Transformer power usage

Yes.

"Scott"

** Weird is more like it.

** No.

** No.

Now piss off - you stupid TROLL..

.. Phil

I am curious. Does a transformer draw (considerable) power even with no load.

I have a cheapo, unregulated 88W 120VAC to 12VAC transformer/timer (landscape lighting) in which the timer had failed. I also happened to have a small 120V photocell switch (activates in darkness). When I removed the timer mechanism, I noted the timer motor was running off of the 12V side of the transformer, meaning the transformer was always energized.

With the photocell wired in-line prior to the transformer, there is a small power draw (

John, Thanks for the explanation and terminology for further reading. Indeed the unloaded transformer was quite warm. Scott

Pay no attention to Phil Allison - sometimes he goes off his meds.

No, a transformer with no load will draw very little power. With no load, it's merely an inductor, drawing only magnetizing current.

Of course, with the timer motor running off the secondary, it will draw whatever power the timer motor uses, plus some losses, which are usually negligible.

To verify this, just feel the transformer with your hand. If you can rest your hand on it, then everything is OK.

So don't worry. :-)

Cheers! Rich

No. Stop misleading the newbies.

Thanks, Rich

It depends on what you mean by "quite warm". If you can hold your hand on it for more than, say, 5 or 10 seconds, then there's nothing to worry about.

If you could fry an egg on it, you probably have a problem. :-)

Hope This Helps! Rich

Phil, It was not my intent to troll. Your answers are appreciated, however terse. Pissin' off! Scott

Well, it's true in some parts, it's obvious there is power being drained while not having any attached device.. There is no such thing as a 100% power efficient xformer. As you and others can argue the point, it's just what it is, pointless.

So, yes, the statement is true as far as the poster is concerned.

Going into details of why it happens, isn't what I think the poster was looking for. Because to be frank about it, I'm sure the poster does not care as to why, just closure on their assumption.

I don't know what he considers a considerable amount of power, but the fact that it's using power, makes my statement not false!.

If the poster wants to know the technical details, as to why, i'm sure you'll be willing to step up to the plate. Just remember, it's hard to be on top and stay there.

So, if you want to make a mountain out of an ant hill, go for it. I'll just sit back and be amused.

--
No, it isn\'t.

Without knowing what the OP means by \'considerable wattage\' your answer
is, at best, irresponsible.

"Scott"

** FYI pal - the un-loaded power loss of a 300VA toroidal mains transformer is about 3 to 4 watts.

The un-loaded power loss of a typical 300VA E-core type is about 6 to 8 watts.

Bored with trolling yet ??

.... Phil

Thank you for the continued response. Actually I am interested in the 'why' as well as a definitive 'yeah' or 'neigh', despite my lack of details and tentative grasp of electronics. By my simplistic thinking, tying each end of a wire to AC mains should draw current and use it up as resistive heat. I believe I am underestimating the function of the inductor of the transformer's primary.

I am sorry I did not measure the current while it was powered but unloaded. I will take some measurements this weekend for my own curiosity. I am fairly certain what I saw was simply high resistive losses due to the aging steel core.

For arguements sake, I would consider "Considerable" to be 50% or more of the loaded wattage.

Thanks! Scott

Indeed it does Rich.

I could maintain contact for 10 to 15 seconds after it had been plugged in for more than 6 hours unloaded. I imagine the corrosion spots on the edge of steel laminate core of the transformer may indicate resistive losses.

Thanks! Scott

Phil, Thank you for the details. This is the kind of information I was hoping to find.

Only trolling for info, Scott

Resistive losses are losses due to the resistance of the windings (Joule effect). Losses in the core are due to magnetic hysteresis of the material and eddy currents induced inside the laminates. The effect of a surface defect on these losses is probably negligible.

v.

Oh well,.

Don't give enough; Give to much;

What's the difference. Seems that some one can always find fault.

--
When there\'s fault to be found, or for refusal to admit to a fault, of
course.

Why should it be any other way?

JF

Thanks. My bad choice of words. I was thinking the surface corrosion may have increased the magnetic losses through increased eddy currents and produced more heat. I am probably wrong about that, since the resistive element accounts for the majority of the losses and probably heat. It just seemed odd to me that something that runs that hot without a load was wired to be energized all the time, and was hoping its age contributed to the heat. Scott

Like I say, if you can put your hand on it, it'll be fine. They design those things right on the bleeding edge, because if you can save a penny apiece on a million units, that's $10,000 in your pocket. :-)

Cheers! Rich