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Guest

Sat Jan 19, 2019 12:45 am   



Quote:
"
Has he got a web site - I could do with a good laugh.



Quote:
When unloaded, power transformers have lots of undesirable signal-handling
features.



** More and worse drivel than the last lot.

Maybe he has a minor in AP. AudioPhoolery.


Guest

Tue Jan 22, 2019 6:45 pm   



On Thursday, January 17, 2019 at 4:19:56 PM UTC-5, Phil Allison wrote:
Quote:
mako...@yahoo.com wrote:




Core saturation is not a function of load "TO A FIRST ORDER APPROXIMATION".

Only the primary voltage matters.


** And of course the input frequency - the two operate in reverse proportion.


But to a second order, if the transformer core is near saturation
unloaded, when you load the secondary, the primary current and the
primary resistance will in effect LOWER the primary voltage and
reduce the core saturation.


** True even when the applied primary voltage has no changed one tiny bit cos it is coming form the mains supply.


So considering the second order effect of primary winding resistance,
yeah, loading a transformer _may_ reduce the distortion a little.


** With a tube amplifier, the effect can be very marked - since the voltage applied to the primary drops when a load is applied to the secondary.

The source impedance of a pentode or beam tube output stage is pretty high, triodes are somewhat better.

Only those amplifiers with large NFB ratios avoid the issue.


..... Phil


yep good point...

so it is very possible for a tube amp to have a bit less transformer saturation distortion when loaded compared to unloaded.

i.e. the distortion can go DOWN when loaded.


m

Look165
Guest

Tue Jan 22, 2019 7:45 pm   



NO !

Saturation is a value coming from the magnetic core, yes.

But H (magnetic strength) is directly proportional to the current, not
to the voltage, at constant frequency.
The load is very important.
This leeds the core to the satruration point if too high.

A free transformer (without load) rarely comes to saturation.

Eddy's current (we call it Foucault's current in France) are
proportional to I^^2, like copper losses.

makolber_at_yahoo.com a écrit le 22/01/2019 à 18:39 :
Quote:
On Thursday, January 17, 2019 at 4:19:56 PM UTC-5, Phil Allison wrote:
mako...@yahoo.com wrote:



Core saturation is not a function of load "TO A FIRST ORDER APPROXIMATION".

Only the primary voltage matters.

** And of course the input frequency - the two operate in reverse proportion.

But to a second order, if the transformer core is near saturation
unloaded, when you load the secondary, the primary current and the
primary resistance will in effect LOWER the primary voltage and
reduce the core saturation.

** True even when the applied primary voltage has no changed one tiny bit cos it is coming form the mains supply.


So considering the second order effect of primary winding resistance,
yeah, loading a transformer _may_ reduce the distortion a little.

** With a tube amplifier, the effect can be very marked - since the voltage applied to the primary drops when a load is applied to the secondary.

The source impedance of a pentode or beam tube output stage is pretty high, triodes are somewhat better.

Only those amplifiers with large NFB ratios avoid the issue.


..... Phil
yep good point...

so it is very possible for a tube amp to have a bit less transformer saturation distortion when loaded compared to unloaded.

i.e. the distortion can go DOWN when loaded.


m




Phil Allison
Guest

Tue Jan 22, 2019 10:45 pm   



Look165 wrote:

Quote:
NO !

Saturation is a value coming from the magnetic core, yes.

But H (magnetic strength) is directly proportional to the current, not
to the voltage, at constant frequency.


** WRONG !!!

The applied AC voltage and frequency are what matter.


Quote:
The load is very important.
This leeds the core to the satruration point if too high.


** TOTAL BOLLOCKS !!!


Quote:
A free transformer (without load) rarely comes to saturation.



** Try using an unloaded 120V supply transformer on 240V and see what happens.

Others here have it right cos they know that they are talking about - you don't.

Piss off you bloody idiot.



..... Phil

Fox's Mercantile
Guest

Tue Jan 22, 2019 10:45 pm   



Or, you know, you COULD just look this shit up and learn
how it works.
<https://www.ieee.li/pdf/introduction_to_power_electronics/chapter_12.pdf>

--
"I am a river to my people."
Jeff-1.0
WA6FWi
http:foxsmercantile.com


Guest

Tue Jan 22, 2019 11:45 pm   



it is about current,

the so called magnetizing current that flows even with no load.

the additional current that flows in the primary when the secondary is loaded IS CANCELED by the current in the secondary.

So it is all about the current that flows only due to the primary inductance and not due to the load current.

Yours is a common mis-conception. I'm glad to help you learn.

m



On Tuesday, January 22, 2019 at 1:13:17 PM UTC-5, Look165 wrote:
Quote:
NO !

Saturation is a value coming from the magnetic core, yes.

But H (magnetic strength) is directly proportional to the current, not
to the voltage, at constant frequency.
The load is very important.
This leeds the core to the satruration point if too high.

A free transformer (without load) rarely comes to saturation.

Eddy's current (we call it Foucault's current in France) are
proportional to I^^2, like copper losses.

makolber_at_yahoo.com a écrit le 22/01/2019 à 18:39 :
On Thursday, January 17, 2019 at 4:19:56 PM UTC-5, Phil Allison wrote:
mako...@yahoo.com wrote:



Core saturation is not a function of load "TO A FIRST ORDER APPROXIMATION".

Only the primary voltage matters.

** And of course the input frequency - the two operate in reverse proportion.

But to a second order, if the transformer core is near saturation
unloaded, when you load the secondary, the primary current and the
primary resistance will in effect LOWER the primary voltage and
reduce the core saturation.

** True even when the applied primary voltage has no changed one tiny bit cos it is coming form the mains supply.


So considering the second order effect of primary winding resistance,
yeah, loading a transformer _may_ reduce the distortion a little.

** With a tube amplifier, the effect can be very marked - since the voltage applied to the primary drops when a load is applied to the secondary.

The source impedance of a pentode or beam tube output stage is pretty high, triodes are somewhat better.

Only those amplifiers with large NFB ratios avoid the issue.


..... Phil
yep good point...

so it is very possible for a tube amp to have a bit less transformer saturation distortion when loaded compared to unloaded.

i.e. the distortion can go DOWN when loaded.


m




whit3rd
Guest

Wed Jan 23, 2019 12:45 am   



On Tuesday, January 22, 2019 at 10:13:17 AM UTC-8, Look165 wrote:

Quote:
Saturation is a value coming from the magnetic core, yes.

But H (magnetic strength) is directly proportional to the current...
A free transformer (without load) rarely comes to saturation.


NO, that's exactly backwards: a 'free' transformer with negligible secondary current
DOES near-saturate. The primary current and secondary current are in
the opposite direction, so load (secondary) current CANCELS
the magnetization caused by the drive (primary) current.

A lot of secondary current (high load current) removes the
risk of saturation.

Phil Allison
Guest

Wed Jan 23, 2019 12:45 am   



whit3rd wrote:

Quote:


NO, that's exactly backwards: a 'free' transformer with negligible
secondary current DOES near-saturate.
The primary current and secondary current are in
the opposite direction, so load (secondary) current CANCELS
the magnetization caused by the drive (primary) current.

A lot of secondary current (high load current) removes the
risk of saturation.


** While adding load current does not directly alter the magnetising current in the primary, it does reduce the effective AC supply voltage seen by the primary.


This is due simply to the resistance of the primary winding - current flow produces a voltage drop which must be subtracted from the external supply voltage to accurately model what is going on.

Eg, say the primary current due to load is 1 amp and the winding has 5 ohms resistance - then the effective voltage is 5 volts LESS than the AC supply.


..... Phil

..... Phil

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