I needed to do these tests because I have to decide if I need to use gears or other power transmission mechanisms, in which case I would change the design a bit.
It is not enough to make the propellers rotate, it is necessary to generate an adequate voltage and current value for storage in batteries and subsequent use, hence the need for these mechanisms may arise.
We should remember that I already tried to rewind BLDC motors to get higher voltages. The ferromagnetic cores of the stator have limited space for the copper wire and to increase the number of turns per pole it is necessary to use finer gauge wires which greatly limits the output power. Since this Wind Turbine has to be small because it is "portable" I find this solution unfeasible for the power I want with this new prototype. If the power is not something of primary interest, then I recommend building the Prototype 1 which is much simpler than this and guarantees about 3-6W of Power without major complications.
During the first phase of the tests I verified that the propellers could rotate and start the movement by themselves without gears. In this case, the motor is directly coupled to the hub as it was assembled in the previous Log. Unfortunately there was no wind at all that day and I had to use a common household fan. You may not see it in the video, but the fan blades are much shorter than the wind generator blades. This constitutes a limitation, but in spite of it it began to rotate. From my previous experiments I have been able to learn that if it works with the turbulent and relatively low flow that a fan provides it will do very well in real world conditions. Luckily nothing came off or flew away hahaha!!! The maximum voltage obtained was 2.66V, a bit low for my needs. This voltage value corresponds to about 400 RPM according to my previous experimental results. I know that this voltage value could be increased in suitable wind conditions. My intention is to manage to charge 18650 lithium cells connected in parallel until they reach their maximum voltage of 4.2V. The number of cells in parallel will depend on the generation current. BMS, Buck boost converters, Power Meter and others are required that when I finish this part of the Project I will have to integrate.
During the second Phase I did some tests on the generator, but this time coupled to gears with a 1:4 ratio. As can be seen, it is not capable of starting the movement on its own, although it is capable of sustaining it without problems once a minimum RPM has been reached. An automatic angle of attack variation system would perhaps be a benefit. A higher angle of attack would guarantee the start of the rotation and then the angle of attack would be decreased to achieve higher RPM and improve efficiency. This would make this project much more complex and would also make it more expensive, something that I prefer to avoid.
I think I am going to redesign the generator to integrate a 1:2 ratio power transmission system. I would like to know your opinion.
See you in a next Log!!!