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Re: Re: Re: low mod 12v conversion
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Posted by Bob M on February 25, 2004 at 08:23:57 from (165.170.128.66):
In Reply to: Re: Re: low mod 12v conversion posted by buickanddeere on February 25, 2004 at 06:07:20:
Hey B&D - I gotta disagree with your analysis! It is correct ONLY when resistance a circuit is increased by the same percentage as the voltage. However in this situation the field winding resistance remains unchanged. By Ohm's law E = I*R (rearranged I = E/R), when voltage is doubled and resistance stays constant, current is doubled. Therefore since heating is given by W = I^2*R, when you double the current you QUADRUPLE the heating. Or calculate it another way: Heating is also given by W = I * E. By feeding the fields 12 volts you have doubled BOTH voltage and current. Consequently you have quadrupled the heating. Real world experience: A couple years ago a buddy did a quick 12 volt conversion on an old Minne Mo by simply mounting a 12 volt regulator and changing the battery. It worked, but he observed the generator case became unusually hot after running a while. The system worked for several months, then the generator just quit. When we opened it up afterward we found the field windings' insulation (lacquer and tape) charred and burned - obviously from prolonged overheating.
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