Rotor Current:

 

 

Fig: 1

 

Fig. (1) shows the circuit of a 3-phase induction motor at any slip s. The rotor is assumed to be of wound type and star connected. Note that rotor e.m.f./phase and rotor reactance/phase are s E₂ and sX₂ respectively. The rotor resistance/phase is R₂ and is independent of frequency and, therefore, does not depend upon slip. Likewise, stator winding values R₁ and X₁ do not depend upon slip.

Since the motor represents a balanced 3-phase load, we need consider one phase only; the conditions in the other two phases being similar.

 

At standstill. Fig. (2 (i)) shows one phase of the rotor circuit at standstill.

 

Fig: 2

 

When running at slip s. Fig. (2 (ii)) shows one phase of the rotor circuit when the motor is running at slip s.

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