What are the power losses in a transformer? 1

[bpelec]

I need to design a transformer. I want to optimise my design by trying to minimise power losses. As far as possible, I want to express all the power losses in terms of the dimensions and physical properties of the transformer. From the research I have done so far, I have identified the following power loss mechanisms:

1) Winding losses (I^2*R losses in the windings).

2) Core losses, consisting of eddy current losses and hysteresis losses.

I have also come across the term 'core loss factor', that is often provided by core manufacturers and has the units of W/m.

My questions are these:

1) If I multiply the 'core loss factor' by the volume of my core do I get the combined effects of eddy current loss and hysteresis loss? If not, what should I be doing?

2) What is the role of leakage inductance in power loss in the transformer? Does the leakage inductance just affect the power factor? I have seen a couple of equations that will calculate the leakage inductance as a function of the winding configuration - is there a better way?

3) What is the role of the magnetising inductance in power loss in the transformer?

3) Have I missed anthing out?

As I mentioned above, I want to express these losses in terms of the physcial properties of the transformer, such as the dimensions and material properties. I know that once I have made a prototype, I can find all these losses experimentally...

Thank you in advance for your help. Please let me know if I can provide any more information.

Best regards,

BPELEC.

 

[motorspert]

bpelec,
I guess it depends on how big the transformer is to be. Large transformers have eddy current losses in the conductors to be concerned with and stray losses in the transformer support stucture.

However, i assume in will be a smallish Tx. In answer to your question on core losses, the factor given by the material manufacturers is usually W/kg at a particular flux denisty eg 1.0T They will often give the loss factor at 1.5T as well. The losses increase with flux density roughly as a square ratio.

You are right leakage inductances do not produce losses, they just affect regulation

 

[ScottyUK]

A couple of books I've used in the past for transformer design are 'Soft Ferrites' by Edgar Snelling and the 'Soft Ferrites' Databook MA01 which was published by Philips Components (now Ferroxcube).

Snelling gives a marvellously detailed derivation of the two core factors C₁ and C₂ and gives some excellent notes on designing power transformers. The Philips book is less detailed but also shows the principles of designing a transformer core. The principles are valid for low frequency iron-cored transformers too, at least in the smaller sizes.

http://www.bookfinder4u.com/IsbnSearch.aspx?isbn=0408027606&mode=direct

http://www.ferroxcube.com/

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One day my ship will come in.
But with my luck, I'll be at the airport!

 

[CKent]

what about the effect of aging on the losses of transformer...I mean, how do the age of the transformer affect its losses, both copper and core losses?