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Anonymous Poster

Pulley Ratios and Power

05/31/2009 10:07 PM

pulleys and ratio ,power.If you had a 14 inch pulley on the motor shaft,[motor is 1 hp] and a 2 inch pulley on a generator shaft and it reaches will say 50 rpm. and make will say 30 volts at 10 amps. I just put in all the figures that i could think of.Their just examples to use. My question is if I "increased BOTH pulleys to be the SAME ratio would all out put stay the same/or would it be easier . I know that If I just change the small pulley that it would take Less power from the motor.A friend and I were talking about this.Its about a wind turbine. I have the 14 inch pulley on the mail shaft and a 1 1/2 pulley on the alternator.It only have to do 2 rpm to reach 12 volts.

Lot of fun.

Thanks to all .in adv.

Johnny
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sb
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Join Date: Mar 2007
Posts: 2550
Good Answers: 103
#1

Re: Pulley and ratio

05/31/2009 11:57 PM

The pulley ratios will govern the RPM, neglecting the slips,

n1/n2 = d2/d1

where n and d are the RPM and pulley diameters.

The powers at the input and output will be same with the efficiency of the drive

so

P2 = ηP1

but the torques, being RPM dependednt will be different

τ2ω2 = ητ1ω1

Here since you are working on a wind turbine, you must run the generator at the speed and changing the pulley ratio will change the speed at the generator stage. How do you control that?

Using a small pulley does not take less power, it require lesser torque since the RPM increases. But the generated power remains same.

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