relation betwee motor speed and current drawn..

hi,
i have a motor E10-12 1200KV brushless outrunner motor. this motor is rated for 41amps maximum current draw.
I am controlling the speed with a speed controller.
my doubt is how can i relate motor speed to the maximum current it draws?
i am guessing that it will draw the maximum 41 amps only when it is at maximum speed. If i reduce the speed, the amount of current it draws should also reduce.

correct me if i am wrong..

Regards
skr

Hi,

You're mistaken in assuming the maximum current draw will happen at maximum speed. It is in fact vice versa. At zero rpm the motor will be able to draw the largest current, this usually happens when the motor is accelerated from stand-still.

When the motor is running at maximum speed with no mechanical load on the motor shaft the motor will use very little energy as it only has to provide the mechanical energy for overcoming the friction in the bearings and against the air.

The two operating conditions I have mentioned above are two opposite extreme cases.

The current draw at any given time is heavily dependent on the mechanical energy being drained from the motor shaft.

So you will not be able to make a correlation between power input and rpm.