Protection of VFD-Driven Motors in Plastics Production

This document is a technical report that outlines the challenges associated with variable frequency drives (VFDs) used in plastics production processes. It describes how VFDs can induce damaging voltages on motor shafts, leading to premature bearing failure and significant production downtime. The report details the solution provided by AEGIS® Shaft Grounding Rings, which offer a low-impedance path to ground for these harmful voltages, thereby protecting motor bearings. The effectiveness of the AEGIS® Rings is demonstrated through a case where a 300 HP motor experienced bearing failure due to VFD-induced voltages. After installing the grounding ring, the voltage was reduced from 28.8 V peak-to-peak to a safe level of 2.0 V peak-to-peak. The report emphasizes the importance of proper installation and adherence to best practices to ensure long-term protection against electrical bearing damage.