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VFD grounding

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T

timmer

Member
Location
Phila PA
Occupation
engineer
250hp VFD and motor ,was installed without ground ( emt is only bond) can I install a separate ground conductor only conduit? what size ground conductor ?
 
T

timmer

Member
Location
Phila PA
Occupation
engineer
pre-mature 250 hp motor failure (1.5yrs old) drive tech suggests bond the motor to the drive enclosure, more for VFD / motor functionality than code requirement
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
timmer said:
pre-mature 250 hp motor failure (1.5yrs old) drive tech suggests bond the motor to the drive enclosure, more for VFD / motor functionality than code requirement
Click to expand...
The drive tech is giving bad advice. You cannot ground or bond your way out of electrical problems.

In any case, the EG terminal on the drive is already bonded to the case of the VFD which is bonded to the sheet iron by the mounting bolts and the sheet iron is bonded to the enclosure by the mounting means. So what he is asking for is already in place.
 
petersonra

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
Speedskater said:
While EMT has a lower end-to-end resistance than wire,
it can be less reliable in exposed situations.
Click to expand...
That's just not true. A properly installed piece of EMT is very reliable. A badly installed wire can be unreliable. Do it right and either works.

If it gets damaged, it needs to be repaired instead of pretending a wire fixes everything. You do not want exposed EMT to be energized and not trip the OCPD.
 
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