Fisher Price Motor Power

[vamfun]

Originally Posted by Al Skierkiewicz

As a reminder, the FP motors have had a thermal protective device internal to the motor for the last year of two. It keeps the motor from smoking but it lets go when you need it the most if you haven't done your calculations correctly. Please be aware that covering the holes in the frame is a good way to find out how the thermal device works. It is in series with one of the brushes and you can see it using a bright light if you look.

Interesting Al... so we won't trash the motor if it overheats? That's somewhat comforting. I have been worried about stalling the front roller which is driven by a FP. We designed it to keep the friction loads under the torque limit but perhaps in some type of collision we could stall it.

Question to you and Joe J.: What continuous current do you think can we run if we are in stall without tripping the internal protective device? With cooling Joe says .35 to .4 of stall is ok so we are driving a max of .4*70*12= 336 watts.
Without the cooling how much do we have to derate the power?

We are driving it with a Victor but maybe we could switch to a JAG and use the current monitor on the CAN buss to compute the heat input to the motor with time and shut it down sensibly.