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What Is an Energy Efficient Transformer?

By T.S. Adams
Updated May 17, 2024
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A transformer is an electrical device which transfers electrical energy from one electrical circuit to another. While ordinary transformers cost a substantial amount of power loss to a line, resulting in roughly 40 to 50 percent of all transmission and distribution losses, an energy efficient transformer is designed to be more efficient and reduce the amount of power loss that occurs when the energy is transferred. An energy efficient transformer accomplishes this by using extremely conductive materials, including electrical steel and easily magnetized materials.

Transmission and distribution losses are some of the biggest enemies to efficient power transfer in transformers. These losses are natural losses of attrition which occur as electricity moves through the line. Much like a dragging cloth along a piece of sandpaper, where tiny portions of the cloth will be snagged during the process, some of the power flowing through a transformer is similarly "snagged" and displaced by the substances through which it moves. The amount of "snagging" that occurs is largely dependent on the conductivity of the materials through which the electricity flows; highly conductive materials can pass a charge with much less of a snagging effect.

The efficacy of a modern energy efficient transformer is roughly twice that of a comparable transformer from the 1970s. This means that while an average transformer results in 40 to 50 percent power loss — in other words, only half of the power moving through the transformer actually makes it to the next circuit — the power retention of an energy efficient transformer is much higher, suffering only 20 to 25 percent loss. Much of the power loss in traditional transformers comes from the substances used in their creation; standard steel and other ordinary metals tend to impede the flow of electricity to a degree where much of the power is lost through heat conversion.

A modern energy efficient transformer solve this problem through its conductive construction materials. When created from materials that have a higher conductivity, such as steel specifically designed to hold an electrical charge, energy efficient transformers retain more of their original power, allowing more to be funneled into the adjoining circuit. An amorphous metal transformer is one good example of this; the core of the transformer is made from material which can easily be magnetized and demagnetized, resulting in not only better power transfer, but reduced carbon dioxide transmissions when generating power from fossil fuels.

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Discussion Comments
By anon1006718 — On May 08, 2022

"This means that while an average transformer results in 40 to 50 percent power loss — in other words, only half of the power moving through the transformer actually makes it to the next circuit — the power retention of an energy efficient transformer is much higher, suffering only 20 to 25 percent loss"


Transformers are 40-50% _OF_ the power loss, but the efficiency of a transformer itself is easily over 80%. Most of that power loss in a transformer is to heat caused by I^2*R (power) losses in the windings and core loss in iron at low frequencies (50 or 60 Hz depending on your country standards).

You are comparing apples and oranges here.

This is why high voltage transmission lines are used. Since power lost is a function of current (assuming constant resistance), increasing the voltage reduces the current and the losses. See ohms law, or E=I*R, where E is the voltage, I is the current and R is the resistance.

But that high transmission voltage (easily in the hundreds of kilovolts or higher range) needs to be converted to lower voltages like 120V or 240V (again depending on the country and the service) for local use.

So the efficiency gains from high voltage transmission make the I^2 * R (Power = Current squared times Resistance) losses and iron losses* of transformers a higher percentage of the overall loss. Hence the 40-50% loss figure. That is NOT the same as the transformer efficiency, which is obliqeuly referred to in the quoted sentence.

Creating higher efficiency transformers may increase their efficiency a small amount, but the impact on the overall transmission loss is reduced by the fact that the transformer losses are only 40-50% of the total losses. The impact of this small decrease in total transmission loss is far less than it appears from the article.

Perhaps checking with a power transmission expert would be better than pulling numbers off Wikipedia.

*Iron losses are losses in the actual transformer core material. Decreasing core losses can be done by increasing the steel permeability - greatly increasing the core material cost. On the other hand, power converters utilize high permeability steel core material (even ferrites) and much higher frequency conversion to reduce core losses. The converter block shown in the article uses active power conversion - something that is not feasible over a few hundred KW because of the cost of the active switching elements (transistors, SCR's, MOSFET's or even vacuum tubes). Converters are great and can be very efficient for a laptop computer, but are not easily scaled up to community distribution.

This article is very misleading, at best.

By anon1006716 — On May 08, 2022

Are you confusing a transformer with a power converter (pictured)? Efficiency of iron core transformers is easily above 80%

Please identify your reference material showing such an absurdly low transformer efficienct!

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