Source of information: http://www.powertransformer.us/choosingcustomtransformermanufacturer.htm
Choice of power transformer is a very important task. Therefore, this article describes the key points on which we should pay attention.
Look for manufacturer that will offer you a quality transformer. As with all of us, cost is always the primary consideration. But look at the overall picture, transformer usually have a long life expectancy and you must factor in the energy cost and the maintenance cost. Take in these following consideration:
1. Aluminum-wound transformers are sometimes less expensive initially, but copper coils reduces electricity bills. Data based on a popular 45 kVa size shows a $1000.00 per year saving, in 10 years this is a saving of $10,000. Copper's higher strength and corrosion resistance compared with aluminum means connections stay tight longer, thus reducing life-cycle cost.
2. A conventional transformer that uses stacked lamination core assembly and 90 degrees square corners contribute to high core losses. Look for transformer with oval shape wound core to ensures that the flow of magnetic flux is carried in the direction of cold-rolled grain oriented steel for minimal core loss.
3. All energized transformers "hum". This "hum" is due to the alternating flux in the core producing a phenomenon known as magnetostriction. Transformer "hum" , commonly referred to as "noise", is primarily produced by the core at a fundamental frequency of twice the applied frequency. Noise is an inherent characteristic of the core and cannot be completely eliminated. When selecting a transformer, make certain that the sound levels presented by the manufacturer have been measured in accordance with the American National Standards Institute, and certified by the manufacturer. NEMA Publication No. ST20 and ANSI Standard C89.2 establishes maximum sound levels for dry type transformers. Also Anti-vibration isolators between the element and enclosure reduce vibration transfer to the surrounding structure and in turn ensures quieter operation.
4. A well designed transformer, operating within the temperature limits of its insulation system, will have a life expectancy of 20 to 25 years. The design life of transformers having different insulation systems is the same, (lower temperature systems will have the same life as higher temperature systems). The class of insulation used in a particular transformer is a design consideration and such factors as voltage regulation, material cost and availability are factors that the designer must consider.
5. Manufacturer should offer you a warranty- Transformers should be warranted against defects in materials, workmanship and performance for 10 years from date of manufacture.
6. Transformers should be UL listed
for non-sinusoidal current loads of a specified K Factor (UL Standard
1561)CSA certified and labeled as such.
7. Customer Service is always the backbone in any successful company. When you make that initial call to the manufacturer you should feel that all the staff is helpful, courteous, and knowledgably. Most manufacturer will give you a list of their customer. Contact these customer and ask about their experience they had with the manufacturer.
8. The engineer staff and technical support will be the people you will be dealing with extensively in the purchase of your transformer. Make sure you feel they are knowledgeable and helpful. You should receive a complete shop drawing that give you detail specification if you are buying a dry type transformer. Typical performance data should be submitted for approval on all transformers. If you need a custom transformer or product for a specific requirements, make sure they have a experienced design engineering department. They should provide you with rapid turnaround of designs and prototypes of custom products.
9. Choose a Manufacturer that can offer you fast, reliable on time service for your transformer . If it is a stock item, turnaround should be in 48 hrs. For custom design transformer a 2 or 3 days turnaround is not unusual. Let them know your time table and they should work hard to meet your needs. Don't forget that buying the transformer is only the beginning of a relationship with a supplier. You will want to have fast, reliable service for any replacement deadlines that you may require.
10. The manufacturer should be in good standing with the Better Business Bureau. Make sure your manufacturer offer a quality product, on time service, integrity, and superior customer service.