Stator failure- Northern Lights 6kw

[Dockhead]

Originally Posted by DotDun

FWIW, this issue is what drove my decision to look at Mase. Mase has a line of generators (IS - "intercooler") that has a water/air heat exchanger on the raw water line between the inlet and water pump">raw water pump. The alternator cooling fan circulates air through the heat exchanger keeping the air in the case vs. a NL design where it dumps the hot air into the engine room. Even with 90°F raw water temp, the temperature inside the case never goes above 105°F (Mase's claim, I've never measured it).

Yes, the additional heat exchanger is yet another failure point, and yes, I've replaced one due to my own stupidity ($250), but I think it's worth it to keep the unit a lot cooler. With the heat exchanger ahead of the raw water pump, if it does develop a leak, the raw water pump sucks air and the unit shuts down. Which is better than on the other side of the pump where it would spray water all over the inside of the case.

Clever design, IMO!

That is interesting, and it reminds me of certain smaller gensets with air cooled engines, which cool the air flow through the engine using a sea water heat exchanger.

This would make a lot of sense if you have no way to get cool air into your generator, or if the water is a lot cooler than the ambient air temperature, but I think if your ambient air temperature is anywhere near the water temperature, this would be a backwards way to do it compared to just increasing the air flow.

I am able to keep my engine room within 10C of the ambient air temperature just with the standard blowers.

[DotDun]

Originally Posted by Dockhead

That is interesting, and it reminds me of certain smaller gensets with air cooled engines, which cool the air flow through the engine using a sea water heat exchanger.

This would make a lot of sense if you have no way to get cool air into your generator, or if the water is a lot cooler than the ambient air temperature, but I think if your ambient air temperature is anywhere near the water temperature, this would be a backwards way to do it compared to just increasing the air flow.

I am able to keep my engine room within 10C of the ambient air temperature just with the standard blowers.

But, water, even if it's same temperature as ambient air (and still 10°C cooler) is a much better conductor of temperature than the air in your engine room. With Mase, the heat inside the case goes out with the exhaust vs. dumping it in the engine room (and re-circulating back into the generator case).

I bought the Mase so I wouldn't have to install engine room blowers. My boat doesn't have them, and I didn't/don't want to start cutting holes for vents and install fans.

It's just a different way to handle the heat inside the generator case.

[a64pilot]

Originally Posted by boatbod

Stators burn up when the lacquer insulation on the wire fails. Can be overheating due to excessive current, lack of airflow or simply old age.

Bingo, this is it, maybe a function of years of running hot, a little salt water, or just salty air, or any number of things. It is no different than an alternator on your engine, just bigger and more expensive of course.
Even my little Nexgen has thermal protection, I would suppose all do, it's in the form of the output circuit breaker.
What causes a circuit breaker to trip is heat, doesn't matter where this heat comes from, it can be ambient heat or heat from the electrical circuit, either way it gets hot and the circuit opens. I know because I have had it. Happen to me, it's what drove me to use aircraft Scat hose for the air duct as opposed to the cheap vinyl bilge blower hose that gets hot and collapses, then temps inside the sound shield skyrocket.


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[Dockhead]

Originally Posted by DotDun

But, water, even if it's same temperature as ambient air (and still 10°C cooler) is a much better conductor of temperature than the air in your engine room. With Mase, the heat inside the case goes out with the exhaust vs. dumping it in the engine room (and re-circulating back into the generator case).

I bought the Mase so I wouldn't have to install engine room blowers. My boat doesn't have them, and I didn't/don't want to start cutting holes for vents and install fans.

It's just a different way to handle the heat inside the generator case.

That makes sense.

One thing I didn't understand, however, was "the heat inside the case goes out with the exhaust vs. dumping it in the engine room". Does the heat exchanger cool the air before or after it is blown through the generator?


BTW, I am also a Mase generator owner -- 13.5kW standby generator at my lake house. Seems to be a good unit.

[DotDun]

Originally Posted by Dockhead

That makes sense.

One thing I didn't understand, however, was "the heat inside the case goes out with the exhaust vs. dumping it in the engine room". Does the heat exchanger cool the air before or after it is blown through the generator?


BTW, I am also a Mase generator owner -- 13.5kW standby generator at my lake house. Seems to be a good unit.

The input air to the alternator is sucked thru the air/water heat exchanger lowering the air temperature and raising the raw water temperature (before it goes to the raw water pump). Since the case has very little venting (just enough for combustion air = constant negative pressure inside the case vs. outside the case), the exhaust air from the alternator stays inside the case where it is recirculated back thru the air/water heat exchanger. The raw water goes on to the water/water heat exchanger cooling the engine fresh water, then on to the exhaust elbow then out it goes. Hence, the alternator heat goes out the exhaust water combined with both the engine heat and exhaust heat.

[Dockhead]

Originally Posted by DotDun

The input air to the alternator is sucked thru the air/water heat exchanger lowering the air temperature and raising the raw water temperature (before it goes to the raw water pump). Since the case has very little venting (just enough for combustion air = constant negative pressure inside the case vs. outside the case), the exhaust air from the alternator stays inside the case where it is recirculated back thru the air/water heat exchanger. The raw water goes on to the water/water heat exchanger cooling the engine fresh water, then on to the exhaust elbow then out it goes. Hence, the alternator heat goes out the exhaust water combined with both the engine heat and exhaust heat.

Got it. I guess that will be very good if there's a big difference between the temperature of the air the generator is sucking in vs the temperature of the sea water. Ambient air and sea water temps where I am now are about the same; in fact water is a bit warmer (20C vs 16C). Since my engine room is kept at no more than 10C more than ambient by the blowers, I don't think this system would do me much good. But great for you without blowers.

[captainjay]

This isn't that un common and there are lots of factors, heat, corrosion, etc. You need to do a good assessment of the whole genset condition before deciding what to do. $4000 for the back end installed sounds about right. The back end will be between $2 and $3 grand. The rest is likely the labor to install. If the engine and sound shield have any issues at all now is the time to asses that. Oil leaks? Rusted out sound shield? Bad latches? All of this adds up and sometimes just replacing the whole generator makes more sense in the long run. We have had to do this to several charter boats. In a lot of cases the might as wells and while where at it repairs to the additional parts of the genset can drive the costs up to close to replacement cost of the whole thing.

Jay

[Pelagic]

That is true Jay, hopefully the OP can remove the whole unit for assessment.
Shame with only about 4500hrs on it, but this is when those hard to reach and see maintenance issues, raise their ugly heads!

[meatservo]

DC circuit breakers are thermal, AC circuit breakers are magnetically tripped...






meatservo

[GordMay]

Originally Posted by meatservo

DC circuit breakers are thermal, AC circuit breakers are magnetically tripped...
meatservo

Not true!

ie:

➥ https://www.bluesea.com/products/cat...rcuit_Breakers

➥ Magnetic Single Pole Circuit Breakers | Ancor

➥ Carling Technologies Hydraulic Magnetic Circuit Breakers

[meatservo]

Originally Posted by GordMay

Not true!

ie:

➥ https://www.bluesea.com/products/cat...rcuit_Breakers

➥ Magnetic Single Pole Circuit Breakers | Ancor

➥ Carling Technologies Hydraulic Magnetic Circuit Breakers

Good point, airplane thing...

I stand corrected.


meatservo

[Greg4cocokai]

I had my stator rewound in Australia on my 7.6BTD Westerbeke for $700au. I took it apart myself and took it to a motor rewinder. He had to do it twice as he didn't get it tight enough to fit back together! A bit frustrating but no extra charge and came to the boat to help make sure it went together right. He also set htz and voltage to specs. Still going after 6yrs and 1,000 hrs.


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[a64pilot]

Used to be that rewinding electric motors was common, then they became expendable, a little like TV's I guess, who repairs TV's anymore?

But for $4K I sure would give it a go, I'd look for someone who rewinds, I know they are out there, right beside the Cobbler I bet.

[David Hughes]

Originally Posted by a64pilot

Used to be that rewinding electric motors was common, then they became expendable, a little like TV's I guess, who repairs TV's anymore?

But for $4K I sure would give it a go, I'd look for someone who rewinds, I know they are out there, right beside the Cobbler I bet.

It's $2000 for a rewind from Broward Armature. They have a good reputation.


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[tanglewood]

I've been following this same discussion over on TrawlerForum..

Correct me if I'm wrong, but last I heard there was still no diagnosis of what's wrong with the generator. Something created a bunch of smoke -yes. But nobody has looked into it to sort out what actually failed, let along what the corrective action is. The original post went straight from "there was a ton of smoke" to "how much does a new stator cost". Nobody has diagnosed this as a failed stator.

So unless there is now a diagnosis of exactly what failed, this discussion is all just wild fantasy with no basis in reality.

For what it's worth, the NL generators are specified for continuous duty, full load, at 130F ambient (outside the enclosure). There are vents on the case and they need to be kept clear per the installation instructions. So saying that the heat rise in the stator is not accounted for in the design is just making stuff up.