alternator frequency????

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alternator frequency????

So I've wasted entirely to much time trying to figure out where I am going wrong here.

An alternator containing eight poles per phase is turning at 1500 RPM. What is the output frequency?
Help: Output frequency calculation for three-phase alternator

the formula I used to find the 100hz is Frequency=poles X speed/ 60x2
so 8x1500/120=100
Am I doing something wrong here??

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Originally Posted by GavinK5
That's kind of what I was thinking, however there were 2 of these questions with different values and I missed both of them using this formula. Taking my 3 next week and would really like to be sure I am doing this correctly, last time I took the test I missed passing by 2 questions. I do not want to repeat that.

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Originally Posted by lester mcmanaway
That's kind of what I was thinking, however there were 2 of these questions with different values and I missed both of them using this formula. Taking my 3 next week and would really like to be sure I am doing this correctly, last time I took the test I missed passing by 2 questions. I do not want to repeat that.
Dang, sorry to hear about that. Check out some of these formula examples:

Source: http://electrical-engineering-portal...ase-alternator

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Originally Posted by GavinK5
Dang, sorry to hear about that. Check out some of these formula examples:

Source: http://electrical-engineering-portal...ase-alternator
appears to be right in line with what I was thinking, wondering why it was marked incorrect. The only other thing that trips me up a little is when " poles per phase" is mentioned. So are you assuming 3 phase at that point and using the given poles per phase x3?

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Originally Posted by lester mcmanaway
appears to be right in line with what I was thinking, wondering why it was marked incorrect. The only other thing that trips me up a little is when " poles per phase" is mentioned. So are you assuming 3 phase at that point and using the given poles per phase x3?
Good question. I would assume that the number of poles given is the total for all three phases.