How will change rotar EMF and reactance under running condition.

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When we supply three phase input to the rotor of the motor then voltage is induced in the rotar e2 and current I to start flowing. The frequency of rotar and voltage of rotor at stand still is equal to supply frequency. Because relative velocity is maximum at a stand still when s= 1 between status flux and rotar.

Let at stand still S =1 ,

E2= stand still rotar induced EMF per phase

f2 = rotar current frequency at stand still

X2 = stand still rotor induced reactance per phase.

when rotor starts rotating then relative velocity between rotor and stator flux decreases then induced voltage E2  start decrease.

When  rotor speed catches rotating flux speed than relative velocity becomes zero that is S= 0 then induced voltage then become zero.

let's say for a slip 's' the rotor induced EMF will be s times the induced emf at a stand still.

Therefore under running condition

Rotar induced EMF running condition

Er = s E2

Frequency of induced EMF at running condition

fr = sf2

Since frequency of induced EMF is reduced so the reactance will also reduce.

Xr = sX2

Where Xr, Er, fr are induced reactance,  rotor EMF and frequency under running condition respectively.

Impedance triangle of induction motor at running condition.





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