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Cooling of alternator with ambient air

Cooling of alternator with ambient air

Cooling of alternator with ambient air

Our alternator 950 kW 400 V is cooled by an internal fan by taking ambient air. There is an outer casing over the alternator with filters. Our plant has lots of burnt coal ash particles. These dust particles are entering inside the alternator. Can we remove the casing over the alternator and install filters directly over the openings of the alternator where air enters? Every 1-2 days we clean the filters. The casing is not 100 % protected against dust.
Once since installation in 2015, the stator was damaged and we have to rewind it. Thanks

RE: Cooling of alternator with ambient air

SA07: You best bet is to improve the existing enclosure against ingress of coal dust and ash particulate. Block the seams, better filtration, etc. The problem with removing the "housing" and exposing the alternator directly to the particulate is that the stuff will accumulate on every exposed flat surface, acting like a thermal blanket and causing increased thermal stress in the machine. Add to that that some of the particulate is probably not completely combusted, so it remains flammable. If the surface temperature of the alternator gets high enough (under the blanket) then a fire will start - which could be a much more deadly proposition than simply having to rewind the machine every once in a while. Chances are good that your alternator enclosure (the way the brackets mount to the frame, the way filters sit in their housings, the way the shaft seals match up to the shaft, etc.) leave quite aa few gaps for possible contaminant ingress as well - which are not trivial to fix.

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RE: Cooling of alternator with ambient air

That looks like a silent enclosure over the alternator. Once you remove it, the purpose is lost. Improve the filters (lesser mesh size) of the enclosure, arrest the leaks etc. Of course, this means more frequent cleaning and changing of filters and lesser air flow for alternator cooling.

For such a polluted environment, a CACA cooled alternator should have been chosen.


RE: Cooling of alternator with ambient air

CACA or CACW are ALWAYS the optimum solution for a constant running (base load) generator (alternator). Unfortunately, this increases the size and cost of the generator.

if you work out the annual airflow, take an estimate of the dust concentration (even in 'clean' air) that is an awful amount of dust in comparison to the internal air volume of the machine. This applies to any size of machine, since we are talking about ratios.

From the photo this is a generator inside some form of enclosure. I assume that the aperture we are looking through is where the filters are removed from?

1. Do not put filters directly on the generator. You may have difficulty with the limited space available to design filters with a large area and low pressure drop (the generator fan may not have capacity for extra pressure drop through filters.
2. Like edison123 says, make sure there are no leaks where ‘dirty' air can get in. I can see a gap around the coupling! See if you can add a baffle and seal around or behind the coupling.
3. Talk to a filter manufacturer. He may take an air sample. ‘Burnt coal ash’ will have corrosive chemicals in it. If the aperture had a flat screen of filters, think of putting a three sides arrangement over each intake. Ducting the intake air from a higher level may help as gravity often keeps dust near the ground. Perhaps ducting the generator exhaust air to outside the canopy may help reduce any recirculation of air.

please let us know how you get on.

RE: Cooling of alternator with ambient air

Thanks for your advice

RE: Cooling of alternator with ambient air

I suggest you duct fan supplied air to provide slight positive pressure on the enclosure. Duct the air from a cleaner area so you aren't throwing away money in filters every 1-2 days.

RE: Cooling of alternator with ambient air

The existing open air cooling can be converted to CACA or CACW (if you have sufficient water source) with some derating of the alternator protecting the windings from external contamination.


RE: Cooling of alternator with ambient air

Valuable tips and guidance given to you in an early post hold true now. What changes have you implemented to insulate your Generator (alternator) from overheating? Your facilities isolation from Mainland repair resources is understood. Attempting to meet the Islands projected increase and reliance on renewables, will certainly put your already stressed systems on a path of unsustainability. There is little to be done. (Save retrofit) Your facility has exceeded max. output potential. P.S: Continue with your fire suppression upgrades throughout the facility. Good luck

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