Wednesday, March 23, 2011

Re: [Electric Boats] Re: Water Cooled Electric Drive

 

Motor heat has two completely sources. 

Resistance in the windings causes them to become hot under high currents. 

Running a motor at very high speed will cause eddy current losses in the lamination steel. This is why the stator is made of thin plates, not a single hunk of steel. As the magnetic fields change direction during normal motor operation, a small current is generated within the steel. By using thin sheets insulated by a layer of oxides, the currents are kept low. As the frequency increases, however, the losses become higher and higher. 

The sweet spot is between the two extremes, about 50 to 80% of no load motor speed, to get the most power out. 

Arby Bernt
AMeP

--- On Wed, 3/23/11, GNHBus@aol.com <GNHBus@aol.com> wrote:

From: GNHBus@aol.com <GNHBus@aol.com>
Subject: Re: [Electric Boats] Re: Water Cooled Electric Drive
To: electricboats@yahoogroups.com
Date: Wednesday, March 23, 2011, 4:03 AM

 

This is an interesting statement Jim,
Are you discussing a specific electric motor, or does this happen with all electric motors?
I think "lugging" is understood, like "bogging down" ????
Under what conditions does this "lugging" occur ?
 
In a message dated 3/22/2011 8:16:06 P.M. Eastern Daylight Time, luv2bsailin@yahoo.com writes:
 

Hi Guys,
Another thing to keep in mind regarding motor heat is that reduction ratio can make a big difference. If you're "lugging" the motor by having too low a ratio it will get hot.
Jim

--- In electricboats@yahoogroups.com, Mike <biankablog@...> wrote:
>
> When I did my install I kept part of the old exhaust hose and port it connected to in case I needed to use it for an exhaust port to remove heat from the battery or motor area.
> http://biankablog.blogspot.com/2009/02/going-electric-part-6-scene-of-grime.html
>  So far I have not seen the need to use for that function with my ASMO system. Though I may use it as an extra cockpit drain or bilge pump at some point. If you are converting to electric propulsion you might want to keep it availible. Just make sure it is sealed and above the waterline until you need it.
>  
> Capt. Mike
> http://biankablog.blogspot.com
>
>
> --- On Tue, 3/22/11, Steve Dolan <sdolan@...> wrote:
>
>
> From: Steve Dolan <sdolan@...>
> Subject: RE: [Electric Boats] Re: Water Cooled Electric Drive
> To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
> Date: Tuesday, March 22, 2011, 6:45 PM
>
>
>  
>
>
>
>
> My 144v system is vented with an exhaust fan mounted at the stern and vented out at the stern. Fresh air is ducted to the front engine bay bulk head and drawn across the system then exhausted out. No problems to this point with overheating but that may be another advantage for the larger system.
>
> Steve in Solomons MD
>

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