Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 30th November 2006, 08:38 PM   #1
abj1 is offline abj1  Australia
diyAudio Member
 
Join Date: Jan 2005
Location: Melbourne
Default Full-wave bridge

Quick dumb question: Rectifier spec sheets talk about max RMS voltage per plate for standard full wave setups which is fine but what is the situation with using them with a hybrid (with SS - Graetz bridge?) bridge from say a 300-0-300 traffo - if for argument sake I was to use a 6X5 (with a 350V max spec) as the hollow-state component? Is the max RMS from the centretap to each end (happy to create a bipolar supply if needs be) or from end to end (ie would the RMS seen by the rectifier be 300 or 600V)?
TIA,
Andrew.
  Reply With Quote
Old 30th November 2006, 11:06 PM   #2
diyAudio Member
 
Dave Cigna's Avatar
 
Join Date: Oct 2003
Location: Finger Lakes, NY
In a bridge rectifier (hybrid or not) the 'top' and 'bottom' pairs of diodes work independently in the same way as a FW CT rectifier. If you use a CT in the transformer you'll get a bipolar supply. If you don't use the CT (or there isn't one) then you can think of the two supplies as being stacked on top of each other.

Hope that made sense. The short answer: the 6X5 would see 300 Vrms.
  Reply With Quote
Old 22nd August 2007, 07:13 AM   #3
diyAudio Member
 
Join Date: Aug 2003
Location: Near Rotterdam
Default Hybrid bridge with GZ34

Hello,

The 480 0 480 V connection on my Bartolucci mains transformer W-272 can be used for a hybrid full wave bridge. I have two questions about this as.
a. Can the two 480 V windings simply be wired in parallel so more current can be drawn? As there is only one 0 connection for the two windings (for a traditional CT connection I think) the phase cannot be changed.
b. Can the GZ34 be used as a rectifier? This full wave rectifier accepts 450 0 450 V as a maximum on the plates. I my understanding of the previous posts in this thread the solid state diodes would take half of the 480V. Which would mean that the GZ34 only sees 240 -240 V on the plates. Is this correct?

In the attached picture I have drawn the schematics. I intend to use a choke input filter for optimal current draw (well, with a small input C may be to dampen the voltage peaks a bit).

Can you comment please?

Best, Arjen.
Attached Images
File Type: gif gz34_hybrid.gif (9.1 KB, 365 views)
  Reply With Quote
Old 22nd August 2007, 09:56 AM   #4
diyAudio Moderator Emeritus
 
ray_moth's Avatar
 
Join Date: Jan 2004
Location: Jakarta
No, Arjen, I'm afraid you can't do that. It puts a dead short across the transformer secondary that will destroy it. Even if you could disconnect the center tap and use the two halves in parallel, it wouldn't give you any more current with a bridge rectifier than you could get with a conventional 'full-wave' rectifier using the center tap in the usual way. Don't forget that a bridge rectifier places a load on the winding for 100% of the time, while a 'full wave' rectifier only loads each half of the winding 50% of the time.

The 'full wave' center tap approach is your your best option, IMHO. You can overcome the voltage restriction by using a pair of TV damper diodes instead of the GZ34 and the result could even be less 'noisy'.
  Reply With Quote
Old 22nd August 2007, 10:23 AM   #5
diyAudio Member
 
Join Date: Aug 2003
Location: Near Rotterdam
Hello Ray_moth, others,

Thanks for your clear reply.
I already was afraid the existing wiring would not allow this because of the phase connection.
The transformer is all-epoxy potted, so no rewiring option.

I will use some 12D4 damper diodes with controlled heater warm-up instead with the 'full wave' center tap approach. It will cost another socket and indeed there is the reward of obtaining a less 'noisy' result. They can handle some 155 mA and that will be enough for the application.

For the sake of learning the second question remains relevant: Suppose the transformer would have allowed to rewire the secundairies into the correct phase to use them in parallel in a hybrid bridge rectifier, would the GZ34 see only 240 -240 V on the plates? If so would there be any other risk involved that prevents the use of such a configuration?

Best, Arjen.
  Reply With Quote
Old 22nd August 2007, 01:24 PM   #6
diyAudio Moderator Emeritus
 
ray_moth's Avatar
 
Join Date: Jan 2004
Location: Jakarta
Hi Arjen,

See Dave Cigna's response earlier in the thread. If you have a 480v rms winding then each diode will see 480v rms. A bridge arrangement does not 'share' the voltage between the diodes.
  Reply With Quote
Old 22nd August 2007, 03:22 PM   #7
diyAudio Member
 
Join Date: Aug 2003
Location: Near Rotterdam
Hello Ray-moth,

Thank you for the confirmation.

Best, Arjen.
  Reply With Quote
Old 22nd August 2007, 05:42 PM   #8
diyAudio Member
 
Dave Cigna's Avatar
 
Join Date: Oct 2003
Location: Finger Lakes, NY
Actually, I was wrong in my old post. With both FWCT and bridge rectifiers each diode sees the voltage of the entire winding, from end to end.

But, Ray got it right despite my original mistake; with a 240-0-240 transformer each diode sees 480Vrms.

-- Dave
__________________
January 20, 2009: Bush's last day
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
PSU Question...Full Wave Bridge zxx123 Tubes / Valves 3 25th January 2008 07:04 PM
Full wave vs full wave bridge rectifier jeff mai Parts 31 11th February 2005 11:43 PM
Full Wave Bridge Rectifier Recommendations Please. goskers Solid State 2 5th November 2004 02:30 AM
Anyone interested in some FRED full-wave bridge rectifiers? Maxhawk Solid State 1 15th October 2002 06:36 PM


New To Site? Need Help?

All times are GMT. The time now is 04:03 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2