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From: whit3rd on 24 Jun 2010 13:47
On Jun 23, 10:04 pm, "Steve Sousa" <etst...(a)yahoo.com> wrote:

> I live in a 230V area but need to use a 120V fan to repair an amplifier.
> I can only get 230V fan motors here, so i was wondering if i can simply
> remove turns from a 230v shaded pole motor to make it into a 120v one?

Rewinding the mains-powered parts of a fan is a bad idea.
Better ideas: get a 120V fan motor, find an alternate power
source (there's a DC supply somewhere in the amplifier,
can it drive a DC fan?), use a small boost transformer or
autotransformer.

Quickest solution might be to use a 'standard' computer-parts
fan (takes DC power) with a 230VAC wallwart power brick.
From: Robert Macy on 24 Jun 2010 15:53
On Jun 23, 10:04 pm, "Steve Sousa" <etst...(a)yahoo.com> wrote:
> Hello:
>
> I live in a 230V area but need to use a 120V fan to repair an amplifier.
> I can only get 230V fan motors here, so i was wondering if i can simply
> remove turns from a 230v shaded pole motor to make it into a 120v one?
>
> Thank you.

do you have room for other components? use two identical fans wired in
series?
or, use a 120/120 isolation transformer with 230 across both [properly
phased] and tap off the 115 for the fan,
or, add a series inductor? some transformers are built very well and
can be abused. 120/12.6 filament transformer. place the 12.6Vac
winding in series. That will put 120+ across the secondary, but might
take it, plus the inductance is smaller looking into that winding and
you might get the right voltage drop, experimentation required.
or, use a series cap? something like 22uF to 33uF AC cap [note: AC
cap, not some electrolytic, unless rated for it, they're not made to
have this much AC current go through and electrolytic requires
nonpolar, or two back to back] - require experimentation.

or, if there is enough DC power: buy a DC fan rated for the same air
flow against head pressure and use it.

From: Phil Allison on 24 Jun 2010 20:12

"Robert Macy"
"Steve Sousa"

>
> I live in a 230V area but need to use a 120V fan to repair an amplifier.
> I can only get 230V fan motors here, so i was wondering if i can simply
> remove turns from a 230v shaded pole motor to make it into a 120v one?
>

do you have room for other components? use two identical fans wired in
series?

** Read the question - idiot.

The OP needs a 120 volt fan and has not got one.


or, use a 120/120 isolation transformer with 230 across both [properly
phased] and tap off the 115 for the fan, or, add a series inductor?

** Read the question - idiot.

The OP needs a 120 volt fan and has not got one.

Jeez wot a macaroon.


..... Phil





From: PeterD on 24 Jun 2010 20:37
On Thu, 24 Jun 2010 23:04:00 +1000, Sylvia Else
<sylvia(a)not.here.invalid> wrote:

>On 24/06/2010 9:46 PM, PeterD wrote:
>> On Thu, 24 Jun 2010 15:29:35 +1000, Sylvia Else
>> <sylvia(a)not.here.invalid> wrote:
>>
>>> On 24/06/2010 3:04 PM, Steve Sousa wrote:
>>>> Hello:
>>>>
>>>> I live in a 230V area but need to use a 120V fan to repair an amplifier.
>>>> I can only get 230V fan motors here, so i was wondering if i can simply
>>>> remove turns from a 230v shaded pole motor to make it into a 120v one?
>>>>
>>>> Thank you.
>>>>
>>>>
>>>
>>> No. It's highly unlikely that the wire used in the motor is more than
>>> 100% overspecified, so if you remove turns from it to make it run at the
>>> same speed on 120v, it will overheat, because the current will
>>> approximately double.
>>>
>>> Sylvia.
>>
>> There is one high labor alternative that might work...
>>
>> Take the current wire on the motor, and find the center, break it at
>> that point, so you have two 120 volt windings. Put in parallel for 120
>> volts, and series for 240 volts.
>>
>> But, IMHO, hardly worth the effort, but technically feasible.
>
>I'm not sure it's advisable either. There's every chance the enamel will
>be damaged in the process. If he's lucky, any short will appear as soon
>as he turns it on. If he's unlucky, it will occur when he's not looking.
>
>Sylvia.

Advisable, probably not, but a theoritical solution, however! <bg>
From: Phil Allison on 24 Jun 2010 21:00

"Steve Sousa"
>
> I live in a 230V area but need to use a 120V fan to repair an amplifier.
> I can only get 230V fan motors here, so i was wondering if i can simply
> remove turns from a 230v shaded pole motor to make it into a 120v one?


** That idea is never gonna work - have you ever seen the insides of such a
fan ??

One possibility is to connect a capacitor in * series * with the fan of
such a value that it causes the inductance of the motor to resonate at the
supply frequency. This will increase the voltage across the fan above the
incoming supply.

A 230 volt, 120mm fan I tried resonates with about 3uF in series.

With 120 volts AC input, the voltage across the fan became 165 volts and the
speed was then close to that with 230 volts.
Worth a try.

Use a cap rated for 240 volt AC operation.


..... Phil





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