1️⃣ Continue running in the same direction as before
2️⃣ Run in the opposite direction
3️⃣ Not run
4️⃣ Get damaged
✅ Answer
✔️ Option 1: Continue running in the same direction as before
📖 Detailed Solution
🔹 Basic Concept: Direction of Rotation
In a 3-phase slip-ring induction motor, the direction of rotation depends only on the phase sequence of the stator supply, not on the rotor connections.
✔️ The stator produces a rotating magnetic field (RMF).
✔️ The direction of this rotating field is decided by the phase sequence (RYB or RBY).
✔️ The rotor always follows this rotating magnetic field.
🔹 Role of Slip Rings
✔️ Slip rings belong to the rotor circuit.
✔️ They are used to connect external resistance.
✔️ They carry rotor current only.
Interchanging slip ring leads:
✔️ Changes internal rotor current path.
✔️ Does NOT change stator phase sequence.
✔️ Does NOT change RMF direction.
🔹 Effect of Interchanging Slip Ring Leads
When any two slip ring leads are interchanged:
✔️ Stator phase sequence remains same.
✔️ Rotating magnetic field remains same.
✔️ Direction of rotation remains same.
👉 Therefore, the motor continues to rotate in the same direction.
❌ Why Other Options Are Incorrect
2️⃣ Run in the Opposite Direction ❌
Direction reversal happens only when two stator supply lines are interchanged.
Changing rotor leads does not reverse RMF.
3️⃣ Not Run ❌
Rotor circuit remains closed.
Current still flows.
Torque is produced.
So, motor continues running.
4️⃣ Get Damaged ❌
No abnormal voltage or short circuit is created.
No overheating occurs.
Hence, no damage happens.
📌 Important Related Concept: Direction Reversal
✅ How to Reverse Direction of an Induction Motor
To reverse direction:
➡ Interchange any two stator supply phases.
Example:
RYB → RBY
YBR → YRB
This reverses RMF and motor direction.
⚠️ Important Note
Phase interchange should be done after stopping the motor.
If done while running:
❌ Braking torque is produced
❌ High mechanical stress
❌ Electrical stress may occur
📊 Key Difference Table
| Connection Changed | Effect on Direction |
|---|---|
| Stator Supply Lines | Direction Reverses |
| Slip Ring Leads | No Change |
⭐ One-Line Exam Note
Interchanging any two slip ring leads does not change the direction of a 3-phase induction motor because direction depends only on stator phase sequence.
📌 Final Conclusion
Changing rotor (slip ring) connections does not affect the rotating magnetic field. Therefore, the motor continues to run in the same direction.