How does rating of motors decided ?

How does rating of motors decided ?
Some questions like what is an Induction motor, what is the working principle, what is the slip, what is the torque etc etc etc......can be easily found in hell number of books both offline and online. But there is a question even google was unable to track it that perfect. 

When I am giving training on induction motors for a set of maintenance engineers, there came a question from a participant  " Why are motors rated for some specific power values like 3.7kW, 5.5kW,7.7kW and so on...but not 3.2kW, 5.4kW.....?? "

All silence for a moment...I somehow managed to skip from answering that question, but later scouted for the answer with proper description in many platforms both online and offline. Till now I didn't get the satisfactory explanation for the same.

So thought to scout for a perfect answer through this post from all the professionals over there !!

Request to please post your answer in the comments section below so that all others can have access to the answers.



1 comment:

  1. Motors used to be rated in Horse Power (760W) and variants of horse power were developed. Seems we have moved away from the old rating method.

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