[Amps] Isolation Transformer

[Dr. David Kirkby]

David C. Hallam wrote:
> I recently picked up a medical grade 3KVA toroidal isolation 
> transformer.  It has dual primaries and secondaries so in addition to 
> being a isolation transformer it can be used as a step up/down 
> transformer.  I had two ideas in mind.  One was to use it as a 1:1 
> isolation transformer when working on radios with a hot chassis.  The 
> other was to use it as a 2:1 step down transformer for a linear map I 
> have with a 120V primary transformer.  This thing draws too much current 
> to use on 120V unless you have a special dedicated line.  With this 
> transformer I could step down a 240V line to 120V.  Since this is an 
> isolation transformer, I am assuming I would need to have a direct 
> ground connection for the amp.  I am I correct or is something else needed?
> 
> David
> KW4DH


Virtually all transformers sold today are isolation transformers, in that they 
do provide isolation between primary and secondary. An 'auto-transformer' does 
not, but they are quite rare beasts. So for your purposes, this is nothing 
more/less than the typical transformer you are used to.

A medical grade isolation transformer has a very high degree of isolation - 
above that typically provided by a normal transformer. It will provide several 
kV is isolation, and have little leakage current (down in the uA if I recall 
correctly).

To use as 240 to 120 stepdown, just connect the earth of the incoming power to 
the earth of the amplifier.

As for a hot chassis, I could potentially see some use, but I'd avoid them, and 
prefer not to comment any more on that issue.

Dave