-
An induction motor having full load torque of 60 Nm when delta-connected develops a starting torque of 120 Nm. For the same supply voltage, if motor is changed to star -connection, then starting torque developed will be _______ Nm .
-
- 40 Nm
- 80 Nm
- 150 Nm
- All of the above
Correct Option: A
With Delta Connection :
| Starting current per phase = | ||
| √R² + X² |
| ∴ Starting torque = | = 3 RI2 | |
| s |
| since , s = 1 = | ||
| R2 + X2 |
With Star Connection :
| Starting current / phase = | ||
| √R² + X² |
∴ Starting torque = 3 RI2
| = 3 × R × | = | ||
| 3 (R2 + X2) | R2 + X2 |
| ∴ New starting torque = | = 40 Nm | |
| 3 |
