3S7b: (20 min.) Case Study – Bearing defects caused by electricity. New methods to detect electric problems in machines

Harald Reiners, Manager Condition Monitoring Services, FAG Industrial Services


A large number of bearing defects is caused by electrical problems. In many cases these bearing defects show typical signs like riffles in the outer race. But new studies show that electrical influence can also be a trigger for white etching cracks (WEC). A phenomena which can lead to an early bearing defect and can only be detected in a laboratory with complex methods.
There are many studies about current problems due to vfd driven motors. The protection of the bearings in electric motors is often done by isolating one bearing or by using shaft grounding methods. But who is taking care of gear boxes, main bearings in windturbines or other drives? How is it possible to detect if there is any current source which can lead to current flow through a bearing and hence to a early bearing defect..
This presentation will show new measurement methods to detect critical electric situation in machines. Measurements which can be done from outside of motors, large bearings like main bearings on wind turbines, paper machines … as well as from inside of gear boxes and several other machines.


Harald Reiners, born 1966 in Germany, got his training as an electronic engineer. After that he worked in a computer company for 14 years as the head of the hardware department. 2002 he joined the condition monitoring group of FAG Industrial services as a field service engineer which he is now leading for 9 years. As a level III certified specialist he did condition monitoring in several industries as wind power, marine, oil and gas, paper and steel. Additionally, he worked as a trainer and developed several special condition monitoring hardware and solutions.