Induction Motor rating

[biswaIITH]

Had once faced the following question in one interview...
In AC machines rating is done on the basis of heating and hence losses in them hence in VA

Why is the rating of Induction motor in KW where as transformer and alternators are in VA????

 

[kappa_am]

Because the indicated power on a motor is output power which does active work. but in the other mentioned devices output is electrical and my feed a load which has a reactive element, and hence it include reactive power.

 

[biswaIITH]

So AC motors are rated in KW and AC generators are rated in VA...But what if the same induction motor operates as induction generator???
How will u define the rating den???

 

[kappa_am]

the meaning of the question is obvious. alternator has defined meaning.
and about the second question what if a induction machine is used as generator. Induction generators needs a capacitor bank to excitation. this bank generates reactive power almost equal to reactive power that machine consumes in motoring state. in a specific operation point in generating and motoring state the losses are almost equal. so the indicated number on plate is output power of the installation.

- - - Updated - - -

the meaning of the question is obvious. alternator has defined meaning.
and about the second question what if a induction machine is used as generator. Induction generators needs a capacitor bank to excitation. this bank generates reactive power almost equal to reactive power that machine consumes in motoring state. in a specific operation point in generating and motoring state the losses are almost equal. so the indicated number on plate is output power of the installation.