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Joined: Jul 2005
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No need to worry! Firstly, no harm will come of the difference in frequency. Being an induction motor the fan will turn slightly slower, but so what? It certainly won't be noticeable in terms of performance. The heat rise is insignificant, especially for this sort of thing. As to voltage dropping devices, the easiest way is to use a capacitor. It will need to be rated at 400VAC even though it will appear to be dropping only 120V. Because the motor is inductive the voltage across the capacitor can actually be higher than expected. A motor start capacitor is ideal. The value will have to be found by experiment; at a guess start with around 4uF and go from there keeping an eye on motor voltage.
The other voltage dropping device I like using is an incandescent light bulb. I have not tried using a fluorescent light choke but see no reason why it too could not be used provided one of suitable inductance can be found. Resistors are another option but for the value required for this is not easily obtainable and needs to be well ventilated.
A cheap stepdown transformer is the other option, particularly if there's any doubt about the insulation of the fan at 230V.
I've been running Yankee stuff like this for years with no problems at all. In fact I fitted a 115V fan in series with a 2uF 400VAC capacitor into a fan heater, as a replacement, which has been pretty much in daily use for about 15 years.

Joined: Jun 2004
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I agree with Aussie240. A capacitor or fluorescent choke in series with the fan should do the trick. The capacitor option is the best bet since this will produce less heat than the choke, is much easier to tweak to get the correct fan voltage, and is less fussy about the amount of line current it passes.
Although the fan motor will probably produce a little more heat on a 50Hz supply, since it is being well cooled by the fan airflow the net effect should not be significant.

Last edited by Paulusgnome; 07/27/07 06:06 PM.

Mark aka Paulus
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Originally Posted by Alan Belson
in fact there were / are dozens of other frequencies in use.


40Hz for one. Didn't one of our antipodean members say that was used in Western Australia at one time?

I have Garrard turntable documentation which shows motor pulleys available for 40Hz in the early/mid 1950s.

Joined: Mar 2005
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Just some thoughts.

An Induction motor's speed is strictly a function of frequency, less slip due to demand.

So a 60hz fan motor will run about 17% slower, say 83% of original design rpm, if wired to a 50 hz supply.

Power used is a function of work done and the running stable amperes in an induction motor stator are a function of demand.

Work done by fan blades is the cube of blade rpm.
So running at 83% speed, power demand is reduced to 57% of original wattage.

The 230vac voltage is 192% higher than 120vac, so amperes reduce to about 30% of the original amperes on 120v 60hz. In fact with reduced loading, the motor slip will be less.

So the speed is less, power is less, amps are less, slip is less, and probably start period to full rpm is less.

I have 3 x 4ft diameter 230vac 50hz ceiling fans in my shop. They take 34 seconds to come up to full speed, which implies the stators are wound to take a fairly high starting current over a prolonged start period.

So my question is; will this 120v 60hz unit, bought from the States, be damaged by a higher voltage but reduced hz? I assume the unit's wiring insulation can take 600v. Seems theoretically not. Cooling parameters can't be that critical.

Or am I missing something?

Alan



Wood work but can't!
Joined: May 2004
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Originally Posted by Alan Belson

Surge; Ask around in Singapore with a pic, chances are the Chinese have already copied the design for Europe and are knocking them out for $5!

$5
Are you kidding? A basic 56" (3 blades) [this manufacturer produce 35% (national) & 30%( int'l) in fan market ] costs ~$19 in China.
"You get what you paid for" fits even in China, not every Chinese product is "crap".

Joined: Mar 2005
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Whoa there son, calm down, I never said they were crap, just maybe available and at a low price.

$19!

I won't comment futher, we don't do contension.


Wood work but can't!
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Originally Posted by pauluk
Originally Posted by Alan Belson
in fact there were / are dozens of other frequencies in use.


40Hz for one. Didn't one of our antipodean members say that was used in Western Australia at one time?


Yep, 256/440V @ 40 Hz was in Western Australia for a while, replaced by 240/415V @ 50 Hz. Adelaide had 210V @ 50Hz, now 240V & some remote cattle stations were 240V & 60Hz (ex-US Gov't gensets), now 240V @ 50Hz.

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The railways in Switzerland, Germany, Austria use 15,000 Volts single phase at 16 2/3 Hz frequency.
Earlier series traction motors designed for dc could also run on ac with reduced sparking on lower frequencies.
In the USA was / is? 25 Hz in use for electric railway traction.
Lower frequencies means bigger machines.

The main reason the airforce opted for 400 Hz is to reduce the size and weight of electrical equipment.
Look at a switch mode power supply. It runs on many kHz and are very compact in relation to their power output.


The product of rotation, excitation and flux produces electricty.
Joined: Mar 2007
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I've noticed that onboard our aircraft, there are standard NEMA 5-15 outlets in the galleys, which are rated at 120V 400Hz. I wonder what would happen if some pushy first-class executive decided to plug his laptop in there? There are 12V convenience outlets at every seat (at least in first class), but I'll bet someone has tried it. I'm sure your fan would really move air around on that.

Last edited by noderaser; 08/05/07 06:11 PM.
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Originally Posted by noderaser
120V 400Hz. I wonder what would happen if some pushy first-class executive decided to plug his laptop in there?

Actually I'd expect it to work ok as the supply is fed straight into a bridge rectifier. The switchmode power supply runs off DC (AC mains RMS x 1.4142). The only limitation would be the switching speed of the diodes but that would only become significant well into the KHz region.

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