3-phase gen for single phase use?

[TimWA]

16KW diesel ex long-haul refrig generator, four conductors in the SO cord output whip, reading 220V equally between three hot legs & 120V from each to the ground. Can I hook up any two of the hot legs to two sides of a single phase panel, cap the third, and the ground for neutral? Do I get the full gen output that way or a portion thereof? Thank-you,
-Tim

 

[chris kennedy]

Most 3? genny's I have dealt with can be configured for 1?. Not sure about something as small as a 16, did you check the manual?

 

[TimWA]

Thanks, no manual with it unfortunately.

 

[GoldDigger]

16KW diesel ex long-haul refrig generator, four conductors in the SO cord output whip, reading 220V equally between three hot legs & 120V from each to the ground. Can I hook up any two of the hot legs to two sides of a single phase panel, cap the third, and the ground for neutral? Do I get the full 16KW gen output that way or a portion thereof? Thank-you,
-Tim

You need an actual neutral from the generator, not just ground if you will be feeding 120V loads. And you need an EGC as well as a neutral, whether the generator is being hooked up as SDS or non-SDS. Four conductors is not enough for that if you do not re-use the unused third phase conductor (which may not be allowed.)

Also you cannot have 120V L-N and 220V L1-L2-L3 coming from the generator. You would get 208V or else more than 120V. You cannot have both.

It is OK, if you take care of EGC and neutral properly, to connect two of the three phases to a 120/240 single phase 3-wire panel. But you cannot feed any 240V loads that actually need 240V or that cannot accept two ungrounded inputs. For example, for safety any switch which is part of your 240V equipment would have to interrupt both wires.
As long as you have only 120V loads and make it clear on the panel that it does not supply 240V, you may be OK.

You will get less than full generator output, but more than 2/3 of the nominal output. For more precision on that you would need to check the generator data.

 

[iceworm]

16KW diesel ex long-haul refrig generator, four conductors in the SO cord output whip, reading 220V equally between three hot legs & 120V from each to the ground. Can I hook up any two of the hot legs to two sides of a single phase panel, cap the third, and the ground for neutral? Do I get the full gen output that way or a portion thereof? Thank-you,
-Tim

You need to re-measure the leads. Your numbers are off. There a couple of ways it can be hooked up - but none of the ways match your voltages.
You should see:
Line to Line = 208V
Line to Neutral = 120V
This will be 208/120 Wye

OR​

Line to Line = 240
L1 to neutral = 120
L2 to neutral = 208
L3 to neutral = 120
This will be 240/120 Delta

After you get the new voltages readings, open the connection box and see how many leads there are - if you get lucky, there will be twelve.

We will need this before we can go any further.

Ice

 

[TimWA]

You need an actual neutral from the generator, not just ground if you will be feeding 120V loads. And you need an EGC as well as a neutral, whether the generator is being hooked up as SDS or non-SDS. Four conductors is not enough for that if you do not re-use the unused third phase conductor (which may not be allowed.)

Also you cannot have 120V L-N and 220V L1-L2-L3 coming from the generator. You would get 208V or else more than 120V. You cannot have both.

It is OK, if you take care of EGC and neutral properly, to connect two of the three phases to a 120/240 single phase 3-wire panel. But you cannot feed any 240V loads that actually need 240V or that cannot accept two ungrounded inputs. For example, for safety any switch which is part of your 240V equipment would have to interrupt both wires.
As long as you have only 120V loads and make it clear on the panel that it does not supply 240V, you may be OK.

You will get less than full generator output, but more than 2/3 of the nominal output. For more precision on that you would need to check the generator data.

Ok I get it, two hot legs can energize a single-phase panel in the regular way as long as only 120V loads supplied, 240V loads won't work. Yes I should run a dedicated neutral and keep the EGC as EGC. +2/3 output only, bummer. Thanks.

 

[TimWA]

You need to re-measure the leads. Your numbers are off. There a couple of ways it can be hooked up - but none of the ways match your voltages.
You should see:
Line to Line = 208V
Line to Neutral = 120V
This will be 208/120 Wye

OR​

Line to Line = 240
L1 to neutral = 120
L2 to neutral = 208
L3 to neutral = 120
This will be 240/120 Delta

After you get the new voltages readings, open the connection box and see how many leads there are - if you get lucky, there will be twelve.

We will need this before we can go any further.

Ice

Ok will recheck voltages this time with my bench meter, and count terminal box leads, thanks.

 

[qcroanoke]

Thanks, no manual with it unfortunately.

I would google or bing the manufacturer to see if a manual is available on line. Of course you will also need model number. As posted if it is a 12 wire generator you may be able to rewire it for the voltage you need and not have to do all the jerry rigging.

 

[StarCat]

Output

Output

The OEM or possibly an Engineer can give you a diagram typically to re-wire the stator for single phase output.
The difference in what they will carry is significant. If you expect to load it heavy you will need it configured for Single phase.

 

[GoldDigger]

The OEM or possibly an Engineer can give you a diagram typically to re-wire the stator for single phase output.
The difference in what they will carry is significant. If you expect to load it heavy you will need it configured for Single phase.

Even if you reconfigure it for single phase (using a twelve lead winding set and the wiring diagram shown here or on some generator web sites), you will still not get the full power output of the generator.
When you use a zig-zag connection to combine two windings in series to produce an output of the same phase as the third winding, you will not get equal current sharing, since the DC resistance of two windings in series is twice that of a single winding.
And you will get twice the single-winding output current rather than three times the current.
As a result, you will relatively efficiently deliver about 2/3 of the rated generator power without any gross current imbalance to interfere with generator operation.
But not the full output power that the windings could produce via three phase.

 

[rlundsrud]

single vs three phase

single vs three phase

If the generator is a 208 Y and not a 240 delta, why not just use it as a 3 phase?

Bob

 

[Tom Jones]

You also need to consider which legs are regulated and which are not.

What kind of loads are you powering? If you only have 120v loads, then you will get the same power from two legs of 120/208 as you would if you convert the machine to double delta 120/240. So no point in doing extra work. If all your higher voltage loads are OK with the 208, then you might want to leave it wye connected also. This all varies by the situation.