I have an alternator with three phases with no neutral. Can I use a star or wye connection on these wires to create a neutral? Voltage from any wire to the alternator body reads zero.
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1\$\begingroup\$ It seems that the only way to create a "true" neutral is to use a transformer delta -> wye. \$\endgroup\$Antonio51– Antonio512025-11-25 18:39:43 +00:00Commented Nov 25 at 18:39
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1\$\begingroup\$ What would you make the star connection from? \$\endgroup\$Andy aka– Andy aka2025-11-25 18:39:57 +00:00Commented Nov 25 at 18:39
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\$\begingroup\$ and what would that "connection" consist of? If you're just shorting all three phases together, that can't work, right. \$\endgroup\$Marcus Müller– Marcus Müller2025-11-25 18:58:57 +00:00Commented Nov 25 at 18:58
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1\$\begingroup\$ But maybe the problem is easier than we think: Could you tell us what you need the three phases and the neutral line for (by editing your question, not just in the comments, please)? Maybe this is more of a problem of nomenclature than anything else. \$\endgroup\$Marcus Müller– Marcus Müller2025-11-25 19:01:17 +00:00Commented Nov 25 at 19:01
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5\$\begingroup\$ Does the alternator winding have six terminals, or three, or four? \$\endgroup\$Whit3rd– Whit3rd2025-11-25 20:42:19 +00:00Commented Nov 25 at 20:42
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1 Answer
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You can use an "NGT" "Neutral Generating/Grounding Transformer".
https://en.wikipedia.org/wiki/Grounding_transformer
This is effectively just a star/wye wound (or zig-zag wound) primary transformer with no secondary. The neutral is picked up from the star point.
I've used one in the past to generate a neutral from a rotary phase converter which used a delta wound motor.
Depending on the maximum phase imbalance you need to support, the transformer sizing can be much smaller than the overall system load.
Whether you can ground this neutral point depends on whether your three phases are floating or already earthed in some fashion. In your case it sounds like you could ground the neutral if needed.
