Drill motor Demagnetization and lowered-torque woes

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Posted by Joe Balint at 04/25/2001 1:03 AM EST


Engineer on team #537, Domo ARIGATO, from Sussex Hamilton HS and GE Medical Systems.


In Reply to: a couple things
Posted by Ken Patton on 04/23/2001 12:22 AM EST:



: You should rule out the 30A circuit breakers as a source of the problem. Check to see if they are getting hot (a sign that they might be tripping), or even replace them with fuses (just to test). If they are tripping, you will see the speed controller lose power.
: What is your gear ratio, and how bad is your drivetrain friction under load? These are primary sources of loading for the motors.

: Ken

Ken-
From what we observed the motors were not getting hot and the circuit breakers were not tripping. That's one of the things that was bugging me. If we were generating enough of a Magnetic Field to de-mag the motors, wouldn't that amount of current trip the breakers? But my educated guesstimate is that the answer lies in the fact that when we are commanding these direction changes, we are on the ramp with two goals. our gear ratio is around 22:48 (I remember ordering these sprockets, but I wasn't on Drivetrain this year so I'm not positive about this ratio), each drill motor is driving both front and rear wheel assemblies. Each assembly is actually 2 8" wheel chair wheels bolted together and grooved for traction. So this is the most I've ever loaded these drill motors (by design) and I think it is feasible that this load is too much and falls into that part of the demagnetization curve that the design notes warn about causing permanent torque loss by demagnetiztion. We'll see what we find during the analysis. -joe