V0V Generator

[Andrew_van_Zyl]

Sorry to bring this up again but can anyone point me in the right direction?

I tested 140V L-E, and 80V N-E.

Adendorff assure me that if I bond neutral and earth I will get 220V V00. I've popped two Automatic Voltage Regulators since attempting this. Adendorff are unable to tell me why this is happening.

My City Power arrangement is 3 phase, neutral and earth are bonded and then separated in the DB.

I use a 3 phase changeover switch with live from the gen supplying all 3 phases.

Please excuse my crude drawing of the installation

Any suggestions how I can make this safe (apart from setting fire to the thing)?

[Derlyn]

One question. Did you get those readings with no load or was that with a load connected ?

When checking generator voltages, always do it with a load connected. A 40W incandescent lamp as load will work.

If your readings stay the same with a small load connected, then it's a VOV wound alternator and the neutral and earth cannot be connected together without first removing the centre tap earth connection on the stator.

If you bridge neutral and earth on a VOV wound alternator, you are basically shorting out half the windings on the stator and somethings gonna pop.

[GCE]

SANS requires a 4 pole change over
You could be creating problems with your neutral still linked to mains and earthing the incoming neutral
You may have become a better earth star point for the street

[Andrew_van_Zyl]

Light bulb moment... of course! This forum has been so incredibly generous with their time and knowledge - thank you.

As I see it I have 2 issues - a N & E bonding issue, and potentially a V0V issue (to be tested as per Derlyn)

I plan to replace the current 3-pole with a 4-pole changeover, and change the earthing arrangements to isolate the 2 supply systems to work independently as below:



All good?

[Isetech]

The bond must be on the generator, not the grid power.

[Derlyn]

Both the grid and the alternator must each have their own bonds .

ie. When installation connected to grid, the bond is on the grid.
When installation connected to alternator, the bond is on the alternator.