Has anyone experienced an issue like this in the past? I have read through numerous posts and did not come upon any electrical fluting beyond the motor. And Ron Brook, no, the motor does not have shielded cable, and there will be no intention of replacing the current cable with shielded cable. I noticed you're quite knowledgeable and passionate about the correct installation of VFD drive systems. Much more than our electrical group for certain.

Thanks, Rocking Pine.


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Dear Pine
I'd experienced a similar case a year ago with forced draft fan with VFD.
Generally, the electrical charge flows through shaft to bearing then to motor body finally to the ground. unfortunately in your case motor and pump have same structure so I think the best solution is to use shaft grounding ring "SGR" which can help to dissipate the charge without affecting the pump "structure".
There are other solutions ,but sometimes not valid, to use ceramic bearing or to coat the outer ring of bearing "but it may need some machining processes with motor bearing house".
Yeah I have come across something similar. The ones I have seen have been in paper machine drives with the current not correctly going to ground but going through a drive shaft and into gearbox input shaft bearings. Have also seen in a motor that drives a vacuum pump with gearbox in between and the gearbox bearings and gear teeth showed signs of fluting.

I think most issues were caused by incorrect grounding so I think you might want to look into that. If that doesn't help then you would need to look into shaft brushes and cabling. I think using ceramic bearings is just an expensive temporary fix where are actually not fixing the problem.

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