'Scuse me Teach ...

andrew Ivimey · Post by **andrew Ivimey** » Wed Apr 18, 2012 5:01 pm

transformer ratios

If the primary is 5000 and the secondary is 16, what is the ratio?

and

if the primary is 5000 and the secondary is 250, what is the ratio, please?

And so I don't have to exasperate you on this, what is the formula? Then I can do it for myself!

cheers

pre65 · Post by **pre65** » Wed Apr 18, 2012 5:09 pm

It was the square root of the division of primary over secondary... I believe.

5000 divided by 16 = 312.5

Square root of 312.5 = 17.67

5000 divided by 250 = 20

Square root of 20 = 4.47

PS I know what you're doing.

Lee S · Post by **Lee S** » Wed Apr 18, 2012 5:15 pm

PPS - I know what you did last summer !!

pre65 · Post by **pre65** » Wed Apr 18, 2012 5:18 pm

Lee S wrote:PPS - I know what you did last summer !!

Let's twist again ?

andrew Ivimey · Post by **andrew Ivimey** » Wed Apr 18, 2012 5:34 pm

Well let's hope it still is.

So, the square root of the primary over the secondary.

That makes 3000 primary and 8 secondary as 19.36 to 1 ???

p.s. do I know what I'm doing?

pre65 · Post by **pre65** » Wed Apr 18, 2012 5:41 pm

andrew Ivimey wrote:Well let's hope it still is.

So, the square root of the primary over the secondary.

That makes 3000 primary and 8 secondary as 19.36 to 1 ???

p.s. do I know what I'm doing?

Yep, 19.36 is what I make it.

Perhaps a clever person will confirm the formula.

PS this seems to confirm the theory----

http://www.maxmcarter.com/classecalcs/tratiocalc.html

Toppsy · Post by **Toppsy** » Wed Apr 18, 2012 5:41 pm

Here is a Transformer Turns Ratio Calculator for you Andrew:

http://www.maxmcarter.com/classecalcs/tratiocalc.html

AH! I see Phil beat to me it .

andrew Ivimey · Post by **andrew Ivimey** » Wed Apr 18, 2012 5:50 pm

Aha! makes it even easier - ta muchly.

Paul Barker · Post by **Paul Barker** » Wed Apr 18, 2012 5:52 pm

You have the right formula.

If Andrew is trying to establish which voltage torroidal power transformer to use as a parafeed output transformer then don't forget to compensate for the 10% to 15% underwind of the primary in small torroids which takes care of "regulation" 5% to 10% in large ones.

The primary is wound right near the knee of the bh curve so that the -3db point will probably be 50hz -6db at 25hz for audio purposes.

However since most of us haven't a clue what we are really hearing and if a parafeed cap is chosen to lift the bass response by the resonant tank principle, though artificial and poor in phase response most people are fooled into hearing great bass. It actually sounds good.

Paul Barker · Post by **Paul Barker** » Wed Apr 18, 2012 5:55 pm

As the poor primary L of the opt is parallel with the series choke make sure that is at least 50 henry (100 is better) to eliminate the possibility of worstening the situation, or use a CCS.

Mike H · Post by **Mike H** » Thu Apr 19, 2012 1:23 pm

pre65 wrote:
andrew Ivimey wrote:Well let's hope it still is.

So, the square root of the primary over the secondary.

That makes 3000 primary and 8 secondary as 19.36 to 1 ???

p.s. do I know what I'm doing?
Yep, 19.36 is what I make it.

Me too.

Turns / Volts ratio = square root of impedance / inductance ratio.

Impedance / inductance ratio = (turns / Volts ratio) squared (to the power of 2, or multiplied by itself)

audio-talk

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