Re: [CAD_CAM_EDM_DRO] Re: Plasma table gear reduction

As usual it is more complicated than that. The motor speed is dependent
on the supply voltage - the resistive voltage drop in the windings.

For instance say you have a motor with 1 ohm winding resistance and you
are running it at 5A with a 30V supply. The resistive voltage drop will
be 1 * 5 = 5V so the motor only 'sees' 25V.

The big problem with running servos slow is heat. For the same output
power if you halve the speed you double the torque required. Current is
proportional to torque so the current doubles. Now for the killer - the
heat squares! (heat = I^2 * R). To make matters worse the slower the
armature turns, the less effective the cooling is.

Les


Roy J. Tellason wrote:

>On Monday 20 December 2004 12:13 pm, turbulatordude wrote:
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>>As for the de-rating. As it appears to me, a 3/4hp dc motor at 90
>>volts would be something like a 1/4 hp at 30 volts ? That 3,000 rpm
>>would then be 1,000 rpm (still shakey on this after reading notes on
>>DC motors)
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>>So, the motor range would be from zero to 1,000 RPM. and 0-30 volts.
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>I'm wondering if this stuff would really be as linear as all that...
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