GE Industrial Solutions Dry-Type General Purpose Power Transformers - Manual (Page 6)

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Even if evidence of overheating is noticed, external fans (fans blowing on the outside of the enclosure or louvers) must not be
directed toward the transformer. This practice can result in mis-directed airflow that can retard or stop normal convection through
the transformer coil. As a result the transformer will further overheat creating a risk of fire and failure may result in a short period
of time.
8.2 Over-excitation
Operation at voltages in excess of rating may cause core saturation, excessive core losses, overheating and abnormally high noise
levels. Special care should be taken where higher than rated primary voltage is anticipated. Most general-purpose dry type
transformers incorporate primary taps to be able to match the supply voltage. Dry type general-purpose transformers are designed
to reach rated temperature rise above ambient air temperature when operated continuously at rated voltage, frequency and load.
WARNING
SERIOUS OVERHEATING RESULTANTING IN FIRE DAMAGE MAY RESULT IF THE UNIT IS OPERATED FOR
SUSTAINED PERIODS ABOVE RATED VOLTAGE OR CURRENT AND/OR AT OTHER THAN RATED FREQUENCY.
9.0 Troubleshooting
Problem: Circuit breaker trips on start up
Possible causes:
Circuit breaker incorrectly sized for kVA rating of transformer.
Circuit breaker instantaneous trip (if applicable) set too low.
Supply voltage too high, over voltage being applied to transformer.
Supply voltage cables incorrectly connected to transformer secondary.
Transformer being reverse fed. If the transformer is being reverse fed, i.e. if the supply lines are connected to the
transformer secondary terminals, the initial inrush current can be up to 10 times the normal expected inrush.
Primary ground cable connected to transformer secondary neutral bus.
Problem: Wrong secondary voltage or secondary voltage drifts
Possible causes:
Improper grounding.
Incorrect installation, review nameplate connection diagram.
Primary taps jumpers incorrectly installed.
Measurements must be taken with a true RMS meter.
Problem: Transformer noisy
Possible causes:
Transformer not installed per the recommended installation procedures outlined in this publication. Review paragraph
5.4 of this publication.
Supply voltage to transformer higher than voltage rating of transformer.
Transformer over loaded.
Transformer enclosure panel screws not securely tightened.
Rubber isolation pad hardware not properly installed.
Shipping braces not removed.
Sound reverberating from reflecting surfaces.
Problem: Transformer runs hot
Possible causes:
Overvoltage being applied to transformer.
Transformer being loaded at greater than nameplate kVA rating.
Higher than recommended (30C average / 40C maximum) ambient air.
Transformer enclosure ventilation openings obstructed or high content of dust and/or lint in transformer air ducts.
Load contains large amount of harmonics.
NOTE
GENERAL PURPOSE TRANSFORMERS RUN HOT! UNITS RATED 150C RISE, LOCATED IN 40C AMBIENT, CAN
HAVE ENCLOSURE TEMPERATURES CLOSE TO 90C/194F WHEN FULLY LOADED.