I am using a BLDC 3-phase hub motor and recently installed a motor controller rated for 3000 W (I originally had a 1200 W controller installed).
The motor is rated for 500 W nominal and 800 W peak, but is currently probably producing approx 1000 W power at the wheel (with the 3000 W controller installed).
I was wondering what design aspects of my BLDC motor would be the limiting factors (in terms of max. useful output power). I think it's one of the following things:
- Stator magnetic core is saturated (I need a wider or bigger diameter stator) **
- Winding diameter too small
- Permanent magnets need to be bigger (not sure if this would do much) ***
- Motor needs better cooling *
*(probably not a big factor since motor performance when motor is cold is not far off from the power output (useful) I got with the 1200 W controller)
**What design changes (for example, more layers, other shape of magnetic core) would positively influence the magnetic saturation point (make it so that this point is reached later/at a higher amount of magnetic flux produced?
***The permanent magnets (36 pieces if I counted correctly) are approximately 3 mm thick, 40 mm in height.
I'm running the motor at 72 V (84 V when the battery is fully charged); it originally was intended for 36 V/42 V.
The power output/torque produced by the motor did increase after switching to the 3 kW controller but not by a lot. It appears most of the extra power going to the motor are going into heating up the motor.
The motor gets significantly hotter (gets hot in shorter amount of time) than with the previous controller.
The motor is running with Hall sensors connected to the controller (motor controller supports Hall sensors).
Wires from controller to hub motor (3-phase wires) are 16 mm2 each so probably not a limiting factor.
The performance appears a tiny bit better when the motor is cold, but the output is still quite comparable to the 1200 W controller.
Does the number of windings have any influence on the efficiency of the motor? I'd think longer overall path length of windings within motor would result in more voltage loss thus less efficiency.
The winding wire diameter is approx 1.5-2 mm. I'm not sure how many layers of windings there are unfortunately (have not rewound this motor yet).
Stator's magnetic core outer diameter is approx 25 cm, stator's magnetic core inner diameter is approx 15 cm. See image:
Note: the currently used wires are much thicker than the ones in the photos, it's an old photo.
What changes could I theoretically make to my motor to get more power output at the wheel?