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Old 11-16-2008, 10:34 PM   #1
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Computing amperage


The manual for my ceiling fan says that on medium it uses 32 watts and .51 amps. But this does not make sense to me because 32watts/110 Volts = .29 amps or 32watts/120 volts = .27 amps. Am I missing something?

It does have a light kit which uses two 60 watt bulbs which should be drawing 1.09 amps whenever the light is on, but I don't think that has to do with the computation for the fan itself.

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Old 11-16-2008, 10:47 PM   #2
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Computing amperage


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Originally Posted by farmerde View Post
The manual for my ceiling fan says that on medium it uses 32 watts and .51 amps. But this does not make sense to me because 32watts/110 Volts = .29 amps or 32watts/120 volts = .27 amps. Am I missing something?

It does have a light kit which uses two 60 watt bulbs which should be drawing 1.09 amps whenever the light is on, but I don't think that has to do with the computation for the fan itself.
This could be explained by the power factor of the motor not being exactly balanced. The motor is inductive.

http://en.wikipedia.org/wiki/Power_factor

The light is not counted in that nameplate rating on the motor.

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Old 11-16-2008, 10:55 PM   #3
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Computing amperage


Your math would be correct if the fan was a purely resistive device. However, it is inductive so you would have to include the cosine of the angle between the voltage and the current.
By the numbers posted, it appears the cosine would have to be about .51 or roughly 60 degrees (which might be about right in a fan with little load on it).
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