ECE 4411 Equivalent Circuit of an Induction Motor Rotor Consider just a single phase. The power and torque developed by the motor will be three times that of one phase.

ECE 4412 The rotor resistance depends upon the rotor conductors as well as an external rheostat if the machine has a “wound rotor”. The reactance of the rotor is caused by “leakage” flux and is called the “leakage reactance”.

ECE 4413

4 The equivalent circuit in terms of slip is shown below.

ECE 4415 The blocked-rotor voltage and rotor inductance are constant and the rotor resistance varies with the slip.

ECE 4416 Magnitude and Phase of the rotor current

ECE 4417 Locus of the Rotor Current Plot the magnitude and phase of the rotor current as functions of the slip.

ECE 4418 Amperes and Degrees

ECE 4419 I r and θ r are maximum at blocked rotor and approach zero as the rotor accelerates to synchronous speed. Amperes and Degrees

ECE Phasor Diagram of the rotor current “Blocked Rotor” (s=1) Synchronous Speed (s=0)

ECE Equation of the semicircle tangent to the horizontal axis at the origin with a diameter of E BR /X BR.