Does anyone know what’s the maximum reasonable motor current for a typical 6384 motor?
At what point does stator saturation set in?
Is there an easy way to figure it out experimentally?
The saturation is a gradual decline of torque vs amp at higher current but i don’t think there’s any other method of getting it than loading motor and measuring torque per amp.
you can measure this by building a small motor rig, if you have a 3d-printer and some 3d sketching skills it could probably be done in a day.
Large, high pitch propeller as the load
Motor fixation that allows the motor fixation to rotate and push a lever against a scale.
Plot the measured torque while varying the motor current set in the controller.
I have some dyno plots somewhere, let me check.
Unfortunately they didn’t put enough current into the motor to show saturation as the red torque vs current line doesn’t show any knee.
(This is a 6374 motor plot from here:
Torque Curves for SK3's || 6354 260KV || 6374 149KV || 6374 192KV || - ESK8 Electronics - Electric Skateboard Builders Forum | Learn How to Build your own E-board)
But the saturation isn’t like dropping off a cliff on these motors, it’s a gradual decline of torque per amp and efficiency, therefore you can saturate the motor quite a lot during starts (when you’re running a wet outrunner where the cooling is excellent)
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Hi Lars, thanks for the explanation and those graphs are interesting.
As you mentioned, too bad the graphs only show up to 60 amps.
What max amp settings are people here using for their 6384 or 6374? Would 120A be too much?
It depends on kV, did a quick check and on 6374 i’ve found from 3-8Nm as max torque stated by different sellers.
T=(9.55/kV)*I solve for I
I=T*kV/9.55
For 8Nm and 120kV —> needed current is 100A
Then at max torque there is saturation so more current is needed in reality to get the max torque.
Leaving the theory behind, I’d say 120A is probably OK and this is what i’d set if i had this motor but i’d try carefully before going out for a ride on the water. Give it some seconds bursts of full throttle, stop, lift out of the water and feel the temperature with hand before using any longer period of time.