Induced E.M.F in synchronous Generator:
e = B l v volts
where
B = flux density Wb/sqm
v = velocity (m/s) of movement
l = length of conductors in meters.
Frequency of Synchronous Generator:
The frequency of the voltage generated is given by
f = NP/120
where P is the total number of poles and N is the speed in r.p.m.
Breadth factor of Synchronous Generator:
(Kb) = Voltage obtained in multi-slots winding / Voltage obtained if the windings were all concentrated in one slot
Thus breadth factor is always less than unity.
Mathematically,
Kb= (sin δ n/2 )/ (π sin δ/2)
where n is the number of slot and is the slot pitch.
Pitch factor of Synchronous Generator:
Shortening the pitch of the coil has the same effect as the distribution of the winding. When the turns of the windings do to span a complete pitch there occurs a slight loss in the induced emf. A pitch factor ( Kp ) is given by
Kp = cos θ/2
for a coil which extends over (180° - θ) instead of 180°.
Magnitude of Induced emf in alternators / phase:
ERMS = 4.44 Kp Kb φ f.T. volts
Synchronous Reactance:
Xs = XL + XA
where
XL = Leakage reactance;
XA = Armature reactance.
Synchronous Impedance:
Zs = (R2 + X2s )1/2
SYNCHRONOUS GENERATOR CHARACTERISTICS:
(1) Open Circuit Characteristics of Synchronous Generator:
(Magnetisation Curve).
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