I am looking for a solution to third-harmonic induced problems. The industrial facility in question is fed with a three-phase 400V arrangement, with no neutral, from a 10 kV/400V delta-star transformer (with an earth taken from the star-point secondary).This distribution configuration feeds many large three-phase loads. Single-phase 230V loads are then accomodated by the provision of multiple 50 kVA 400V/230V delta-star transformers distributed throughout the plant, with the secondary star-point providing the neutral. The problem arises due to the fact that the majority of the transformers are designated as lighting transformers, and feed high-frequency fluorescent lighting loads, which produce high levels of harmonic currents (especially third)in the circuits.The transformers being generally approx. 90% loaded are starting to overheat, but more importantly there are very high rates of failure with the fluorescent tubes and electronic ballasts. My questions are (a) has anyone heard of harmonic producing electronic loads, producing harmonics, being themselves subject to failure from the effects of harmonics especially as in the situation above where the harmonics may be "locked" into the secondary circuit, and (b)are there any prooven solutions which are not "tuned" to specific fixed load conditions ? The solution must address the lamp failures as much as, if not more than, the transformer overheating.
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