# TRANSFORMER EFFICIENCY

Discussion in 'Electronic Design' started by uchethegenius1@gmail.com, Jan 9, 2014.

1. ### Guest

How do you derive the efficiency of a transformer from the first principle of electric circuit.

, Jan 9, 2014

2. ### Phil AllisonGuest

<>

> How do you derive the efficiency of a transformer from the first principle
> of electric circuit.

** Efficiency = power out / power in ( times 100 for percent ).

Now YOU get to explain WFT you really want to know.

..... Phil

Phil Allison, Jan 9, 2014

3. ### George HeroldGuest

On Thursday, January 9, 2014 11:49:51 AM UTC-5, Tim Wescott wrote:
> On Wed, 08 Jan 2014 23:14:49 -0800, uchethegenius1 wrote:
>
> > How do you derive the efficiency of a transformer from the first
> > principle of electric circuit.

>
> With great difficulty.
>
>
> There are a lot of factors at play, some of which are dependent on
> haracteristics of the materials involved that aren't always easy to pin
> down. Moreover, how you use the transformer in your circuit matters.
>
> Finally, for some applications the efficiency doesn't matter nearly as
> much as other things; usually bandwidth or fidelity of reproduction.
>
> Factors that I know of are:
>
> The resistance of the windings,
> the resistivity of the core material,
> the thickness of the laminations (if any),
> the nonlinear magnetic properties of the core material,
> the overall shape of the core and windings
>
> I'm sure there's more.

Hi Tim, If you wanted to keep it simple isn't there some leakage inductance(or is leakage the wrong term) that you see modeled as being in parallel (I think) with the primary, and given the leakage inductance and the windingresistance you could calculate some loss.

George (not a transformer guy) Herold
>
>
>
> I suspect that even in this day and age of high-falutin' computerized
>
> finite-element analysis, you'll still find that in practice anyone who
>
> can build you a transformer and have it possess the correct efficiency by
>
> design is someone who has designed and tested dozens or hundreds of
>
> similar transformers and is leaning on a wealth of practical information,
>
> rather than analysis from "first principles".
>
>
>
> --
>
>
>
> Tim Wescott
>
> Wescott Design Services
>
> http://www.wescottdesign.com

George Herold, Jan 9, 2014

Tim Wescott <> wrote:

> On Wed, 08 Jan 2014 23:14:49 -0800, uchethegenius1 wrote:
>
> > How do you derive the efficiency of a transformer from the first
> > principle of electric circuit.

>
> With great difficulty.
>
> There are a lot of factors at play, some of which are dependent on
> characteristics of the materials involved that aren't always easy to pin
> down. Moreover, how you use the transformer in your circuit matters.
>
> Finally, for some applications the efficiency doesn't matter nearly as
> much as other things; usually bandwidth or fidelity of reproduction.
>
> Factors that I know of are:
>
> The resistance of the windings,
> the resistivity of the core material,
> the thickness of the laminations (if any),
> the nonlinear magnetic properties of the core material,
> the overall shape of the core and windings
>
> I'm sure there's more.
>
> I suspect that even in this day and age of high-falutin' computerized
> finite-element analysis, you'll still find that in practice anyone who
> can build you a transformer and have it possess the correct efficiency by
> design is someone who has designed and tested dozens or hundreds of
> similar transformers and is leaning on a wealth of practical information,
> rather than analysis from "first principles".

If you are really determined, you could try studying some of the heavy
electrical engineering textbooks from the 1940s and 50s. They will give
the sort of information you need, but mainly aimed at the design of
massive power-distribution transformers where you really do have to
calculate first and build later.

That will give you some idea of the factors at work and the ball-park
figures you can expect, then you will have to scale everything to suit
the size of transformer you are interested in.

--
www.poppyrecords.co.uk

5. ### Robert BaerGuest

wrote:
> How do you derive the efficiency of a transformer from the first principle of electric circuit.

WHAT "first principle"?
From the theoretical definition? Answer is 100 percent.

Ignore the bushwah and look at losses: IR winding losses and induced
magnetic core losses; that will get you close to measured losses.

Robert Baer, Jan 10, 2014