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Old 14-09-2016, 05:47   #61
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Re: Stator failure- Northern Lights 6kw

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Originally Posted by Dockhead View Post
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.
Agreed. I read your original inquiry as a two part questions, but sounds like it wasn't. I thought the two parts were 1) impact of reducing speed from 60hz to 50hz, and 2) impact of operating at 110V and 2x the current vs 230V and 1x current.

I was addressing part 2, which perhaps exists only in my imagination.

I completely agree about part 1.
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Old 14-09-2016, 05:49   #62
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Re: Stator failure- Northern Lights 6kw

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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?
Thermal load is related to power, not amps.

When it's producing 110v and 50a (5500w) it's actually producing the same heat as producing 220v and 25a (5500w). In the 110v configuration, you are paralleling the windings, in the 220v they are configure in serial. Hence, each winding is producing the same amount of power.

The thermal savings is due to slowing down the unit to get 50hz vs. 60hz.
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Old 14-09-2016, 05:51   #63
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Re: Stator failure- Northern Lights 6kw

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Originally Posted by a64pilot View Post
. . .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?
Water cooling is great, because water can carry about 4000 times more heat than air, per unit of volume. So you can transfer heat from one place to the other with far smaller volume of the cooling medium.


But we have not been talking about water cooling anything but more air. If it were possible to water cool the alternators and the generator heads, it would greatly reduce the engine room temperature problem. But we've just been talking about processing the engine room air to cool it down, versus just blowing in already naturally cool air. The water is great for carrying the heat, but you still have to blow around air, in order to transfer heat from air to water. You have to recirculate larger, and depending on the size of the heat exchanger and temperature differences involved, maybe much larger volumes of air, to get the same cooling effect as a given volume of naturally cool air, if your water temp is the same as the ambient air temp.
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Old 14-09-2016, 05:52   #64
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Re: Stator failure- Northern Lights 6kw

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Originally Posted by DotDun View Post
Thermal load is related to power, not amps.

When it's producing 110v and 50a (5500w) it's actually producing the same heat as producing 220v and 25a (5500w). In the 110v configuration, you are paralleling the windings, in the 220v they are configure in serial. Hence, each winding is producing the same amount of power.

The thermal savings is due to slowing down the unit to get 50hz vs. 60hz.
There you go. Parts 1 and 2 of the questions - at least as I read it, and apparently DotDun as well.
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Old 14-09-2016, 05:54   #65
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Re: Stator failure- Northern Lights 6kw

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Originally Posted by DotDun View Post
Thermal load is related to power, not amps.

When it's producing 110v and 50a (5500w) it's actually producing the same heat as producing 220v and 25a (5500w). In the 110v configuration, you are paralleling the windings, in the 220v they are configure in serial. Hence, each winding is producing the same amount of power.

The thermal savings is due to slowing down the unit to get 50hz vs. 60hz.
That makes sense; thanks.
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Old 14-09-2016, 05:55   #66
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Re: Stator failure- Northern Lights 6kw

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Originally Posted by Dockhead View Post
Water cooling is great, because water can carry about 4000 times more heat than air, per unit of volume. So you can transfer heat from one place to the other with far smaller volume of the cooling medium.


But we have not been talking about water cooling anything but more air. If it were possible to water cool the alternators and the generator heads, it would greatly reduce the engine room temperature problem. But we've just been talking about processing the engine room air to cool it down, versus just blowing in already naturally cool air.
I believe Fischer-Panda has water cooled generator head on some models......don't know if it has a separate heat exchanger our shares the fresh water from the engine.
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Old 14-09-2016, 05:55   #67
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Re: Stator failure- Northern Lights 6kw

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Originally Posted by tanglewood View Post
Agreed. I read your original inquiry as a two part questions, but sounds like it wasn't. I thought the two parts were 1) impact of reducing speed from 60hz to 50hz, and 2) impact of operating at 110V and 2x the current vs 230V and 1x current.

I was addressing part 2, which perhaps exists only in my imagination.

I completely agree about part 1.
Actually I was indeed asking about your Part 2. Dot Dun seems to have answered it.
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Old 14-09-2016, 06:15   #68
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Re: Stator failure- Northern Lights 6kw

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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....
There's a fallacy here, I think --

Say the cooling effect of a given amount of fresh air keeps the engine room temp to ambient +10. But that doesn't mean that this cooling effect is "not enough". On the contrary, this is quite good. Usual standard for engine rooms on large power boats is +30F.

To get the same cooling effect recirculating air over a heat exchanger, with water temp = ambient air temp, you must circulate MORE air over the heat exchanger, maybe many times more.

That's because no matter how big the heat exchanger is, and how much 20C water you circulate through it, you will never get 20C air coming out of the other end of it. Maybe many times more air -- double, triple, 5x, depending on the amount of heat you need to move and other parameters of the system.

Heat exchangers produce resistance to air flow through them by the nature of how they work (contact of the air flow with the vessels containing the water). Maybe some really big heat exchanger might have less resistance than some really horrible duct work, but it's hard to imagine. Plus remember you will be moving greater volumes of air through the heat exchanger, than you will need to move through a duct.

So in any case, you're going to spend more energy moving air over the heat exchanger to create cooler air, than it will take to bring in air which is already naturally cool, and cooler than what you can ever manufacture with a heat exchanger using water at the same temp. Then moving the water through the heat exchanger also costs energy.

Maybe worthwhile as a desperate measure in a boat so badly designed that there is really no way to increase the duct area. But I guess in 99% of boats, you can run another duct through a transom or just chop a hole in the deck, increase the size or number of the blowers, and get a much better cooling effect.
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Old 14-09-2016, 07:05   #69
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Re: Stator failure- Northern Lights 6kw

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There's a fallacy here, I think --

Say the cooling effect of a given amount of fresh air keeps the engine room temp to ambient +10. But that doesn't mean that this cooling effect is "not enough". On the contrary, this is quite good. Usual standard for engine rooms on large power boats is +30F.

To get the same cooling effect recirculating air over a heat exchanger, with water temp = ambient air temp, you must circulate MORE air over the heat exchanger, maybe many times more.

That's because no matter how big the heat exchanger is, and how much 20C water you circulate through it, you will never get 20C air coming out of the other end of it. Maybe many times more air -- double, triple, 5x, depending on the amount of heat you need to move and other parameters of the system.

Heat exchangers produce resistance to air flow through them by the nature of how they work (contact of the air flow with the vessels containing the water). Maybe some really big heat exchanger might have less resistance than some really horrible duct work, but it's hard to imagine. Plus remember you will be moving greater volumes of air through the heat exchanger, than you will need to move through a duct.

So in any case, you're going to spend more energy moving air over the heat exchanger to create cooler air, than it will take to bring in air which is already naturally cool, and cooler than what you can ever manufacture with a heat exchanger using water at the same temp. Then moving the water through the heat exchanger also costs energy.

Maybe worthwhile as a desperate measure in a boat so badly designed that there is really no way to increase the duct area. But I guess in 99% of boats, you can run another duct through a transom or just chop a hole in the deck, increase the size or number of the blowers, and get a much better cooling effect.
And it's this claim of inefficiency that I questioned earlier. My generator is using the same fan as yours (alternator fins). Hence, the fan on my generator moves the same amount of air that the fan on your generator moves. My heat exchanger has 420cm2 of opening which is the source of air for the fan, I believe this is close to the size of the intake vent on the side of your generator. The air in my generator runs 15°F above the cooling source (raw water). I'll bet yours is no better. Hence, I don't buy the level of inefficiency with heat exchangers that you propagate. It's all in the design of the heat exchanger, i.e. cm2 of fin area.
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Old 14-09-2016, 11:43   #70
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Re: Stator failure- Northern Lights 6kw

My understanding is that the primary purpose of the Fresh/Salt water heat exchanger is to cool the engine block and (wet cool with raw water) the very hot exhaust gasses in a marine installation to maintain optimum temp.

That a well designed engine room brings in a large amount of outside fresh air normally directed to wash under the cooler skin plates of the bilges, before a large portion is consumed by the air intakes and combustion of the running engines.

That with all engines running, your fresh air intake should be slightly less than the engine room's exhaust fan capacity, so that a slight vacuum is felt when opening the ER door.

That is why ER fans generally have variable speeds on the intake and exhaust fans of a well insulated engine room to keep that internal air balance, depending on what engines are running.
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