Inscrivez-vous ou connectez-vous pour rejoindre votre communauté professionnelle.
The Initial torque of the single phase induction motor is very small so they can not take self start , we use a capacitor to give them a starting torque . while3 ph has self start due to high torque , this high torque can also be improved to avoid current over shoot
3-phase induction motors are self starting due to high stating torque while1-phase induction motors use capacitor to build up starting torque in order to start it.
Hi
Basically , Single Phase motors are not exceeding0.5 HP . It means that single phase motor has no significant Starting Torque . we use a capacitor in the starting winding to make a phase difference between the two fluxes of the running and starting winding.
Three Phase Motor has different starting torque as per exceeding rating. As the rating will be increased , starting torque will be increase so we reduce the starting torque by using different starter type.
For Example :
Three phase motors not exceeding10 HP to be direct on line (7.46Kw)
Three phase motors over10 HP but not exceeding50HP to be automatic star delta magnetic non reversing type with3 pole overload relay and low voltage protection (7.46Kw -37.3 kw)
Three phase motors over50HP to be multiple step auto transformer non reversing magnetic type with3 pole overload relay, low voltage protection and used Soft Starter.