Re: (ET) E20 motor at 48V

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SteveS Wrote
>I thought the E20 was about 4-5 Hp with peak HP of 20 (hence the E-20 as 
>in equal to a ICE with 20 HP). 

There is another big difference in the rating of ICE and electric motors. 
An ICE is rated (usually) not as raw HP but a braking HP (BHP) which is a
measure of how difficult the engine is to stop.  As such it includes the
rather considerable angular momentum of the motor.  In fact this is so
common that unless both BHP and HP are mentioned any mention of HP when
referrring to an ICE is almost certainly BHP.  BHP can be anywhere from 3 -
10X the motor HP.

As far as the motor curves I haven't seen them so I can't comment beyond
there usual form.

>I don't think the 1 hour continuous 
>rating would be a problem, I should be so lucky to be able to run a hour 
>on the batteries I'll be able to carry!

Current carrying capability is probably proportional to I*I*t (I squared
t).  Basically you are limited by the amount of internal heat you generate
in the motor wiring.  Once the inner wires are hot it can take them a long
time to cool back down.

Whatever you do keep an eye on the motor temperature at least to begin
with.  If it gets to 50C (too hot to hold your hand on, not too hot to
touch), it's time to stop and let it cool.  The inner wiring will be a lot
hotter.

Robert


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