Why polarity test is necessary for a transformer?

What is polarity test of transformer?

Polarity means the direction of the induced voltages in the primary and the secondary winding of the transformer. If the two transformers are connected in parallel, then the polarity should be known for the proper connection of the transformer.

What test proves polarity?

There are three checks of polarity during testing – dead and live testing and visual inspection and while they all confirm correct/incorrect polarity they do not necessarily check for the same thing.

Why does AC change polarity?

As the wire spins and periodically enters a different magnetic polarity, the voltage and current alternate on the wire. This current can change direction periodically, and the voltage in an AC circuit also periodically reverses because the current changes direction.

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