3 phase gen set neutral/earth

[davesparks]

I suspect the degree of imbalance to cause problems is probably 30% of the total capacity, not 30% of any light load. It is rated around 24A per phase so I would aim for less than 8A imbalance.

No, 30% of the actual loading is what I have always worked to.
The voltage regulators can get very upset if a light load is running imbalanced in my experience.
They seem to be more tolerant of imbalance once they've got a bit of load on them.

I once arrived on an event site to start setting up and found one of the pair of 200KVA generators on and hunting. The site guys had started it up themselves and plugged in a few single phase leads to run their tools, kettle etc, mostly on the same phase.
The cause of the hunting was the AVR having gone kaput likely caused by the unbalanced light loading.

As I said, this is just personal experience so may not be technically correct.

 

[pc1966]

That is interesting, so not really an issue for the alternator but something odd with the AVR? Will bare that in mind!

 

[davesparks]

Sorry if I should have mentioned that before but I have measured this and I am getting 230v between the earth and phase conductors. Does this mean that the earth conductor can be used safely to do what I spoke about above and split the supply before the 230v install?.

No, just no, don't do it!

The earth is unlikely to be the correct size. Also it may not go directly to the star point, it probably has half a dozen connections along the way to various bits of metal which may or may not have slightly high resistances, you could end up with current flowing through metalwork that was never intended to have current flowing through it, or random voltages on exposed metalwork.
Not to mention the disaster that will result if that connection to the star point were to fail.
[automerge]1587731298[/automerge]

That is interesting, so not really an issue for the alternator but something odd with the AVR? Will bare that in mind!

Out of balance can cause plenty of issues for the alternator and the engine too, especially on big generators with big out of balance conditions.
But older AVRs (I don't think recent ones suffer so badly) seem to be somewhat over-dramatic.

 

[Apex13]

No, just no, don't do it!

The earth is unlikely to be the correct size. Also it may not go directly to the star point, it probably has half a dozen connections along the way to various bits of metal which may or may not have slightly high resistances, you could end up with current flowing through metalwork that was never intended to have current flowing through it, or random voltages on exposed metalwork.
Not to mention the disaster that will result if that connection to the star point were to fail.
[automerge]1587731298[/automerge]


Out of balance can cause plenty of issues for the alternator and the engine too, especially on big generators with big out of balance conditions.
But older AVRs (I don't think recent ones suffer so badly) seem to be somewhat over-dramatic.

Ok, thanks, I understand that the earth conductor may not be going straight to the alternator as it probably does tag the trailer chassis/frame etc on the way and therefore isn't able to be used as the neutral but being that there is 230v present between the phase and earth conductors am I right in assuming that the earth does in some way return to the alternator and therefor should be possible for me to run a new conductor or better, a full new supply from there to the panel, giving me my neutral?
If this is possible, does this mean the existing earth core would be better to be disconnected as we are not sure where it runs to, or is it then creating potential problems without re-earthing everything that it may be tagging along the way again? I would be expecting to bond the frame of the trailer etc as part of the new install anyway but not knowing what else the original earth is tagging along the way is it better left intact if it goes back to the alternator eventually anyway?
Thanks