Re: Saturation in transformers.



Jerry wrote:

> The simple answer to your toroid question is this:
>
> Saturation occurs when the excitation losses in the core
> are excessive and reflect an excessive primary no load current.
>
> The quantity that you are looking for is VA/lb. loss:
>
> i.e If you experience any value over 10VA/lb. you are
> in or approaching saturation.
>
> For example: If your toroid weighs 4 lbs. and you had
> 40 VA, the primary no load current would be .3333Amperes.
>
> That amount of current would occur at 16 kilogausse @ 60Hz.
>
> Normally we do not design for any flux density higher than
> 14kilogausse, so these losses are not prohibitive.
>
> I know that Patrick is going to bite his tounge at any flux
> density over 10KG, but I design for the high volume world
> where economics do come into play. Also, we use other
> core materials in the 26Ga. non-oriented steel arena.
> Most toroids are wound with thin, grain oriented steel.

Your explanation wouldn't be easy for anyone without serious knowledge
to follow.

The design parameters for all transformers are related as follows :-

Fs = 22.6 x V x 10,000
------------------
B x Np x Afe

Where
Fs = frequency of saturation,
22.6 is a constant for all equations,
V = voltage in rms across the primary,
Np = primary turns,
B = maximum allowable magnetic field strength in Tesla in the core,
Afe = cross sectional area of the central core leg, in square mm.

The saturation is a voltage caused phenomena.

Power trannies may well be run at 1.6Tesla, but not
those in well designed audio gear where 1T is more appropriate.

Your reference to W/Lb losses isn't the whole story.

GOSS will have much lower W/Lb than non oriented SS.

Each type of steel will saturate at nearly the same B.

If you want a quiet running tranny that won't get hot, you must use more
turns
and iron for the same VA compared to what is done in the commercial
world
where many makers don't care that their trannies are mechanically noisy
and/or get roasting hot.

There is a whole lot more that helps at my website,

http://www.turneraudio.com.au

Patrick Turner.


>
>
> Hope this helps.
>
> Jerry

.

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