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Unread 06-01-2006, 12:30
Andy A. Andy A. is offline
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Re: capacitors in parallel with motors

A capacitor would only cause a sluggish response if it were in series with the motor. In that case, the motor would at times see a reduced voltage as the capacitor charges, and at other times see a higher voltage then the victor is outputting as the capacitor discharges. It would have to be a very large capacitor to be noticible, which means that it would probably be of the electrolytic kind. And we all know how much they like reverse current when you try to drive backward! They are used on large motors, such as in Electric cars. Because the starting current on a large motor is so high, it can draw the supply voltage very low and give poor performance. A large capacitor (or several smaller ones) can be used in series with the motor to keep the voltage from dropping to severely under acceleration.

If the capacitor were in parallel, bridging the positive and negative terminal, the function would be to filter out all the noise that a motor produces. They are common on DC motors. Typically, they are very small, on the order of 1uf or smaller, and of a type that isn't harmed by reverse current. My guess is that most of the motors we use already have filters installed in side of the motor can. In any case, it doesn't matter because the Victors are not going to mind either way.

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Unread 06-01-2006, 13:57
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Re: capacitors in parallel with motors

I do not think that there are any motors that have a cap already built in, but i could always be wrong, and the VICTOR is a motor controller designed specifically to deal with providing power to a motor almost completely isolated from the rest of the cicuitry, that said i'm pretty sure that whatever company manufactures them has engineers who have thought of the ways that they could best reduce electrical noise caused problems when the VICTOR is used correctly
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Unread 06-01-2006, 14:50
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Re: capacitors in parallel with motors

Capacitors are not only not needed but also illegal. The Speed controllers have built in noise suprression to prevent any nasties from ending up back at the RC.
The effect of haniing a big cap across the motor just compounds the start current and run responses. Don't forget that a capacitor looks like a dead short when discharged. When a capacitor is charged to some voltage and the supply voltage is reversed, the charge must be removed before the new voltage will charge the cap. This precludes using electrolytic capacitors which can't have a polarty reversal without spectacular self destruction. Some motors (in the far distant past) have had small caps installed, internally, across the brush assembly to try and quench brush noise. Currently supplied motors do not have any of these internal components to my knowledge.
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