# Why we should not give dc supply to Transformer

## Why we should not give dc supply to Transformer:

Transformers are the static device; it just transfers the energy from one winding to another winding without changing frequency. It works under the principle of electromagnetic induction. It just electrically separated and magnetically coupled.   In this tutorial we are going to see Why we should not give dc supply to the Transformer.

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As above we said transformer works in electromagnetic induction. Consider voltage V applied voltage in primary of the coil, I is the primary current and XL is the inductive reactance of the coil

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As we know

V= XL  X I   —————————1

• Current I = V / XL —————1a

Here XL = 2 * pi * f * L  ————2

L is the inductance of the coil

F is the applied frequency

Pi= 3.14 constant

For Pure DC does not have any frequency, so that frequency f=0 subsitude in equation 2

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Hence XL = 2 * pi * 0 * L

• XL =0 , then subsidute this value in equation 1a
• Current I = V /0
• I = infinity

While giving DC supply to the transformer, transformer coil act as short circuit then current goes infinity, due to this reason transformer does not operate with dc supply. That’s why we should not give dc supply to the transformer.

Normally during testing time the transformer’s manufacturer is giving allowable dc supply to the new transformer to test its current carrying capacity.