VFD grounding
- Thread starter timmer
- Start date
- Location
- New Jersey
- Occupation
- Journeyman Electrician
IMO no. What's wrong with the EMT as the EGC?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
IMO you can but what purpose would it serve?
The EMT is a better EGC than any wire.
The EMT is a better EGC than any wire.
ptonsparky
Tom
- Occupation
- EC - retired
IMO, As far as the NEC, nothing, unless the installation manual says otherwise.
Reading some on EMI/RFI and as I understand at the moment, EMT may not be the best.
ptonsparky
Tom
- Occupation
- EC - retired
Search for Applied EMI/RFI Techniques on the Automation Direct website. Fairly short, unsophisticated and may be just another opinion.
I would imagine there are multiple other sources in way more detail.
I would imagine there are multiple other sources in way more detail.
ptonsparky
Tom
- Occupation
- EC - retired
From what I understand the motor should be EG to the ground terminal directly next to the load terminals.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
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.
ptonsparky
Tom
- Occupation
- EC - retired
Nothing in the AD PDF is intended for premature motor failure.
How old is the motor? VFD rated?
What distance from the drive?
Voltage?
Speedskater
Senior Member
- Location
- Cleveland, Ohio
- Occupation
- retired broadcast, audio and industrial R&D engineering
While EMT has a lower end-to-end resistance than wire,
it can be less reliable in exposed situations.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
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.
ptonsparky
Tom
- Occupation
- EC - retired
Load reactor or filter?
D. Castor
Member
- Location
- Port Angeles, Wash
- Occupation
- Electrical Engineer
What's the theory on how the lack of a ground wire caused a phase-to-phase short?
An EGC in a conduit separate from the phase conductors in the EMT will not be an effective ground for fault current. If the concern is EMI, the EMT should provide reasonable shielding. For 20 feet, you could replace the circuit entirely with Okonite C-L-X and get three ground wires inside the aluminum cladding.
An EGC in a conduit separate from the phase conductors in the EMT will not be an effective ground for fault current. If the concern is EMI, the EMT should provide reasonable shielding. For 20 feet, you could replace the circuit entirely with Okonite C-L-X and get three ground wires inside the aluminum cladding.