General Information of a 3-phase induction motor

General Information of a 3-phase induction motor


A. C. System is universally used for generation of electricity and so also for transmission and distribution on account of it's various advantages. 
Induction motor
General Information of a 3-phase induction motor



As a electrical drive,A.C.3-phase and single phase motors are therefore find the wide
applications in various inctustries.Out of the so many types of 3-phase A.C.motors,the


3-phase inductiton motor is very popular in the industrics due to its following
merits:


  1. Compact and very simple construction.
  2. Shape and weight is small in comparison with other types.
  3. Cheaper in cost.
  4. Very easy for repairs and rewinding.
  5. Maintenance cost is very low.
  6. In operation it requires less attention.
  7. Efficiency is hetter.
  8. Frictional losses are lesser.
  9. It is self-starting.
  10. On higher loads it operates at a reasonably better power-factor.
  11. Starters required for controlling the initial current are of very simple in construction and therefore cheaper in cost.
  12. Used for various purposes universally under any climatic conditions.
  13. Its speed slightly decreases on load about 4 to 5% only.
  14. Sparkless operation. 

In splite of the above different qualities of the 3-phase.Induction motor following are the drawbacks due to which it is not used in few cases.


Drawbacks:

  1. Wide range and smooth speed variation is difficult.
  2. Speed variation arrangements are not reliable and not cheaper.
  3. Its efficiency decreases if speed variations are done.
  4. Starting torque is not more and it is inferior.

  • Due to the above drawbacks of the motor it is not used where higher starting torque isrequired and where frequent speed change is required.Otherwise these motors meet therequirements of the industries and find a large range of applications.
  • To understand the working of an induction motor the students should revise the portionof“Transformer",which they are studying in the subject"Transformer".Refer Chapter1 of this book.'
  • The induction motor theory is in many respects similar to transformer theory and manya times the induction motor is said to be Generalised Transformer.

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