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In industry, Neutral - ground connection

1K views 10 replies 7 participants last post by  andrew79 
#1 ·
We had purchased CNC mc along with servo stabilizer. Our electrical source from Electricity board is 3 phase with neutral only.
We are make separate earthing by using earth bit and connected to the CNC via copper plate.
But CC service engineer came and checked the voltages between the ground and neutral, mulimeter shows 9.3VAC. And he complained earth fault.
Kindly suggest me, how to recover this issue? Can we connect the neutral to the ground copper rod together? acceptable or not?
[CNC mc doesn't needs neutral connection except servo stabilizer]
Kinldy suggest me assap.
 
#4 · (Edited)
You may not connect neutral to ground at branch circuit receptacles or inside appliances.

Like in a household electrical system you ground the neutral (bond the neutral to the grounding electrode conductor) only at the first main disconnect which can sometimes be upstream of what you consider to be the main breaker panel.

In a branch circuit it is possible for neutral to ground to measure some voltage. This should be negligible, generally no more than a volt or two, but will tend to be larger if more amperes are being drawn. Significant ground to neutral voltage under "normal" conditions may mean a loose connection somewhere, either in the neutral path back to the panel or the ground path (equipment grounding conductor) back to the panel.

If you drive a rod or bury a copper plate for use as a ground, that must be interconnected (aka bonded) with existing ground rods for the building using #6 gauge copper wire as a GEC (can end at and be clamped to an existing such #6 copper wire and need not be splice free).

In most parts of the U.S. only a licensed electrician may do work in buildings other than single family houses.
 
#7 ·
In most parts of the U.S. only a licensed electrician may do work in buildings other than single family houses.
I think it's pretty clear that this guy is not in the US or Canada.
 
#5 ·
You.ve got a potential difference between your main ground and your new ground. Hire someone to wire it correctly.
 
#6 ·
You guys totally screwed this up, and should get an electrician to do the installation. Neutral and ground MUST BE BONDED AT THE SERVICE, and your machine MUST BE CONNECTED TO THE SYSTEM'S GROUNDING BUS. It sounds like you installed a separate grounding electrode for this machine only, and connected the chassis to only that electrode and not to the system's grounding bus. This is a dangerous condition. You have no protection from ground faults, because it is unbonded.
 
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