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.htmlFor example, if the rotational speed is 100 rpm, enter "100." Multiply this number by 60 to convert it from feet per minute to feet per hour. Divide this number by 5,280, which converts feet per hour to miles per hour. Push the equal sign to see the speed in mph.
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.
You didnt take into account the pulley ratio of 1:4.5 we are not building a direct drive unit
The 1750 rpm is the starting point for the rpm the 1:4.5 pulley ratio turns your 1750 rpm into 7875 rpm which is then enough to power the generator at full power.
A simple bathroom fan dont have enough torque that is why you use a bigger motor that does have some torque to it and if it uses 5 amps great if it uses 10 amps ok and so on.
The goal is to use the least amount of energy to get the 7875 rpm needed to turn the generator head.
The belt surface speed needs to be at 7875 rpm which is equivalent to a 47 mph wind. Now you have 83 amps of charging power instead of 500 watts of charging power that you initially started with.
A car alternator for example does not run at the rpm the engine is running at the pulley configuration takes the 2000 rpm from the cars engine and turns it into about 6000rpm at the alternator.