Transformer

Hello Guest,

I have applied DC to a transformer, more than once.

This was needed to properly test the transformer with DC Output test equipment, such as Kelvin Bridge, Megger and the like.

If you mean DC at the same voltage as the norm,al AC, then the transformer will heat up, and (depending on design)

Kind Regards....

This question has come up more than once.Some times I wonder wheteher the forum is meant for basics like this?

Actually this is quite an interesting subject.

The first two posts have assumed its a power transformer, but it could be a ratio transformer, in which case the core would become magnetised and the error and lack of sensitivity of the ratio transformer would be lacking.

However, this can easily be overcome by demagnetising the core by applying a relatively large low frequency ac to the windings and gradually reducing the amplitude to zero.

Ratio transformer should never have dc applied to them.

The Primary will act like and inductor, DC current will increase linearly with time until the current is limited by the supply or the circuit resistance. The secondary will output current/voltage only while the current is changing and before the core saturates.

Hello Guest,

I have thought about your Question, and there are transformers which are designed for use in Magnetic Amplifier circuitry, which have DC applied to a control winding.

The DC current in that control winding, varies the magnetic coupling between the transformer primary and secondary, thus a small control current, may easily control a very large output current, in other words: "Magnetic Amplifier" technology.

Also there are AC transformers, used at Radio Frequencies, TV Frequencies, and above, which have both DC and AC in the windings, while they are being used.

So you need to correctly specify exactly what transformer, installed in what situation, and then you may well receive a proper answer.

Reply here, with

Kind Regards....