Question about autotransformer ( 230V to 115V ) - diyAudio
Go Back   Home > Forums > Amplifiers > Power Supplies

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 31st May 2007, 11:17 AM   #1
hates ground loops
diyAudio Member
 
Rodeodave's Avatar
 
Join Date: Dec 2004
Location: in the alps
Blog Entries: 1
Default Question about autotransformer ( 230V to 115V )

Hi everyone,

I've go a question concerning an autotransformer which I want to use to convert 230V 50Hz AC to 115V 50Hz AC. I'll be using it to power a friend's Hello Kitty toaster (don't laugh) that was bought in the US. The mains here in Europe are 230V50Hz...I'm not concerned about the frequency nor the missing galvanic isolation from the mains voltage (provided that the autotransformer is wired correctly, the voltage taken from the bottom up, it should be ok). I assume that toasters don't count or require mains isolation...

Well, the toaster is said to consume 850W so I bought an 800W autotransformer (2:1, Siemens, 17 Euros), which hopefully will do the job.

My question is: Besides a switch, a fuse (230V4A slow blow @ mains in), a X2 capacitor (1uF, also @ mains in) and the wiring from them mains and to the toaster, do I need anything else to get this toaster toasting?

I'm asking because the guy who sold it to me via some internet-online-thingy said something about some diode I'd have to use but I've never heard of/seen/used such a thing along with an autotransformer. He sent some diode (metal case and the dimensions a little smaller than 1N5407, but can't read what is printed on it) but won't respond to any question.

Thanks for reading, Dave
__________________
Gravity - Making the G since 13.7 billion B.C.
  Reply With Quote
Old 31st May 2007, 11:52 AM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
I don't know what the diode is for.
The toaster will run at 800W continuously.
You may find that the autotransformer runs more than warm when loaded like this. The saving is that toasters only get used for minutes at a time (unless you run a B&B/hotel).

Consider the possibility of having to go to 1.5kVA.
__________________
regards Andrew T.
  Reply With Quote
Old 31st May 2007, 12:14 PM   #3
paulb is offline paulb  Canada
diyAudio Member
 
Join Date: Jun 2001
Location: Calgary
Maybe you can toast more bread on the transformer while it's running the toaster.
  Reply With Quote
Old 31st May 2007, 02:44 PM   #4
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva


In the good old days, a series diode was employed to get 110V RMS out of 220V AC mains. This works only for very simple loads like incendescent lamps and resistive heaters, though. Note that this is a really nasty practice because DC is effectively drawn from the mains line and a DC offset is created that leads to all kind of trouble with transformers and inverters.

There are other non-harmful ways to power 110V resistive loads from 230V mains without transformers, like a triac based circuit skipping every other mains cycle (power level may be further adjusted by changing the cycle skip ratio...)
__________________
I use to feel like the small child in The Emperor's New Clothes tale
  Reply With Quote
Old 4th June 2007, 12:42 PM   #5
hates ground loops
diyAudio Member
 
Rodeodave's Avatar
 
Join Date: Dec 2004
Location: in the alps
Blog Entries: 1
Quote:
Originally posted by Eva


In the good old days, a series diode was employed to get 110V RMS out of 220V AC mains.
Wow, that's really nasty.

I finished the autotransformer-project and tested it successfully. I included a fuse (4A slowblow), a switch, a thermal fuse (117C) and a X2 cap. The autotransformer hums a bit but does not run hot at all. Like I said, the autotransformer is rated @ 800W, the toaster's bottom-print sez it consumes 850W. Hmm...

Thank you all for your replies. I'll post some pics later.

C ya, Dave
__________________
Gravity - Making the G since 13.7 billion B.C.
  Reply With Quote
Old 4th June 2007, 02:11 PM   #6
diyAudio Member
 
megajocke's Avatar
 
Join Date: Jan 2003
I don't think you are going to have any problems with 5% overload for a intermittent duty load like your toaster Some transformers can take like 100% overload for several minutes due to high thermal mass... So 5% is nothing. Maybe if your hobby is toasting bread all day long it will start to complain
  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
Help Convert Bryston BP-20 PS from 230v to 115v ainami Solid State 5 12th December 2008 07:01 AM
115v conversion fro 230V Cambridge Audio CD4 and Dacmagic 2i taskerc Digital Source 4 7th February 2006 08:02 PM
Transformer hook-up question to 115V AC line Joseph0 Tubes / Valves 10 19th August 2005 03:00 PM
Looking for 230V >1KVA variac and 230V-230V mains isolation transformer offers Eva Swap Meet 1 28th July 2005 04:00 PM


New To Site? Need Help?

All times are GMT. The time now is 10:04 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