09-15-2012 12:06 PM
We are encounting a problem with one of our TUG boats, equipped with Gen Set CAT 3304. We are forced to repair the generator (model SR4-60Hz/440V/1800RPM) due to bad insulation to one of the winding.
Winding#1-Lead T1 : 550MOhm
Winding#2-Lead T2 : 550MOhm
Winding#3-Lead T3 : 0.11MOhm
We are in possession of spare generator CAT 3304 50Hz/380V/1500RPM and my question is: Can we use the stator of the spare unit or can we use complete unit if we swap the excitation from the old unit?
What is the way to remedy the old unit? Can we repair the insulation without rewinding?
The old unit Specs:
CAT Genset 3304
Arrangement number: 4W-8958 Arra
Kindly ask for opinion and advices.
09-15-2012 04:31 PM
The same generator arrangment number has available rating in 50 and 60 Hz from 55 to 125 ekiW, not need to swap anything unless it's bad, just run the 50 Hz nameplated generator at 1800 for 60 Hz and adjust the voltage. Make sure AVR connections are correct.
09-17-2012 03:40 AM
Thank you for the precise information.
I have an additional question in respect with the excitation.
The unit with 50Hz plate excitation voltage is 42V/8.2Amps and the unit on 60Hz the excitation is 33V/6.5Amps. Will that be an obstacle to exchange the unit?
09-17-2012 10:02 AM
No, actually what you will see in practise with many dual rated generators is that the lower speed rating requires a higher field output to make the rated voltage. Has to do with the winding designs, essentially this is a 60Hz machine that will operate within thermal limits if properly applied at 50 Hz.
To prevent confusion at a later date, you may want to contact your local dealer and ask them to get you an updated nameplate. If the unit has been sitting around for some time, make sure you do a complete megger test on it, just to make sure you don't have any problems after the swap. Also pay attention to the generator rear bearing, I have found in the past that units that had spent most of their life at 50 Hz then rerated had bearing problems a short time later. Since the bearing is the same for both ratings, I had always figured it was due to the fact at a lower speed the bearing would take more abuse and it hadn't been maintained properly, at the higher speed those deficiencies showed up quickly.
Hope that helps, Mike L.
10-25-2016 05:02 PM
We have two SR4 generators of 500 KW at 1800 rpm and 600 volts. We want to use them on a boat that the voltage is 440 volts. The serial number of one generator (they are twins) is 5NA07963 and the arrengement is 5N5079.
Can it possible only by adjusting the voltage regulator.