Answer :

Ans. 4.21

Given that,

Number of poles (P) = 4

Frequency (f) = 50 Hz

Synchronous speed,$N_s=\frac{120\times 50}{4}=1500rpm$

No load:

Slip at no load, s₀ = 1 % Rotor speed at no load,

N₀ = N_s (1 – s) = 1500(1 – 0.01) = 1485 rpm

Full load:

Slip at no load, s = 5 % Rotor speed at no load,

Speed at full load, N = Ns (1 – s) = 1500(1 – 0.05) = 1425 rpm

% speed regulation$=\frac{1485-1425}{1425}\times 100=4.21\mathrm{\%}$