Lower voltage diode the other side of a step up transformer?

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This is very noticeable with small transformers ( ie in wall warts) that run near full saturation when off load. When rated load is applied, magnetising current drops due to *primary IR voltage loss* so it matches or falls below that due to supplying the secondary. The two are easily distinguished on a scope as the peak values are 90 degrees out of phase.

Unlike load current, mag peaks close to zero applied volts.

.... Phil

The avalanche breakdown mechanism is different from the low voltage Zener breakdown mechanism, which doesn't operate at breakdown voltage higher than about 6 volts

And if the diode model is accurate you will learn something useful.

Like all items of folk wisdom, they are over-simplifications. John Larkin may know enough to spell out why, but he hasn't bothered here.

Joh Larkin's reading comprehension is down there with Flyguys. I'm all in favour of buying off-shelf transformers if you can find one to do the job.

The problem is that you rarely can.

As to why he thinks I don't understand the basics of transformer design, the answer has to be that he doesn't, and thinks that boB does, which is hilarious.

That isn't generally an issue. It is inherent they will conduct a small current, but that will naturally equalise as they get close to their breakdown voltage.

In life and reality things are not so black and white. Those prophesies are reserved most appropriately for colour blind art students.

If you were able to use a simulation tool like LT Spice, you would understand that the problem isn't nearly as severe as you might think. The back emf from the transformer would continue the sinusoidal waveform well beyond the crossing point.

Mr Kingsey, if so inclined and capable, could measure the resistance of his transformer and measure the average DC current into his circuit to confirm.

I would expect for a standard transformer, for the average (DC) current to be 1/10 of the resistance alone. BICBW

They aren't any kind of prophecy - just ill-informed speculation.

The "back emf from the transformer"?.

confirm.

He's an idiot who couldn't find his bottom with both hands.

Current is measured in amp. Resistance is measure in ohms. If you had specified the voltage you were thinking about, you might have said something intelligible, but as it is you are just adding to the ill-informed speculation.

Wrap yourself up and get yourself delivered some place where you won't have internet access.

That's OK, Bill. But at least we know what works for transformer design in a product.

There may be some confusion between inductor magnetics and transformer magnetics design going on down there. It's all the same thing in the end.

Try operating a transformer designed for 50/60 Hz operation with decreasing frequency and watch the magnetizing current rise as it startes to go into saturation. Lower frequency means higher volt-seconds.

You have to reduce the exitation voltage as you decrease the frequency to keep the V-S from increasing and saturating the core in a transformer.

boB

Not exactly. To understand a transforner you need to understand the transformer equation

V1 = L1.dI1/dt + M. dI2/dt

V2 = M.dI1/dt + L2. dI2/dt

where M is the mutual inductance between the primary L1 and the secondary L2 and M= k (L1.L2)^0.5

k is the coupling cofficient, typically 0.999 for ungapped ferrite pot cores but dropping to perhaps 0.98 for gapped pot core and RM core pairs.

Transformer texts are remarkably reluctant to use it - I finally got to see it in Siemens application note and found it very informative.

It lets you stop thinking about leakage inductance. which is a very unhelpful concept.

Of course it does.

There are more fundamental ways of looking at it.

It would be an issue if they fail shorted. I have had many zeners shorted and blowing a resistive fuse. Unfortunately, they usually take out other components before blowing.

F*ck off you pompous ass. It's fun to play with things you don't understand.

You seem to an awful lot of playing with things you don't understand.

No idea what you mean by dots.

Dots are little round filled circles. They indicate winding polarity.

If you think you understand everything, there's nothing to learn.

The smart ones do their research first before asking the sorts of questions I was asking when I was 8.

Otherwise you are indeed correct. There is a saying, the more you know, the more you realise you don't know.

Now if Mr Kinsey asked a question about LTSpice I would be far more impressed.

Then the proper response to any SED posting is "look it up."

Or use LTSpice. If Mr Kinsey troubled to so use it, it would go some way to show he's not so much of a troll.

That is what I did and the result was largely as expected. Putting a diode, resistor and inductor in series as a starting point is hardly rocket science.

No. It is to tell them where to look it up, ideally backed up by brief indication of what they will find there.

Commander Kinsey can be relied to fail to look it up, and to fail to comprehend eventhe simplest explanation.