Why Can’t a Transformer Be Operated with a DC Supply?
A transformer fails to function on a DC (Direct Current) supply as its working principle requires changing magnetic flux, which DC does not provide.
Key Reasons
Faraday’s Law: Electromagnetic Induction
Faraday’s Law states that a changing magnetic field is required to induce voltage in the secondary winding. This is how transformers work.
AC (Alternating Current) is continually changing direction, creating the necessary magnetic field.
DC is constant, no change in current implies no change in magnetic flux, hence no voltage is induced in secondary coil.
Core Saturation
With DC, the current is constant, resulting in a steady magnetic field.
The transformer’s iron core quickly saturates due to the lack of flux reversal.
This produces an excessive magnetizing current, that can overheat the winding and destroy the transformer.
High Current Draw
Transformers are built with low winding resistance to reduce AC losses.
When DC is used, there is no inductive reactance, only resistance, so the current gets dangerously high, possibly leading to burnout.
In simple terms, transformers need alternating current (AC) to function. Applying direct current (DC) can result in overheating, core saturation, and, eventually, transformer failure.
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