ground to neutral voltage

H

Thread Starter

haseeburrehman

We have a UPS of 10kVA and trying to run a machine on this UPS. UPS is an online UPS and supply comes through this UPS. When power supply is there the GROUND to NEUTRAL voltages are about 6 volts while phase to neutral voltages remain 220V constant because UPS also supply constant 220V supply. but it is written in machine manual that for the safe operation of machine the voltage between neutral and earth must be less than a volt. Now if power supply interrupted then UPS shift supply to battery bank and in that case voltage between ground to neutral are zero. now the question is it safe to operate the machine with neutral to ground voltages between 5 6 volts whereas phase to neutral voltages are still 220V?

another thing which i want you to clear it to me that is it necessary to earth the neutral wire in single phase system? because if we ground the neutral wire by combining it to the earth wire the stray voltage disappear between neutral and ground.

Waiting for your reply. thanks in advance
 
R
An On-line UPS is normally working, AC input through a rectifier to battery, battery through an inverter to output AC.

In North America the neutral is normally grounded but you would have to check the code for your area.

The fact that the neutral to ground shifts from 6V to zero may be voltage drop on your main power panel, When the panel is alive heavy current causes the drop, when the power trips there is no longer a heavy load so the Voltage drop is less.

I suggest you trace the path of the neutral from the power panel, if it just goes in and out of the UPS there's nothing can be done.
Having said that I don't think 6V on the neutral is a big concern.

Roy
 
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