Renewable Energy Questions/Discussion > Wind and Hydro

Figuring RPM's from frequency

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alvin:
 Hi all

 I have a single phase 8 pole alt. At 10 Hz it is producing 1 amp. I don't have a tach. So would 10 Hz times 60 seconds divided by 8 poles
equal 75 RPM be right ? 

Thanks
Alvin

frackers:
Do you mean 8 poles or 8 magnets. If 8 magnets then its 4 poles (pairs) so you're actually seeing 150rpm.

Just got my controller to read RPM accurately and my Piggott 10ft 6 pole (Otherpower stator) 24 volt machine is cutting in at 150rpm and just over 1kw at 280rpm. Information I've managed without for 3 years but interesting none the less :)

ChrisOlson:

--- Quote from: alvin on January 31, 2012, 07:14:26 pm --- I have a single phase 8 pole alt. At 10 Hz it is producing 1 amp. I don't have a tach. So would 10 Hz times 60 seconds divided by 8 poles
equal 75 RPM be right ?

--- End quote ---

The formula is:
rpm = freq x 120 / # of poles

--
Chris

alvin:
Thanks frackers and ChrisOlson for the response. It is 8 magnets and 8 coils. 150 rpm's sounds more like it. The most I've seen is 10 amps. I did not measure the frequency at that point, but it must not be linear.

This is my first attempt. Sticker shock from the NEO's led me to use microwave magnets on one disk and 2.5"X1/8" round neo on the other. 
Alvin

rossw:

--- Quote from: alvin on February 01, 2012, 04:19:12 am ---Thanks frackers and ChrisOlson for the response. It is 8 magnets and 8 coils. 150 rpm's sounds more like it. The most I've seen is 10 amps. I did not measure the frequency at that point, but it must not be linear.

--- End quote ---

Frequency is completely linear with RPM. Double the RPM and you must double the frequency.

Current won't be linear function of RPM when charging a battery though.

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