50kw diesel generator 12 lead, from 120/208 to 277/480

[TravisLatiolais]

Hello all, i've been watching forum for a while now. There are very good and interestng posts here. I finally built up the courage to ask my first question, so here it goes. I need to rewire a 50kw diesel 12 lead generator from 120/208 to 277/480. The generator is now wired as 120/208.(1&7 to L1) (2&8 to L2)
(3&9 to L3) (4,5,6,10,11,12 tied together and to neutral tap).
I believe to get 277/480 i need to rewire as follows1 to L1)
(2 to L2) (3 to L3) (4&7 together) (5&6 together) (6&9 together)
(10,11,12 together and to neutral tap).I think i am on the right track, any suggestions?

 

[wayne440]

My suggestion- get hold of the documentation for your particular generator if possible.

 

[ccjersey]

Wiring the 12 leads properly is only part of the process of reconnecting for different voltages.

You may/most likely also need to configure the voltage regulator/exciter supply/reference voltage sources for the higher voltage! Just depends on the design of the generator controls.

Be very cautious, magic smoke is expensive to replace!

 

[LionelHutz]

This soulds like the typical 12 lead NEMA or North American motor wiring. I'll point out that it appears each coil is 120V. So, if you put 2 coils in series you get a coil that is 240V. Connect the coils from each phase into a Y and you would get 416V phase to phase.

So, the generator would have to run at 115% of the present output voltage to produce 277/480V. The generator might be capable of this but the manufacturer should be consulted. Besides, as already pointed out, you'll likely have to scrounge up some documents to figure out how to reconnect the regulator and possibly change or reconnect some other parts in the unit due to the output voltage change.

 

[waross]

You are on the right track but

(5&6 together)

This should be (5&8 together). I am sure you know that and this is just a typo.
That should give you 416 Volts. Check the rating plate and if the set is rated for 480 Volts, (It will be very unusual if it is not capable of 480 Volts) just turn the voltage adjustment on the Automatic Voltage regulator until the output comes up to 480 Volts.
CAUTION: Be sure that the AVR sense leads are still connected to 240 Volts. That will be tapped off your 4-7 and 5-8 connections. (and 6-9 if three phase sensing is used).
If the AVR is self powered the power leads must be connected to 240 Volts (4-7, 5-8, and 6-9). If the set is equipped with a Permanent Magnet Generator that will power the AVR with no change in power connections.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TravisLatiolais]

Thanks guys for your response. It is greatly appreciated. After 2 days of calling Kohler, I got in touch with someone who can send me wiring specs. As far as voltage regulator, he did not have an answer and will call me back tomorrow. I will keep everyone informed on any progress i get. Thanks