Transformer FAQ
What is transformer K-factor?
K-factor indicates the transformer's ability to carry specified nonlinear load currents without exceeding its thermal limits.
Direct answer
A K-rated transformer is designed to withstand additional heating caused by harmonic currents from nonlinear loads. The rating does not remove harmonics from the electrical system. It normally involves conductor, neutral, magnetic and thermal design measures that allow the transformer to carry the specified harmonic load within its temperature limits.
Why it matters
Servers, variable-frequency drives, rectifiers and switched-mode power supplies can produce harmonic currents. These currents increase winding and stray losses and may cause excessive neutral current.
What K-factor does not mean
K-rating is a harmonic-withstand specification. It is different from harmonic mitigation, phase shifting, filtering or power-quality correction.
Information required
Provide the load type, harmonic spectrum or design K-factor, neutral loading, capacity, voltage ratio, enclosure, ambient temperature and applicable standard.
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