Ground (Earthing) to Neutral Voltage

Are both UPS are properly earthed to the same earth or separated earth.?

yes, both ups are connected to the same earthing point properly.

If both are properly earthed, then why is this number of any interest?

The purpose of the earth conductor is to operate the circuit protective device(s) in the event of a fault.

Do you get the same 6 VAC at the wall socket with the UPS unplugged?

yes sir,I am getting 6vac at the wall socket with the both ups unplugged.

dear,

earth connectivity of 6V socket is not proper. Since, 2nd socket has 0.002 V with the same electrode.

Just check - earth conductor continuity from 6V socket up to the electrode, ( wire must run seperately - direct from socket to earth & nott via other circuits )

If confident about the earth wire cotinuity, then just replace the socket. Earth PIN may not be proper.

I am sure, your problem will be solved.

sir ,my doubt is here .....

why does difference of neutral to earthing voltage in both ups output? while both ups are connected to same parallel socket one is showing 6vac and another is showing 0.002vac.I have interchanged the power connector is showing same problems.(But main power socket (where is the ups plugged ) has 6vac in neutral to earthing.)

First, did I understand you correctly when you said the 6 VAC is present at the wall outlet or did you mean that the 6 VAC is present at the UPS, regardless if the UPS is plugged in or not?

My guess is, since you stated that the 6 VAC potential between ground and neutral is present at the wall outlet with both UPSs disconnected, the two UPS are internally wired slightly different or an internal component may be bad in the one.

Another tact to try to isolate the problem:

Try the two UPSs on a completely different circuit (different breaker or even another house).

If they both work correctly, then you can be sure it is the house wiring.

Did anyone say in all of that if he lived in an apartment complex or condo. Might have a bearing on the discussion.

If that was true I would be giving some people too much credit. ;-)

Dear AH.. hat's off to you. Your knowledge base exceeds my expectations of your age in the photo! MIT grad? I'm the one who "learnt" OHM's law the hard way back when they had awesome flyback voltages to play with and purdy blue lights inside those vacuum tube rectifiers. (X-rays?) Yes, I was the teenaged mad experimenter who snap, crackled & popped every immaginable device of the era. I wonder when that 60 hz humm's gonna stop?

Seriously though, what are your thoughts on negating entropy?

I know, they say it can not be done. Who's they?

"Seriously though, what are your thoughts on negating entropy?"

A good breakfast!

You can't effectively take on the day if you are not properly nourished!

------

When I was in high school I met this guy that introduced me to building tube amps. That was how my electronics education actually started. To me they were really cool and exotic. ICs and transistors were too passé. I just completed a 60 WPC stereo tube amp from scratch (well, I did not wind the transformers) last Fall using the old KT88s just to recapture the magic again. Fun project and I learned a lot.

It sounds like you had a great childhood and I can see engineering was already running through your blood at an early age. ;-)

My understanding is the blue inside the tubes is a combination of trace gasses and other contaminants that are attached to the metal and glass of the tube. No audio, radio, or TV tube that I know of gets enough voltage to generate X-rays.

First of all thanks to all and specially to you for best cooperation.

sir

I have checked in different place it is showing same problems whatever it was showing but instead of 6vac it showing 1.3vac equal at the main circuit breaker(neutral to earthing voltage) I think both ups are designed in different way.one ups has battery input 110v dc it means it may has auto transformer and another ups has battery input 48 v dc ,it means it it is using step down transformer .conclusion is that auto transformer has common neutral for primary and secondary winding while step down has seperate winding that why one ups(having auto transformer) is directly passing the neutral to earthing voltage and another ups (having step down transformer) is not passing to the output. Am I right?

Vsar brings up a good point. Have you measured the output of the UPS under load?

If you unplug the UPS and measure its output, does it still have the difference between neutral and ground?

Maybe it is a good time to consider calling or writing the manufacture. Sometimes you can get a tech or an engineer that can help you.

Your voltage measuring device may just be picking up / displaying stray voltage readings (not real) coming from oscillators (chopper circuits) built in to the UPS units??

Good point. Do NOT use a DVM to measure this voltage. Use a good old-fashioned analogue meter, because it is not sensitive to odd hi-impedance signals.

The voltage you are seeing at the wall socket between neutral and ground is due to the voltage drop in the neutral conductor. It will vary with the current on the branch circuit.

Six volts is kind of high but not unbelievable.

The difference between the UPSs is due to internal wiring differences. The UPS with the low neutral offset voltage has the output common bonded to the protective ground internally.

The UPS with 6 Volts between common and ground just passes the protective earth (ground) through without bonding it to the UPS output common.

Check it out and see if I am not right.

Sometimes, it think people get too theoretical and over analyze these things.

TT3

Dear Manvendra,

You may check the following points to overcome your problems :

1) In power socket, in opencircuit condition( i.e. on load is connected in the socket), if you find N- E voltage is 6volt A.C., the wiring connections are not healthy. You must check the earthing conneciton, looseness in Neutral connection, conditon of Earth Staton itself It is better to measure the Earth resistance value by a Earth resistance tester. By physical as well as electrical checking methods, you may find out the location of looseness in Neutral in neutral connetion.

2)In the UPS you may please check the mettalic screen between two windings is properly connected to transformer body and transformer body is properly earthed.

Dear Manvendra:

From the problem cited what I feel is that in first UPS (6kVA), there is no isolation between the input and output and the suplly side neutral and earth connections are coming through to the load side. In the second case (5kVA) total isolation is there between input & output by deriving seperate neutral at the transformer secondary.