Hello again,
Hero:
That is interesting because i wouldnt have dreamed you would have
been talking about transformers that are exactly the same after this
question had been posted:
We derailed a bit in the thread, let's start over:
What will the effects be if two different transformers are placed in parallel with two different ratings (one has a bit more or a bit less winding ratio than the other)?
Freakazo:
The resistance of a transformer can be measured with an ohm meter
if the resistance is high enough, or with a current and use Ohms Law.
After measuring both primary and secondary the two resistances
can be added together after reflecting either the secondary resistance
to the primary or the primary to the secondary. The reflected resistance
is proportional to the square of the turns ratio.
For example,
We have a transformer with 4 ohm primary and 1 ohm secondary,
and the turns ratio is 1:0.5 (step down 2 to 1).
With no load and 10v on the primary, we get 5v on the secondary.
With load however, we have to take the resistances into account.
To reflect the primary resistance to the secondary, we take the
4 ohms and multiply by the square of the turns ratio. The turns
ratio would be 0.5 here so the square of that is 0.25, so we multiply
0.25 times 4 and get 1 ohm, so we add that to the 1 ohm secondary
and we get 2 ohms in the secondary. Thus, the transformer looks
like an ideal transformer with turns ratio 1:0.5 with 2 ohms in the
secondary.
If we now connect a load of 23 ohms on the secondary we get 200ma
to flow because we have to add that 2 ohms secondary resistance to
the 23 ohms. We get 25 ohms total and 5v/25ohms=200ma.
Reflecting the resistance this way helps to determine the effects
of connecting two different transformers in parallel.
In general though, if the transformers are not very close to being the
same it's not a good idea.