How do I improve the polarisation Index results on a large generator?

Question

I am working on a Brush Induction generator in West Africa. The polarisation index test is just below 2. I’m injecting 5,000 VDC using a Fluke 150B. The generator typically produces 22MW at base load. Its rainy season here (aprox. 28 deg C) and the alternator has been stood a couple of months within an enclosure for a few months without heaters. I am now able to run the heaters for approximately 12 hrs per day but that is all. I have the possibility of using a large welding machine on site. The results have not really improved during the last week, do I need to be more patient or try something else. Before this unit was moved the PI value was 3.5.

Answer 1

hey, I think you should consider the ammount of time that it was exposed tothose conditions whitout heaters, maybe you should wait a bit more, if it doesn`t work IEEE has a standard that can help you imporvethis indicator, i guess is IEEE 44.3.

if you find the solution let me know, please.

Answer 2

Spray a moisture remover once the generator is stopped for a long period.Install infra-red heater bulbs around the generator casing.