In article ,
Randy or Sherry Guttery wrote:

Ken wrote:

So, what is the design method for a transformer that saturates easily?

Without getting into a bunch of formulae, etc. (which I'd probably screw
up anyway)... a couple of factors - 1) absolute minimum core to couple
the windings - i.e. magnetically "starved". 2) no gaps in the core - let
the DC current's field circulate well - such that it "interferes" with
the AC field. The core can only hold so much flux - if DC is "pushing"
the field one way -- the AC (when it opposes) is only going to "reduce"
it - not reverse it - (or not fully reverse it) so that the coupling
becomes very inefficient. If you look at most output transformers
designed for single-ended use - they have a gap in the core somewhere.
Obviously - such a gap would not be appropriate for a saturable reactor.

And that sets me pondering again whether the primary "effect" is bucking
or just reactance... Let's say for the moment that bucking is not the
primary mode - and reactance is. Then why the reversed phasing (if
bucking isn't a factor)?

Well - as I just noted - in a true saturable reactor - the DC flux
"overwhelms" the AC flux. Since the AC and DC are additive half the
time - and subtractive half the time - the control isn't going to be
symmetrical. This is overcome in "the real world" by twin reactors -
with the DC "reversed" through one (compared to the other). This way
the "offset" in one reactor is "countered" by the other --- and then
they "switch roles" when the AC reverses polarity. If you look at the
circuit here - (and again - for discussion sake totally ignore bucking)
- the AC is "reversed" all the time at one end - or the other of the
primary -- as the two coils are phase reversed.

Back to saturable reactor theory - when the DC control winding drives
the core into saturation - the reactance in the AC winding drops
dramatically. That being the case with this circuit - then the two
windings would 1) loose coupling so bucking is no longer a factor - and
2) have virtually no reactance in series with the bulb. Then by 1/2 the
AC "reactance winding" reversed - both halves would contribute their
part to the overall source impedance - providing better symmetry.

Now I'm not so sure that pure reactance doesn't play a larger role than
originally thought... That perhaps control is indeed more reactance -
and "bucking" is just a happy "bonus" to the equation...

Is one or the other really necessarily a "bonus", don't they work in
opposite directions assuming the two windings are connected in a
"bucking" configuration? Of course we don't actually know they are
really connected in a "bucking" configuration, we are just speculating
they are because of the way the schematic is drawn.

without taking some measurements (esp. being able to Un-reverse phase
the two windings) - it's hard to guess...

I'm glad you are the one working all this out, I would like to see more
information on the construction of the transformer and the disposition
of the windings before speculating too much. If the transformer is of
open frame construction and is not potted, the OP should be able to
easily determine if an E-core is used and if all the windings are on the
center leg?


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

John Byrns wrote:

Is one or the other really necessarily a "bonus", don't they work in
opposite directions assuming the two windings are connected in a
"bucking" configuration?

No - because "bucking" would be dependent on good coupling... Which
happens when the core is NOT saturated - so saturated - not bucking -
bright.

Reactance drops when saturated - so saturated - low reactance - bright.


Of course we don't actually know they are
really connected in a "bucking" configuration, we are just speculating
they are because of the way the schematic is drawn.

I'd be VERY surprised if they are not... 1) why have two windings if
"bucking" (or as I speculated previously -- phase reversal to provide
symmetry) was not needed? 2) why take the extra effort to draw the
schematic that way?

I'm glad you are the one working all this out, I would like to see more
information on the construction of the transformer and the disposition
of the windings before speculating too much. If the transformer is of
open frame construction and is not potted, the OP should be able to
easily determine if an E-core is used and if all the windings are on the
center leg?

Since I don't have "hands on" access - I am left with few options: 1)
guess. 2) offer to see if I can fix the thing. (did I really say that???).

The thing that bothers me about that is if the laminations (assuming
(that dangerous word!) traditional construction) are welded... it might
be extremely tough to get it apart to get at the bobbins... Yes
pictures worth 1K words...

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

In article ,
Randy or Sherry Guttery wrote:

John Byrns wrote:

Is one or the other really necessarily a "bonus", don't they work in
opposite directions assuming the two windings are connected in a
"bucking" configuration?

No - because "bucking" would be dependent on good coupling... Which
happens when the core is NOT saturated - so saturated - not bucking -
bright.

OK, I see we are going in opposite directions on the coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings. When the transformer becomes saturated decreasing the
coupling, the brightness would have nowhere to go but down due the
residual inductance remaining in the two coils.

So coupling drops when saturated - so saturated - low coupling - dim

This works against the reactance effect you describe below.

Reactance drops when saturated - so saturated - low reactance - bright.

News Flash, I am really liking the theory I advanced a few messages ago
that the "transformer" is not wound like an ordinary transformer, but
instead has one of the secondaries wound on each outside leg of the
E-core.

The reason I am really liking this theory now is that I looked up the
service data for the General Electric E-155 which has the similar
Colorama tuning system, and the "transformer" is constructed exactly as
I speculated in my earlier message. If the S-W "transformer" is built
the same way then it is a whole new ball game.

Of course we don't actually know they are
really connected in a "bucking" configuration, we are just speculating
they are because of the way the schematic is drawn.

I'd be VERY surprised if they are not... 1) why have two windings if
"bucking" (or as I speculated previously -- phase reversal to provide
symmetry) was not needed? 2) why take the extra effort to draw the
schematic that way?

See above.

I'm glad you are the one working all this out, I would like to see more
information on the construction of the transformer and the disposition
of the windings before speculating too much. If the transformer is of
open frame construction and is not potted, the OP should be able to
easily determine if an E-core is used and if all the windings are on the
center leg?

Since I don't have "hands on" access - I am left with few options: 1)
guess. 2) offer to see if I can fix the thing. (did I really say that???).

The thing that bothers me about that is if the laminations (assuming
(that dangerous word!) traditional construction) are welded... it might
be extremely tough to get it apart to get at the bobbins... Yes
pictures worth 1K words...

I have seen several posts in rec.antiques.radio+phono over the years
from people who have rewound the GE "transformers", although I don't
remember who they were from.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

Hi,
John wrote:

I have seen several posts in rec.antiques.radio+phono over the years
from people who have rewound the GE "transformers", although I don't
remember who they were from.

I made some functional equivalents, using modern Arnold tape-wound
cores. Photos, and probably some explanation, were posted on the
Forum at antiqueradios.com, but I can't easily locate them now. It
was several years ago. I still have some of the cores, if I can find
them.

Alan

John Byrns wrote:
In article ,
Randy or Sherry Guttery wrote:

John Byrns wrote:

Is one or the other really necessarily a "bonus", don't they work in
opposite directions assuming the two windings are connected in a
"bucking" configuration?
No - because "bucking" would be dependent on good coupling... Which
happens when the core is NOT saturated - so saturated - not bucking -
bright.

OK, I see we are going in opposite directions on the coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings. When the transformer becomes saturated decreasing the
coupling, the brightness would have nowhere to go but down due the
residual inductance remaining in the two coils.

So coupling drops when saturated - so saturated - low coupling - dim

This works against the reactance effect you describe below.

Reactance drops when saturated - so saturated - low reactance - bright.

News Flash, I am really liking the theory I advanced a few messages ago
that the "transformer" is not wound like an ordinary transformer, but
instead has one of the secondaries wound on each outside leg of the
E-core.

The reason I am really liking this theory now is that I looked up the
service data for the General Electric E-155 which has the similar
Colorama tuning system, and the "transformer" is constructed exactly as
I speculated in my earlier message. If the S-W "transformer" is built
the same way then it is a whole new ball game.

Of course we don't actually know they are
really connected in a "bucking" configuration, we are just speculating
they are because of the way the schematic is drawn.
I'd be VERY surprised if they are not... 1) why have two windings if
"bucking" (or as I speculated previously -- phase reversal to provide
symmetry) was not needed? 2) why take the extra effort to draw the
schematic that way?

See above.

I'm glad you are the one working all this out, I would like to see more
information on the construction of the transformer and the disposition
of the windings before speculating too much. If the transformer is of
open frame construction and is not potted, the OP should be able to
easily determine if an E-core is used and if all the windings are on the
center leg?
Since I don't have "hands on" access - I am left with few options: 1)
guess. 2) offer to see if I can fix the thing. (did I really say that???).

The thing that bothers me about that is if the laminations (assuming
(that dangerous word!) traditional construction) are welded... it might
be extremely tough to get it apart to get at the bobbins... Yes
pictures worth 1K words...

I have seen several posts in rec.antiques.radio+phono over the years
from people who have rewound the GE "transformers", although I don't
remember who they were from.


Regards,

John Byrns

Byrns wrote: OK, I see we are going in opposite directions on the
coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings.

NO. If the coupling were perfect, the light would be dim because the two
windings are bucking their max., preventing current flow to the lamp. Ken

In article , Ken
wrote:

John Byrns wrote:
In article ,
Randy or Sherry Guttery wrote:

John Byrns wrote:

Is one or the other really necessarily a "bonus", don't they work in
opposite directions assuming the two windings are connected in a
"bucking" configuration?
No - because "bucking" would be dependent on good coupling... Which
happens when the core is NOT saturated - so saturated - not bucking -
bright.

OK, I see we are going in opposite directions on the coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings. When the transformer becomes saturated decreasing the
coupling, the brightness would have nowhere to go but down due the
residual inductance remaining in the two coils.

So coupling drops when saturated - so saturated - low coupling - dim

This works against the reactance effect you describe below.

Reactance drops when saturated - so saturated - low reactance - bright.

News Flash, I am really liking the theory I advanced a few messages ago
that the "transformer" is not wound like an ordinary transformer, but
instead has one of the secondaries wound on each outside leg of the
E-core.

The reason I am really liking this theory now is that I looked up the
service data for the General Electric E-155 which has the similar
Colorama tuning system, and the "transformer" is constructed exactly as
I speculated in my earlier message. If the S-W "transformer" is built
the same way then it is a whole new ball game.

Of course we don't actually know they are
really connected in a "bucking" configuration, we are just speculating
they are because of the way the schematic is drawn.
I'd be VERY surprised if they are not... 1) why have two windings if
"bucking" (or as I speculated previously -- phase reversal to provide
symmetry) was not needed? 2) why take the extra effort to draw the
schematic that way?

See above.

I'm glad you are the one working all this out, I would like to see more
information on the construction of the transformer and the disposition
of the windings before speculating too much. If the transformer is of
open frame construction and is not potted, the OP should be able to
easily determine if an E-core is used and if all the windings are on the
center leg?
Since I don't have "hands on" access - I am left with few options: 1)
guess. 2) offer to see if I can fix the thing. (did I really say that???).

The thing that bothers me about that is if the laminations (assuming
(that dangerous word!) traditional construction) are welded... it might
be extremely tough to get it apart to get at the bobbins... Yes
pictures worth 1K words...

I have seen several posts in rec.antiques.radio+phono over the years
from people who have rewound the GE "transformers", although I don't
remember who they were from.


Regards,

John Byrns

Byrns wrote: OK, I see we are going in opposite directions on the
coupling effect.
If the coupling were perfect when the core is not saturated, then the
light would be as bright as it could get due to the bucking effect of
the two windings.

NO. If the coupling were perfect, the light would be dim because the two
windings are bucking their max., preventing current flow to the lamp. Ken

NO, assuming there is no saturation in the core and the coupling is
perfect the reactance of the two windings connected to "buck" would be
very low and the light would be bright, if they are connected to aid
then the total reactance would be four times the reactance of a single
winding and the light would be dim. When we are talking about "perfect"
coupling we are simply talking about a choke with two windings and
considering what the reactance the two series connected windings would
be with the two possible phasing connections.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

John Byrns wrote:

NO, assuming there is no saturation in the core and the coupling is
perfect the reactance of the two windings connected to "buck" would be
very low and the light would be bright, if they are connected to aid
then the total reactance would be four times the reactance of a single
winding and the light would be dim. When we are talking about "perfect"
coupling we are simply talking about a choke with two windings and
considering what the reactance the two series connected windings would
be with the two possible phasing connections.

Now you've lost me - if there is no saturation - then reactance is max -
regardless of "phasing"... particularly in a three-legged config. (where
coupling is insignificant). The only effect phasing would have would be
symmetrical control - and particularly with an E config. cancellation of
the induced AC field before it combines with (to aid or buck) the
control field.

What am I missing?????

best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

In article ,
Randy or Sherry Guttery wrote:

John Byrns wrote:

NO, assuming there is no saturation in the core and the coupling is
perfect the reactance of the two windings connected to "buck" would be
very low and the light would be bright, if they are connected to aid
then the total reactance would be four times the reactance of a single
winding and the light would be dim. When we are talking about "perfect"
coupling we are simply talking about a choke with two windings and
considering what the reactance the two series connected windings would
be with the two possible phasing connections.

Now you've lost me - if there is no saturation - then reactance is max -
regardless of "phasing"... particularly in a three-legged config. (where
coupling is insignificant). The only effect phasing would have would be
symmetrical control - and particularly with an E config. cancellation of
the induced AC field before it combines with (to aid or buck) the
control field.

What am I missing?????

Notice I said "When we are talking about 'perfect' coupling we are
simply talking about a choke with two windings and considering what the
reactance the two series connected windings would be with the two
possible phasing connections." The "perfect" coupling in this example
implies that all three windings are are on the center leg of the core,
and with the primary disconnected we have a simple choke with two equal
windings. Assuming the choke is perfect, the inductance is zero when
the two coils are connected in the series "bucking" configuration, and
is four times the inductance of one winding when they are connected in
series aiding. You can prove this by either measuring a two winding
choke, or by writing the loop voltage equations for both configurations.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/

In article ,
says...



Hi John ... well you found him ... actually a friend of mine had them
wound ... for his E-155 and my E-155 and a few spare parts ... and yes
my buddy Kim Herron has a couple cores rewound that are left... he had
the transformer company in Grand Rapids, Michigan rewind them for us..

and yes its a 3 winding arrangement... nothing like a normal transformer..
so do you have your iron core?

John k9uwa


I have seen several posts in rec.antiques.radio+phono over the years
from people who have rewound the GE "transformers", although I don't
remember who they were from.
John Byrns

In article 3Njai.154612$_c5.5197@attbi_s22,
TUFF (John Goller, k9uwa) wrote:

In article ,
says...

Hi John ... well you found him ... actually a friend of mine had them
wound ... for his E-155 and my E-155 and a few spare parts ... and yes
my buddy Kim Herron has a couple cores rewound that are left... he had
the transformer company in Grand Rapids, Michigan rewind them for us..

and yes its a 3 winding arrangement... nothing like a normal transformer..
so do you have your iron core?

Hi John,

It's not my radio, Randy and I were simply discussing over on
alt.binaries.pictures.radio how the "Stewart-Warner reactance dimmer"
might actually work. This discussion is the result of a post by "Dave
Burson" on alt.binaries.pictures.radio who has a S-W model R-1822 with
an open primary on the reactance control "transformer". I cross posted
the discussion here because I remembered that someone here had talked
about fixing a similar problem on a GE set before. Dave hasn't
responded yet with any information on the physical construction of the
S-W "transformer", whether it's construction is similar to the GE
"transformer" or is different.


Regards,

John Byrns

--
Surf my web pages at, http://fmamradios.com/