You are not applying 500w you are using 500w to turn the motor which in return is creating the rotational speed of 1750 rpm.
So i am applying 500w of rotational speed that is then converted to the equivelent of 47 mph wind with a pulley
I want to ask and i already said that an extractor of air that consumes 150 watts has 1750rpm. How is that different from consuming 500 watts instead of 150 watts? As I see what we need is 1750 rpm right to give air blowing speed of 47mph?
also to convert rpm to mph, https://sciencing.com/convert-rpm-mph-calculator-2854.html
Using that webpage to calculate it, it gave me the number of 20 mph, 1750 x 60 =105.000, divide by 5280 = 19.88 mph.
Maybe your 500 watts 1750rpm is not 1750rpm, more like 4200rpm. That explains why it uses 500 watts. 3 x 150w = 450 watts.
The noise a 4200rpm generates kill everything in few meters.
Also what i think is the most important is the cfm and the cfm is related to diameter and rpm.
Generating electricity from wasting electricity, i wonder is that is really viable or just a waste of time.
The wind turbine works better with? 30cm, 40cm, 50cm, 60cm, 70cm exhaustor? and I guess it has to be very close or with a good connection with pipes, cause it can not have any leaks.