A Rule of Thumb For Transformers

As fuel costs rise and strength outages become more common around the country, the strength generation and dispensing system in the US has come into sharp focus. So too has the need to conserve energy and the need to invest in energy-efficient products of all types. Of particular interest are products like strength transformers that keep energized and consume energy 24 hours a day.

The transformer is a basic part of the energy grid. If already a single unit shuts down for a short period of time, a large number of households and commercial establishments are plunged into darkness resulting in a substantial economic loss.

Unfortunately, a meaningful amount of equipment in the public utility grid is over 40 years old and needs to be replaced in the near future. According to the Department of Energy (DOE), dispensing transformers which are 30 years old or more can waste between 60 and 80 billion kWh yearly. A better designed transformer could provide an annual energy savings of up to $1 billion. consequently, maintenance, retrofitting and purchasing of new transformers are fast becoming imperatives.

The Importance of Transformers

The dispensing transformer – is the most important single piece of electrical equipment installed in an electrical dispensing network. It also has a large impact on a network’s overall cost, efficiency and reliability. Selecting and acquiring energy-efficient dispensing transformers which are optimized for –

* A particular dispensing network

* The utility’s investment strategy

* The network’s maintenance policies

* Local service and loading conditions

– will provide definite benefits (improved financial and technical performance) for both utilities and their customers.

As climate change looms on the horizon, there is also an increased interest in the protection of the ecosystem from greenhouse gas emissions. The regulatory requirement now is to install high-efficiency dispensing transformers that have less energy losses, which ultimately results in fewer pollutants being released into the ecosystem.

Transmission Losses

Transformers aren’t perfect devices; they don’t transform 100% of the energy input to usable energy output. The difference between the energy input and that which is obtainable on their output is quantified as energy loss. There are two types of transformer losses: no-load losses and load losses.

* No-load losses

No-load losses are also referred to as chief losses. This loss is calculated based on the amount of strength required to magnetize the chief of the transformer. Since most dispensing transformers are energized 24/7, no-load losses are present at all times, whether a load is connected to the transformer or not. When lightly loaded, no-load losses represent the greatest portion of the total losses.

* Load losses

Load losses however, are those losses incident to carrying a load. These include winding losses, stray losses due to stray flux in the windings and chief clamps, and circulating currents in similar windings. Because load losses are a function of the square of the load current, they increase quickly as the transformer is loaded. Load losses represent the greatest portion of the total losses when a transformer is heavily loaded.

Deciding which Transformer to buy

Many electrical dispensing utilities claim that they buy dispensing transformers using some kind of loss evaluation procedure. However, transformer cost continues to be a major factor in calculating which transformer to buy. The elements in a transformer, design, construction and installation all affect its cost. For example amorphous metal chief transformers have 75% less no-load loss than a silicon steel chief transformer but cost 25% more than a silicon steel transformer.

Transformer losses affect the cost of design, construction and installation. The transformer manufacturer typically incorporates the cost of losses in the cost of the transformer in optimizing transformer design.

Most companies buying transformers look at the quotation instead of the total cost of ownership (TCO). The TCO over the life of the transformer tends to be high in less energy-efficient transformers, while the initial cost is higher and the TCO low for energy-efficient transformers.

The payback period for investing in high-efficiency transformers however is comparatively short – often less than 2 years. The Internal Rate of Return in energy efficient transformers is consistently above 10% and sometimes as high as 70%.

Making buying decisions for a large strength transformer is more complicate than simply comparing manufacturer prices. It requires a company to know its requirement and compare not just the cost of transformers but also the TCO over a two- to three-decade period. If this is precisely done, the cost-efficient solution always turns out to be the energy-efficient transformer, already though it has a slightly higher initial cost.

When purchasing transformers, there is no question of a ‘short-term’; these infrastructure investments are typically made with 30 to 50 years of service in mind. Energy-efficient transformers are consequently definitely the only way ahead, given the strong economic case they make over the long run.

Leave a Reply