| Author |
Message |
Bob
Guest
|
 Posted:
Wed Nov 09, 2005 5:42 am Post subject:
Hey Phil, about transformers... |
|
|
Hi Phil,
Saturation is caused only by an excessive input voltage, right? The amount of
power taken out doesn't relate to saturation? In other words, overloading the
output is not a saturation problem? If you do put too much of a load on a
transformer, does the magnetization in the core decrease? I know that the heat
loss increases, maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
Saturation can be seen in the distortion of the (sine) input, but would not be
the same in an overload condition, which would have less distortion but a lower
power level ?
Transformers are complicated, but you seem to be an expert!
Thanks for any info you can clue me in!
|
|
| Back to top |
|
 |
Bob
Guest
|
| Posted:
Wed Nov 09, 2005 5:42 am Post subject:
Re: Hey Phil, about transformers... |
|
|
On Wed, 9 Nov 2005 13:11:05 +1100, "Phil Allison" <philallison@tpg.com.au>
wrote:
| Quote: |
"Bob"
Hi Phil,
Saturation is caused only by an excessive input voltage, right?
** Or lower that designed frequency, the two are quite proportional as
well.
A 20 % increase in voltage has the same effect as a 20 % reduction in
applied frequency.
The amount of
power taken out doesn't relate to saturation?
** It does - when the effective primary voltage is reduced by the
secondary load.
Effective primary voltage = AC supply - I x R loss in the primary.
In other words, overloading the
output is not a saturation problem?
** Long as the load is symmetrical - ie not half wave.
|
Would that cause a DC current in the core? If one had 2 transformers and used
them as the sources in a full wave supply, as if they were one CT transformer,
each supplying half the wave, I understand that would cause a sort of DC
imbalance... true?
Now if I use a 12v CT transformer to supply the 6v filaments in an amp, should I
make sure the currents are balanced to make best use of the capability of the
transformer? EG an EL84 on one side and 2 12AX7a's on the other? If it was way
out of balance would I expect the voltage to change? ( I know I should go try
it! Maybe if I get a minute tomorrow... )
| Quote: |
If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
** Yes.
I know that the heat
loss increases,
** Just follows I squared R for primary and secondary.
maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
** Not true and not relevant.
|
OK that's good to know, I remember something about a saturated reactor losing
it's inductance. We used to have special power supplies using them, but they
seem to be out of favor today!
| Quote: |
Saturation can be seen in the distortion of the (sine) input, but would
not be
the same in an overload condition, which would have less distortion but a
lower
power level ?
** Saturation is seen as distorted current in the primary when the applied
voltage is too high or the applied frequency too low. It is most obvious
when the transformer is not loaded or lightly loaded.
It is also obvious when the primary VA ( rms amps x rmse volts) exceeds the
maker's rating while the secondary VA is still comfortably within rating.
Transformers are complicated,
** Not very.
but you seem to be an expert!
** Not at all.
I just don't let the suckers hoodwink me !!
......... Phil
|
Thanks |
|
| Back to top |
|
|
Phil Allison
Guest
|
| Posted:
Wed Nov 09, 2005 5:42 am Post subject:
Re: Hey Phil, about transformers... |
|
|
"Bob"
| Quote: | Hi Phil,
Saturation is caused only by an excessive input voltage, right?
|
** Or lower that designed frequency, the two are quite proportional as
well.
A 20 % increase in voltage has the same effect as a 20 % reduction in
applied frequency.
| Quote: | The amount of
power taken out doesn't relate to saturation?
|
** It does - when the effective primary voltage is reduced by the
secondary load.
Effective primary voltage = AC supply - I x R loss in the primary.
| Quote: | In other words, overloading the
output is not a saturation problem?
|
** Long as the load is symmetrical - ie not half wave.
| Quote: | If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
|
** Yes.
| Quote: | I know that the heat
loss increases,
|
** Just follows I squared R for primary and secondary.
| Quote: | maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
|
** Not true and not relevant.
| Quote: | Saturation can be seen in the distortion of the (sine) input, but would
not be
the same in an overload condition, which would have less distortion but a
lower
power level ?
|
** Saturation is seen as distorted current in the primary when the applied
voltage is too high or the applied frequency too low. It is most obvious
when the transformer is not loaded or lightly loaded.
It is also obvious when the primary VA ( rms amps x rmse volts) exceeds the
maker's rating while the secondary VA is still comfortably within rating.
| Quote: | Transformers are complicated,
|
** Not very.
| Quote: | but you seem to be an expert!
|
** Not at all.
I just don't let the suckers hoodwink me !!
.......... Phil |
|
| Back to top |
|
|
Pooh Bear
Guest
|
| Posted:
Thu Nov 10, 2005 5:42 am Post subject:
Re: Hey Phil, about transformers... |
|
|
Bob wrote:
| Quote: | Hi Phil,
Saturation is caused only by an excessive input voltage, right?
|
Strictly the volt-time figure. This effectively takes into account the input
frequency.
| Quote: | The amount of
power taken out doesn't relate to saturation? In other words, overloading the
output is not a saturation problem?
|
Indeed.
Power output is largely limited in practice by IR losses and the attendant temp
rise ( especially with low loss cores ).
| Quote: | If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
|
No.
| Quote: | I know that the heat
loss increases, maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
|
You're way off the mark here. You seem to have some erroneous ideas.
| Quote: | Saturation can be seen in the distortion of the (sine) input, but would not be
the same in an overload condition, which would have less distortion but a lower
power level ?
|
Uh ?
| Quote: | Transformers are complicated, but you seem to be an expert!
|
I bet he hasn't designed any unlike me !
Graham |
|
| Back to top |
|
|
Phil Allison
Guest
|
| Posted:
Thu Nov 10, 2005 5:42 am Post subject:
Re: Hey Phil, about transformers... |
|
|
That Graham Stevenson MORON makes an Ass of himself - AGAIN !
| Quote: | Bob wrote:
The amount of
power taken out doesn't relate to saturation? In other words, overloading
the
output is not a saturation problem?
Indeed.
Power output is largely limited in practice by IR losses and the attendant
temp
rise ( especially with low loss cores ).
|
** Err - that would be " I squared R " losses.
Core loss is normally small and gets smaller when a full load is applied.
| Quote: | If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
No.
|
** WRONG !!!
Of course it decreases - due to primary IR voltage drop.
| Quote: | Transformers are complicated, but you seem to be an expert!
I bet he hasn't designed any unlike me !
|
** Figured out how a wound toroidal core works yet - FUCKHEAD ????
Its very different from a stacked lamination type.
How pig ignorant can you get.
............ Phil
|
|
| Back to top |
|
|
Bob
Guest
|
| Posted:
Thu Nov 10, 2005 5:42 am Post subject:
Re: Hey Phil, about transformers... |
|
|
On Thu, 10 Nov 2005 01:44:12 +0000, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:
| Quote: |
Bob wrote:
Hi Phil,
Saturation is caused only by an excessive input voltage, right?
Strictly the volt-time figure. This effectively takes into account the input
frequency.
The amount of
power taken out doesn't relate to saturation? In other words, overloading the
output is not a saturation problem?
Indeed.
Power output is largely limited in practice by IR losses and the attendant temp
rise ( especially with low loss cores ).
If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
No.
|
All I know about this is that the secondary current induces a counter EMF that
opposes the primary EMF, so an overload may create a total reduction in the
entire core, since the primary voltage must decrease?
| Quote: |
I know that the heat
loss increases, maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
You're way off the mark here. You seem to have some erroneous ideas.
|
I was going by the idea that L decreases in a saturated core, does it not? If
you measure the L of one winding and then use DC on another winding to saturate
the core, the L decreases... I think!
| Quote: |
Saturation can be seen in the distortion of the (sine) input, but would not be
the same in an overload condition, which would have less distortion but a lower
power level ?
Uh ?
|
Does the waveform of an overloaded transformer have less distortion then a
saturating transformer?
| Quote: |
Transformers are complicated, but you seem to be an expert!
I bet he hasn't designed any unlike me !
|
I just buy them off the shelf, but I like to know what I'm buying!
|
|
| Back to top |
|
|
Patrick Turner
Guest
|
| Posted:
Thu Nov 10, 2005 3:18 pm Post subject:
Re: Hey Phil, about transformers... |
|
|
Bob wrote:
| Quote: | On Thu, 10 Nov 2005 01:44:12 +0000, Pooh Bear
rabbitsfriendsandrelations@hotmail.com> wrote:
Bob wrote:
Hi Phil,
Saturation is caused only by an excessive input voltage, right?
Strictly the volt-time figure. This effectively takes into account the input
frequency.
The amount of
power taken out doesn't relate to saturation? In other words, overloading the
output is not a saturation problem?
Indeed.
Power output is largely limited in practice by IR losses and the attendant temp
rise ( especially with low loss cores ).
If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
No.
All I know about this is that the secondary current induces a counter EMF that
opposes the primary EMF, so an overload may create a total reduction in the
entire core, since the primary voltage must decrease?
|
Well consider that you are one of the many whose knowledge of electro-magnetics
is not as complete as it could be.
Saturation effects and distortion currents can be explored without the presence
of a secondary winding.
So what relevance has the "counter EMF"?
| Quote: |
I know that the heat
loss increases, maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
You're way off the mark here. You seem to have some erroneous ideas.
I was going by the idea that L decreases in a saturated core, does it not? If
you measure the L of one winding and then use DC on another winding to saturate
the core, the L decreases... I think!
|
Forget thinking if it is really guessing.
Examine a tranny with an AC source and a CRO, and a better understanding
of what actually happens should become apparent to you.
| Quote: |
Saturation can be seen in the distortion of the (sine) input, but would not be
the same in an overload condition, which would have less distortion but a lower
power level ?
Uh ?
Does the waveform of an overloaded transformer have less distortion then a
saturating transformer?
|
It depends.
The overloaded non saturating tranny will not have serious V or I distortion
depending on the source impedance.
But the current wave may be seriously distorted in a tranny that is saturated even
without a load.
You need to examinea real tranny with a variac,
If you don't look, yer won't know, my granpa said.
| Quote: |
Transformers are complicated, but you seem to be an expert!
I bet he hasn't designed any unlike me !
I just buy them off the shelf, but I like to know what I'm buying!
|
That's impossible unless you know what to look for.
Patrick Turner.
|
|
| Back to top |
|
|
Phil Allison
Guest
|
| Posted:
Fri Nov 11, 2005 5:43 am Post subject:
Re: Hey Phil, about transformers... |
|
|
"Bob"
| Quote: | But the flux in the core doesn't change appreciably with load.
Again. The flux doesn't really change very much.
|
| Quote: | I'm trying to learn as much as I can!
|
** Then keep away from this Pooh Brain Fuckwit.
The load on a transformer can *dramatically* affect primary current and
core saturation:
I have a 30 VA rated toroidal, as used in a small pro-audio product:
1. With a AC supply of 125 volts and no load it draws 270mA rms.
2. With a 15 watt resistive load the AC draw DROPS to 160mA rms !!!!
3. With a 25 watt resistive load the AC draw comes back to 270mA rms.
Notes:
In the no load case, the current waveform is very peaky.
In the two resistive load cases it is close to a good sine wave.
Conclusions:
With no load, the core was highly saturated.
With a 15 watt load or more the core is clear of saturation.
The maker of the product this transformer is used in has taken full
advantage of the a constant applied load to optimise the transformer.
......... Phil |
|
| Back to top |
|
|
Bob
Guest
|
| Posted:
Fri Nov 11, 2005 5:43 am Post subject:
Re: Hey Phil, about transformers... |
|
|
On Fri, 11 Nov 2005 13:41:40 +1100, "Phil Allison" <philallison@tpg.com.au>
wrote:
| Quote: |
"Bob"
But the flux in the core doesn't change appreciably with load.
Again. The flux doesn't really change very much.
I'm trying to learn as much as I can!
** Then keep away from this Pooh Brain Fuckwit.
The load on a transformer can *dramatically* affect primary current and
core saturation:
I have a 30 VA rated toroidal, as used in a small pro-audio product:
1. With a AC supply of 125 volts and no load it draws 270mA rms.
2. With a 15 watt resistive load the AC draw DROPS to 160mA rms !!!!
3. With a 25 watt resistive load the AC draw comes back to 270mA rms.
Notes:
In the no load case, the current waveform is very peaky.
|
When you say current waveform - do you have a current probe on your scope? I can
borrow one from work I think...
| Quote: | In the two resistive load cases it is close to a good sine wave.
Conclusions:
With no load, the core was highly saturated.
With a 15 watt load or more the core is clear of saturation.
The maker of the product this transformer is used in has taken full
advantage of the a constant applied load to optimise the transformer.
........ Phil
|
So the EMF produced in the secondary affects the primary to the same power level
minus the leakage inductance factor? The primary inductance increases when the
transformer is out of saturation?
Got to hit the books again... can't wait to get my Hammond toroids to play with! |
|
| Back to top |
|
|
Pooh Bear
Guest
|
| Posted:
Fri Nov 11, 2005 5:43 am Post subject:
Re: Hey Phil, about transformers... |
|
|
Phil Allison wrote:
| Quote: | Conclusions:
With no load, the core was highly saturated.
|
Which means it's a poor example to use you fathead.
Bad design isn't an excuse for you to spout rubbish about general theory.
Graham |
|
| Back to top |
|
|
Phil Allison
Guest
|
| Posted:
Fri Nov 11, 2005 5:43 am Post subject:
Re: Hey Phil, about transformers... |
|
|
** Graham Fuckwit Stevenson = pommy MORON and TROLL from HELL
He don't know shit from chocolate about transformers or any damn thing.
........... Phil |
|
| Back to top |
|
|
Bob
Guest
|
| Posted:
Fri Nov 11, 2005 5:43 am Post subject:
Re: Hey Phil, about transformers... |
|
|
On Thu, 10 Nov 2005 09:18:57 GMT, Patrick Turner <info@turneraudio.com.au>
wrote:
| Quote: |
Bob wrote:
On Thu, 10 Nov 2005 01:44:12 +0000, Pooh Bear
rabbitsfriendsandrelations@hotmail.com> wrote:
Bob wrote:
Hi Phil,
Saturation is caused only by an excessive input voltage, right?
Strictly the volt-time figure. This effectively takes into account the input
frequency.
The amount of
power taken out doesn't relate to saturation? In other words, overloading the
output is not a saturation problem?
Indeed.
Power output is largely limited in practice by IR losses and the attendant temp
rise ( especially with low loss cores ).
If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
No.
All I know about this is that the secondary current induces a counter EMF that
opposes the primary EMF, so an overload may create a total reduction in the
entire core, since the primary voltage must decrease?
Well consider that you are one of the many whose knowledge of electro-magnetics
is not as complete as it could be.
Saturation effects and distortion currents can be explored without the presence
of a secondary winding.
So what relevance has the "counter EMF"?
|
That's how transformers work...
| Quote: |
I know that the heat
loss increases, maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
You're way off the mark here. You seem to have some erroneous ideas.
I was going by the idea that L decreases in a saturated core, does it not? If
you measure the L of one winding and then use DC on another winding to saturate
the core, the L decreases... I think!
Forget thinking if it is really guessing.
|
I try not to guess... the above statement is quite true...
| Quote: | Examine a tranny with an AC source and a CRO, and a better understanding
of what actually happens should become apparent to you.
|
I should play around a bit more on the bench...
| Quote: |
Saturation can be seen in the distortion of the (sine) input, but would not be
the same in an overload condition, which would have less distortion but a lower
power level ?
Uh ?
Does the waveform of an overloaded transformer have less distortion then a
saturating transformer?
It depends.
The overloaded non saturating tranny will not have serious V or I distortion
depending on the source impedance.
But the current wave may be seriously distorted in a tranny that is saturated even
without a load.
|
Of course the wave would be distorted in a saturated transformer - but now I
imagine that an overloaded transformer won't have a clipped waveform...
| Quote: | You need to examinea real tranny with a variac,
If you don't look, yer won't know, my granpa said.
Transformers are complicated, but you seem to be an expert!
I bet he hasn't designed any unlike me !
I just buy them off the shelf, but I like to know what I'm buying!
That's impossible unless you know what to look for.
|
I look for voltage and current ratings, then size and price. Now I'm looking for
reduced outside field for use in a guitar combo.
The only testing I've done so far is on 'long term' temperature rise and on
ripple on fully loaded test power supplies. I have a source of surplus
transformers and also tons of scrap, lots of times containing un marked units.
If they have a sufficient weight for the VA I want to pull and a useful voltage,
I test them for use.
I also test various supplies such as doublers and triplers, and also various
caps that I can get. all for their practical use in amps, of which I've already
built a few dozen, some at surprisingly low cost to me!
And as we all know here - it's tons of fun!
And a great chance to increase my knowledge, thanks to all you useful guys!
Bob Flint
Amp builder since 1967
| Quote: | Patrick Turner.
Graham |
|
|
| Back to top |
|
|
Bob
Guest
|
| Posted:
Fri Nov 11, 2005 5:43 am Post subject:
Re: Hey Phil, about transformers... |
|
|
On Fri, 11 Nov 2005 01:11:40 +0000, Pooh Bear
<rabbitsfriendsandrelations@hotmail.com> wrote:
| Quote: |
Bob wrote:
On Thu, 10 Nov 2005 01:44:12 +0000, Pooh Bear
rabbitsfriendsandrelations@hotmail.com> wrote:
Bob wrote:
Hi Phil,
Saturation is caused only by an excessive input voltage, right?
Strictly the volt-time figure. This effectively takes into account the input
frequency.
The amount of
power taken out doesn't relate to saturation? In other words, overloading the
output is not a saturation problem?
Indeed.
Power output is largely limited in practice by IR losses and the attendant temp
rise ( especially with low loss cores ).
If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
No.
All I know about this is that the secondary current induces a counter EMF that
opposes the primary EMF, so an overload may create a total reduction in the
entire core, since the primary voltage must decrease?
No.
The secondary load increases the primary current. You might suppose this increases the
total flux but the two cancel each other out.
I don't know where you got the idea about EMF.
|
Standard handbook of the A.R.R.L.
| Quote: |
I know that the heat
loss increases, maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
You're way off the mark here. You seem to have some erroneous ideas.
I was going by the idea that L decreases in a saturated core, does it not? If
you measure the L of one winding and then use DC on another winding to saturate
the core, the L decreases... I think!
But the flux in the core doesn't change appreciably with load.
What you say about using DC to saturate a core has been used in old lighting controls
btw. See 'saturable reactor'.
|
I know - I work with them. I have one here I want to play with sometime, its
rated 20 amps.
| Quote: |
Saturation can be seen in the distortion of the (sine) input, but would not be
the same in an overload condition, which would have less distortion but a lower
power level ?
Uh ?
Does the waveform of an overloaded transformer have less distortion then a
saturating transformer?
There is not really any such thing as an 'overloaded transfomer' per se. There's one
that's going to burn out long term of course !
Again. The flux doesn't really change very much.
Transformers are complicated, but you seem to be an expert!
I bet he hasn't designed any unlike me !
I just buy them off the shelf, but I like to know what I'm buying!
Most ppl do.
I however have been obliged to learn rather more about them.
Graham
|
I'm trying to learn as much as I can! |
|
| Back to top |
|
|
Pooh Bear
Guest
|
| Posted:
Fri Nov 11, 2005 5:43 am Post subject:
Re: Hey Phil, about transformers... |
|
|
Bob wrote:
| Quote: | On Thu, 10 Nov 2005 01:44:12 +0000, Pooh Bear
rabbitsfriendsandrelations@hotmail.com> wrote:
Bob wrote:
Hi Phil,
Saturation is caused only by an excessive input voltage, right?
Strictly the volt-time figure. This effectively takes into account the input
frequency.
The amount of
power taken out doesn't relate to saturation? In other words, overloading the
output is not a saturation problem?
Indeed.
Power output is largely limited in practice by IR losses and the attendant temp
rise ( especially with low loss cores ).
If you do put too much of a load on a
transformer, does the magnetization in the core decrease?
No.
All I know about this is that the secondary current induces a counter EMF that
opposes the primary EMF, so an overload may create a total reduction in the
entire core, since the primary voltage must decrease?
|
No.
The secondary load increases the primary current. You might suppose this increases the
total flux but the two cancel each other out.
I don't know where you got the idea about EMF.
| Quote: | I know that the heat
loss increases, maybe this has to do with loss of inductance reactance? The
current is more in phase so there is more R loss?
You're way off the mark here. You seem to have some erroneous ideas.
I was going by the idea that L decreases in a saturated core, does it not? If
you measure the L of one winding and then use DC on another winding to saturate
the core, the L decreases... I think!
|
But the flux in the core doesn't change appreciably with load.
What you say about using DC to saturate a core has been used in old lighting controls
btw. See 'saturable reactor'.
| Quote: | Saturation can be seen in the distortion of the (sine) input, but would not be
the same in an overload condition, which would have less distortion but a lower
power level ?
Uh ?
Does the waveform of an overloaded transformer have less distortion then a
saturating transformer?
|
There is not really any such thing as an 'overloaded transfomer' per se. There's one
that's going to burn out long term of course !
Again. The flux doesn't really change very much.
| Quote: | Transformers are complicated, but you seem to be an expert!
I bet he hasn't designed any unlike me !
I just buy them off the shelf, but I like to know what I'm buying!
|
Most ppl do.
I however have been obliged to learn rather more about them.
Graham |
|
| Back to top |
|
|
Phil Allison
Guest
|
| Posted:
Fri Nov 11, 2005 11:45 am Post subject:
Re: Hey Phil, about transformers... |
|
|
"Bob"
| Quote: | When you say current waveform - do you have a current probe on your scope?
|
** All you need is a low value resistor ( 1 ohm or 0.1 ohm ) in series with
AC supply - preferably in the neutral.
Then a small isolation transformer with a 1:1 ratio (or close to that) to
feed the scope with the voltage across the resistor.
I actually use a more elaborate set up with a Hall effect sensor and 3.5
digit true rms amp meter, but started out with just a moving iron amp meter
and a transformer isolated current sense resistor.
BTW
You must have a Variac to get anywhere with transformer testing.
......... Phil |
|
| Back to top |
|
|
|
|
|
|
Profile
Log in to check your private messages
Log in