The difference in speeds of various fan types

zaveri
Member • Aug 1, 2013

The difference in speeds of various fan types

I was just browsing through some catalogs of fans yesterday, and i discovered one thing: while table fans and pedestal fans have their speed in the range of 1000-2000 RPM, ceiling fans have it only in the range of 360-450 RPM.

Does anyone here knows why this difference exists. ?

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Jeffrey Arulraj

Member • Aug 1, 2013

I can imagine one thing the role played by the fans are different

Ceiling fan just circulates the air by pushing air from the top to the bottom and like wise

whereas the table fans and pedestal fans have no reference plane behind them and so the work they do is higher than that of Ceiling fan

Higher work Higher speed

Ceiling fans the upper portion is just a chunk of air ready to be circulated so easier and lesser speed

Pedestal fans voidance area behind Higher speed Higher amount of air gushed towards the human who is enjoying the gentle breeze

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zaveri

Member • Aug 2, 2013

Is there any other reason for it ?

has the unique construction of the ceiling fan motor also got something to do with it ?

now what would happen if a ceiling fan was designed to run at a speed of 1000 rpm and above

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Jeffrey Arulraj

Member • Aug 2, 2013

If rpm of ceiling fan is increased the rate of air circulation will be really high that can make us feel really uncomfortable to us

That is why we have lesser speed in ceiling fans

About the new designs I am not aware of it can you pls share it with us here in CE

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lal

Member • Aug 2, 2013

I believe it is because of the size of fins. Ceiling fans usually have large fins where as the pedestal fans have smaller fins. For the same effect, due to large fins, ceiling fans need lesser revolutions per minute when compared to the smaller fins of pedastal fans.

Not exactly sure. Will have to do a search.

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zaveri

Member • Aug 2, 2013

#-Link-Snipped-#

you are right.

only thing is those components are not called "fins", but they are called "blades" technically.

#-Link-Snipped-#

i did not mean any new designs.

what i meant to point at was that the ceiling fan motor has a different type of construction altogether. the armature is the stator, while the field electromagnet is the rotor, which is quite unlike in any other motor.

i wonder if this type of construction is limiting the rpm. maybe the electrical guys may know better.

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zaveri

Member • Aug 3, 2013

Conqueror
About the new designs I am not aware of it can you pls share it with us here in CE

As for new designs there are many.

one which i will mention right now is the Havells Opus , the fan cum chandelier.

Check it out here :

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zaveri

Member • Aug 3, 2013

And here is a giant with 21 speeds !

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CE Designer

Member • Aug 5, 2013

To add to this, large blades can cause noise at high speeds due to the vortex that form at the tips of each blade.
Pedestal fan blades are secure with a nut and are surrounded by guards which makes them safer at high speeds. Ceilings fans just hang off the ceiling by a rod. They are not really fixed axially on both planes. At high speeds higher than what they are designed for they can become unstable due to the dynamic forces acting on them. This can cause noise, wobble and the blades can tear/break.

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Ramani Aswath

Member • Aug 5, 2013

There is a quantity called swept volume for fans. It refers to the amount of air displaced per revolution. With its large sweep diameter a ceiling fan cam move a large volume of air at a lower speed. Being smaller in diameter a table fan has to move at a higher RPM for the same air displacement. The higher velocity of air from a table fan is not too disturbing because of the oscillation, which is absent in ceiling fans.

There are other considerations like uniform large volume air movement and such which also modify ceiling fan design.

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zaveri

Member • Aug 5, 2013

CE Designer
To add to this, large blades can cause noise at high speeds due to the vortex that for at the tips of each blade.
Pedestal fan blades are secure with a nut and are surrounded by guards which makes them safer at high speeds. Ceilings fans just hang off the ceiling by a rod. They are not really fixed axially on both planes. At high speeds higher than what they are designed for they can become unstable due to the dynamic forces acting on them. This can cause noise, wobble and the blades can tear/break.

check out the video of the "big ass fans" which i have posted here.

then by the explanation which you have given, doesn't that fan become unsafe as well ?

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Sarathkumar Chandrasekaran

Member • Aug 5, 2013

The main criteria is that of its own weight ,size of blades and motor used.Consider table fan-it has an powerful motor and an output shaft which holds the blades.These blades are small and less weight so that they spin at high rpm.
On the other hand ceiling fans has different construction-It dont have a separate motor(motor itself spins) and due to more weight and gravity it spins slowly.

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