Hi Andrew,
While I prefer that my motor runs at a temp where I can hold my hand to it under most conditions, it seems that the motor casing is not a great indicator of the internal winding temps. I know that when I'm running more than 4000W into my motor, the winding temps run up to 65-70C and yet the motor housing is still comfortable to touch. The motor manufacturer spec's the winding temps at no more than 150C, but the motor housing temp can change for a variety of reasons. Like someone else mentioned, an 85% efficient motor will be producing 600W of heat with a 4000W input, but the motor will have varied success at dissapating that heat, especially in the closed bilge of a cruising boat.
And as far as heavily loading my electric motor, I figure that with a displacement of more than 4900Kg, it's a pretty heavy load no matter how you look at it.
Just as a curiosity, can you tell us more about your electric boat(s)?
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, "Andrew Gilchrist" <andrew@...> wrote:
>
> Michael
>
> The most accurate way of telling whether the motor is comfortably loaded is
> temperature. Hot motors are either running inefficiently ie very heavily or
> ultra lightly loaded or due to poor cooling.
>
> Safe temperatures are when you can hold your hand to the motor indefinitely.
> i.e about 42 Celcius unless otherwise specified....
>
> Andrew Gilchrist
>
> www.fastelectrics.com
>
> 612 4982 5481
>
> Australia
>
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