Transformers in Series
Country: United States
Date: May 2007
How do you connect two transformers
together to increase an AC potential?
The short answer to your question is "you cannot ...at least not safely".
A transformer is designed to operate from a specified voltage. If you try
to operate it from a different voltage than it is specified for, you risk
fire, or a minor explosion.
Let's say you have two transformers that are intended to operate from 120 V
AC (the power that comes from an AC wall plug), and they have an output
voltage of (let us say) 400 Volts AC. Then, you attempt to connect the primary
of the second transformer to the 400 Volt output of the first one, in the hope
of getting a much higher voltage at the second transformer's output.
This will not work, because you will be feeding 400 volts (in this example) to
a transformer that was designed to accept only 120 Volts. Several problems
immediately occur. First, the second transformer will likely "saturate"
(which is an effect where the transformer stops acting like a transformer, and
instead acts like a short circuit). The second thing is that the insulation
inside the transformer is not designed for high voltages, and may fail and
cause a dangerous short circuit.
You have no doubt heard the advertising disclaimer "Don't try this at home".
Well, this certainly applies here! I strongly urge you NOT to "try this at
Electrical potential is measured in volts. Electrical current is measured in
amperes. You calculate electric power by multiplying volts times amperes.
That product is measured in watts. For example if you have 110 volts causing
2 amperes to move you have 22 watts of power.
Now to your question. You can increase the electrical potential - volts - by
using a transformer with a primary with fewer turns than in the secondary.
The increase in voltage will equal the ratio between the number of turns in
the windings. Twice the number of turns will give you twice the voltage.
This is called a "step-up" transformer.
However, the power in and the power out will remain the same (minus the losses
because the transformer is inefficient). The result of increasing the voltage
will be a decrease in the amperage in the secondary. If you double the voltage
you will half the current.
Now your thought of using two transformers... You could do this, by running the
secondary of a step-up transformer into the primary of another step-up
transformer. This would be a strange system and would have more losses of
power than would one transformer to do the complete job.
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Update: June 2012