When choosing a transformer, there are two primary concerns: the load and the application. Several factors must be evaluated carefully while making the choice, to ensure that the needs of both primary concerns are met.
To use a clich, it is typically a no-brainer to choose smaller transformers. A unit with a kVA rating that is larger from the anticipated load can quickly be picked up. But if you are selecting a large unit for an electrical utility system, to be part of a large distribution network, you are typically making a much larger investment; thus the evaluation process is much more detailed and elaborate. With over 90 years of experience in this industry, Pacific Crest Transformers has put together a quick checklist to help you make your choice judiciously.
There are three major questions that influence your choice:
- Does the chosen unit have enough capacity to handle the expected load, as well as a certain amount of overload?
- Can the capacity of the unit be augmented to keep up with possible increase in load?
- What is the life expectancy of the unit? What are the initial, installation, operational, and maintenance costs?
Evaluation Factors
The cost and capacity of the transformer typically relate to a set of evaluation factors
1.Application of the Unit
Transformer requirements clearly change based on the application.
For example: in the steel industry, a large amount of uninterrupted power is required for the functioning of metallurgical and other processes. Thus, load losses should be minimized which means a particular type of transformer construction that minimizes copper losses is better suited. In wind energy applications, output power varies a great extent at different instances; transformers used here should be able to withstand surges without failure. In smelting, power transformers that can supply constant, correct energy are vital; in the automotive industry, good short-term overload capacity is a necessary attribute. Textile industries, using motors of various voltage specifications, will need intermittent or tap-changing transformers; the horticulture industry requires high-performance units that suit variable loading applications with accurate voltage.
These examples serve to underline that type of load (amplitude, duration, and the extent of non-linear and linear loads) and placement are key considerations. If standard parameters do not serve your specific application, then working with a manufacturer that can customize the operating characteristics, size and other attributes to your needs will be necessary. Pacific Crest regularly builds custom transformers for unique applications.
2.Insulation Type (Liquid-Filled or Dry Type)
While there is still debate on the relative advantages of the available types of transformers, there are some performance characteristics that have been accepted:
Liquid-filled transformers are more efficient, have greater overload capability and longer life expectancy.
Liquid-filled units are better at reducing hot-spot coil temperatures, but have higher risk of flammability than dry types.
Unlike dry type units, liquid-filled transformers sometimes require containment troughs to guard against fluid leaks.
Dry type units are usually used for lower ratings (the changeover point being 500kVA to 2.5MVA). Placement is also a crucial consideration here; will the unit be indoors serving an office building/apartment, or outdoors serving an industrial load? Higher-capacity transformers, used outdoors, are almost always liquid-filled; lower capacity, indoor units are typically dry types. Dry types typically come in enclosures with louvers, or sealed; varnish, vacuum pressure impregnated (VPI) varnish, epoxy resin or cast resin are the different types of insulation used.
3.Choice of Winding Material
Transformers use copper or aluminum for windings, with aluminum-wound units typically being more cost-effective. Copper-wound transformers, however, are smaller copper is a better conductor - and copper contributes to greater mechanical strength of the coil. It is important to work with a manufacturer that has the capability and experience to work with either material to suit your specific requirement.
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More about PCT: http://www.pacificcresttrans.com
