Reply
 
Thread Tools Display Modes
  #1   Report Post  
Tube747
 
Posts: n/a
Default Question about Low DCR power transformer for filament supply

Hello RATS!
I am looking for a low DCR power transformer for filament supply of rectifier
tube because some one told me that the low DCR power transformer the better
regulation it is.

I want to use the 6D22S rectifier tube (2 for full wave rectification).
Therefore, the power transformer for the filament of this tube is going to be
6.3V 4A, will it be ok?

Each 6D22S with the heater spec. 6.3V 0.9A.

Also, if I order a power transformer which has a lowest possible DCR on the
secondary winding with centre tap and lowest possible ACR on the primary
winding, will it be damage the tube (6D22S)?

I saw a transformer like that from my friend's place for the 6D22S which look
like a 300VA transformer and quite heavy as a filament transformer for only
6.3V @ 4A. Any problem if using such as transformer with the rectifier tube
like 6D22S?

Thanks!


  #2   Report Post  
Fred Nachbaur
 
Posts: n/a
Default

Tube747 wrote:
Hello RATS!
I am looking for a low DCR power transformer for filament supply of rectifier
tube because some one told me that the low DCR power transformer the better
regulation it is.

I want to use the 6D22S rectifier tube (2 for full wave rectification).
Therefore, the power transformer for the filament of this tube is going to be
6.3V 4A, will it be ok?

Each 6D22S with the heater spec. 6.3V 0.9A.

Also, if I order a power transformer which has a lowest possible DCR on the
secondary winding with centre tap and lowest possible ACR on the primary
winding, will it be damage the tube (6D22S)?

I saw a transformer like that from my friend's place for the 6D22S which look
like a 300VA transformer and quite heavy as a filament transformer for only
6.3V @ 4A. Any problem if using such as transformer with the rectifier tube
like 6D22S?

Thanks!


The DC resistance of a filament winding has very little to do with
anything, at least directly. Since the load is essentially constant,
there's no real concern about "regulation" of a filament transformer.

By choosing a transformer that has the correct voltage at the rated
current, you will automatically take into account DC resistance and
other transformer losses. If you choose a transformer with a far higher
rated current than what you actually need, your voltage will tend to be
higher. For 6.3 volts at 1.8 amperes a 4A transformer would be more than
adequate, the voltage might be a bit higher than ideal, but if you get
one from a reputable manufacturer it shouldn't exceed the tubes' rating.

On the other hand, the DC resistance of the plate winding (HT winding)
can play an important part in determining final output voltage,
regulation, and even the maximum safe input capacitance of the filter
network. The effects of this are easy to simulate using a program like
Duncan Munro's "PSU Designer II".

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

  #3   Report Post  
Ronald
 
Posts: n/a
Default

6.3V should have rang the bell .... It's indirect heated , so forget about
my argument !!
So it's a heater supply , not a fiament supply !!!

Ronald .

"Ronald" schreef in bericht
...
I would use a 12.6V 0.9A and take the CT between the tubes , not on the
tranny .
Gives a cleaner sound since the trash from the mains get less chance

.......

"Mikkel C. Simonsen" schreef in bericht
...
Tube747 wrote:

Hello RATS!
I am looking for a low DCR power transformer for filament supply of
rectifier tube because some one told me that the low DCR power
transformer the better regulation it is.


I would say that regulation is a non-issue here. The load is constant so
regulation doesn't matter.

I want to use the 6D22S rectifier tube (2 for full wave
rectification). Therefore, the power transformer for the filament of
this tube is going to be 6.3V 4A, will it be ok?


Yes, probably. What you need is a transformer that will supply the tubes
with 6.3V with a 1.8A load. It doesn't really matter if the transformer
has a 2A or 200A rating as long as the voltage is correct at 1.8A.

I would get a 3 or 4A transformer.

Best regards,

Mikkel C. Simonsen





  #4   Report Post  
Mikkel C. Simonsen
 
Posts: n/a
Default

Ronald wrote:

6.3V should have rang the bell .... It's indirect heated,
so forget about my argument !!
So it's a heater supply , not a fiament supply !!!


It seems a lot of people don't know the difference between a heater and
a filament... ;-)

Best regards,

Mikkel C. Simonsen
  #5   Report Post  
FC5687
 
Posts: n/a
Default

Each 6D22S with the heater spec. 6.3V 0.9A.

Sorry I make a mistake, the tube has a heater spec. 6.3V 1.9A, not 0.9A!


  #6   Report Post  
FC5687
 
Posts: n/a
Default

On the other hand, the DC resistance of the plate winding (HT winding)
can play an important part in determining final output voltage,
regulation, and even the maximum safe input capacitance of the filter
network. The effects of this are easy to simulate using a program like
Duncan Munro's "PSU Designer II".


Hi Fred!
If I order a power transformer for the HT supply with a low DCR on the
secondary winding, is it necessary to have a low "ACR" on the primary winding?

Cheers,
Tube747
  #7   Report Post  
Fred Nachbaur
 
Posts: n/a
Default



FC5687 wrote:
On the other hand, the DC resistance of the plate winding (HT winding)
can play an important part in determining final output voltage,
regulation, and even the maximum safe input capacitance of the filter
network. The effects of this are easy to simulate using a program like
Duncan Munro's "PSU Designer II".



Hi Fred!
If I order a power transformer for the HT supply with a low DCR on the
secondary winding, is it necessary to have a low "ACR" on the primary winding?

Cheers,
Tube747


No, you don't need to worry about it. As far as your circuit is
concerned, you can lump the primary and secondary DCR's, as well as all
other losses, into a single equivalent resistance on the secondary side.
In other words: Measure open-circuit voltage, then put a reasonable load
onto it and measure the loaded voltage. Subtract loaded voltage from
open-circuit voltage, and divide by load current. This gives the
effective series resistance on the secondary side, which is the value
you'd put into your simulator.

Transformers are usually rated in terms of output voltage at a given
maximum current. It's very rare that a manufacturer would bother
publishing the DC resistances, and other loss factors, because it would
not be meaningful to very many end users.

The thing you have to watch out for, that trips up a lot of people
building power supplies, is that the DC current you can get out of a
transformer (using a capacitor-input filter) is somewhat less than the
maximum rated AC current. This is because of the high current spikes
required to recharge the capacitor; since power and therefore heating is
proportional to the square of the current, there will be a lot more loss
during these high-current spikes.

I stay with reasonable input capacitor values (usually around 100 uF)
and choose a transformer with 50% higher rating than the DC current I'll
be drawing, so far that rule of thumb has always worked out. However, if
I'm using Hammond transformers, I'll push them closer to the limit
because they are more conservatively rated.

Cheers,
Fred
--
+--------------------------------------------+
| Music: http://www3.telus.net/dogstarmusic/ |
| Projects, Vacuum Tubes & other stuff: |
| http://www.dogstar.dantimax.dk |
+--------------------------------------------+

  #8   Report Post  
Mikkel C. Simonsen
 
Posts: n/a
Default

Fred Nachbaur wrote:

I stay with reasonable input capacitor values (usually around 100 uF)
and choose a transformer with 50% higher rating than the DC current I'll
be drawing, so far that rule of thumb has always worked out. However, if
I'm using Hammond transformers, I'll push them closer to the limit
because they are more conservatively rated.


As far as I remember the current ratings on Hammond transformers (at
least the plate winding) are DC ratings based on a cap input filter.

Best regards,

Mikkel C. Simonsen
  #9   Report Post  
Tube747
 
Posts: n/a
Default

No, you don't need to worry about it. As far as your circuit is
concerned, you can lump the primary and secondary DCR's, as well as all
other losses, into a single equivalent resistance on the secondary side.
In other words: Measure open-circuit voltage, then put a reasonable load
onto it and measure the loaded voltage. Subtract loaded voltage from
open-circuit voltage, and divide by load current. This gives the
effective series resistance on the secondary side, which is the value
you'd put into your simulator.


Are you meaning that the ACR is not what I concern as long as power transformer
goes and DCR on the secondary winding is what I need to pay attention on?

Transformers are usually rated in terms of output voltage at a given
maximum current. It's very rare that a manufacturer would bother
publishing the DC resistances, and other loss factors, because it would
not be meaningful to very many end users.

The thing you have to watch out for, that trips up a lot of people
building power supplies, is that the DC current you can get out of a
transformer (using a capacitor-input filter) is somewhat less than the
maximum rated AC current. This is because of the high current spikes
required to recharge the capacitor; since power and therefore heating is
proportional to the square of the current, there will be a lot more loss
during these high-current spikes.

I stay with reasonable input capacitor values (usually around 100 uF)
and choose a transformer with 50% higher rating than the DC current I'll
be drawing, so far that rule of thumb has always worked out. However, if
I'm using Hammond transformers, I'll push them closer to the limit
because they are more conservatively rated.


I am currently using tube rectification and choke input right after the power
transformer in seqeunce. Therefore, do I have to worry about the rectifier tube
damage by inrush current due to the power transformer with low DCR on the
secondary winding?


Thanks again!


Cheers,
Fred



Reply
Thread Tools
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
here is how firewire ports fail George Pro Audio 13 September 11th 04 09:11 PM
Power conditioner or power cord or something else chord Audio Opinions 13 July 19th 04 08:09 AM
System warm-up James Harris Audio Opinions 69 May 19th 04 04:09 AM
rec.audio.car FAQ (Part 2/5) Ian D. Bjorhovde Car Audio 0 March 6th 04 07:54 AM
FS: SOUNDSTREAM CLOSEOUTS AND MORE!! Nexxon Car Audio 0 November 21st 03 03:59 AM


All times are GMT +1. The time now is 09:19 PM.

Powered by: vBulletin
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AudioBanter.com.
The comments are property of their posters.
 

About Us

"It's about Audio and hi-fi"