PQ CORNER Power Factor Correction and Harmonic Resonance: A Volatile Mix

16 EC&M June 2003 I ndustrial and commercial customers constantly scrutinize their monthly electrical usage, looking for ways to save money. Installing power factor correction capacitors can reduce costly penalties imposed by the utility and help pay for the capacitors in a relatively short amount of time. The payback period can be as short as four to six months for capacitors installed on power systems in locations like hospitals and paper mills. However, you can’t indiscriminately add power factor correction capacitors to a system without understanding how their presence will affect the system. Variable frequency drives (VFDs) for motors, DC power supplies for computers, electronic ballasts for fluorescent lighting, and other non-linear loads can create harmonics. If you don’t consider the existence of these harmonic sources and the inductive reactance of the existing system, you’ll create the potential for harmonic resonance.