Stand Alone 3 phase question

[Pezz351]

First a disclaimer - I am not going to do this install.

I have a diesel generator 20kW 3 phase 230V four wire (i am assuming wye, but not sure)

I need to hook it up to 3 pieces of equipment that take 480/277V 26 amps maximun.

This is a complete stand alone system.

What do I need in between the two? I think I will need a Wye/Wye transformer around 30kVA. What about a load center or distribution box? Basically what is the best way to hook this up and where do I go for the equipment?

 

[itsmoked]

First a few questions.

1) Are these "loads" 3 phase?

2) What are the three loads?

3) Is any single phase required?

4) Stand alone as out in a field no pre-existing grounding?

 

[SomeYahoo]

You also might want to check with the genset manufacturer to see if you can "re-wire" the generator to give the output you want. Often times, it is just switching around a few leads in the junction box and viola! you have 480V three phase.

 

[Pezz351]

itsmoked -
1) yes the loads are 3 phase

2) an air compressor, and 2 mixing tubs

3) no, not right now

4) I can ground the system, I have a deep water pipe nearby

GensetGuy - My generator is a Delco 3E-5891M2, behind a Detroit 2-71 engine, probably 30 years old. Any idea where I can find that kind of information?

 

[SomeYahoo]

Sorry, my quickie search didn't turn up anything. Maybe someone here can help you out with some way to test it out.

Interesting that it seems to be a 1200 RPM unit... I've never dealt with one and may throw my idea out the window. Phasing may not work with the lower speed.

 

[itsmoked]

That Generator was used by the thousands in Fruit Growers Express and PFE refrigerated rail box car service. They are pretty bullet proof. (Even the one some idiots pulled out of a car with an underrated fork lift that subsequently flipped over injuring two people ran fine after the event)

To hook it up you generally will need/want:

1) A breaker between the generator and transformer/s

2) A 3phase Dry type transformer or 3 single phase transformers. The three would probably cost slightly more but be much easier to lay hands on.

3) A breaker panel to hold three 3-phase breakers for your three loads.

4) At least one 10ft ground rod. Which will go to the breaker panel. Possibly one to go next to the generator, especially if there is much distance between the two.

5) Then disconnects for each of your loads. Switches that are mounted next to or on the equipment to allow immediate shutdown/disconnect if a problem arises, (head caught in belt, etc)

You can often use fuse/disconnect boxes which are sometimes easier to find and cheaper, with copper tubing replacing the fuses for your disconnect. I would never consider using fuses to protect ANY motor as they frequently blow only one, leaving the motor single-phased which leads to comments like, "itsmoked", before you figure out why its making a different sound.

6) Appropriately sized wire to hook all this up.

What else have I forgotten guys?

Now sometimes you can not use disconnects if the breaker panel is within, (I don't recall 5 feet?) of the machinery as the breakers themselves are then concidered the disconnects.

 

[itsmoked]

GensetGuy; Yes! they are 1,2OO RPM sets.

 

[alehman]

Grounding should be considered carefully.

You should ground the generator neutral, if in fact it is wye connected. This connection can be at the generator or at it's circuit breaker. If the generator is remote, install a ground rod as mentioned above.

The neutral of the transformer secondary should be grounded at the transformer or at the panel it feeds.

Install equipment grounding condcutors sized per the NEC, with all circuits. The generator and transformer grounds will connect togather at the transformer. If these are in a building, the generator neutral and transformer ground both need to be connected to a common grounding electrode system (building steel).