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Tips on Transformer K-factor

Category: PQ Theory, PQ Data Analysis, Analyzing Waveforms, Harmonics/Interharmonics

PMI's new white paper describes Transformer K-factor, supported by detailed tips for analyzing and recording K-factor!


Tips when making K-factor measurements:


  • Make your measurements in a “normal” steady-state waveform cycle, before or after a waveform transient.
  • Periodic capture waveforms are preferred for K-factor calculation.
  • Pay attention to the amount of current (RMS value) that is involved in large K-factor measurements.  If the current is low compared to the 60 Hz transformer rating, the K-factor may not be an issue.
  • Infrequent and short- lived mild surges and waveform anomalies rarely adds much to transformer heating.  When analyzing RMS current for transformer heating 5 or even 15 minute averages are appropriate.


Proactive monitoring of transformer load should be done to detect excessive heating that eventually causes the transformer to fail.  If a customer is planning a large expansion or load increase, before and after measurements should be performed.


Usually when a transformer fails, it happens very suddenly, interrupting customers and requiring immediate attention. A proactive approach is always better than having to put out fires.

Download White Paper Here