Harmonic Filtering and IGBT Rectifiers
Q: What is harmonic filtering?
A: Harmonic filtering is necessary for large 3-phase UPS plants to limit the electrical noise the rectifier generates back into the Eskom power grid. Bad harmonic distortion can prevent a building’s power-factor correction from working — driving up electricity costs unnecessarily — and can affect other equipment connected to the building supply, including overheating UPS cables and supply distribution boards.
Effects are invisible to the eye but real. The accepted target is less than 3% total harmonic current distortion (THDi) back into mains.
Technology evolution: historically achieved with a 12-pulse rectifier; modern Riello UPS units use an IGBT rectifier instead, which is far more effective and requires less bulk.
Connections
- Eskom — referenced, source: https://standbysystems.co.za/ups-batteries-questions-and-answers/