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A 6-pole, 3-phase, 60 Hz induction motor runs at 1000 rpm developing maximum torque. Rotor resistance per phase is 1.2 ohms. Neglecting star tor impedance, for developing maximum torque, the external resistance to be connected in series with each rotor phase will be
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- 7.2 ohms
- 6 ohms
- 1.44 ohms
- 1.2 ohms
Correct Option: B
For maximum torque,
| = x2 | |
| s |
| where, s = | = 0.2 | |
| 1000 |
| ∴ x2 = | = 6 ohms | |
| 0.2 |
