Isolation transformer wiring - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

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 28th April 2008, 04:24 PM   #1
diyAudio Member
 
Join Date: Oct 2005
Default Isolation transformer wiring

I've purchased a 230V 1000VA isolation transformer. This has a single primary and a single secondary.

See the attached pic.... Should I connect the secondary neutral to ground?
Attached Images
File Type: gif isolation transformer wiring.gif (12.4 KB, 423 views)
  Reply With Quote
Old 29th April 2008, 04:14 AM   #2
diyAudio Member
 
Join Date: Dec 2007
Location: Phoenix, AZ
Hello sharpi, Is the chassis of the component(s) you are plugging into the iso tranny connected to the earth conductor? If so, then connecting the secondary of the iso tranny neutral would be unnecessary. If the component(s) do not have the chassis connected to earth, it would be wise to do so, for your own and others safety. One of the purposes of an isolation transformer is to create a balanced power signal to the component you are powering. This tends to help reduce hum problems. The iso tranny also helps filter out high frequency signals on the AC lines, due to the intrinsic low pass behaviour of a transformer. If you connect one of the legs of the secondary of the transformer to earth, you may actually induce noise into the AC power going into your component(s). Hope this helps.

Peace,

Dave
  Reply With Quote
Old 29th April 2008, 05:25 AM   #3
TheMG is offline TheMG  Canada
diyAudio Member
 
Join Date: Jan 2008
Typically in isolation transformers the GND connects to GND. The secondary of the transformer is left floating.

This is safe, because as the name implies, the isolation transformer isolates the power from the mains, in other words the secondary winding is at a zero voltage potential to ground.

Connecting the GND to the secondary actually defeats most of the purpose of an isolation transformer.
  Reply With Quote
Old 29th April 2008, 07:59 AM   #4
diyAudio Member
 
Join Date: Oct 2005
Thanks for the replies. The attached components will all have earthed cases, so I'll not attach a secondary to ground.
  Reply With Quote
Old 7th May 2008, 08:47 AM   #5
diyAudio Member
 
Join Date: Oct 2005
I installed the isolation transformer with neither secondary connected to ground.

The transformers in both my preamp and power amp have started to buzz - not dramatically, but louder than when connected directly to the mains.

The isolation transformer is a 1000VA (and remains cool during use) so I don't think the problem is a lack of current...

Any ideas?
  Reply With Quote
Old 8th May 2008, 10:07 AM   #6
diyAudio Member
 
Join Date: Oct 2005
Problem solved!

The transformer was not truly 1:1, so my kit was getting 254VAC when the mains was sitting at 242VAC. The high voltage was causing the buzzing.

I swapped primary and secondary windings to make a step down (rather than step up) transformer. Now my kit is getting 230VAC and transformer hum is lower than when the kit is connected directly to the mains.

Sound wise, the addition of the isolation transformer seems to have added some warmth and fine detail. I was worried that running my amp from the transformer would reduce bass power but this hasn't happened - if anything, bass focus and depth has increased.

I guess my 25wpc chip amp doesn't suck too much current so the 1000VA isolation transformer isn't being worked too hard.
  Reply With Quote
Old 8th May 2008, 01:22 PM   #7
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Kona, Hawaii
Blog Entries: 4
Quote:
Originally posted by sharpi31
[B] Now my kit is getting 230VAC and transformer hum is lower than when the kit is connected directly to the mains.
Hey that's cool! The UK has some high mains voltages. I'll bet a lot of gear is happier at 220-230.


Quote:
I guess my 25wpc chip amp doesn't suck too much current so the 1000VA isolation transformer isn't being worked too hard.
Yeah! No doubt !


The balanced power thing became popular in recording studios about 10 years ago. Those guys seemed to love it. Mostly for the lower noise floor.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 8th May 2008, 01:47 PM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by panomaniac
The UK has some high mains voltages. I'll bet a lot of gear is happier at 220-230.
no.
the UK had and still has 240Vac mains power.
It used to be +-6%.
We have been forced to respecify it to conform to the EC requirement of 220/240Vac.
We complied with this by increasing the -ve tolerance to -10%, but without changing our supply voltage.
We are now 216V to 254V, instead of the former 226 to 254Vac. But we are still a nominal 240Vac mains supply.
As far as I know we never deliberately use the 216 to 226Vac range for load shedding. Instead we use frequency to adjust to the load as demand varies.
__________________
regards Andrew T.
  Reply With Quote
Old 9th May 2008, 04:24 AM   #9
Pano is offline Pano  United States
diyAudio Moderator
 
Pano's Avatar
 
Join Date: Oct 2004
Location: Kona, Hawaii
Blog Entries: 4
Thanks Andrew, that's all news to me.

Kinda surprising, the change, as you are an island nation. The EU is not going to force you to give up your big, bulky mains plugs are they?


Back in the old days I saw 245 or even 250 on British mains. Luckily not every day. That had to be pushing some of the gear that was really made for 220V but sold in 240V counties.
__________________
Take the Speaker Voltage Test!
  Reply With Quote
Old 9th May 2008, 08:47 AM   #10
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by panomaniac
Back in the old days I saw 245 or even 250 on British mains. Luckily not every day. That had to be pushing some of the gear that was really made for 220V but sold in 240V counties.
I regularly see 238 to 248Vac on my supply.
The 220/240Vac unified spec is specifically there to ensure manufacturers build equipment that is safely capable of operating properly over the full range of available voltage.
__________________
regards Andrew T.
  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
isolation transformer atmars Tubes / Valves 4 31st May 2008 01:24 AM
Wiring a Step Down Transformer for Isolation ak_47_boy Power Supplies 6 24th June 2007 05:35 PM
Ground isolation network / power switch wiring DcibeL Power Supplies 2 5th April 2006 01:43 AM
transformer isolation dmitriy167 Solid State 24 2nd March 2005 04:01 AM
Isolation Transformer HarryHaller Solid State 9 5th August 2002 01:30 PM


New To Site? Need Help?

All times are GMT. The time now is 05:37 PM.


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