What is the frequency of rotor current of a 50 Hz induction motor operating at 2% slip?

A) 1 Hz
B) 100 Hz
C) 2 Hz
D) 50 Hz

✅ Answer:
A) 1 Hz

🧠 Detailed Solution

🔹 1. Given Data:
Supply frequency → f = 50 Hz
Slip → s = 2% = 0.02

🔹 2. Formula Used:

f_r = s × f

Where:
f_r = Rotor current frequency
s = Slip
f = Stator frequency

🔹 3. Calculation:

f_r = 0.02 × 50 = 1 Hz

❌ Why Other Options Are Wrong

B) 100 Hz ❌ → Rotor frequency cannot exceed supply frequency
C) 2 Hz ❌ → Incorrect calculation
D) 50 Hz ❌ → This is stator frequency (only at starting rotor frequency = 50 Hz)

📌 Key Points

• Rotor frequency = Slip × Supply frequency
• At starting (s = 1) → Rotor frequency = 50 Hz
• At normal running → Rotor frequency is very low

🎯 Final Conclusion

✔ Rotor frequency = 1 Hz
✔ Correct Option → A