[archiver]

Posted by Joe Johnson at 1/20/2001 3:33 PM EST


Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.


In Reply to: Re: How do people get hot motors?
Posted by Patrick Dingle on 1/7/2001 9:57 AM EST:



Mechanical Power OUT maximizes at 1/2 the stall torque
with the motor running at 1/2 the free speed.

The Electrical Power IN, peaks at the stall torque.

The amount of heat generated is

Mechanical Power Out - Electical Power In

It is this term that makes the motors hot.

In general, the Efficiency Curve :

(Mechanical Power Out) / Electical Power In

Looks like this:


S.....**..................
P....*...*................
E...*......*..............
E...*.........*...........
E..*.............*........
D..*................*.....
...*...................*..
/..T...O...R...Q...U...E..

The important thing to know is it peaks over on the far
LEFT side of the Torque curve.

THE BOTTOM LINE IS THIS:
If you have a certain amount of mechanical work you
want to do in a certain amount of time, you a have
established how much mechanical power you need (e.g.
get a robot and 2 goals up an incline in 6 seconds).

In order to heat your motors up the least while doing
this work is to design a geartrain that loads the
motors in the 1/5 - 1/3 of stall torque range.

Good luck and low motor temps to us all in 2001!

Joe J.