Stator failure- Northern Lights 6kw

[DotDun]

Originally Posted by Dockhead

So to have an equal cooling effect from x m3/hour of fresh air coming in at 20C, you would have to move x m3/hour of air through heat exchangers plus enough to make up for the inefficiency of the heat exchanger. This will vary according to size and design of the heat exchanger and volume of water you circulate through it, but will never be 100%, so you will never get hot air cooled down to the same temperature as the incoming sea water.

On top of that, to move x volume of air through heat exchangers will take a lot more power than to move the same volume of air into the atmosphere through ducts, unless you have some really awful ducts and some really gigantic efficient heat exchangers, but never anything like a typical case.

So if the sea water is the same temp as the ambient air, you will have a LARGER air handling installation, maybe much larger, PLUS the whole extra system of heat exchanger and sea water circulation, just to get the same effect.

Not sure I agree with the analysis, but I do admit I'm outside my knowledge base.

1) The air/water heat exchanger on my Mase 7.6kw is ~300mm x 140mm x 80mm and has raw water running thru it. I have to believe this is close to the size of the venting on a similar sized (8kw) NL genset. No extra effort for air movement, it's using the standard fins on the (Mecc-Alte) alternator. And yet it keeps the alternator cooler (per marketing literature) than an air-cooled NL (for example).

2) If what you say above is true, why don't we see more air-cooled engines in cars? Take the radiator out, put fins on the cylinders and let the fan cool the engine?

[Dockhead]

Originally Posted by DotDun

Not sure I agree with the analysis, but I do admit I'm outside my knowledge base.

1) The air/water heat exchanger on my Mase 7.6kw is ~300mm x 140mm x 80mm and has raw water running thru it. I have to believe this is close to the size of the venting on a similar sized (8kw) NL genset. No extra effort for air movement, it's using the standard fins on the (Mecc-Alte) alternator. And yet it keeps the alternator cooler (per marketing literature) than an air-cooled NL (for example).

2) If what you say above is true, why don't we see more air-cooled engines in cars? Take the radiator out, put fins on the cylinders and let the fan cool the engine?

The system on your Mase is designed exactly to deal with the case where you have no access to cool air. It makes perfect sense for cooling a generator inside a hot engine room. Because there is your difference in temperature -- seawater at 20C or whatever, versus your 40C or 50C engine room.

But this makes no sense for cooling a whole engine room -- if you have any source of cool air (and it would be weird if you didn't). If sea water temp and ambient air temp are similar, you will have to handle a greater volume of air, and on top of that you will have to handle the sea water. This is obvious if you think about it.

Air cooling versus water cooling of cars is a completely different case. A water cooled car is using water to get the heat from the engine into air. What you are proposing is the opposite -- getting heat from air into water. If you can just vent the hot air into the atmosphere, this is much simpler and more efficient than processing it through a heat exchanger. IF the air you vent to the atmosphere can be replaced with fresh air at the same temperature as the water.

If the water is 10C cooler, or 20C cooler, then it might look different.

[tanglewood]

Originally Posted by Dockhead

Yes, maybe I will. That's a great idea. I have the Maretron temperature module, and already monitor these things:

1. Engine room temperature at the top of the space, opposite from the blower intakes.

2. Temperature of the sea water pump of the generator (proxy for sea water flow).

3. Coolant temperature of the generator.

4. Core temperature of the school bus alternator on the main engine.

I use the ring-under-bolt thermocouples like what you describe. The data is really interesting and useful to have.

I have two more vacant slots in the Maretron TMP module so would be easy to do. Thanks.

While I'm at it I think I'll put the last thermocouple on my calorifier, so I can see when the hot water is ready, without wasting water to feel it.

Keep in mind that 2 of the 6 ports on the Maretron temp device are exclusively for EGT temp probes and won't work with the under-bolt sensors. Don't ask me how I know.... but they are electrically incompatible. You could probably find other sensors that are compatible with the EGT ports, but I don't know what the specs are.

[tanglewood]

Originally Posted by Dockhead

The system on your Mase is designed exactly to deal with the case where you have no access to cool air. It makes perfect sense for cooling a generator inside a hot engine room. Because there is your difference in temperature -- seawater at 20C or whatever, versus your 40C or 50C engine room.

But this makes no sense for cooling a whole engine room -- if you have any source of cool air (and it would be weird if you didn't). If sea water temp and ambient air temp are similar, you will have to handle a greater volume of air, and on top of that you will have to handle the sea water. This is obvious if you think about it.

Air cooling versus water cooling of cars is a completely different case. A water cooled car is using water to get the heat from the engine into air. What you are proposing is the opposite -- getting heat from air into water. If you can just vent the hot air into the atmosphere, this is much simpler and more efficient than processing it through a heat exchanger. IF the air you vent to the atmosphere can be replaced with fresh air at the same temperature as the water.

If the water is 10C cooler, or 20C cooler, then it might look different.

In the cooling-challenged ERs that I'm familiar with, the limiting factor is the duct space to get air into and out of the ER. It's an exercise in venting through a straw. The attraction to a sea water heat extractor is that it would greatly reduce the need to pull air in and send it our of the ER, and you could instead circulate it within the ER, passing it through the cooler with large, slow moving fans that quietly move a lot of air.

Anyway, it's an interesting mental exercise to contemplate it.

[Dockhead]

Originally Posted by tanglewood

Keep in mind that 2 of the 6 ports on the Maretron temp device are exclusively for EGT temp probes and won't work with the under-bolt sensors. Don't ask me how I know.... but they are electrically incompatible. You could probably find other sensors that are compatible with the EGT ports, but I don't know what the specs are.

Yes, but the other two ports work with any standard Type K thermocouples!!

See: What temperature probes are compatible with Maretron’s Temperature Monitor (TMP100)?

I've already bought a few. Type K thermocouples have an enormous range of -270C to +1260C.

[Dockhead]

Originally Posted by tanglewood

In the cooling-challenged ERs that I'm familiar with, the limiting factor is the duct space to get air into and out of the ER. It's an exercise in venting through a straw. The attraction to a sea water heat extractor is that it would greatly reduce the need to pull air in and send it our of the ER, and you could instead circulate it within the ER, passing it through the cooler with large, slow moving fans that quietly move a lot of air.

Anyway, it's an interesting mental exercise to contemplate it.

Yes -- this is certainly true, and I think I mentioned that. Turning to water despite the inefficiencies makes perfect sense if you don't have access to fresh cool air in adequate quantities. Just like the Mase system.

Water has specific heat of more than 4x that of air, and besides that, is almost 1000x denser. So it's a terrific medium for transferring heat, and if you have problems moving enough air, it's a great thing.

[a64pilot]

Just so everyone understands, all automobiles are air cooled, only vehicles I. Know of that are truly water cooled are boats.


Sent from my iPad Pro using Cruisers Sailing Forum

[DotDun]

Originally Posted by Dockhead

Yes -- this is certainly true, and I think I mentioned that. Turning to water despite the inefficiencies makes perfect sense if you don't have access to fresh cool air in adequate quantities. Just like the Mase system.

Water has specific heat of more than 4x that of air, and besides that, is almost 1000x denser. So it's a terrific medium for transferring heat, and if you have problems moving enough air, it's a great thing.

You keep mentioning efficiency, but I think you missed my point. The air in my Mase is pulled thru an opening (in the heat exchanger) that is 300 mm x 140 mm, about the same size as the vent opening in the case of an ambient air cooled generator. Using raw water that is the same temperature as ambient air, it does a better job than the air cooled unit. So, how is air more efficient?


Sent from my iPhone using Cruisers Sailing Forum

[Dockhead]

Originally Posted by DotDun

You keep mentioning efficiency, but I think you missed my point. The air in my Mase is pulled thru an opening (in the heat exchanger) that is 300 mm x 140 mm, about the same size as the vent opening in the case of an ambient air cooled generator. Using raw water that is the same temperature as ambient air, it does a better job than the air cooled unit. So, how is air more efficient?

How could it possibly do a better job? The only purpose of the heat exchanger is to lower the temperature of the air going into the generator head unit.

If the water circulating through the heat exchanger is the same temperature as the air, the heat exchanger won't have any effect at all except cause resistance and reduce the air flow. If the air is 20C and the sea water is 20C then the air will come out of the heat exchanger just like it went in with no change of temperature.

The only purpose of the Mase system is to deal with overheated engine room air. In that case, the sea water will be much cooler than the hot engine room air, and the heat exchanger will actually do something useful.

The same principle does not apply to an entire engine room where you will surely have access to real ambient air.

To put some random numbers to it --

If you have 20C sea water, and 20C ambient fresh air, but your engine room is 40C, and you can't get fresh air directly into your generator, your Mase system will let you process that 40C air through the heat exchanger and get the temperature of the air coming into the generator enclosure down to maybe 25C or 30C, which is very useful, by circulating the air through a heat exchanger before blowing it into the generator enclosure.


But if you are trying to deal with the whole engine room, why would you "process" the 40C air inside? Instead of just blowing it out to the atmosphere and bringing in already existing 20C air, which doesn't need to be processed? You can't make 20C air out of 40C air using 20C sea water because heat exchangers aren't that efficient. You might make 25C air if you have a big heat exchanger and blow a ton of air through it. But why? Maybe only if you have some impossible situation with the ducts and can't get enough fresh air in, but I've never seen a boat so badly designed.

[Dockhead]

Bit (still more) of thread drift, but here's a question about generator heads and stator temperatures --

Most generators can be configured to produce either 110v @ 60hz or 220 @ 50. They produce less power in their 220v configuration because the engine runs at 1500RPM instead of 1800RPM.

So the same generator head is being used to produce about 25% less power, but then a bunch less amps, since the voltage is double. Less than half of the amps. Is the thermal load on the generator head related to power produced, or to the amperage?

If the latter, then in 220v mode these generators will be massively derated, no?

[Pelagic]

Originally Posted by Dockhead

If the latter, then in 220v mode these generators will be massively derated, no?

Yes.. That is correct...in the late 80's I worked directly with the head design engineer of Northern Lights in Seattle to spec out Generators for a +50m Feadship project that would be both Lloyd's & UMS certified

As it would be their very first Feadship installation they worked hard to provide me all the global and technical data for me to review the pros and cons of 50Hz vs 60Hz.

50Hz at 1500Rpm was torsionally the quietest and more stable for the best MTBF.
Most common power supply in Ports worldwide.
Generator is de-rated @ 1500 compared to 60Hz running at 1800Rpm

For those 60 Hz Generators running at 1200 Rpm, they were considered too close to the diesels engine's natural critical speed of around 1130 RPM to be recommended. More vibration, less quiet and higher MTBF.

My own NL Gen on Stargazer would be rated at 12kw if operating at 60Hz, but it is only rated at 10Kw for my 50Hz choice.

[tanglewood]

Originally Posted by Dockhead

Bit (still more) of thread drift, but here's a question about generator heads and stator temperatures --

Most generators can be configured to produce either 110v @ 60hz or 220 @ 50. They produce less power in their 220v configuration because the engine runs at 1500RPM instead of 1800RPM.

So the same generator head is being used to produce about 25% less power, but then a bunch less amps, since the voltage is double. Less than half of the amps. Is the thermal load on the generator head related to power produced, or to the amperage?

If the latter, then in 220v mode these generators will be massively derated, no?

In the handful of generators that I've delved into, there are multiple 110V windings. Wire them in parallel if you only want 110V service @ 2x the current. Wire them in series if you want 220V service. Utilize the tap where the two series-wired windings join if you want North American 110/220V split phase. Power delivered is the same regardless of configuration, and assuming a balanced load for split phase. I expect dissipated power would be the same too.

[Dockhead]

Originally Posted by tanglewood

In the handful of generators that I've delved into, there are multiple 110V windings. Wire them in parallel if you only want 110V service @ 2x the current. Wire them in series if you want 220V service. Utilize the tap where the two series-wired windings join if you want North American 110/220V split phase. Power delivered is the same regardless of configuration, and assuming a balanced load for split phase. I expect dissipated power would be the same too.

Ah, yes, but this is not American 220v split phase @60hz. This is European single phase, at 50hz.

The engine speed is reduced to 1500rpm from 1800rpm and the power is reduced, if you switch it over from U.S. to European power. On my generator, from 8kW to 6.5kW.

[DotDun]

Originally Posted by Dockhead

....
The same principle does not apply to an entire engine room where you will surely have access to real ambient air.

To put some random numbers to it --

If you have 20C sea water, and 20C ambient fresh air, but your engine room is 40C, and you can't get fresh air directly into your generator, your Mase system will let you process that 40C air through the heat exchanger and get the temperature of the air coming into the generator enclosure down to maybe 25C or 30C, which is very useful, by circulating the air through a heat exchanger before blowing it into the generator enclosure.


But if you are trying to deal with the whole engine room, why would you "process" the 40C air inside? Instead of just blowing it out to the atmosphere and bringing in already existing 20C air, which doesn't need to be processed? You can't make 20C air out of 40C air using 20C sea water because heat exchangers aren't that efficient. You might make 25C air if you have a big heat exchanger and blow a ton of air through it. But why? Maybe only if you have some impossible situation with the ducts and can't get enough fresh air in, but I've never seen a boat so badly designed.

I think you demonstrated the main point. As tanglewood stated, you can't get enough air into the engine room. On your boat, you stated the engine room air is 10C above outside air. If you could get 'enough', it would be the same temperature as outside air. Since that is the 'sink' to start cooling the generator, you'll always be at least 10C higher temperature inside the generator compared to raw water cooled. Plus you are burning what? 250W? running engine room blowers? The raw water is "free". That is not more efficient (using 250W and have a 10C hotter generator).

I believe you can design a system to move/circulate a lot more air inside the engine room than you can bringing in outside air. The amount of outside air you can bring in is restricted by the openings, both entrance and exit, that have to be shielded from bringing in water (rain, green, etc.)

But, that's an experiment for someone who has an engine room heat problem.....I have no blowers nor a hot engine room....

[a64pilot]

RE generating ratings.
It's power as in Wattage produced that is the limit usually due to heat, a likely reason for de-rating is the generator is air cooled and since it's spinning slower, so is the cooling fan, so less cooling.
It could of course be due to less power being produced by the engine running at a lower RPM also, depends on if the generator is engine limited or generator limited.
My little Nexgen has a 6 KW generator head, but the little motor couldn't make 6 KW, so it's a 3.5 based on engine output.

Water cooling anything has usually several advantages, much easier to regulate temp and it is easier to maintain a more even temperature, and you can remote mount the heat exchanger (radiator)
However water cooling is usually more complex with more failure points
I'm no computer guy, but don't high speed computers use liquid cooling now?