Interesting facts about Transformers

5 Interesting Facts About Transformers You Should Know

Transformers were first developed in the 1880s and today they form the backbone of modern power systems. Without transformers, transmission and distribution of electricity over long distances would be extremely inefficient and cumbersome.

Here are some fascinating facts about transformers that every electrical engineer, student, or enthusiast should know:

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1. Transformers Don’t Work on DC

Transformers only work on alternating current (AC), not direct current (DC).

• Reason: Transformers rely on a time-varying magnetic field to induce EMF (electromotive force) in the secondary winding. DC has a constant value, so no changing flux is produced, and hence no EMF is induced.

• Effect of DC Supply:

  • Transformers have high inductance and low resistance.

  • When connected to DC, inductance offers no opposition (since the current is constant).

  • This results in excessive current flow, which can overheat and burn the windings.

👉 That’s why DC supply to a transformer is dangerous.

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2. Transformers Are Connected in Parallel, Not in Series

In power systems and industries, transformers are usually operated in parallel instead of series.

• Advantages of Parallel Operation:

  • Load sharing: When demand increases beyond one transformer’s capacity, another transformer is connected in parallel to share the load.

  • Reliability: If one transformer fails, others can continue supplying power.

• Why Not Series?

  • In series, the current remains the same for all units.

  • No effective load sharing takes place.

  • Failure of one transformer disrupts the entire supply.

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3. Copper Wound Transformers Are Preferred Over Aluminium

Although aluminium is cheaper, copper windings are widely used in transformers because of their superior properties.

Advantages of Copper Windings:

• Stronger, harder, and more ductile compared to aluminium.

• For the same rating, an aluminium-wound transformer needs a 1.6–1.8 times larger cross-section (due to aluminium’s higher resistivity). This makes the overall transformer bulkier and more expensive (more steel, tank, and oil required).

• Copper improves the energy efficiency and performance of the transformer.

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4. Transformers Are Always Stationary

Unlike motors and generators that have moving/rotating parts, a transformer has no moving components.

• The primary and secondary windings are wound on a laminated iron core.

• Everything is stationary and enclosed inside a transformer tank filled with oil.

• This makes transformers mechanically simple, robust, and long-lasting.

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5. Transformer Tank is Made of Steel (Not Conductive)

The transformer tank is made of carbon steel (mild steel).

• A natural question arises: If it’s metallic, why doesn’t the transformer tank carry current?

• The answer is insulation:

  • The windings are insulated from the tank using transformer oil, which prevents any leakage current from reaching the tank.

  • Hence, the outer body remains safe from conducting current.

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✅ Key Takeaway:
Transformers are simple yet powerful devices that make modern electrical systems possible. From their inability to work with DC to their stationary design and preference for copper windings, each fact highlights why transformers are designed the way they are.

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