Posted by John T on January 12, 2012 at 11:12:03 from (66.87.2.100):
In Reply to: follow up posted by teddy52food on January 12, 2012 at 09:19:37:
Hang in there Teddy, you got it basically right, I wasnt aware of the previoius discussion you mentioned. In a world of perfect zero resistance and perfect magnetic property conductors (doesnt exist) wattage would remain the same and as voltage increases current therefore decreases YET VOLTS X AMPS (Watts) is the same (or very close subject to heat and magnetic losses etc).
HOWEVER energy isnt created or destroyed ITS ONLY CHANGED IN FORM when you change electrical energy into rotational mechanical motor energy (its HP is a function of Torque x RPM) and anytime you pass current through a non zero resistance conductor some of the energy gets dissipated in the form of heat THAT DOESNT GO INTO CREATING MOTOR HP. That being said, if youre passing less current there less I Squared R wasted heat energy so the whole conversion/operation (electrical energy into mechaical) can be a bit more efficient at higher voltages.
NOTE HOWEVER its not quite that simple since in many AC motors the run windings are simply wired in series for 240 volt operation but paralell for 120 so theres still some current through all that wire.
ALSO as my friend Jim notes eddy currents use up some energy and waste it as heat and thats another factor in this discussion. Thats why magnetic cores in coils etc are laminated which reduces that problem to some extent.
ALSO a motor is mostly an inductive load with a lousy power factor which corrective counterbalancing capacitance can inprove and that also plays a part in this discussion
Sooooooooo some things may not be quite as simple as they first appear to a person unfamilar with all this electrical stuff AND IM LONG RETIRED AND RUSTY ON ALL THIS MYSELF so no warranty lol
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