Quote:
Originally posted by jaydee116
I spent several months messing with pots and any fan rated over the pot makes the pot fry when the pot is turned down. The more you turn the pot down the hotter it gets. I fried several 3watt pots on 5watt fans when turning them down. I I run the pot wide open then the pot works fine at ever tripple the rated the fan. The pot is doing all the work not the fan.
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Yes, I wrote too simplistically. What resistance pot were you using?
Pots/rheostats should be sold with a current rating as well as a wattage rating. (Quality vendors do give both these specs as well as an end to end voltage spec.)
You are right, it is possible to burn up a pot while dissipating less than the pot's rated power. When the total resistance of the pot is higher than necessary for the job, you can get too much power dissipation in a small portion of the pot's resistance.
Ideally the resistance of the pot should be chosen so that when it is at maximum resistance, the voltage across it is 6V. (With the fan in series.) This will prevent the problem of excessive power dissipation in a small portion of the total resistance.