Isolation transformer draws excessive current under no load condition

[Phil Allison]

"Robert Macy"


** Is there any way to shut fools like you up ??
----------------------------------------------------

Adding caps will indeed have NO effect on the tranny, but WILL improve
the PF as seen by your AC mains,

** Absolute BULLSHIT !!!!!!!!!

which means the amount of power you
drop in your wiring [and pay for] will be less.

** Absolute IDIOCY !!!!!!!

Adding caps is a STANDARD way to adjust power factor to 1.

** But never used with an off load transformer - because that idea is 100%
STUPID.

YOU are an obsessed IDIOT with a one track mind.

Piss off.

I stand by what I said as technically correct.

** LOL - that only makes you a BIGGER fucking idiot.


Many, many technical journals, text books, and supporting calculations
based upon terms of definition confirm what I said.


** Shame you cannot supply one that backs up your idiotic comments about
unloaded transformers.

Listen PAL !!!!!!!!

YOU are nothing but a lying, bullshitting NUT CASE !!

Clueless to the core.

FOAD.




.... Phil

 

[Phil Allison]

"Robert Macy = Troll "


** Is there any way to this MORON up ??

( Load of totally absurd crap deleted )



.... Phil

 

[Phil Allison]

"Robert Macy"

** Is there any way to shut fools like you up ??
----------------------------------------------------

Shame you cannot supply one that backs up your idiotic comments about
unloaded transformers.

Listen PAL !!!!!!!!

YOU are nothing but a lying, bullshitting NUT CASE !!

Clueless to the core - pun intended.

FOAD.



.... Phil

 

[Sylvia Else]

...snip...


Noted, and thanks.
...snip...

Adding caps will indeed have NO effect on the tranny, but WILL improve
the PF as seen by your AC mains, which means the amount of power you
drop in your wiring [and pay for] will be less.

Adding caps is a STANDARD way to adjust power factor to 1. Used by the
industrial power consumers that are heavily penalized for lagging
power factor. It is cheaper for them to add a building full of caps,
just to shift their PF and pay less for power.

If you do the analysis of power consumption throughout a standard AC
mains power distribution, you will find that a lagging power factor
[caused by motors, etc] INCREASES the power required to simply get
billable wattage to you. And, it's surprisingly large.

But, except for the extra power dissipated in the household wiring, is
not measured by the meter, and not included in the billed energy units.

Sylvia.

 

[Sylvia Else]

...snip...

Adding capacitance in parallel has no effect on the tranny whatsoever -
and it will make the PF worse.

Noted, and thanks.
...snip...

Adding caps will indeed have NO effect on the tranny, but WILL improve
the PF as seen by your AC mains, which means the amount of power you
drop in your wiring [and pay for] will be less.

Adding caps is a STANDARD way to adjust power factor to 1. Used by the
industrial power consumers that are heavily penalized for lagging
power factor. It is cheaper for them to add a building full of caps,
just to shift their PF and pay less for power.

If you do the analysis of power consumption throughout a standard AC
mains power distribution, you will find that a lagging power factor
[caused by motors, etc] INCREASES the power required to simply get
billable wattage to you. And, it's surprisingly large.

But, except for the extra power dissipated in the household wiring, is
not measured by the meter, and not included in the billed energy units.

Sylvia.

True!

Today, the only way that utilities companies can bill for this lost
energy is by assigning a 'penalty' for bad PF.

I'll bet with today's smarter metering, they'll figure a way to
measure it real-time and bill for it.

And if we correct our power factor, our bills will be lower than they
are now.

Oh, wait a minute, what was I thinking?

Sylvia.

 

[Phil Allison]

"Robert Macy" = one stubborn fucker

A cap does improve PF...

** But only with theoretical transformers - NOT real ones.

First, use a Linear Model to represent the isolation transformer.

** Waste of fucking time and effort - as it only repeats the same FUCKWIT
error you have been sprouting here all along.

The primaries of REAL commercially made E-core transformers are NOT
linear inductors !!!!!!!!!!!

The off load primary current at rated voltage is *dominated by the third
harmonic * of the AC supply frequency.

The laminated iron core is then saturating, quite heavily.

JW's 1kVA iso tranny is a very typical example of this fact.

You will NOT find this information on webs sites that merely discuss
transformer basics.

You WILL find this if you test a cross section of commercial E-core
transformers with the aid of a variac, RMS current meter and a scope
monitoring the current waveform.

This has NOTHING do with badly or well made transformers - all makers do it
to save weight and cost.

BTW:

I happen to own a 1kVA transformer very similar to that described by the OP.

Tested as above, these are the figures:

VAC A rms I peak

30 0.08 0.11
50 0.11 0.14
70 0.20 0.35

90 0.45 1.0
110 1.0 2.0
120 1.4 2.9
130 2.2 4.6


Up to 70 volts AC, the tranny is approximately linear with an effective
inductance of about 1.1 H.

At and above 90 volts AC it suddenly changes - current starts to increase
exponentially and the wave becomes very peaky with a 1:2 ratio between rms
and peak values.

At 130 VAC input, effective primary inductance ( based on simplistic
calculations) has dropped to less than 0.2H due to core saturation.

I must have tested hundreds of E-core trannys this way in the last 20 years
or so and ALL do much the same thing.

Toroidal and C- core types are different.


..... Phil

 

[Cydrome Leader]

...snip...

Adding capacitance in parallel has no effect on the tranny whatsoever -
and it will make the PF worse.

Noted, and thanks.
...snip...

Adding caps will indeed have NO effect on the tranny, but WILL improve
the PF as seen by your AC mains, which means the amount of power you
drop in your wiring [and pay for] will be less.

Adding caps is a STANDARD way to adjust power factor to 1. Used by the
industrial power consumers that are heavily penalized for lagging
power factor. It is cheaper for them to add a building full of caps,
just to shift their PF and pay less for power.

If you do the analysis of power consumption throughout a standard AC
mains power distribution, you will find that a lagging power factor
[caused by motors, etc] INCREASES the power required to simply get
billable wattage to you. And, it's surprisingly large.

But, except for the extra power dissipated in the household wiring, is
not measured by the meter, and not included in the billed energy units.

Sylvia.

yes it is. the problem with low power factors is the power loss before the
meter, which isn't measured and can be huge for large customers.

If at home, I toss a giant capacitor or huge inductor across the line, my
meter will pick up all the wiring and heating losses from the capacitors
or inductor.

It will not measure the losses to the power company for me circulating 100
amps to and from the power grid. the power companies losses on that will
be larger than mine, plus it wastes capacity of the grid itself.

For residential customers in the US, it's just assumed we're not idling
huge motors or testing capacitor banks in the dining room, so the
utilities don't pay attention to us.

 

[Cydrome Leader]

Hi all,

Is there any reason that a 120VAC to 120VAC isolation transformer would
draw 2.54A on its primary when there is no load present on it's secondary?

Part reference:
http://www.temcoindustrialpower.com/products/Transformers/FT2036.html

datasheet:
http://attachments.temcoindustrialpower.com/product_info/Federal_FB_1Ph_120x240Pri.pdf

I finally got around to wiring this transformer, and I noticed something
that doesn't seem quite right to me. I have it wired for 120VAC (H1
connected to H3 and H2 connected to H4) and it seems to be working as I
get about 120VAC on the secondary, ( wired X1 to X3 and X2 to X4) but with
no load on the secondary, the transformer is drawing 2.54 Amps.

Looking for a sanity check I guess. I'm beginning to think the thing may
be defective... Email to the Temco has produced no response as of yet.

I just ran a test I have on a similar transformer. Mine is a cutler hammer
1.5kVA unit in the same type of metal box and potted in expoxy and sand -
nothing special.

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.

 

[Phil Allison]

"Cydrome Leader"

I'd say your transformer is bad or somehow connected wrong.

** No way.

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

10 degrees temp rise and a PF of 0.15 is A-OK.



..... Phil

 

[Cydrome Leader]

"Cydrome Leader"



** No way.

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

10 degrees temp rise and a PF of 0.15 is A-OK.



.... Phil

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

 

[Phil Allison]

"Cydrome Lunatic"

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

** ROTFL - you are one colossal, know nothing bloody fool.



..... Phil

 

[Phil Allison]

"spamtrap1888"
"Phil Allison"

** No way.

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

10 degrees temp rise and a PF of 0.15 is A-OK.

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


** Why should it ?

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

 

[William Sommerwerck]

"Cydrome Lunatic"

** ROTFL -- you are one colossal, know[-]nothing bloody fool.

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
0.065 amps. (The display doesn't have enough resolution.) That's 4% of the
rated load. Not bad.

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.

 

[Cydrome Leader]

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?

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.

 

[Ian Jackson]

In message

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.

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.

 

[Phil Allison]

"William Sommerwanker TROLL"


** Big shame narcissistic fucking idiots like you still roam the earth.

FOAD now !!

 

[William Sommerwerck]

"William Sommerwanker TROLL"
** Big shame narcissistic fucking idiots like you still roam the earth.
FOAD now !!

ROAR!
I am a tyrannosaur! I will rip off your limbs with my silly two-fingered
arms, and greedily scarf them down.
If you are still alive after all your limbs have been consumed, I will bite
through your skull and savor the crunching sound.
ROAR!

 

[William Sommerwerck]

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!

 

[josephkk]

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?

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.

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

?-)