Calculating Rotations and Slip in an Asynchronous Motor

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    Asynchronous Motor
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Discussion Overview

The discussion revolves around calculating the number of rotations of the rotary magnetic field, the slip of an asynchronous motor, and the frequency of the rotor current. It includes a homework problem involving the relationship between line frequency, number of pole pairs, and rotor speed.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant states the number of pole pairs (p = 2) and line frequency (f = 50 Hz) as part of a homework problem.
  • Another participant provides a formula to calculate the stator rotation (N_s = 120f/p) based on the line frequency and number of pole pairs.
  • A participant defines slip (s) as s = (N_s - N_r) / N_s, where N_s is the stator electrical speed and N_r is the rotor mechanical speed.
  • There is a reiteration of the slip formula, confirming its components and expressing gratitude for assistance.

Areas of Agreement / Disagreement

Participants appear to agree on the definitions and formulas related to the calculations, but the discussion does not resolve the specific numerical calculations or the application of the formulas to the homework problem.

Contextual Notes

The discussion does not clarify the assumptions behind the definitions of slip or the specific values needed for calculations, such as the rotor mechanical speed (N_r).

Who May Find This Useful

Students working on problems related to asynchronous motors, electrical engineering, or those preparing for exams in related fields may find this discussion relevant.

Marketgirl
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Homework Statement


number of pole pairs p =2
line frequency f=50hz
number of rotations n=1250 1/min


Homework Equations





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

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

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