GATE EE 2026 Set 1 — Question 21

MCQ+1 / -0.33EasyDeep Bar & Double CageThree-Phase Induction MachinesElectrical Machines

Electrical Machines → Three-Phase Induction Machines → Deep Bar & Double Cage

Last updated 5 September 2026

Question

Which one of the following options is correct regarding the typical double-squirrel-cage structure used in induction motors?

Correct answer (A) At starting, a larger portion of the rotor current flows in the outer cage Solution In a double-squirrel-cage induction motor, the outer cage is designed with high resistance and low reactance, while the inner cage has low resistance and high reactance. At starting, the rotor frequency is high (equal to the supply frequency), which makes the reactance of the inner cage very high. Consequently, the rotor current is forced to flow primarily through the outer cage. This high-resistance path provides the high starting torque required. At rated speed, the slip and rotor frequency are low, making the reactance of the inner cage small, so the current flows through the low-resistance inner cage for efficient operation. Turn this into a strength. Explore AI-powered practice and doubt support with Success Tracker.

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Correct answer (A) At starting, a larger portion of the rotor current flows in the outer cage Solution In a double-squirrel-cage induction motor, the outer cage is designed with high resistance and low reactance, while the inner cage has low resistance and high reactance. At starting, the rotor frequency is high (equal to the supply frequency), which makes the reactance of the inner cage very high. Consequently, the rotor current is forced to flow primarily through the outer cage. This high-resistance path provides the high starting torque required. At rated speed, the slip and rotor frequency are low, making the reactance of the inner cage small, so the current flows through the low-resistance inner cage for efficient operation.

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