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
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