Hi dear 'ask me' community,

I have a 30KW generator with a automatic transfer switch - it has a three phase input U, V, W and N which
Needs to be connected to the city power it then has an output that goes to the building. How do I know
Which phase of the city supply needs to go to the U, V, W and N (neutral). Can an incorrect phase
Connection cause damage to the generator - how can I avoid this!

Your help will be greatly appreciated!

Thanks - Maruli!

Please explain your experience with 3 phase.

I am not familiar with the code letters you refer to "U, V, W and N (neutral)".

Am I correct you are not located in the USA or Canada?

Are you familiar with a Phase Rotation instrument?

Use a phase sequence meter. Phase Rotation

Contact the transfer switch manufacturer. As long as the generator and the utility are providing power from the same phase you should be OK as long as the transfer switch doesn't detect phase reversal. Confirm with manufacturer.

My opinion on this is that this is ABSOLUTELY NOT a DIY job. You should NOT be messing with this stuff, especially if you have to come to a DIY site to ask questions.

PLEASE call in a professional to do this job for you!

Quote:

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Originally Posted by tkrussell

Please explain your experience with 3 phase.

I am not familiar with the code letters you refer to "U, V, W and N (neutral)".

The generator is a Chinese product - looks like they are using German notation - what I can see from
the circuit diagram supplied, U=L1, V=L2, W=L3.

Am I correct you are not located in the USA or Canada?

Yes I am located in South Africa.

Are you familiar with a Phase Rotation instrument?

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No - but I would presume it could tell be the 120 deg difference between the phases.

Thanks.:)

Quote:

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Originally Posted by KeepItSimpleStupid

Use a phase sequence meter. Phase Rotation

OK - will try to get hold of one!

Contact the transfer switch manufacturer. As long as the generator and the utility are providing power from the same phase you should be OK as long as the transfer switch doesn't detect phase reversal. Confirm with manufacturer.

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Will check with manufacturer first.

Thanks for all your information - much appreciated!:)

Quote:

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Originally Posted by stanfortyman

My opinion on this is that this is ABSOLUTELY NOT a DIY job. You should NOT be messing with this stuff, especially if you have to come to a DIY site to ask questions.

Oh I did not know that this is a DIY site I thought I could ask any questions!:(

PLEASE call in a professional to do this job for you!

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Being in Africa it's often the case that the professional can blow-up your equipment - so it's better
To research and know exactly what needs to be done yourself!:)

Ok.

Any generator system needs a transfer switch, either a manual unit or automatic.

This isolates the utility line from the generator output, so the load only connects to either the utility or the generator, and there is no chance of the gen power getting out into the utility lines.


Simply use a phase rotation instrument to check and note the rotation of utility lines and of the gen output at the transfer switch. If the gen output is different that the utility, simply switch any two wires of the gen output.

Now the load will be fed by either the genset or utility with matching rotation, or sequence, of phases.

Quote:

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Originally Posted by maruli

Being in Africa it's often the case that the professional can blow-up your equipment - so it's better
to research and know exactly what needs to be done yourself!:)

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Here is yet ANOTHER case of knowing your location FROM THE START would have been a BIG help. :rolleyes:

Quote:

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Originally Posted by tkrussell

Ok.

Any generator system needs a transfer switch, either a manual unit or automatic.

OK

This isolates the utility line from the generator output, so the load only connects to either the utility or the generator, and there is no chance of the gen power getting out into the utility lines.

OK

Simply use a phase rotation instrument to check and note the rotation of utility lines and of the gen output at the transfer switch. if the gen output is different that the utility, simply switch any two wires of the gen output.

OK I have read up on a phase rotation instrument, and I will be able to obtain one locally!

Now the load will be fed by either the genset or utility with matching rotation, or sequence, of phases.

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Your information has helped me a great deal - thank you very much!! :) :) :)