[ARC5] Smart People: 60Hz Transformers Faster?

[Brian]

Hello Dave,

In general, you can use a transformer at a higher frequency than that for 
which it was designed. But there is a limit. It is to do with the quality of 
the iron. As the frequency gets higher, some transformer-specified irons / 
steels will start absorbing much more energy than at the rated operating 
frequency. Running a transformer designed for 60 Hz at 800 Hz should be OK - 
but you will be carrying more iron than you need.

People who claim that they have used power transformers as audio 
transformers are often old folks for whom presbycusis has set in and they 
can't hear that the high frequencies are severely distorted and / or 
attenuated. While the transformation ratio may be OK, the impedance matching 
will be all over the place. Another problem with using power transformers 
for audio work is that there is usually DC flowing, which alters the 
behaviour of the iron - the whole hysteresis curve gets shifted up, one side 
of the audio wave flat-tops and the transformer heats up. If there is enough 
heating the iron can be permanently damaged.

You can also stuff a transformer by having net DC flowing when you use 
half-wave rectification - doesn't matter if it's at 60 or 800 Hz. Most 
computer SMPSUs rely on half-wave rectification - and electricity supply 
authorities get upset because of the net DC flow in their distribution 
transformers.

73 de Brian, VK2GCE.

On Monday, November 23, 2015 4:47 AM, Scott opined:

I used to use power transformers for pp output transformers and they worked 
fine. I expect 400 Hz to work fine, too.

/Scott Robinson

> On Nov 22, 2015, at 7:59 AM, David Stinson <arc5 at ix.netcom.com> wrote:
>
<snip>>
> But what about running a 60 Hz transformer at 400?
> Saturation shouldn't be a problem, but what about hyste...hister... yeah 
> those loses.
>
<snip>>
> 73 Dave S.