| Possible Cause | Suggested 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 Cause | Suggested 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 Cause | Suggested Remedy |
|---|---|
| Winding failure - lightning; overload; short-circuit from foreign object or low strength dielectric | Check winding; remove foreign object or damaged material; repair or replace parts of insulation materials. |
| Possible Cause | Suggested 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 place | Replacement enclosure parts available if inhibiting safe operation or visual integrity. Check our Accessories page. |
| Enclosure visually unattractive | Paint available for our standard gray units. See our Touch Up Paint information under "Miscellaneous for all" section on our Accessories page. |
| Possible Cause | Suggested Remedy |
|---|---|
| Overload | Too small neutral conductor: replace. Severe unbalance between phase: rebalance and equalize loads. |
| One leg of wye bank open | Check 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 Cause | Suggested Remedy |
|---|---|
| Open neutral unbalanced loads | Check neutral connections. See "Hot neutral line" above. |
| Possible Cause | Suggested Remedy |
|---|---|
| Open neutral on wye bank ground in winding of one transformer in wye | Check neutral connections and load balance. Check values of voltages between phases and phase-to-ground voltages. Vector should indicate source of trouble. |
| Possible Cause | Suggested Remedy |
|---|---|
| Grounds on two legs of delta (delta collapse - loads "single phasing") | Remove grounds from at least one leg of delta source. |
| Possible Cause | Suggested 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 Cause | Suggested 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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