# Re: NST's in parallel

Original poster: "Christoph Bohr" <cb@xxxxxxxxxxxxxxx>

Hello Drake.

> All i know is that you connect the cases together and
> connect the positive and negative leads together (there's probably
> more to it than that).

Only a bit more, the phasing of the transformers must be right
so that the currents add to each other... this can be found by trial and
error easily. Just connect all primarys and one side of the secondary.
move the other two secondary wires closely together and switch on.
There should be no arcing between the two. If there isn't just connect
the wires, if there is, reverse polarity.

>  Also it has been said that it is best if the
> NSTs are the same voltage,
Very important or the transformers will exchange currents between
themselves. Its not that everything will burst into flames within seconds,
but can destroy transformers. Minimal differences are inevitable even
with two identical transformers and can be tolerated.

> amperage,
no, same Voltage, different amerage will work, each xformer just adds
its share it is able to supply. Though this is physically not entirely correct
it will work for our use.

> brand name
not at all neccessarry, but nice to have.

>> to wire up some NSTs in parallel with different voltage and amperage
>> ratings?  If so how would you calculate the total wattage?
Physically there might be a solution to this, but unless you are looking for
an HV-bonfire only use identical voltages. However, you could  reduce
the voltage of the bigger transformer with a variac until it matches the
smaller ones voltage... but I fear that might result in phasing problems.

> about the same voltage/amperage transformers but different brands?
usually no problem. It is helpfull if you can measure the real voltage as
it might differ more or less from the nameplate rating.

best regards

Christoph Bohr