Inverter Output - Handling phase-neutral aspects

A lot of contributors will not reply to a question this incomplete and undefined.

You will need to come up with a list of details of what you might consider to connect to what it has to ne connected to. Is this unclear enough?

It is advisable to wire the thing up in accordance with the manufacturer's instructions.

... and local electrical code.

Quite.

A very important subject about which most of the people are not care about.

It is not advisable because of the risk associated with such interconnection.

These two sources of supply should be considered as two individual sources of power; like, the one is private generation and other is public utility. Even for a LV switchgear, where we use an engine generator as a standby, the incomer breaker for the utility side should be with switched four pole version. This is a code requirement also.

Dear Musthapha

The OT comes from me. First because you do not even tell what inverter you have in mind.

Second because you don't tell what grid you have

Third because (except in the US model) you cannot connect a inverter (output) to a grid without using the neutral anyhow, since it is one of the two wires you cannot work around. D.

The input live(s) & neutral must be connected to the input supply, but the outputs are switch-mode, generally pseudo-sine-wave. Three phase versions are without neutral, single phase versions have two opposing live outputs.

For this reason there should be no attempt to tie 'neutrals' together: not only will this induce potentially life-threatening voltages in the neutral line but also cause spiking in the input supply.

Most inverters I have used require external smoothing devices to operate at near sine-quality. General rule: if it whistles, smooth it.

With the kind of inverters I think you have, you better stay far away from all the wires of the grid.

Grid tie inverters can be connected on a permanent base to the grid. And also in the US when 120 Volts types are used in a split phase.

The neutral there is not connected when L1 and L2 are used as 240 volts output.

A breaker or fuse is the only thing needed between.

OP does not mention whether is is a grid-tie inverter, or for variable speed drive of a.c. motors, hence the different suggestions.

It would help if he came back to clarify.

They rarely come back...

I have not seen an inverter (assuming you mean 3 phase) with an output Neutral connection. Can't see how that could be done without a transformer.

If you mean single phase as per a battery to AC mains inverter then no - isolate both active and neutral from the grid.

Assuming you have a single phase inverter that produces a mains voltage from say a 12 volt battery (because you did not correctly specify!! ), for the moment.

My personal take would be to ground the inverters ground connection/mental frame to house ground ( assuming that this house ground is fully and correctly bonded to REAL ground!!

Then tie the output marked as Neutral (not all countries mark/polarize the neutral, then all equipment used MUST have a double pole on/off switch), to ground, but only at the inverter.

Then when wiring units to the inverter, make sure that you always supply phase (the output pin that is not earth and not neutral!!) to the "correct" side in countries where this is a requirement, the UK for example.

(Note. In the UK the single phase plug fuse is only in the phase line and much equipment only has an off/on switch that switches the phase line only - when correctly connected of course!)

I would also add a modern form of an "Residual-current device", see this link:-

http://en.wikipedia.org/wiki/Residual_current_circuit_breaker

or whatever they are called nowadays, to drop the phase (not the neutral!) in the event of a fault current. There are some nice units around for usage on portable electrical equipment, with an even lower current sense that the usual 30ma., which I can say from personal experience, is still quite painful!!!

I am assuming that some sort of over current protection (even if its just a fuse, but a CB is better!) is already in place as the above only drops the supply in the case of a partial short to ground.

Most people do none of the above and risk a possibly fatal shock from over the counter battery to mains inverters units they have purchased, been given or found on ebay......

NO

Not advisable. keep it simple and separate.

Is this a UPS type or a Frequency converter?

If a UPS, what type?

That is why you should keep it separate : Separate inputs from Outputs to be on the safe side. The manufacturer would have tied the Neutrals if needed, from within the unit.