a small puzzle

Bill Martin · 2016-09-10T18:46:55+00:00

A little OT, but what the heck, there are electrons involved. Noticed some oddness re. a small ATV winch, 12VDC powered, with a PM brushed motor and an up/down reversing switch: It runs slower in the down direction than in the up direction...checked the resistance of the armature/brush dc path, same in either polarity. Checked the switch box, again, the same in both directions. What the heck! It does seem reasonable to run slower in the "unload" direction, but how is being done? Not really interested in tearing everything down to the bare bones to figure it out! One other interesting anomaly: The motor is tagged as 2.5hp, but given the approximately .5ohm armature resistance that I measure, that's about 24amps stalled rotor... 12V * 24A is 288 Watts, how in heck is that 2.5Hp? :-) Maybe those Chinese horses are really tiny? Bill

a small puzzle

Sep 10, 2016 42 Replies

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rickman 9 years ago

It was? I thought you were saying it produced lots of power but no work. The only difference between work and power is that power is a rate while work is a quantity.

Rick C

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tabbypurr 9 years ago

to be pedantic it drops, there's no 100% efficient gearing.

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Bill Martin 9 years ago

Guess I was unclear, that happens sometimes...but in general, power goes in, work comes out. For motors, at least, generators are opposite. So, to finish off this dead horse, the thing is "consuming" max power at stall & producing no work. Time to bury the poor horse, starting to stink! :-)

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