Re: Transformer question - over volting

• To: tesla-at-pupman-dot-com
• Subject: Re: Transformer question - over volting
• From: NickandSim-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
• Date: Tue, 27 Jul 1999 20:17:43 -0600
• Approved: twftesla-at-uswest-dot-net
• Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi All,
         recently there have been several posts about running 120V 
transformers or variacs off 240V and I would like to make a point here.  
A transformer can take a certain number of volts per turn at a give power 
level.  For different input voltages you wind a different number of primary 
turns.  If you over volt it the power input you are trying to put through that 
core is way above what the core can take saturating the core, the saturated 
core sinks a huge amount of power from the mains which completely destroys 
the primary windings and probably melts the secondary as well.
A transformer can be run below its rated input voltage but *never* above by 
more than 10% or so. If you do try to run a transformer above it rated 
voltage by much you are guaranteed to let the smoke free in big way.  
You can very easily and cheaply buy conversion auto transformers to step up 
or down between 240V and 120V, If anyone in the UK needs one I have pair of 
these rated at about 600VA which I will sell for about £10 each.  Most 
variacs also have a 120V and 240V tap to allow them to be used to step up or 
down between these *and* provide variable voltage output at the same time.  

Keeping the smoke in in GB
Nick Field

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