What is the difference between A/C (air conditioning) fan motors that use a start capacitor and say a ceiling fan that doesn't. Type slow because I'm not too bright and getting worse...
- posted
5 years ago
Fan motor capactitor use.
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- posted
5 years ago
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!
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Bill
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- posted
5 years ago
What makes you sure that it doesn't? Just because it's not separate and visible, doesn't mean there isn't one inside.
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- posted
5 years ago
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...
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- posted
5 years ago
AFAIK, they are both AC induction motors and you need a phase shift, generated somehow, to get them moving.
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- posted
5 years ago
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 torque.- Vote on answer
- posted
5 years ago
The question remains which of those is in most ceiling fans and does it use a cap? Looks to me like most are split-phase, in which case they use a cap and are in the same category as the AC motor.
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- posted
5 years ago
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.
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- posted
5 years ago
snipped-for-privacy@aol.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 pole motors.
Leads to the next question: How do they perform different speeds?
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- posted
5 years ago
They just drop the field voltage and allow the rotor to slip. That is why some of them "moan". As I said some high end fans now use brush less DC motors and pulse width controllers.
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- posted
5 years ago
:
I thought they had different windings with different numbers of poles in there, using different number of poles to get a 3 speeds.
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- posted
5 years ago
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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- posted
5 years ago
[snip]
Varying the voltage is possible, but would be very wasteful. Dimmer controls vary duty cycle.
I know about a the 3-speed (inside fan) motor in the A/C where I used to live. It has 4 wires, common and one for each speed.
Here, I have a 3-speed ceiling fan control that has only 2 wires.