Torque Under Running Conditions
Torque under Running Conditions:
Let the rotor at standstill have per phase induced e.m.f. E2, reactance X2 and resistance R2. Then under running conditions at slip s,
If the stator supply voltage V is constant, then stator flux and hence E2 will be constant.
where K2 is another constant.
It may be seen that running torque is:
(i) directly proportional to slip i.e., if slip increases (i.e., motor speed decreases), the torque will increase and vice-versa.
(ii) directly proportional to square of supply voltage (E2 α V) .
It can be shown that value of K1 = 3/2 πNs where Ns is in r.p.s.
At starting, s = 1 so that starting torque is