Insulation Resistance Test for Alternator

Warm it all up and dry it all out.

many thanks Mr.Tornado

how to dry out this alternator at the working power plant?

My first answer was the simplest, but in many cases small amounts of moisture are the problem, and warming works to fix it, Some kind of heater/blower can help, but make sure it doesn't exceed the temperature limit of any wire insulation involved. If the insulation has micro-cracks in it, such as from over-voltage breakdown, the drying-out idea may not work. Test the insulation again (and maybe yet again) until the value is acceptable.

Thanks a lot once again for your valuable suggestions Mr.Tornado

I tried with blower to clean-up the windings.after the cleaning i took the IR reading its not improved still the same value. And one thing is happened. That is taking the voltage from the megger 30 v before cleaning and now taking around 80v while injecting 500v test voltage.

"you forgot to click the PA box, that's awkward." What's awkward is inverting the "AP" box to "PA" box

Sounds like you need to redip the coil....call in some pro's....

https://www.youtube.com/watch?v=3s1QPleyJGU

Isolate the machine i.e., cable connection etc. Pl. clean the winding thoroughly with cleaning solvent; inspect the winding very carefully and thoroughly to detect any crack in winding, hot spot mark due to local overheating, mechanical injury etc. If the above defects are not found, then cover the machine suitably and apply nos of 300 watt GLS lamps for local heating.Blower fans and thermometer must be placed inside for hot air blowing and temperature monitoring. The temperature rise must be well within the insulation class of the winding.At least 24hours continuos heating is required for moisture removal.Then measure the IR value.In this process it is expected that IR value will be improved.If IR value is found low, continue the process with close monitoring and maesurement of IRvalue in hot condition.After improvement of IR value, apply air dry varnish by pouring method so that entire winding get varnish.Start the blower fans for drying varnish for complete drying. Measure IR value and it is expected that machine will be suitable for run.

Manindra

Hire a professional to guide you. While Tornado's suggestion is a good starting point, there are many other reasons for poor IR besides excessive moisture. You need to determine if there is any tracking, dust, powder, contamination, mechanical/electrical failure, etc. that is causing this condition.

If it is other than just a wet winding, then drying it out will only cause the problem to reoccur when the moisture does, and if the machine is energized at the time you may get an arc and/or ground fault that will leave with a failed machine.

Do it right or do it over, it's your choice.