1️⃣ Flux that leaks through the machine
2️⃣ Flux that links both stator and rotor windings
3️⃣ Flux that links none of the windings
4️⃣ Flux that links the stator winding or the rotor winding but not both
✅ Answer (Detailed Solution Below)
✔️ Option 4: Flux that links the stator winding or the rotor winding but not both
📖 Detailed Solution
🔹 In an induction motor, magnetic flux is divided into two parts:
Mutual (Main) flux
Leakage flux
🔹 Mutual flux links both stator and rotor.
🔹 Leakage flux links only one winding.
🔹 It may link:Only stator winding, or
Only rotor winding.
🔹 It does not contribute to torque production.
🔹 It produces leakage reactance.
🔹 Leakage reactance reduces voltage and torque.
👉 Hence, leakage flux links only one winding.
⚙️ Types of Flux in Induction Motor
✔️ Mutual Flux → Links stator and rotor
✔️ Leakage Flux → Links only one winding
📈 Effect of Air Gap on Leakage Flux
🔹 When air gap increases:
Magnetic coupling decreases.
Main flux decreases.
Leakage flux increases.
Leakage reactance increases.
Torque decreases.
❌ Why Other Options are Incorrect
(1) Flux that leaks through the machine ❌
🔹 Too vague.
🔹 Does not define linking property.
(2) Flux that links both windings ❌
🔹 This is mutual flux, not leakage flux.
(3) Flux that links none ❌
🔹 Flux must link some part of winding.
📌 Additional Information
If Air Gap is Increased:
🔹 Permeability decreases
🔹 Magnetizing inductance decreases
🔹 Magnetizing current increases
🔹 Leakage flux increases
🔹 Power factor decreases
🔹 Maximum torque decreases
📌 Key Exam Notes
⭐ Mutual flux → Produces torque
⭐ Leakage flux → Produces reactance
⭐ Leakage flux ↑ → Torque ↓
⭐ Air gap ↑ → Leakage ↑
📝 Final Summary
📍 Leakage flux is the magnetic flux that links only stator or rotor winding but not both, and does not contribute to torque.
👉 Hence, Option 4 is Correct.