[ARC5] Transformer Hum

[hwhall at compuserve.com]

Transformer noise is often from moving parts. (Yeah, transformers aren't supposed to have moving parts.) Normal magnetic fields in the windings can sometimes cause one or more turns to "wiggle" a bit and can also cause core laminations that aren't tightly secured to buzz. You didn't mention how loud the hum was. 

I used to listen to one of my CW transmitter power transformers hum as a sort of sidetone. With key up there was a mere whisper of a hum from the supply and with key down the volume of the hum went up. Seemed to be normal operation and never caused any problems.
 

 Wayne
WB4OGM

 

-----Original Message-----
From: Robert Eleazer <releazer at earthlink.net>
To: arc5 <arc5 at mailman.qth.net>
Sent: Tue, Mar 10, 2015 8:06 pm
Subject: [ARC5] Transformer Hum


I had a transformer for some lights fail at home so I started going though a
pile of unknown transformers to see if one would do the job.  A nice big hefty
one had two black wires and three red wires; two of the red wires had stripes. I
decided that the back wires, with a DC resistance of about 45 ohms, were the
primary and the red ones a center tapped secondary.

I hooked up my Variac and
found that the secondary voltage came right on up, topping out at 194V with 120V
on the primary - but just before it maxed out, the transformer started
humming.

Would y'all take the humming as an indication the transformer
voltage is too high?  In any case I was looking for one with a 12VAC output, so
it won't do anyway.

Thanks,

Wayne   

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