Saturday, June 20, 2009

[Electric Boats] Re: motor overheating



The amount of current that an electric motor demands is dependent on load. As a propellor increases in rpm, the power required increases exponentially.

Once you have installed your electric motor in your boat, you then run your motor at full throttle. If the motor draws more than the maximum continuous power rating, you need to choose a smaller propellor or a different gear ratio.

If you do not change the propellor or the gear ratio, the motor will develop maximum amperage at a lower voltage and will be less efficient. It will still work though. It will be working harder and you will be compromising efficiency and range.

THe most important thing is to have an ammeter on the system and not exceed the maximum amperage of the motor or controller. The maximum amperage of the motor or the controller is dependent on how well either is heat sinked.

The Sevcon millipak controller can run continously at about 95 amps and the Mars motor can run continuously at up to 120 amps. All depending on ambient temperature and heat sinking. Providing cool air will help. Mounting the controller to a heat sink with thermal paste and providing a fan for the controller will help too. Keeping the controller away from the motor so they do not share the same heat buildup helps too.

James

www.propulsionmarine.com

--- In electricboats@yahoogroups.com, "constancedraper" <drmark.draper@...> wrote:
>
> What are the circumstances under which the motor overheats? How fast, how long,etc.
>
> md
>
> --- In electricboats@yahoogroups.com, "rbrt.beebe" <rbrt.beebe@> wrote:
> >
> > I installed the Thunderstruck sailboat kit in my Hunter 27.
> > I'm having problems with the motor overheating.
> > I've adjusted the packing gland so as to have the proper drip for cooling and the prop shaft is turning freely.
> > I would appreciate any other considerations/advice to resolve this condition.
> > Thanks,Bob
> >
>

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