Offshore oil drilling platforms typically use generators to provide power. Complications can occur when large variable frequency drives (VFD) or DC drives are used for down-hole/product pumping or drilling applications. This paper discusses the problems (flicker, mechanical resonance, poor power factor, high harmonic current, and reduced production capacity) that occurred on one North Sea oil drilling platform, and shows how an active harmonic filter corrected these problems. Data from power analyzers are presented to define the scope of the problem and the results of the applied solution. An economic evaluation defines the payback from increased production