Interesting question. I'm not an expert on this, but I knew just
enough to type out an answer. I was on the right track ( %-)),
but someone explained it better at the link below (so I deleted
what I wrote)! HTH!
Resistance to startup- i.e., overcoming inertia- is the issue.
High in an AC compressor (needs a boost from a capacitor) but low in a
ceiling fan (no capacitor necessary).
Think of it like a morning coffee-jolt...
The fastest way to stop a bad guy with a gun is a good guy with a gun.
We finally get to say "split phase" and be correct. The capacitor
actually does "split" the single phase in conjunction with the start
winding in the motor and it creates a temporary "2 phase" system for a
second until the motor gets out of locked rotor.
Smaller motors may be "shaded pole" that create a magnetic shift in
the motor windings themselves without a capacitor. Usually, if you
look you will see a much larger gauge winding there, maybe only one or
2 turns. That creates the shaded pole.
They are not particularly efficient and they have very low starting
torque but if it is a $12 fan from Walmart, what do you expect?
The other place you see shaded pole motors is in small gear head
motors like you might see on a refrigerator defrost timer. Since the
gear reduction is so great and the load so low, they don't need much
On Thu, 26 Jul 2018 17:15:06 -0700 (PDT), trader_4
A ceiling fan is usually a split phase motor with a start capacitor
but it is not a very big capacitor since they don't need a lot of
torque. The cheapest ones might even have a shaded pole motor and a
top of the line model may have a brushless DC motor.
email@example.com posted for all of us...
I never knew they had capacitors in them. Of course I didn't do a through
exam of any on a ladder or destruction. I always assumed they were shaded
Leads to the next question: How do they perform different speeds?
On Fri, 27 Jul 2018 16:12:17 -0700 (PDT), trader_4
I suppose some do but they also have dimmer style controls that just
vary the voltage.
The little plastic desk and pedestal fans do have multiple windings as
far as I know.
Larger fans like air handler blowers do use multiple windings.
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