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Dry-type Transformers

A thorough infrared inspection of an electrical transformer can point out symptoms of loose connections as well as other possible problems. When performing an infrared inspection of a dry-type transformer, be certain to include not only the primary and secondary connections but also the following items as well:

1) Inspect neutral and grounding connections for hot spots.

2) Compare phase coils to each other. Transformers with balanced loads will exhibit similar temperatures between windings.

3) Compare each phase coil to itself. Properly operating coils should exhibit no pronounced hot or cold spots.

4) Inspect voltage tap jumper connections. Both connections should be the same temperature. In most cases, the jumper will be colder than the windings.

5) Compare transformer operating temperature to nameplate rating. For long term service, transformers should not operate above their maximum rated temperature.

In conjunction with the infrared inspection, cooling fans should be checked for proper settings and operation.

Finally, transformers require proper air circulation for cooling. To help ensure maximum airflow, transformer ventilation openings should be unobstructed and free from dirt.