Mystery transformer

[GRe]

Some time ago I found a small transformer in the junkbox.
It looks old, like from the forties or fifties era.
I don't remember where it came from or was cannabilized from.
Anyway, today I took the trouble to measure it.

Winding W1:
Rdc = 32ohm
Saturation at about 50V, W2 open
Inductance 8.82H @ 10V/50Hz
Inductance 6.58H @ 10V/100Hz

Winding W2:
Rdc = 29ohm
Saturation at about 37V, W1 open
Inductance 5.36H @ 10V/50Hz
Inductance 4.11H @ 10V/100Hz

Winding ratio N = 1.34
Impedance ratio = 1.79

F-response -3dB @ 27kHz with a 600ohm load on W2

+3dB @ about 80kHz with (almost) no load on W2
+22dB @ 186kHz resonance with (almost) no load on W2

Iron lamination dimensions 48x40x20mm
It's "tarred" and has NO airgap
Beside end taps, no additional taps on W1 and W2

What could the purpose have been?
Anybody any idea???

TIA & regards,
Gio

[Charles]

"GRe" wrote in message
news:5087c1e5$0$6871$e4fe...@news2.news.xs4all.nl...

Telephone application?

[karab...@yahoo.com]

If it was from telco- then most likely to match 600 to 900 .

[Phil Allison]

"GRe"

> Winding W1:
> Rdc = 32ohm
> Saturation at about 50V, W2 open
> Inductance 8.82H @ 10V/50Hz
> Inductance 6.58H @ 10V/100Hz
>
> Winding W2:
> Rdc = 29ohm
> Saturation at about 37V, W1 open
> Inductance 5.36H @ 10V/50Hz
> Inductance 4.11H @ 10V/100Hz
>
> Winding ratio N = 1.34
> Impedance ratio = 1.79
>
> F-response -3dB @ 27kHz with a 600ohm load on W2
>
> +3dB @ about 80kHz with (almost) no load on W2
> +22dB @ 186kHz resonance with (almost) no load on W2
>
> Iron lamination dimensions 48x40x20mm
> It's "tarred" and has NO airgap
> Beside end taps, no additional taps on W1 and W2
>
> What could the purpose have been?
> Anybody any idea???
>

** Almost certainly it's a high quality, 600 ohms line driving transformer.

The primary impedance is about 1000 ohms and so suits cathode drive from a
small power tube, via a coupling capacitor.

Max operating level is about 10 volts rms, with 13 volts drive on the
primary.

Line receiving versions were usually fitted into a ( mu-metal) shielding
can.


... Phil

[GRe]

"Charles" <charles...@comcast.net> wrote in message
news:k69kbt$cbk$1...@dont-email.me...

Could be! Maybe Western Electric?

Not mentioned in yesterday's post; there is a print
in white characters on top of the transformer.

Print: WE1612??
6 420

The last two characters of the first line are too vague to read.

Do you know they used indification no's with "WExxxx"?

Regards,
Gio

[GRe]

"Phil Allison" <phi...@tpg.com.au> wrote in message
news:aes634...@mid.individual.net...

Sounds like a bull's eye shot to me!
With a line transformer application in mind I did some more tests.

Inductance at -20dB steps:
8.8H @ 10V/50Hz (XL= 2.8Kohm)
3.4H @ 1.0V/50Hz (XL= 1.1Kohm)
1.6H @ 0.1V/50Hz (XL= 500 ohm) Z-total about 450ohm
0.9H @ 10mV/50Hz (XL= 280 ohm) Z-total about 270ohm

2.4H @ 10V/1kHz (XL= 15Kohm)
1.2H @ 1.0V/1kHz (XL= 7.5Kohm)
0.9H @ 0.1V/1kHz (XL= 5.6Kohm)
0.5H @ 10mV/1kHz (XL= 3.1Kohm)

Looks like impedances are OK with a possible exception for 50Hz/.1V/10mV
where XL parallel to the reflected 600ohm termination are lowish, about 450
& 270ohm.
Would this imply a lower-R termination for more constant Z to the driver?

Is a lowish impedance at low frequency & voltage of much significance
regarding the low output impedance of a cathode follower/driver?


Square wave test, Vi= 10Vpp/10kHz:
Rise time at W2 = 14猶 with a 600ohm load
Rise time at W2 = 2猶 with a 3600ohm load

Square wave test, Vi= 10Vpp/50Hz:
W2 droop about 7% at the trailing edge vs. leading edge, 600ohm load
W2 droop also about 7% at the trailing edge vs. leading edge, 3600 ohm load

Because of the 14猶 rise time with 600ohm load, while without load
significant ringing is present I wondered if a higher resistance would do
better.
Optimum was found with a 3600ohm load, almost no over- or undershoot.
With the 3600ohm load the -3dB point shifted to about 175kHz.
Would this imply a higher-R termination for a better signal transfer?


Does the above data confirm application as a 600ohm line driver or does it
suggest something else?

Regards & TIA,
Gio

[Don Pearce]

Could you explain these tests in a little more detail? I'm not sure
why the inductance appears to be dependent on the voltage.

d

[Phil Allison]

"GRe"
> "Phil Allison" "GRe"

>>
>> ** Almost certainly it's a high quality, 600 ohms line driving
>> transformer.
>>
>> The primary impedance is about 1000 ohms and so suits cathode drive from
>> a
>> small power tube, via a coupling capacitor.
>>
>> Max operating level is about 10 volts rms, with 13 volts drive on the
>> primary.
>>
>> Line receiving versions were usually fitted into a ( mu-metal) shielding
>> can.
>
>

> Sounds like a bull's eye shot to me!
> With a line transformer application in mind I did some more tests.

** You are wasting your time with irrelevant tests.

The tranny is intended to be driven from a low impedance source ( circa 50
ohms) and that tends to irons out effects due to low magnetisation.

You need a THD meter to make sense of what matters and what does not.



.... Phil

[GRe]

"Don Pearce"

>>
> Could you explain these tests in a little more detail? I'm not sure
> why the inductance appears to be dependent on the voltage.

It's due to hysteresis losses of ferromagnetic materials like the lamination
in transformers.

Take f.e. a mains transformer and measure the current trough the primary,
while the secondary is open:

1) at mains voltage, f.e. 230Vac
2) at about 1/10 of the first, f.e. 24Vac.

Calculate Z from Vac/Iac and XL from Sqrt(Z^2 - Rdc^2).
Than calculate L from XL/(2.pi.f)
Usually Rdc can be ignored, so XL practically equals Z.

3) you will find two quite different figures for the inductance.

Gio

[Don Pearce]

But in your numbers, the inductance is increasing as the voltage
increases. At higher voltage, the current should be higher, so the
core would be more saturated, so the inductance should decrease, not
increase. I think maybe you need to check your calculations.

d

[Phil Allison]

"GRe"

>
> "Don Pearce"
>>>
>> Could you explain these tests in a little more detail? I'm not sure
>> why the inductance appears to be dependent on the voltage.
>
>
> It's due to hysteresis losses of ferromagnetic materials like the
> lamination in transformers.

** You have made a big mistake by separating Don's Q from the original
context.

> Take f.e. a mains transformer and measure the current trough the primary,

** Irrelevant to the falling L value at lower levels in your tests.

That has to do with falling permeability of the core at low I mags.

Odds on the core is made of ordinary transformer steel rather than Mu-metal
or similar.


.... Phil

[GRe]

"Phil Allison"

>
> You need a THD meter to make sense of what matters and what does not.
>

Input f/V/THD Output THD (600ohm terminated)

1kHz/1.0V/0.075% 0.082%
1kHz/3.6V/0.086% 0.101%

3.6V is the max. output for the audio generator.

Can one simply substract THD Out/In numbers to gain THD for the transformer
only?

Gio

[Phil Allison]

"GRe"

"Phil Allison"
>
>> You need a THD meter to make sense of what matters and what does not.
>>
>
> Input f/V/THD Output THD (600ohm terminated)
>
> 1kHz/1.0V/0.075% 0.082%
> 1kHz/3.6V/0.086% 0.101%
>
> 3.6V is the max. output for the audio generator.

** You need to use a much lower frequency.

Transformer non linearity is concentrated at the low end of the audio
band.

> Can one simply substract THD Out/In numbers to gain THD for the
> transformer only?

** To a rough approximation only.

The figures quoted above suggest the tranny is adding almost nothing.

PLUS it is crucial the source impedance be low - like 50 or 100 ohms.

Easy way is to use one channel of a good hi-fi amplifier to buffer the
output of the generator and drop the impedance to near zero.


.... Phil

[GRe]

"Phil Allison" <phi...@tpg.com.au> wrote in message

news:afcl8a...@mid.individual.net...

>
> "GRe"
> "Phil Allison"
>>
>>> You need a THD meter to make sense of what matters and what does not.
>>>
>>
>> Input f/V/THD Output THD (600ohm terminated)
>>
>> 1kHz/1.0V/0.075% 0.082%
>> 1kHz/3.6V/0.086% 0.101%
>>
>> 3.6V is the max. output for the audio generator.
>
>
> ** You need to use a much lower frequency.
>
> Transformer non linearity is concentrated at the low end of the audio
> band.

I used the function generator HV-output(600ohm) for this test.

Input f/V/THD Output THD (600ohm terminated)

200Hz/10V/0.036% 0.049%
100Hz/10V/0.037% 0.077%
50Hz/10V/0.037% 0.170%
25Hz/10V/0.036% 0.442%

So, per "rough approximation" about 0.4% added distortion at 25Hz/10V.
Scoping the distortionmeter's output it looks like mainly 3H, but
seems quite acceptable to me for that frequency and level.

>> Can one simply substract THD Out/In numbers to gain THD for the
>> transformer only?
>
>
> ** To a rough approximation only.
>
> The figures quoted above suggest the tranny is adding almost nothing.
>
> PLUS it is crucial the source impedance be low - like 50 or 100 ohms.

In this case it does'nt seem to make a difference using the function
generator 50ohm or 600ohm output, see below, so I used the latter for
the tests as the max. Vout is about 14V vs. about 7V(unterminated).

At 25Hz/5V/600ohm output, THDout - THDin = 0.307 - 0.034 = 0.273%
At 25Hz/5V/ 50ohm output, THDout - THDin = 0.721 - 0.444 = 0.277%

> Easy way is to use one channel of a good hi-fi amplifier to buffer the
> output of the generator and drop the impedance to near zero.

Only handy in the living room, not on the bench.

Gio.

[Phil Allison]

"GRe"
> "Phil Allison"
>>>
>>>> You need a THD meter to make sense of what matters and what does not.
>>>>
>>>
>>> Input f/V/THD Output THD (600ohm terminated)
>>>
>>> 1kHz/1.0V/0.075% 0.082%
>>> 1kHz/3.6V/0.086% 0.101%
>>>
>>> 3.6V is the max. output for the audio generator.
>>
>>
>> ** You need to use a much lower frequency.
>>
>> Transformer non linearity is concentrated at the low end of the audio
>> band.
>
> I used the function generator HV-output(600ohm) for this test.
>
> Input f/V/THD Output THD (600ohm terminated)
>
> 200Hz/10V/0.036% 0.049%
> 100Hz/10V/0.037% 0.077%
> 50Hz/10V/0.037% 0.170%
> 25Hz/10V/0.036% 0.442%

** No "function generator" I ever heard of has THD figures as low 0.036%.

Post a link for the one you have.

>> PLUS it is crucial the source impedance be low - like 50 or 100 ohms.
>
> In this case it does'nt seem to make a difference using the function
> generator 50ohm or 600ohm output,

** Something is very fishy with your testing and that generator.

>> Easy way is to use one channel of a good hi-fi amplifier to buffer the
>> output of the generator and drop the impedance to near zero.
>
> Only handy in the living room, not on the bench.

** Stop being such a PITA twat.

I posted HOW to do it - whether YOU have such an amp handy or not is
YOUR problem.

What a tedious piss head.



... Phil

[GRe]

"Phil Allison"

>> Input f/V/THD Output THD (600ohm terminated)
>>
>> 200Hz/10V/0.036% 0.049%
>> 100Hz/10V/0.037% 0.077%
>> 50Hz/10V/0.037% 0.170%
>> 25Hz/10V/0.036% 0.442%
>
>
> ** No "function generator" I ever heard of has THD figures as low 0.036%.

Singular H spec. in the 10Hz-50kHz range is =< -65dB (0.056%) for both
outputs.

>
> Post a link for the one you have.

That would disqualify your judgement.

Gio

[Phil Allison]

"GRe"

> "Phil Allison"
>
>>> Input f/V/THD Output THD (600ohm terminated)
>>>
>>> 200Hz/10V/0.036% 0.049%
>>> 100Hz/10V/0.037% 0.077%
>>> 50Hz/10V/0.037% 0.170%
>>> 25Hz/10V/0.036% 0.442%
>>
>>
>> ** No "function generator" I ever heard of has THD figures as low
>> 0.036%.
>
> Singular H spec.

** Wot sort of bullshit is that ????

> in the 10Hz-50kHz range is =< -65dB (0.056%) for both outputs.

** Yawnnnnnn....

>> Post a link for the one you have.
>
> That would disqualify your judgement.

** OK - this dopey game is now over.

You are just another trolling, fucking idiot.

PISS OFF to HELL