Catastrophic motor failure - smells like it killed my new controller as well

[JohnnieB]

Originally Posted by 720Deere

What do you guys think.......7,000+ rpm?

Check with your motor manufacturer for the max RPM.

With 23" tires, you probably won't see 7k, except WOT downhill or on jackstands.

[TerryH]

Agree with Johnny and the others. Just a very momentary blip of the throttle on the drag cart sends the motor to 7k rpm. Not a good idea to run any cart on jack stands for anything other than to verify movement and direction.

Originally Posted by TerryH

Just a very momentary blip of the throttle on the drag cart sends the motor to 7k rpm....

yea ? whats your motor rated at 12,000 rpm ?

[TerryH]

Originally Posted by crash test dummy

yea ? whats your motor rated at 12,000 rpm ?

Yes, but I'm guessing the OP's was not. I honestly never realized that those little blips were pushing the motor that high until I got one with a tach drive. I'm much more careful now. Motors under no load will go into orbit.

[DaveTM]

Just a question out of curiosity.....but my hunting cart alltrax controller is set for max torque and not so much for speed. (48-volt) My top speed on a flat surface is about 7-mph. I've had my cart on jackstands to verify direction and to make sure "stuff" was working properly, but I never did a full out max it, even with the low speed setting of the controller.

Just wondering if, with the speed setting at low, this would still cause such a motor burn? Or perhaps I should say "much less of a chance of a motor burn."

OTOH, I'm glad I read this. I will never give it a full throttle when it's up on stands.

Dave

[sportcoupe]

The motor didn't burn up, it self destructed from exceeding it's rpm limit.

[Volt_Ampere]

It's impossible to protect a solid state motor controller with a fuse. It will protect against slow overloads but not the instant short that is caused when the motor lets go. Even an open circuit when current is flowing can kill the output devices in a motor controller. The inductance causes a huge voltage spike that will rise until something shorts out.

[JohnnieB]

Originally Posted by DaveTM

Just a question out of curiosity.....but my hunting cart alltrax controller is set for max torque and not so much for speed. (48-volt) My top speed on a flat surface is about 7-mph. I've had my cart on jackstands to verify direction and to make sure "stuff" was working properly, but I never did a full out max it, even with the low speed setting of the controller.

Just wondering if, with the speed setting at low, this would still cause such a motor burn? Or perhaps I should say "much less of a chance of a motor burn."

OTOH, I'm glad I read this. I will never give it a full throttle when it's up on stands.

Dave

I take it that you have the Max Output Current slider set to 100% and the Top Speed slider set to 50%.

I'm not quite sure how Alltrtax manages to limit high end torque (top speed) without limiting low end torque, but they would have to use current flow vs voltage as one of the factors and when the expected mechanical load on the motor is removed, that calculation goes out the window, so having the Top Speed slider at minimum may not prevent your motor from over-revving.

[kb1sxv]

Originally Posted by shaferz

yep - i know that now. Hah! Not sure how many rpm's it was actually turning, but i'd imagine if we were on road - wot - i may have been close to this many rpm's? Like i said - glad it happened in the garage and not on the road with wife and kids aboard. Could have gotten ugly real quick.

For anyone interested in more carnage pictures - below are some more shots. Motor was already gone, so i snipped the f1/f2 leads so i could push the armature/endplate out of the back end of the case.









epic carnage.

Mods feel free to sticky this is a maintenance section - never ever ever ever ever go wide open throttle on jack stands. Destruction is imminent.

holy crap! Sorry man :(