Understanding a few critical considerations in transformer design greatly reduces long-term costs without increasing upfront expenditures.
by Ed Sullivan
When power transformers fail, the effects on plant operations can be debilitating. The production gets interrupted, everything grinds to a halt and the effects on the bottom line can be immediate and devastating. This can put a lot of pressure on those in charge of getting operations back up to full-speed.
To make matters worse, since power transformers rarely go down, it is not uncommon for those in charge of purchasing a replacement to have little experience in the process. In addition, for someone who doesn’t regularly purchase transformers, it may seem as though they are more of a commodity item, and hence, can be sourced out to the lowest bid.
However, there are a number of considerations within transformer design and construction that when taken into account can increase long-term savings without significantly increasing upfront expenditures.
“Quality doesn’t always increase the initial purchase price, but it will greatly decrease ongoing operational costs in a number of critical ways,” advises Alan Ober, Chief Engineer at Electric Service Company (ELSCO), an expert with over 40 years of experience in the design and manufacturing of transformers.
Selecting the proper transformer design can actually make a huge difference by extending operating life, decreasing future maintenance and reducing energy bills.
The following tips should be considered when sourcing and installing a new or replacement transformer.
Selecting the right transformer
To maximize the return on investment on what is arguably the heart of any industrial plant it is important to understand some of the basics. Starting from the top, power transformers are required to step-down the higher voltages delivered by the electric utility company at reduced ‘bulk’ rates.
For indoor applications, dry-type transformers are by far the most common due in part to the fact that they are air-cooled, so they pose lower risk of problematic leakage, environmental issues and fire. Since they can safely be used inside a facility, dry-type units can be placed right next to the equipment they are powering which can further reduce costs.
Evaluate winding design
The way in which the coils are wound around the core of a dry-type transformer greatly affects its robustness and ability to survive “impulses” that can occur from phenomena such as switching surges and lightning strikes.
Two of the most common transformer designs today feature either circular (round-wound) or rectangular windings.
While many transformer manufacturers still offer rectangular windings, because they are less expensive to build, they can develop problematic air traps, hot spots and other problems.
The round coil design, on the other hand, provides significant ongoing operational and cost-saving advantages. Round-wound transformers stay cooler, run quieter, and present less risk of short circuit when coupled with a sheet wound secondary.
Consider the material
In addition to the design, the material used for the windings and insulation can greatly affect performance and prevent disastrous emergencies from occurring during the unit’s operating life.
For transformer windings, the most common materials used are copper and aluminum. While copper does have a higher upfront cost, it more than makes up for that by outperforming and outlasting aluminum.
The selection of proper insulation also plays a major part in ensuring transformer reliability. Temperatures can reach 200 degrees C in a dry-type transformer on a daily basis; hence skimping on insulation can lead to disastrous consequences.
Therefore, higher-quality insulation, such as DuPont Nomex® flame resistant meta-aramid insulation, should strongly be considered. This is the same insulation used in the safety gear worn by race car drivers, fire departments, military applications, as well as in numerous electrical applications.
Investigate a “drop-in” solution
Finally, a factor that is often overlooked: The removal of the old transformer and installation of the new one can be time-consuming and costly if not properly addressed beforehand. This is particularly important when there are existing enclosures with dimensional/clearance constraints.
“The transformer manufacturer should be consulted and needs to be capable of slightly modifying the transformer – either new or remanufactured – so that it can be ‘dropped-in’ or mated with the existing transformer infrastructure, meeting UL, IEEE standards plus all required clearances, within a few hours,” says Ober.
He adds that consulting suppliers on a user’s specific application, present and anticipated power supply needs, and getting an informed evaluation of the options available, can lead to the effective selection of a transformer that will pay substantial dividends in performance and greatly reduce the total cost of ownership.
For more information, contact: Electric Service Company (ELSCO); 5331 Hetzel Street, Cincinnati; OH 45227; 800-232-9002 or 513-271-1752; FAX: 513-271-0543; firstname.lastname@example.org or www.electricservice.com.
About the Author
Ed Sullivan, a Los Angeles based freelance writer with over 40 years of experience writing for the energy industry.