What Happens When DC Voltage is Applied to a Transformer's Primary Winding? part i

Uncover the surprising impact of applying direct current (DC) to a transformer’s primary winding and its unexpected consequences in our electrical systems.

Josh Spickett

January 5, 2024  

Transformers are the unsung heroes of our electrical world, quietly enabling the efficient transfer of electrical energy from one place to another. You’ve likely encountered them countless times, whether in your neighborhood’s power distribution network or within your household appliances like microwaves and laptop chargers or even in industrial machinery. These remarkable devices are meticulously designed to operate harmoniously with the ebb and flow of alternating current (AC). However, what happens when we introduce a different player into this electrical symphony – direct current (DC)? In this article, we will investigate to uncover the intriguing consequences of supplying DC voltage to a transformer’s primary winding, revealing the detrimental effects it can have in the world of transformers and electricity.

Understanding How Transformers Work

Before delving into the impact of applying DC voltage to a transformer, it’s essential to grasp the basic operation of these devices. Transformers rely on the principle of electromagnetic induction to efficiently transfer electrical energy from one circuit to another. This process hinges on the constantly changing magnetic field induced from AC current in the transformer winding.

Integral to this process is the concept of Electromagnetic Fields (EMF). These fields are a natural byproduct of the electric currents and magnetic fields within the transformer. EMFs are particularly significant in the context of transformers because they facilitate the induction process that allows for the transfer of energy between circuits. Understanding EMFs helps in comprehending how transformers can efficiently transmit electrical power, even over long distances.

Comparing Outputs AC and DC in Ideal Transformers
Comparing Outputs AC and DC in Ideal Transformers

The Disruption of Electromagnetic Induction

When DC voltage is introduced to a transformer’s primary winding, it disrupts the core principle of electromagnetic induction. Unlike AC, which generates a magnetic field that continuously changes direction, DC voltage creates a static magnetic field. As a result, the transformer cannot function as intended.

One immediate consequence of applying DC voltage is the absence of induced voltage in the secondary winding. At its core (ha!), when there is no fluctuating magnetic field, known as magnetic flux, there’s no mechanism to generate voltage in the secondary coil. This magnetic flux is crucial because it induces an electric current to flow in the secondary coil. This current, in turn, produces electrical output in the secondary circuit. Consequently, if DC current is present, the transformer becomes less capable of efficiently converting electrical energy between the primary and secondary circuits.

However, the consequences of applying DC voltage to the transformer are not limited to this, how to safely use the transformer, and how to protect electrical equipment from DC voltage, stay tuned for the next article, we will continue to explore the secrets of electromagnetism in the transformer.