# Re: what is % impedance of transformer?

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#12048
electricalexpert65
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jatin333 said:

what is % impedance of transformer? how we calculate %impedence of transformer,

what is purpose of % impedence?

Have you ever wondered why the name plate LV Volatge in a transformer is 433V but the name plate voltage of an LV motor is 415V?  Are they both not LV? Yes! the 433 V in a trf. name plate is the open circuit voltage or the no load voltage. But, when you load the transformer, a current would flow thro its windings. As the windings will have an impedance, this current and impedance would very definitely cause a voltage drop within the transformer windings. On emust know the magnitude of this voltage drop. The volatge drop within the transformer's LV windings, with rated load current flowing thro it, expressed as a percentage of the no load voltage of the teansformer is called its percentage impedance.