New Speed Control

[BrianG]

Let's not forget these motors are essentially AC motors. The heat produced is the result of the resistive properties of the coils. There is also the AC inductive part of the current, which does not cause the heat per se. That 108 amps is the combination of the DC resistance and the AC inductive reactance of the motor. All motors will pull the most amount of current at startup since there is no motion and therefore no back EMF so only the motor's DC coil resistance will limit the current. Once the motor gets going, the back EMF from the changing magnetic field creates back EMF which reduces the current. If a motor pulled 108 amps constantly at say, 14 volts, that would be over 1500 watts. It would take a lot more surface area than the motor can to shed that kind of heat!! Take the lightbulb example; ever feel how hot a 75 watt lightbulb gets? And that has about the same surface area as an XL motor, give or take.

[Tom F]

Ahha, another physics person i see ;)

We were doing about that a few weeks ago lol

[BrianG]

:dft001:

Not physics, electronics, but they do overlap. I just saw some posts that seemed to be leading in the wrong direction and thought I'd throw in my $0.02.