RE: [TCML] Controlling Speed of an AC (Muffin) Fan

["Lau, Gary" <Gary.Lau@xxxxxx>]

AC induction motors like what's in the fan you cite really are not really supposed to be speed-controlled.  It may work to some degree, but I doubt it will work well.  But for the purpose of blowing on an RQ gap, I don't think one needs to control the speed.  I don't think there's a critical sweet spot in air flow; anything above some reasonable flow rate is all you need and it won't improve things to have more.  Just apply full power to it.

I mentioned using a lamp dimmer with my sucker gap.  The vacuum cleaner motor used in this gap is called a "universal" AC/DC motor, not an induction motor, and its speed is easily controlled with a dimmer.  And, that gap needs only a fraction of the full-speed airflow that motor is capable of, and full-speed operation is VERY noisy, and I just don't want that noise and that much power being used.

Regards, Gary Lau
MA, USA



> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Brandon Hendershot
> Sent: Saturday, February 27, 2010 5:54 PM
> To: Tesla Coil Mailing List
> Subject: [TCML] Controlling Speed of an AC (Muffin) Fan
> 
> Alright,
> 
> So I plan on purchasing this:
> http://www.mpja.com/prodinfo.asp?number=17780+FN
>   AC muffin fan and I need a way to vary its speed. I was thinking of
> using a rheostat, but Paul suggests otherwise. Then I thought of using
> a dimmer switch, but I remember trying to control my drill press with
> my variac (kinda the same, right?). It wouldn't work because you need
> to control the frequency of the electricity, not the voltage like you
> do with most DC motors.
> 
> Anyway, what do you guys use to control your AC motors on your rotary
> gaps or spark gap fans?
> Thank you,
> Brandon
> 
> P.S: I only opt for AC motors for their immunity to the coils magnetic
> field. One more thing on the topic of fans, should 200 CFM be good
> enough to quench my RQ gap? I'm running a 15/30 NST.
> 
> 
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