Harmonic filter design for mixed single-phase three-phase load

A metals plant contains large 12-pulse rectifier loads and a single-phase induction melting furnace. Recently, the available fault current from the utility increased by 50% due to line improvements. Previously, the capacitor fuses on the induction furnace blew occasionally and replacing them solved the problem. After the utility line improvements, replacing the fuses does not solve the problem, and there are high harmonics throughout the system. Power and harmonic measurements were taken at all significant loads over a period of time to capture the operational cycle of the plant. The system was simulated in EMTP as a three-phase, three-wire system with the single-phase load included. A harmonic filter was designed to mitigate the resonance problem. The design was simulated and validated using the EMTP model.