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I am setting up one of our new work truck it has a Marelli 480 3 phase 55kw gen on the back of it right now i only have it set up for 480 to run our big 40 -25 hp flatsaws.but i also need to get 120v 30a so that our guys can run coredrills and other equipment off of it as well.. i am getting 115 volts off of one of my t6 side legs .... would it be stable enough power to run my power tools or am i going to have to buy a transformer ... and if i need to buy a transformer can any one recommend a small version that i could mount in the truck and just run a couple outlets off for my 120v equipment!
 

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If the load is small you can tap off that leg as long as the other conductor has the same ground reference as the 480 volts. If this is a large amount of 120 get a 3 phase transformer, or in case a smaller amount a single phase 480 t0 120.
 

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Bilge Rat
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This looks like a basic 12 lead generator connected for 277/480 wye.

You can indeed get 120 (or thereabouts....) from it without using a transformer, provided a few conditions are met;

1) The total amp load of the 3ø stuff plus the 120 volt stuff cannot exceed the amp rating of the gen.

2) Generally speaking, most generators can handle a 20% current imbalance, so the 120 load cannot exceed 20% of the rated current of the gen.

3) Use the connection of T10, T11 and T12 as the neutral, and bond it to ground (most likely it already is). T6 (and T9) will be ok for the hot, as would T4 (and T7) or T5 (and T8).
 

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This looks like a basic 12 lead generator connected for 277/480 wye.

You can indeed get 120 (or thereabouts....) from it without using a transformer, provided a few conditions are met;

1) The total amp load of the 3ø stuff plus the 120 volt stuff cannot exceed the amp rating of the gen.

2) Generally speaking, most generators can handle a 20% current imbalance, so the 120 load cannot exceed 20% of the rated current of the gen.

3) Use the connection of T10, T11 and T12 as the neutral, and bond it to ground (most likely it already is). T6 (and T9) will be ok for the hot, as would T4 (and T7) or T5 (and T8).
Doesn't that give you 138 volts?
 
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