Possible CauseSuggested Remedy
High ambient temperature Improve ventilation or relocate unit to cooler location.
Overload Reduce load; reduce amperes by improving power factor with capacitors; check for circulating currents for paralleled transformers - different ratios or impedances; check for open phase in delta bank.
High voltage Change circuit voltage, taps.
Insufficient cooling If other than naturally cooled, check fans, pumps, valves and other units in cooling systems.
Winding failure - incipient fault See "No voltage - unsteady voltage" below.
Short-circuited core Test for exciting current and no-load loss; if high, inspect core, remove and repair; check core bolt, clamps and tighten; check insulation between laminations; if welded together, return to factory for repair or replacement.
High harmonic loads Measure neutral current - replace with K-rated transformer
Possible CauseSuggested Remedy
Overload See "Hot transformer" above.
Metal part ungrounded, loose connection Determine part and reason; check clamps, cores and parts normally grounded for loose or broken connections, missing bolts or nuts, etc.; tighten loose clamps, bolts, nuts; replace missing ones.
External parts and accessories in resonant vibration Tighten items as above; in some cases, loosen to relieve pressure causing resonance and install shims.
Incipient fault - core or winding See above under "Hot transformer."
Possible CauseSuggested Remedy
Winding failure - lightning; overload; short-circuit from foreign object or low strength dielectricCheck winding; remove foreign object or damaged material; repair or replace parts of insulation materials.
Possible CauseSuggested Remedy
Weather, pollution, corrosive or salt atmosphere; overloads Remove rust and deteriorated paint; clean surfaces; repaint with proper paints and sufficient coatings.
Excessive heating discoloration If excessive heating discoloration occurs, check sizing, input voltage, or loading amps.
Enclosure damaged in placeReplacement enclosure parts available if inhibiting safe operation or visual integrity. Check our Accessories page.
Enclosure visually unattractivePaint available for our standard gray units. See our Touch Up Paint information under "Miscellaneous for all" section on our Accessories page.
Possible CauseSuggested Remedy
Overload Too small neutral conductor: replace. Severe unbalance between phase: rebalance and equalize loads.
One leg of wye bank openCheck associated fuse. If blown, remove cause and replace. Check for open circuit in winding of transformer in bank. Measure odd harmonic amps with RMS meter.
Possible CauseSuggested Remedy
Open neutral unbalanced loadsCheck neutral connections. See "Hot neutral line" above.
Possible CauseSuggested Remedy
Open neutral on wye bank ground in winding of one transformer in wyeCheck neutral connections and load balance. Check values of voltages between phases and phase-to-ground voltages. Vector should indicate source of trouble.
Possible CauseSuggested Remedy
Grounds on two legs of delta (delta collapse - loads "single phasing")Remove grounds from at least one leg of delta source.
Possible CauseSuggested Remedy
Open in third transformer of bank; operating in open delta Check fuses on supply to their bank; check winding of transformers in third transformer for continuity.
Possible CauseSuggested Remedy
Open in one phase of delta supply; two transformers now connected across one same phase Check fuse on supply; check supply circuit back to source for open circuit.

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