Induction motor design calculations pdf

Induction motor design calculations pdf main objectives while starting an induction motor are to handle high-starting current and achieve high-starting torque. Share with your Facebook friends!

Usually, this rotor resistance is small, giving small starting torque, but good running conditions. So, the squirrel-cage motor can run only with low-starting loads. If the rotor resistance is increased by some means, then the slip and speed at which maximum torque occurs can be shifted. For that purpose, external resistance can be introduced in the rotor circuit, which is done in the case of slip ring or wound rotor type motors. This happens due to the fact that there is a transformer action between the stator winding and the rotor winding, and the rotor conductors are short-circuited. This causes heavy current flow through the rotor.

If, for reducing this heavy starting current, starting voltage applied is reduced then it affects the starting torque as well. Core loss is due to the main and leakage fluxes. As the voltage is assumed constant, the core loss can also be approximated as a constant. The hysteresis and eddy current loss in the conductors increase the resistance, and the effective resistance is taken at 1.

2 times the DC resistance. The friction and windage loss may be assumed constant, irrespective of the load. Consider a three-phase 440 V, 50 Hz, six-pole induction motor. The motor takes 50 kW at 960 rpm for a certain load. Assume stator losses of 1 kW and friction and windage loss of 1. Hi Sir, if i reduce the speed of my 60kW-6 pole from 1140 to 730rpm, what have i lost?