alt.energy.homepower

-> > Generally, it's better not to short-circuit the motor, but to connect a
-> > resistor across its terminals that has a much higher resistance than
-> > the motor windings, and that is mounted on a heat-sink, or whatever, so
-> > it can dissipate as much heat as is needed. That way, the worst that
-> > can happen is that you burn out the resistor, which would be a lot
-> > cheaper than destroying a motor,
-> >

-> True. But remember that "...a resistor...that has a much higher resistance
-> than the motor windings" is still a pretty low resistance value. Hooking a
-> 1kOhm resistor would be useless. Many DC motor starting resistors are in
-> the range of to ohms. Something like that would work well and they
-> have the power rating needed.

-> daestrom

When it's still turning close to full speed, the motor will act as a
generator producing the same voltage as was being supplied to keep it
running. The maximum current rating of the windings can be estimated
from the motor's power and voltage ratings. So it's easy to calculate a
value for the resistor that will pass the maximum acceptable current
when the motor is acting as a brake. Figuring out its required power
rating is equally simple.

dow