Ns=120f/p. what is 120?
Answers were Sorted based on User's Feedback
Answer / piyush kumar
1. Frequency is given by Ns(rpm) divided by 60 to make it "per second"
2. This is due to one pair of poles so needs to be divided by 2.
3. There are P no of such pole pairs so needs to be multiplied by P.
4. So we get f = (Ns/60)*(1/2)*P
or Ns = (120*f)/P
Hope this explains it !!!
Is This Answer Correct ? | 159 Yes | 25 No |
Answer / subhasish(rimo) sengupta
f=1/T. when,T = time period for one full cycle.
in T seconds, 1 revolution is completed.
So, in 1 second,1/T revolutions or f full waves is formed.
If there are P no. of poles,then P/2 no. of full waves will be formed in one full revolution of the field.
Now, if n=rotation of the field in 1 second,
then f=(P/2)*n
or,n=2f/p.
So, N=(60*2*f)/P , (when N= rotation per min.)
or, N=120f/P.
Is This Answer Correct ? | 102 Yes | 3 No |
Answer / k.prakashchandra
It is N (RPM)and not Ns(RPS) which is =N/60. One south pole
and one north pole produce a cycle. So in one second f= N/60
x P/2 = NP/120. Hence N = 120f/P
Is This Answer Correct ? | 45 Yes | 17 No |
Answer / lokeshraj
the Ns is the speed in rpm so there is a facter 60 is
there. then two poles makes a magnet or passing over two
poles one cycle of output is completed. combining both
there is a 120 factor.....
Is This Answer Correct ? | 36 Yes | 20 No |
Answer / tandel jinal
Here,
If there is 2 Pole rotor then 1 cycle completed in one revolution,
And if 4 Pole rotor then 2 cycles completed in one revolution,
Number of poles increased then cycles also will increased as half of number of poles.
So, 1 rev.- P/2 cycles complete
Now, N = Speed in rpm ( rev. per minute )
N/60 = Speed in rps ( rev. per second )
If,
1 rev. = P/2 cycles
Then, N/60 rev. = ?
P/2*N/60 = f in Hz
f = PN/120 cycle/sec.
So, N = 120N/P.
Is This Answer Correct ? | 8 Yes | 1 No |
Answer / parth
Ns=120*f/p
There are no of pair of pole then p/2.
Ns=1/T in rpm then convert in to rps.
1/T=f.
Ns=60*2*f/p.
Is This Answer Correct ? | 6 Yes | 2 No |
Answer / shriram.n
speed=2*60f/p
where
2=?
60=min.
f=frequency
p=pole
we can find speed of motor through below fprmula also
i.e
speed=60f/p
where
60=min.
f=frequency
p=pairs of poles.
example
s=120*50/4=1500rpm
like s=60*50/2(4pole have 2 pairs)=1500rpm
Is This Answer Correct ? | 17 Yes | 15 No |
Answer / uday
Ns is nothing but the no. of revolutions indirectly seen by
any pole pair( i.e. created or wound inside). so that will
be 50 cycles per sec per pole, in case of 2 pole machine and
it is 3000RPM)
Is This Answer Correct ? | 13 Yes | 12 No |
Answer / aditi
Ns=2f/p rev/s
Multipying by 60 gives Ns in rev/min
and 2 accounts for pole pairs.
Is This Answer Correct ? | 14 Yes | 16 No |
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