Argess

Mattnin: Congratulations.....as far as I am concerned, you've proven the concept (with your overlay graph)......Higher KV (less turns) makes less torque at low speeds than a lower KV (more turns) motor.

I noticed your 7.5 motor speed ended before your torque zeroed out. Using the rpm at max power, it should wind up to about 41,000 rpm.

Using the Torque equation (as a function of N and w) I did for brushed motors, I find about a 7% error using the equation between the max rpms of the two motors. Not great, but I suppose anything under 10% isn't bad when you apply theory to a electro-mechanical device (and not all losses are accounted for).

Using Novak's KV rating of 5800 for the 7.5 and 3300 for the 13.5, I get max rpms of 43500 and 24750. That reduces my torque equation error to about 4%.

Unfortunately, the Torque equation is out by a whopping 25% at zero rpms. I suspect the windings between the two motors may not use the same gauge wire in the turns. Or it may be differences in the rotors, although both appear to use the same rotor, P/N 5908.

I think you mentioned you didn't have a way to measure the current yet, but if you have access to a milliohmeter, could you measure the winding resistance of each motor please?


Edit: Looks like they do use different gauge wire in their stators...at least sometimes:

Novak: "The Velociti Light series is very similar to the original Velociti series but is considered “light” because the wire used to wind the motor is a smaller gauge. Though this may seem like a small change, the ramifications are exciting. The smaller gauge allows for the same top speed, but with slower acceleration and softer braking power."