Study-of-induction motor-3

The descriptive plate (“la plaque signalétique”) of the induction motor of a milling machine shows the following indications:

3 ∼ 50Hz ;    Δ     220V     11A;        Υ       380V       6,4A ;              1455tr/min                cosφ = 0,80
1- This motor is supplied by an electric grid 220 V / 380 V; 50 Hz. How do we have to couple the stator windings of this machine? Justify your answer.
2- Give the number of poles of machine stator.
3- Calculate the nominal slip g_n (in %).
4- A no-load test (“essai à vide”) was performed for this motor powered by the grid mentioned above. We obtained the following results:
– No-load current : I₀ = 3.2A
– No-load absorbed power : Pa₀ = 260W

We neglect the joule losses of the rotor at no-load: P_jr0 .  The mechanical losses P_mec are evaluated at 130 W.
The warm measurement of the resistance of a stator winding gives Rs = 0.65Ω. Deduce the iron losses in the stator at no-load : P_fs0.
In the following, we will consider that the iron losses in the stator is constant and equal to P_fs0.
5- We perform a test in the nominal conditions of the machine:
a) Calculate the stator joule losses P_js                                        b) Calculate the joule losses in the rotor P_jr
c) Calculate the useful torque C_u of the motor                    d) Calculate the efficiency of the motor η