Isolation transformer draws excessive current under no load condition

I just ran a test I have on a similar transformer. Mine is a cutler hammer

it's actually a 240/480 to 240/120 unit, but you can switch the H and X leads with no no big deal.

Anyways, running 125 VAC (line voltage is high around here) across "half" the secondary (X1 and X2 instead of X1+x3 and X2+x4) resulted in 24 watts of loss and a current of 0.5A according to the kilowatt meter. The thing even buzzes somehow.

I'd say your transformer is bad or somehow connected wrong. My transformer is rated 115C rise, so it's probably no winner when it comes to energy efficiency. %Z isn't even listed on the nameplate.

"Cydrome Leader"

The OP's data shows it is operating normally and correctly.

.... Phil

that's a pretty horrible transformer if those parameters are A-OK.

"Cydrome Lunatic"

.... Phil

Why doesn't the transformer data sheet include idle current, power factor, etc.? Or is it embedded in some transformer standard I have to spend 2000 swiss francs to get?

"spamtrap1888" "Phil Allison"

Why doesn't the transformer data sheet include idle current, power factor, etc.?

They are easily measured parameters and of little interest to most users.

If the safety ratings, VA rating, temp rise, dimensions, weight and mounting details are all described - that is enough.

... Phil

Phil, do you know the word "empirical"? If not, you should learn it. Empirical data are knowledge, as assuredly as theoretical considerations.

Last week I measured the no-load drain of a 1.5A isolation transformer. * My Kill A Watt read 0.06 amperes, which could be anywhere between 0.055 and

The OP's transformer seems way out of line. It should definitely be placed off-line. (Ar, ar.)

• I was about to specify 125V, when I realized that, in theory, an isolation transformer should "work" at any voltage -- short (joke intended) of a voltage high enough to break down the insulation, etc, etc, etc.

The only transformers I've seen specs for idle power consumption listed (but not on the nameplate) are for distribution transformers the power company would own. They seem to care about how much money it costs to keep a transformer running for 30 years or until it finally explodes, so every watt counts.

For loose reference, I recall some 1kVA oil filled poole mount distribution tranformers with the real step-lap core idling at 14 watts, or something close to that. They really make 1kVA units for stuff like streetlights and running switchgear. At the 10kVA oil filled ones with the typical step-lap cores, something like 45 watts is normal for some brands.

These monsters aren't really rated the same as smaller EI core potted unit which are only meant to be cheap to produce in mexico or china or wherever they come from these days.

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When I buy transformers I always buy ones rated for 50 Hz, that way on 60 Hz they run cooler. That does not apply to ferroresonant transformers of course, but I have never bought one so it doesn't matter.

In message , snipped-for-privacy@hotmail.com writes

FWIW (and from what I remember), ferro-resonant (constant voltage) transformers usually DO get pretty hot on no load. Regardless of the load current, the input power is fairly constant. What doesn't come out heats up the transformer.

It should have read...

ROAR!

I am a tyrannosaur! I will rip off your limbs with my silly two-fingered arms, and greedily scarf them down. If you remain alive after all your limbs have been consumed, I will bite through your skull and savor your agonized screams of fear and excruciating pain, before you pass forever from this world.

ROAR!

If it is covered under a IEEE standard it would be about uS$100 to $200. I have several of them already, but maybe not the one for your transformer. Nor is the IEEE standard a mandatory one, check local regulation for what is mandatory. =20

Speaking of, i need to go buy some more standards right now.

?-)