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Old 21-01-2014, 05:37   #1
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Acceptable Operating Temperture Range for Large-Frame Alternators

I have two alternators on my main engine -- the regular 12v Yanmar one, which charges the engine start bank, and a large-frame Leece-Neville 110 amps x 24 volts one for charging my domestic bank, regulated by an Adverc regulator.

I have about 1600 hours on the main engine now, and the Leece-Neville has -- knock on wood -- always performed flawlessly -- one of the few systems on the boat which has never given me any trouble.

It puts out a ton of power and charges the domestic bank faster than the 70 amp Victron charger/inverter. It seems to me that the weird Adverc charging regime -- which cycles back and forth from high voltage -- gets more power into the batts faster.

This alternator also does not complain when I put a high AC load on it via the Victron inverter. I have actually washed and dried loads of clothes while motoring in calm weather. But I realize that doing this puts the alternator up to about its maximum output for long periods of time, and it seems to me that it's probably not made for that -- like running an engine at redline. Therefore I do things like this rarely.

But maybe I'm being overprotective? Is it all right to run large-frame alternators -- which are, after all, quite differently engineered from car-type alternators -- at high loads? Is it a question of temperature? I have been checking the temperature of the alternator case while running high loads on it, it seems reasonable -- I've not seen over 70 or 80 degrees C or so, and the data sheet says that 110 degrees is ok. I have a forced-air ventilated engine room which stays fairly cool.

What do you guys think?
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Old 21-01-2014, 05:57   #2
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

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Originally Posted by Dockhead View Post
I have two alternators on my main engine -- the regular 12v Yanmar one, which charges the engine start bank, and a large-frame Leece-Neville 110 amps x 24 volts one for charging my domestic bank, regulated by an Adverc regulator.

I have about 1600 hours on the main engine now, and the Leece-Neville has -- knock on wood -- always performed flawlessly -- one of the few systems on the boat which has never given me any trouble.

It puts out a ton of power and charges the domestic bank faster than the 70 amp Victron charger/inverter. It seems to me that the weird Adverc charging regime -- which cycles back and forth from high voltage -- gets more power into the batts faster.

This alternator also does not complain when I put a high AC load on it via the Victron inverter. I have actually washed and dried loads of clothes while motoring in calm weather. But I realize that doing this puts the alternator up to about its maximum output for long periods of time, and it seems to me that it's probably not made for that -- like running an engine at redline. Therefore I do things like this rarely.

But maybe I'm being overprotective? Is it all right to run large-frame alternators -- which are, after all, quite differently engineered from car-type alternators -- at high loads? Is it a question of temperature? I have been checking the temperature of the alternator case while running high loads on it, it seems reasonable -- I've not seen over 70 or 80 degrees C or so, and the data sheet says that 110 degrees is ok. I have a forced-air ventilated engine room which stays fairly cool.

What do you guys think?

Whites or colour cycle in the washing machine? Temps look fine, helped by the pommie weather no doubt!
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Old 21-01-2014, 06:09   #3
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

I know that the temp sensor on a Balmar regulator starts cycling the alternator at about 160 degree F.

David
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Old 21-01-2014, 06:34   #4
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

Has anyone looked at adding a seawater cooled jacket to an air cooled alternators , any comments. I'm tricking with the idea at the moment

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Old 21-01-2014, 06:42   #5
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

How hot do you expect to run it that you need water cooling? Would the alternative of making a shroud around it and forcing cool air through from an external place be easier and enough cooling? This is how our reefer compressor is cooled and it is remarkable the difference it makes.

I would be concerned about condensation and vibration with a water-cooled jacket on the heat sink.

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Old 21-01-2014, 06:57   #6
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

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How hot do you expect to run it that you need water cooling? Would the alternative of making a shroud around it and forcing cool air through from an external place be easier and enough cooling? This is how our reefer compressor is cooled and it is remarkable the difference it makes.

I would be concerned about condensation and vibration with a water-cooled jacket on the heat sink.

Mark
I suspect the heat sink is too warm for condensation. Vibration , I'm not sure in see the issue. I was examining the BMW water cooled alternator recently. ( it hasn't a good reputation though )

Dave
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Old 21-01-2014, 07:07   #7
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

You're running relatively cool.

There is a rule of thumb that says a 10-degree Celsius (18-degree Fahrenheit) rise reduces the insulation’s useful life by half; while a 10° C (18° F) decrease doubles the insulation’s life.

The National Electrical Manufacturers Association (NEMA) sets insulation temperature standards based on thermal classes, the most common being A, B, F and H.

Insulation Class - Maximum Winding Temp*
A - 105°C (221°F)
B - 130°C (266°F)
F - 155°C (311°F)
H - 180°C (356°F)

* Temperatures are total (ambient + rise), starting with a maximum ambient of 40° C (104° F).

See ➥ motorsanddrives.com - Motor Temperature Ratings
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Old 21-01-2014, 07:09   #8
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

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Originally Posted by goboatingnow View Post
I suspect the heat sink is too warm for condensation. Vibration , I'm not sure in see the issue. I was examining the BMW water cooled alternator recently. ( it hasn't a good reputation though )

Dave
The BMW water-cooled alternator is pure carp -- although this may have nothing to do with its cooling system. I have replaced two of them on my Range Rover at huge expense.

I would think sea water cooling would be a pretty cool (sorry) idea if you can deal with corrosion issues AND if you could think of a way to make it which would be acceptably simple and inexpensive.

It might well be overcomplicating things, plus you have more seawater hoses and fittings to potentially fail and sink your boat.

It may also be gilding the lily depending on what a good, long-life operating temperature is -- the original question of this thread -- hint hint. So if say 80 degrees is perfectly acceptable, and you are already getting that with air cooling, why bother with water cooling?

Perhaps more air is the more practical answer even if more cooling is really worthwhile.

And maybe a still better answer is to simply buy a great big alternator and derate it. If you were to use a 200 amp x 24v alternator and derate it to 120 amps or so, I would think you would be golden -- the existing cooling system and everything else would be more than capable of handling continuous duty at 120 amps. We don't care so much about mass or size (at least those of us on monos). I don't know exactly how you control an alternator so as to reduce the power output, however -- someone who understands these things better will have to opine.
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Old 21-01-2014, 07:15   #9
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

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Originally Posted by GordMay View Post
You're running relatively cool.

There is a rule of thumb that says a 10-degree Celsius (18-degree Fahrenheit) rise reduces the insulation’s useful life by half; while a 10° C (18° F) decrease doubles the insulation’s life.

The National Electrical Manufacturers Association (NEMA) sets insulation temperature standards based on thermal classes, the most common being A, B, F and H.

Insulation Class - Maximum Winding Temp*
A - 105°C (221°F)
B - 130°C (266°F)
F - 155°C (311°F)
H - 180°C (356°F)

* Temperatures are total (ambient + rise), starting with a maximum ambient of 40° C (104° F).

See ➥ motorsanddrives.com - Motor Temperature Ratings
Gord, as usual, you are a treasurehouse of useful information


I do question this, however:

"There is a rule of thumb that says a 10-degree Celsius (18-degree Fahrenheit) rise reduces the insulation’s useful life by half; while a 10° C (18° F) decrease doubles the insulation’s life."

If this is even vaguely correct, then it will be so only within a certain range. I seriously doubt that you get any increased useful life at all, for example, between 20 and 30 degrees C.
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Old 21-01-2014, 07:18   #10
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

Quote:
Originally Posted by colemj View Post
Would the alternative of making a shroud around it and forcing cool air through from an external place be easier and enough cooling? This is how our reefer compressor is cooled and it is remarkable the difference it makes.
I would think just blowing cold air from the bilge onto it would make a huge difference, if extra cooling is needed.

Our alternators are all, after all, air cooled and designed to be cooled by air.
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Old 21-01-2014, 07:19   #11
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

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Originally Posted by Dockhead View Post
The BMW water-cooled alternator is pure carp -- although this may have nothing to do with its cooling system. I have replaced two of them on my Range Rover at huge expense.

I would think sea water cooling would be a pretty cool (sorry) idea if you can deal with corrosion issues AND if you could think of a way to make it which would be acceptably simple and inexpensive.

It might well be overcomplicating things, plus you have more seawater hoses and fittings to potentially fail and sink your boat.

It may also be gilding the lily depending on what a good, long-life operating temperature is -- the original question of this thread -- hint hint. So if say 80 degrees is perfectly acceptable, and you are already getting that with air cooling, why bother with water cooling?

Perhaps more air is the more practical answer even if more cooling is really worthwhile.

And maybe a still better answer is to simply buy a great big alternator and derate it. If you were to use a 200 amp x 24v alternator and derate it to 120 amps or so, I would think you would be golden -- the existing cooling system and everything else would be more than capable of handling continuous duty at 120 amps. We don't care so much about mass or size (at least those of us on monos). I don't know exactly how you control an alternator so as to reduce the power output, however -- someone who understands these things better will have to opine.
This is an update to the DC generator I designed and built , it's capable of 400 A from two alternators. Now I want to incorporate a serious sound shield , but airflow is an issue. Pulling sufficient air adds a considerable amount of noise, even tricking around with baffling

The idea was a stainless steel jacket around about 80 % of circumference the alt. also I am removing all the diodes and of course the regulators to an external enclosure. The jacket will be coupled thermally to the alternator via silicon grease.

I intend to leave on the fans , but the natural air movement inside the enclosure isn't sufficient. The diesel is fed from a separate air plenum


Ps yep , alt went on RR sports at 100k miles , while in France , !!
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Old 21-01-2014, 07:25   #12
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

Quote:
Originally Posted by Dockhead View Post
... I do question this, however:

"There is a rule of thumb that says a 10-degree Celsius (18-degree Fahrenheit) rise reduces the insulation’s useful life by half; while a 10° C (18° F) decrease doubles the insulation’s life."

If this is even vaguely correct, then it will be so only within a certain range. I seriously doubt that you get any increased useful life at all, for example, between 20 and 30 degrees C.
You're absolutely correct. My bad.
The 10°C rule of thumb applies at the insulation's max temp; and does not continue indefinitely.
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Old 21-01-2014, 07:41   #13
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Re: Acceptable Operating Temperture Range for Large-Frame Alternators

@dockhead, Hi. Hey I am also a 24v boat and have large frame alts on my Detroit.
I also have an Adverc 24v Pos regulator to get rid of. Class F insulation should be fine, but if it gets dusty you will find the heat rising. Worst thing for an alternator is that it spins too slow. Those fanblades must fly in order to keep cooling. I have seen the ER air intake led in a duct to arrive at the alternator first, it really worked well. I have recently rewound two of my 24v (28v) alternators that failed due to gummy build up preventing cooling. It was an interesting job, and the fingers really hurt afterwards. I think youre ok, but make sure that the alt is running at the right speed on the mfg curve...
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