A threephase induction motor has the following name plate da

A three-phase induction motor has the following name plate data: Using the data given in the nameplate. determine the following and justify fully your answers a) Explain the meaning of \"Design B\" b) explain the marking S.F. 115 and what it indicates c) Explain what NEMA NOM Efficiency means d) What is the synchronous speed of this motor? e) What a the slip at rated load for this motor? f) What is the expected maximum starting current (inrush) for this motor? g) What is the input power supplied if it is assumed that the motor is operating at its nominal efficiency with rated nameplate values? h) What is the rated output torque for this motor? i) How much reactive power is drawn under rated conditions?

Solution

c) Nema Nominal efficiency is defined as the ratio of output power to input power,

which is expressed as ,

(output/input)*100

d)synchronous speed

n_s = 120f/p

n_{s=120(60hZ)/3}

n_s=2400rpm

e)slip

s(=n₁-n)/n₁

where s= a normal value of slip

n₁=synchronous speed

n=asynchronous speed

as we know synchronous speed =2400rpm