Pleasantly surprised with a quality and informative video. Thanks! Not sure if anyone’s mentioned it, and I know this is an 8 year old video, but there’s a typo in the title cards at the start of the video.
Good catch. Somehow the title template was inadvertently changed deleting the "s" in always. Thank you for your time watching the training. Appreciated.
I have excellent results with these shaft grounding brushes from Helwig too. They are simple to install, not very expensive and last a lot longer than the carbon fiber filament rings.
Yes - the Helwig style high silver content brush is a good solution as well (there are other makers of this style as well). They have the advantage of being easy to monitor for wear and easily replaced during a motor shutdown. We have had an issue where the shaft current was so high that the pig-tail lead melted! This was discussed in our bearing failure analysis video. Since that incident, Helwig has come out with a more hefty version of their shaft grounding brush. Finally, if your shaft current source is an IGBT Variable Frequency Drive (most modern VFD's are), you should check out the CoolBLUE inductive absorbers solution. If proper initial testing (requires specialized test equipment) is performed, these devices are a permanent maintenance free solution for shaft currents. We have a couple of videos here that explain in more detail. Check them out. Thanks for your comments Randy K.
EMF cores stop common mode current before it's get to your motor. This protects your motor insulation that ground rings or insulated bearing don't offer. 3Phi
Great stuff, Very informative...I'm finding (by vibration analysis) quite a lot of our motors running on VFD's have electrical interference, I've reduced a bit by changing the switching frequency of the drive but hoping this will be a better solution.? Will be giving the shaft voltage test a go..not at 4160 volts though!!!
Glad you are able to find and address this somewhat hidden but expensive destruction. You may also want to look into CoolBLUE cores which, once installed, require no maintenance. Check out videos on our channel which discuss this solution to VFD caused shaft currents. Thank you for the kind comments.
The solution is to have the VFD as close to the motor as possible with as short wiring run as possible, also they make special shielded wires for VFD use that you can ground and it greatly reduces the EMI.
wonderful information and i am pressed with the instructor's knowledge and looks professional ...:) while the student looks like he just rolled in dirt, plus the motor is clean...:/
q zorn - thank you for taking the time to watch our training and commenting. The trainer, Jim Hudspeth, has 40+ yrs in the industry and takes great pride in helping others. His current position is full time training of our team and customers at all our plants. Thanks again for investing the time.
does current passing thru shaft also happen to induction motor (with insulated bearing) as it is widely found in VFD motor and what can be the cause for this problem to occur.
Yes - we test run all motors at nameplated running voltage to ensure motor integrity. Issues such as hidden insulation defects and true magnetic center can only be fully discovered by a full voltage test run.
Awesome video. Thank you for this post. I have a 10hp running off a VFD that does not have any shaft brush or a grounding ring. I was told by my journeyman that the bearings on the motor are fluted. Is it too late to install a grounding ring/shaft brush to save it?
Thank you for the compliment. Once your bearings races are fluted, the bearings will continue to degrade at an exponential pace as they are already physically damaged. The interaction between the rolling balls against fluted bearing races will continue to fail the bearings despite measures to remove shaft currents now. We would recommend immediately replacing the bearings before a catastrophic failure occurs requiring complete motor replacement. Bearing replacement now is far more economical. After the bearing replacement, install either shaft grounding or CoolBlue cores to alleviate the bearing damage from shaft currents.
ReedElectric thanks for the response!! The customer is more than likely just going to want to replace the whole motor. I suggested one that already has the aegis grounding kit installed
Excellent catch Dale. Our editor is very embarrassed about the missing 's'. Correction requires replacement which does the disservice of breaking the link to this original video that many other sites have been using for training. Thank you for noting this flaw as well as your positive comments - much appreciated.
