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Join Date: May 2012
Posts: 16

### Wind Power Conversion?

05/20/2012 3:21 PM

If maximum power rating of PM motor is 300W, rated speed 2700rpm, operating voltage 24V & 3 wood blades running at 150rpm attached with the shaft of the motor.

if 175W is the calculated mechanical power from the wind at 6m/s.

what is the output of the motor in terms of volts & amperes?

From my calculations Output voltages = 1.33V ((150/2400)*24V), but how calculate output current if maximum electrical load is attached at the output i.e.175W? because input power to the system is 175W & it must give (175/1.33) =130A?

if it's not given this current which it does, then where is the input power (175W)gone?

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Join Date: Mar 2007
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#1

### Re: Wind power conversion?

05/20/2012 3:34 PM

amps X volts = watts If you're putting out 175 watts at 24 volts then you've got around 7.3 amps....If you're converting wind mechanical force, then you have to allow for efficiency of generator...

http://homepower.com/view/?file=HP102_pg42_Piggott

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#2

### Re: Wind Power Conversion?

05/20/2012 4:59 PM

Look at it this way your motor is rated for 300 watts at a 24 volt input which means it can handle (300/24)= 12.5 amps of current continuously.

If it runs at 2700 RPM at a 300 watt load it produces roughly (2700/24)= 112.5 RPM per volt input.

However as a generator at a 2700 RPM input the output voltage will be less and could be anywhere between 20 - 22 volts no load with a considerable pull down at a 12.5 amp load which makes your wattage output estimates meaningless until the exact volts/RPM at specific loads is known.

Don't be surprised to see your motor only put out 15 volts at 12.5 amps with a 2700 RPM input which also means that if given a proportional voltage drop VS speed at a 150 RPM input and a 12.5 amp load you could see as little as .83 volts output that rises to at best maybe 1.2 volts at no load.

Using PM motors for generators works very well but you either have to get used to expecting the output voltages to be 60 -80% of the rated voltage at the specified RPM and amp capacity or get used to running your motors at 20 - 40% faster shaft speeds to get the equivalent voltage and amperage ratings out it that it had as a motor.

Also just because the wind has X amount of energy in it as a specific speed does not mean that your fixed pitch blades are going to pick that up at 100% efficiency at any RPM rather they will have a sweet spot that is most efficient and any variations above or below will drop off in efficiency rather rapidly, especially when going below.

Given the questions in this thread and your other one you have lots of learning to do regarding wind power and electricity and how they work together.

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#3

### Re: Wind Power Conversion?

05/21/2012 12:11 PM

Depends on the tip speed.

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