What is typical life expectancy of a dry type Transformer?

Dry-type transformer life expectancy

We are frequently asked by designers and engineers what is the life expectancy of a dry-type, air cooled transformer. The question has many varieties. A general purpose transformer, located in a dry area and well maintenance you would expect 25 years life expectancy.

However, the life expectancy of a dry type transformer will depend on a few factors. The various loading, environmental conditions and quality of the build are all key factors on life expectancy.

The Build

Dry-type transformers have no moving parts and are a completely static, solid-state device. Under normal operating conditions, they will have a long and trouble-free life. This is why it is important to ensure that the transformer is designed to meet your application. Also, using the best quality materials is important as not all transformers are manufactured equally, due to there being different grades of lamination and copper. For this reason it is important not to buy transformers solely on price. Knowing who the transformer manufacturer is and how their transformers are designed and constructed is critical.

Insulation classes

It is vital when designing and manufacturing a transformer to use the correct class of insulation. Dry-type transformers are available in three general classes of insulation. The main features of insulation are to provide dielectric strength and to be able to withstand certain thermal limits. Understanding loading and environmental factors will determine your insulation class.

Insulation classes are:

220°C (Class R)
180°C (Class H)
155°C (Class F)
130°C (Class B)
105°C (Class A)

Enclosure

Dry-type transformers are suitable for indoor and outdoor applications. To ensure a long life expectancy, it is important to install dry-type, air cooled transformers in the correct IP Rated enclosure. This ensures environmental factors do not damage the windings over time.

IP Ratings

A number replaced by x indicates that the enclosure is not rated for that spec.

First Digit (intrusion protection)

0. No special protection
1.Protection from a large part of the body such as a hand (but no protection from deliberate access); from solid objects greater than 50mm in diameter
2. Protection against fingers or other object not greater than 80mm in length and 12mm in diameter
3. The Protection from entry by tools, wires etc, with a diameter of 2.5 mm or more
4.Protection against solid bodies larger than 1mm (eg fine tools/small etc)
5. Protected against dust that may harm equipment
6. Totally dust tight

Second Digit (moisture protection)

0. No protection
1. Protection against condensation
2. Protection against water droplets deflected up to 15° from vertical
3. Protected against spray up to 60° from vertical
4. Protected against water spray from all directions
5. Protection against low pressure water jets (all directions)
6. Protection against strong water jets and waves
7. Protected against temporary immersion
8. Protected against prolonged effects of immersion under pressure

The answer

The simple answer is, life expectancy is about 25 years. However this will depend on the transformer being designed correctly, manufactured out of high grade materials and being located in a dry, dust free environment. If you would like to discuss this with one of our team please call 0151 486 6760.

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