TRANSFORMER EFFICIENCY

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

 

[Phil Allison]

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

 

[George Herold]

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

 

[Adrian Tuddenham]

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.

 

[Robert Baer]

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.