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Variable speed drives can induce voltages which build up on a motor shaft and then discharge through the motor bearings. This is due to an unwanted capacitance between the motor stator and the rotor. This ‘shaft voltage’ then builds up to a level which then discharges to ground the only way it can – through the electric motor bearings.

To monitor whether a motor has this unwanted shaft voltage build up, Electro Static Technology have joined forces with Fluke to produce a Fluke Scopemeter which comes with a conductive microfiber probe, which can be placed into contact with a rotating motor shaft to measure any stray voltages which may be present. The Fluke Scopemeter then displays the waveform of the measured voltage, which can be saved for future analysis in the scope’s internal memory.

Induced shaft voltages normally discharge in short bursts, and it’s the bearings which see the brunt of the damaged caused. Voltage discharge through bearings can cause pitting on the bearing races and ridges, called fluting, on the raceway walls. All this can result in noise and vibration and eventual bearing failure. 

Any bearings which have been subjected to the phenomenon above, aptly called electric discharge machining (EDM), will need to be replaced with new components.

Usually the ball mill bearings are the full complement tapered roller bearings which are used in the roll, roll location and the press mechanism. Those ball mill bearings on the transmission device, transportation and other auxiliary equipments are in the class of ball mill bearings.

In a proud tradition, the same families that started the company in 1957 keep EmersonBearing rolling by specializing in bearings for OEM and MRO markets throughout the world. Emerson Bearing’s highly knowledgeable staff housed in their 23,000 square foot facility provide bearings ranging in size from 3mm to tunnel-boring 15-foot-diameter giants.