View Full Version : 40A Breakers popping when using CIMs

02-11-2003, 03:30 PM
Hello everyone :)

We're having a small problem with our CIM motors.

When we're spinning 360 or moving slowly, our one side cuts out. You hear a clicking noise when it comes back on. Our victor on that motor powers down completely, fan and all, and then comes back on. I'm ASSUMING that means it's the 40A breaker popping.

What could be the cause of this problem? What could we do to fix it?

Sorry, I'm not familiar with the electrical portion of it, and we're wired according to specs, so I'm not sure what type of malfunction we could be having. I've switched the breakers around, but to no avail. Switching one breaker over another does increase the time that we can turn/move, but it still does cut out.

WE're using the default code as far as the power to the motors go. Is that our problem?

Any help appreciated.

02-11-2003, 04:01 PM
If it's only tripping when you are turning, then you have too much traction. When you turn, your wheels have to slide accross the carpet. You might want to either:

1) Lower the amount of traction your bot has. This can be as simple as flipping the robot over, and going over the wheels with a file.

2) Incorporate some type of caster that you can lower to the ground for the purpose of turning. We did this last year with pneumatics.

If it's tripping when you're moving forward/backward, then you don't have enough torque. Either use smaller diameter wheels or re-gear the robot (gear it down some more). Often times wheel size isn't taken into account when calculating drive train ratios. Your wheels are just like a large lever, the larger they are, the easier it is to push against you (forces are amplified).

02-11-2003, 04:42 PM
We had the same problem - for about two days - and then here is what we found -

The CIM is designed to run at higher RPM - to stay below a 40 amp continous draw you must keep the motor at 3500 RPM or higher - under that (3500 RPM), and/or under high stress conditions (where the motor is slowed down due to the either weight of the bot or pushing against something), you will be running the risk of blowing the fuses. You can go from a standing start to running because of the time delay that the fuses have built into them - and depending on the "low gear" RPM - will not blow once you are up to speed (has to be above 3500 RPM to not be drawing over 40amps).

The comments made about torgue are right - and in discussion with the folks that make the CIM's - you have to be geared upwards of 25-35 to 1 at a minimum to keep the CIM at a speed that will not blow fuses and keep the speed under 10fps - we started with a 16:1 and will move tomorrow to a 32:1 to stop any problem we have with the popping at lower bot speeds (<10 fps at max speed).

Hope this helped

02-11-2003, 08:51 PM
Is it safe to assume that you guys are using treads? If so, then here's a suggestion that might help. Lower your center bogie roller a slight amount. It helps with turning by keeping your entire track from digging into the carpet.

If you guys aren't using treads than my advice wouldn't be very useful. We robodawgs are tread people.

02-11-2003, 10:14 PM
Thanks for the advice, but we're using wheels, not treads.

And we're at 36:1 in sprockets alone (not taking wheel size into consideration).

But we're big pneumatic wheels. I'm sure that's the main source of our problems.

My biggest concern is that we're only popping on one side. I tried replacing breakers, but that didn't seem to fix it (although, IIRC, it MAY have changed the side of popping).

I'm not sure -- we still have 6 days to figure it out :p

02-12-2003, 07:30 AM

FYI - we had the same problem - popping one side and not the other - and we swapped out the popping breaker for a new one and the problem "went away" - so just maybe?

Good Luck

Al Skierkiewicz
02-12-2003, 07:31 AM
If both sides are identical and you are only tripping the breakers on one side, suspect binding of the mechanicals on that side. If that turns out to be OK, take a look at the wiring to the two motors. Even big wire has some resistance so if you have a lot of wire in the side that doesn't trip then the wire is limiting the current to that motor. It doesn't mean it's correct just that the resistance is keeping the current below trip. If you are using large diameter wheels, you may have to further reduce the speed to get the motor back into a lower current range. The clicking is definitely the circuit breaker. Remember these devices are temperature controlled and a hot breaker will trip at lower current than a cool one.

02-12-2003, 08:34 AM
We just had a similar problem in our robot. We found that the 40amp breaker had blown. When we replaced it with a replacement then the operation went back to normal. Has anyone had any problems of the 40amp breakers blowing out completely?

02-13-2003, 08:06 AM
Hey guys, thanks for all the tips

We're going to emergency ship some more breakers, and we ordered a couple more CIMs -- JUST IN CASE it had something to do with those. We are having it pop on one side, and there is a loose chain there, so we're going to tighten that up today and see what we can come up with.

I did see that when I switched the breaker out, the one side worked better, but it seems that the other ones didn't seem to fix the problem we had. This means either 3 "bad" breakers, or something else we haven't found yet.

Thanks for helping out us rookies :D

Al Skierkiewicz
02-13-2003, 09:30 AM
"Three strikes, you're out!" Look for something else. Loose chain does have a tendency (nasty one too!) to throw up a link and stall the drive intermittantly.