"Power Lost in Silence: Understanding Transformer Losses"
Day 61 of my 100-day journey into India's power sector.
Transformers are the silent workhorses of our electrical power system. They step up and step down voltages, enabling the efficient transmission and distribution of electricity across vast distances.
But while they play a crucial role, no transformer is 100% efficient.
In every transformer, some portion of the input power is inevitably lost — mostly as heat. These losses may seem small, but over time and at scale, they translate into significant inefficiencies and operating costs.
There are several different types of losses in a transformer, each affecting the overall efficiency and performance. There are four main types of losses that occur in a transformer.
These losses can be broadly categorized into:
1) Copper or Ohmic losses
2) Iron/core losses (Hysteresis, and Eddy current losses)
3) Stray losses
4) Dielectric losses
So, what causes these losses? Let’s break it down
1. Iron Loss (Core Loss)
It occurs in the magnetic core of the transformer and is made up of:
Hysteresis Loss: It is caused by the repeated magnetization and demagnetization of the core due to alternating current. It depends on the type of core material and frequency of the AC supply.
Eddy Current Loss: Circulating currents are induced in the core when exposed to a changing magnetic field. These create heat and result in energy loss. Laminating the core helps reduce this loss.
Iron losses are constant and do not vary with the load.
2. Copper Loss (I²R Loss)
It happens due to the resistance in the transformer windings (both primary and secondary). It’s proportional to the square of the load current and increases with the load. Unlike iron losses, copper losses vary with the load.
3. Stray Losses
Some magnetic flux doesn't follow the intended path and induces eddy currents in nearby metal parts, such as the transformer tank or clamps. These cause additional heating and losses.
4. Dielectric Loss
It takes place in the insulating material of the transformer, especially at high voltages. It’s a result of the alternating electric field causing energy dissipation in the insulation.
Ideal vs Practical Transformer
In an ideal transformer:
Power input = Power output
No losses at all
But in a real-world transformer:
Input power = Output power + Total losses
These losses result in heat, which needs proper dissipation to avoid damage and maintain performance.
Why Does This Matter?
Understanding and minimizing transformer losses is key to:
Improving efficiency
Lowering energy bills
Enhancing system reliability
Reducing environmental impact
Modern transformers use CRGO steel, laminated cores, high-conductivity copper, and efficient insulation systems to keep these losses as low as possible. Transformers may be static devices, but their performance depends on how well we understand the dynamic losses happening inside them.