 CIMs working with the mini-CIMs in the shooter?

Re: Using CIMs at 30 amps?
 

I would suggest rethinking the type and number of motors that you need for each application.

Now, to answer your specific question:
You can put any of those motors on a breaker up to 40 amps. Anything lower than that is acceptable. This means you can put a 30 amp breaker on a CIM motor. You may have a problem with tripping the breaker though.

Based on R46 in the manual.

Re: Using CIMs at 30 amps?
 

Ok, thank you for the advice

Re: Using CIMs at 30 amps?
 

Could you please explain the process your team followed that lead to the decision to use 6 CIMs in your shooting mechanism?

Re: Using CIMs at 30 amps?
 

You can run over the circuit breaker amperage for small periods of time, the circuit breakers are thermally controled:

http://team358.org/files/electrical/snap-action_vb3.pdf
http://team358.org/files/electrical/...ec%20Sheet.pdf

Also I wouldn't recommend running mini cims on the drivetrain unless you are geared very slow, around 5-7 feet per second. That would basically max out those motors potential with ~150 pound robot.

Here's a suggestion, what about using Banebot motors and/or Andymark motors for the shooter, and cims on the drivetrain? You may be surprised with the power you can get out of Banebots and Andymark motors, and the torque when they are geared properly. There is also a weight savings going in that direction. 6 shoot cims seems over powered for a 3 pound ball, I don't think they would break a sweat, but I don't know what your setup is either.

Re: Using CIMs at 30 amps?
 

I would rethink using 6 CIM motors on your shooter. You don't need 2000 watts to shoot a 3 pound ball.

A BaneBots CIM-U-LATOR, VexPro CIM-Ile or AndyMark CIM-Sim will allow a BaneBots 550 and/or 775 motor (you're allowed 4 total) or an AndyMark 9015 motor (you're also allowed 4) to mirror a CIM with the exact same mount pattern and the *same* rotation speed as a CIM. All of those motors can be put in 30A slots if you're out of 40A slots.

Re: Using CIMs at 30 amps?
 

A mini-cim has about 70% of the power of a CIM. Do you recommend that robots with CIMs limit themselves to 7-10 feet per second?

Re: Using CIMs at 30 amps?
 

I guess I was unfair with the assumptions I made. I also put loaded speed not free speed which I should have clarified. Assuming single speed 4 cim 7-10 fps would be my recommendation, so thats around 9.5 fps -13.5 fps free speed. Can the motors be pushed faster than that? Yes, but I wouldn't recommend it. Potential turning and acceleration issues depending on the drive train, but every application is different so it's not a be all end all recommendation.

I would be concerned with the decrease in stall torque with the mini cims more than the power loss.

Re: Using CIMs at 30 amps?
 

The breaker rules are written to protect wire and nothing else. Should a branch circuit using #12 wire (or larger) short for any reason, the wire feeding the branch will not melt or catch on fire with a 40 amp (or smaller) breaker. Circuit breakers do not limit the current flow they simply open when the specified trip current is exceeded. However, a six CIM shooter sounds like something I would like to see work. It scares me but I still would like to see it.