# Asynchronous motor question

1. Jun 2, 2013

### Marketgirl

1. The problem statement, all variables and given/known data
number of pole pairs p =2
line frequency f=50hz
number of rotations n=1250 1/min

2. Relevant equations

3. The attempt at a solution

question is number of rotations of the rotary magnetic field (1/min units)
the slip of the machine(s)
the frequency of the rotor current ?

please help me to solve this kind of problems i have like 5 more questions which is smilar to this one so i can learn how to solve others thank you from now good luck at your exams :)

2. Jun 2, 2013

### rock.freak667

If you have the line frequency and the number of pole pairs, you can get the rotation of the stator Ns by using

$$N_s = \frac{120f}{p}$$

where f is the line frequency and p is the number of poles.

How is slip defined?

3. Jun 2, 2013

### Marketgirl

s = Ns-Nr/Ns Ns is stator electrical speed, and Nr is rotor mechanical speed. thank you for your helps sir.

4. Jun 2, 2013

### rock.freak667

Right, so using the formula I gave you above, you can get Ns. They gave you the value of Nr, so can you get the slip?

5. Jun 2, 2013

### Marketgirl

yes sir your help was enough, i wish you best of luck and thank you so much.