Convert 600 Volt Stamford Alternator Output to 400 Volt

You won't have a neutral any more, but I think a relatively small zig-zag transformer can provide that. [??]

If you want to be covert, don't tell anybody.

This is probably doable with changing some things around but the exact configuration and other recommendations I would contact the manufacturer for...

http://stamford-avk.com/products/hc6-4-pole

http://stamford-avk.com/sites/default/files/literature/manuals/A040J849_HC_EN.pdf

The manufacturer will be the best authority to answer this question. I have no idea how their voltage regulation circuitry is configured. I doubt a simple switching between star and delta wiring will work. This is because 600V/√3≅346V This is less than your lowest desired voltage by nearly 9%.

I recommend you get the correct 3 phase step down transformer.

You probably can get this output. But to get 380V rather than the 600/√3 = 346 V you get by changing to delta connection is only possible by increasing the excitation current above the normal value. This causes an increase of rotor temperature rise and rotor operating temperature.

This could easily reduce the rotor life to a fraction of normal, that is 25%, being optimistic. If the generator is well used, that could be a short time.

It depends on the real rating of the generator relative to the engine kW. The standard engine rating was at 15 Celsius continuous, sea level to 150m, while generator rating is continuous at 40 celsius to IEC or British standards.

Many makers gave ratings which were the maximum engine rating for 1 hour in every 12 hours to give a more impressive rating (about 10% higher). Of course, they did not point out the considerable effect on life of pushing the engine to maximum, think 10% normal life. The generator might have been down-sized for 1 hour at the rating at 15 celsius too.

It also matters whether you really need that 963 kVA (which would be 770 kW at 0.8 power factor) or whether your load is 770 kW resistive (1.0 power factor) or less. Such a change may bring the generator back to normal rotor limits.

You need to look carefully at the engine and generator rating plates and the maker's rating curves. You have said nothing about your site temperature or altitude above sea level.

As has been commented, going to the manufacturer with your proposed winding connection change, load requirements, site environment and serial numbers of engine and generator is the sensible course.

Taking a used set, which has not been overhauled, and making changes equivalent to an overload is likely to result in a short, unpredictable, life before expensive damage.

Optimism and "It'll be alright on the day, Bluey!" have no effect on hardware.

Hopefully your instructor is supervising you while your your playing with expensive equipment! Have you even checked Stamford's web site? What happened to the old Volvo? Did it get smoked? It seems that you know just enough to be a danger to yourself ^! and the innocent equipment.

The internet can be your friend and you should learn how to use it. If still in doubt then call the equipment manufacture

I have emailed the manufacturer before i posted it(waiting for the reply) but i thought it is a good thing to learn from someone who knows about it or even practical experience about it. even if it is not possible you may learn a good alternative solution.Most importantly I BELIEVE BY ASKING THIS I MAY LEARN ABOUT A LOT OF RELATED IDEAS IT SHOULDN'T NECESSARILY BE ABOUT WHETHER ABOUT THESE ONE IS POSSIBLE OR NOT.

about the Volvo generator it has been working for more than one year and as i posted i use a resistor between the synchronization module out put and the governor input and it gave it stability.If you are familiar with these you would understand what i mean.Sorry my friend your comment is a judgmental,harsh comment , and no need to write for every question but thanks for your comments .i think it is better to keep all answers or suggestions technical and related.

Still frightened to use the telephone, then?

Why?

I have emailed the manufacturer before i posted it(waiting for the reply) but i thought it is a good thing to learn from someone who knows about it or even practical experience about it. even if it is not possible one may learn a good alternative solution.Most importantly I BELIEVE BY ASKING THIS I MAY LEARN ABOUT A LOT OF RELATED IDEAS IT SHOULDN'T NECESSARILY BE ABOUT WHETHER ABOUT THESE ONE IS POSSIBLE OR NOT.

about the Volvo generator it has been working for more than one year and as i posted i use a resistor between the synchronization module out put and the governor input and it gave it stability.If you are familiar with these you would understand what i mean.Sorry my friend your comment is a judgmental,harsh comment and no need to write for every question but thanks for your comments .i think it is better to keep all answers or suggestions technical and related.

Undefined: <...we...>. Logically, if <...we...> need to ask, then the knowledge lies outside <...we...>, therefore the answer is no.

Is the equipment manufacturer embraced within <...we...>? Do <...we...> have a telephone at hand and the skills with which to use it? CR4 does not offer training in the use of the telephone, despite overwhelming evidence of need for it from a fair percentage of CR4 postings; is this an opportunity for LynDoor Industries or the KrisDel Corporation (rhetorical question - NNTR)?

If you convert it to delta you will get 346V 91% of what you’re wanting, is that close enough?

cant it be increased using the AVR

A simple

telephone call to the equipment manufacturer can answer that one.

Maybe. First it assumes that the range of the AVR will allow for operation/control outside of its nominal range, not all do. Second, because of the change in the winding configuration and your desire to raise the voltage, the field current required may exceed the long term ratings of the excitation system, thirdly, which causes operation into deeper saturation of the iron. And don't forget to derate the machine to 67% of its original ratings.

Call the manufacturer for exact details of how this will affect the stability and life of the machine as well as violate any warranty that's left.

They have these things called transformers. You might want to invest in one.

Okay?

You got any spare 1 MVA capacity three phase step down or buck/boost units laying around?

Odds are the OP doesn't either and probably doesn't want to spend the money to buy one if the generator unit can be reconfigured and adjusted to do what he needs.

my guess: hard to turn that generator down.