Bearing protection for inverter-driven motor

摘要

A refrigerant motor/compressor employs both a serviceable shaft-grounding device and a ceramic coating to protect a rolling element bearing that could otherwise be damaged by high frequency induced common mode voltage and current originating from an inverter that includes a plurality of IGBTs (insulate gate bipolar transistors). The shaft-grounding device includes a stranded copper wire brush that rides against an axial end of the shaft and a high frequency stranded grounding wire that conducts the induced current away from the shaft. The shaft-grounding device is sized and positioned so that it can be momentarily removed for inspection without having to evacuate the refrigerant. The ceramic coating provides an electrical insulating surface on a bearing bracket and other parts that support the bearing. The coating comprises titanium dioxide and aluminum oxide to provide a surface that is sufficiently hard and tough to resist damage during assembly, thereby maintaining the coating's integrity.