Harmonic Current Issues — A Not-So-Harmonious Situation
2. The Pesky Problem of Harmonics
One of the most significant drawbacks of delta-wye transformers revolves around harmonic currents. In a perfectly sinusoidal world, everything would be smooth sailing. But in reality, many non-linear loads, like those found in modern electronics (think computers, variable frequency drives, etc.), inject harmonic currents back into the power system. These harmonics can wreak havoc.
The delta winding, in particular, can act as a sink for these harmonic currents, especially the third harmonic. It's like a drain that gets clogged, leading to increased circulating currents within the delta. This, in turn, can cause overheating, reduced transformer life, and even insulation failure. Nobody wants a transformer meltdown!
Essentially, the delta side provides a low impedance path for these zero-sequence harmonics. These currents circulate within the delta winding, causing increased losses and potential overheating. The wye side, while providing a grounded neutral, doesn't alleviate the problem within the delta.
Mitigating these harmonic issues often involves costly solutions like harmonic filters or oversized transformers that can handle the extra heat. This can significantly increase the initial investment and ongoing operational costs, making it a less attractive option in some situations. A proper harmonics study is required to understand the level of harmonic distortion. Without any study, you are simply guessing.
