A small Portable Wind Turbine, mostly 3D printed!

adriancubasadriancubas 05/20/2022 at 18:300 Comments

I have been experimenting with different motors (generators) in order to increase the generating power of the wind turbine. As I presented earlier during my measurements, the nema 17 stepper motor is only capable of delivering 0.65A of maximum short-circuit current even though the RPM is notably increased. I know I can get more than that.

My first intention was to design a new permanent magnet rotor for the stepper motor and I did so but the results I got were still poor, plus it required modifying the stepper which could be challenging.

I also rewound a 12 pole BLDC motor, salvaged from a LASER printer. This motor initially had 35 turns per pole and I was able to rewind it to 50 turns per pole. In the measurements that I made, I obtained acceptable values of current and voltage to charge lithium ion batteries of the 18650 type. In the end, I discarded it since it has a high mass due to having ceramic magnets in its external rotor.

Looking for alternatives, I found 130kV BLDC motors at a good price on Aliexpress. They are motors used in the Matrice M600 drones of the DJI company. Perhaps they were discarded due to bearing wear or because this Drone is already out of production, I don't know but I do know that its capabilities as generators are exceptional.

Below are the results of the measurements I made. My conclusions from these measurements are as follows:

• They deliver a lot of current even at low RPM. In the measured range, the short-circuit current had a linear growth behavior as a function of the RPM.

• It was verified that they are 130KV motors (revolutions per volt) as can be seen in the trend adjustment equation. To obtain voltages of 5 V or more, more than 600 RPM is required, which leads to the redesign of the generator blade to operate at higher RPM.

• At approximately 840RPM, a charging current of 1A is obtained in an 18650 cell, which exceeds the generation capacities of the stepper motor at the same RPM.

I can tell you that I have already finished the first variant of the Generator Hub (BLDC M6010) and I am now working on the redesign of the new Blade with the GPL software QBlade 0.96.

Greetings to all