Explain the suitability of 3-phase induction motor for traction service.

Explain the suitability of 3-phase induction motor for traction service. 
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Suitability of 3-phase induction motor for traction service because of following points:- 1. It is robust in construction and capable to withstand against continuous vibration. 2. Simple in design & construction. 3. Slip-ring induction has high starting torque when external resistance is added in rotor circuit. 4. Since the torque speed characteristic of the induction motor is markedly steeper, the induction machine can take better advantage of maximum possible tractive effort. 5. No restriction on speed of motor because of absence of commutators. 6. Speed control methods are simple 7. Power to weight ratio of induction motor is much higher than the DC motor. 8. High efficiency. 9. Require little maintenance. Apart from bearing, it has no parts subjected to wear. It is not much effected by dust, vibration and heat 10. Less maintenance. 11. A high mean adhesion coefficient can be expected. 12. The induction motor drives are about 20% energy efficient compared to DC drives. 13. Three phase drives allow regeneration and unity power factor operation. 14. The energy saving due to regeneration and improved power factor are sizable. 15. It operates at high voltage ( 3.3 / 3.7 KV) consequently requiring less amount of current 16. Automatic regeneration is the main advantage of I.M. 17. Trouble free operation.

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