has anyone got experience of regular bearing failures in machines with VSD? the motors in question range from approx 22kw - 250kw and are double star-wound to facilitate a wide speed range. We have been told that the motors and VSDs are matched (not sure who manufactures the motors but inverters are from various sources including Emotron, Bosch, Yasakawa to name a few).
The bearings are not showing the usual ESD damage indications but we are experiencing short life (less than 8000 hours in some cases). The bearings on some units are insulated (80kw plus). I want to know if it is the bearings that re undersized or if there may be another issue