Synchronous Generator : Concepts -- 1

Synchronous Generator : Concepts

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:

(K_b) = 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,

K_b= (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 ( K_p ) is given by

K_p = cos θ/2

for a coil which extends over (180° - θ) instead of 180°.

Magnitude of Induced emf in alternators / phase:

E_RMS = 4.44 Kp Kb φ f.T. volts

Synchronous Reactance:

X_s = X_L + X_A

where
X_L = Leakage reactance;
X_A = Armature reactance.

Synchronous Impedance:

Z_s = (R² + X²_s )^1/2

SYNCHRONOUS GENERATOR CHARACTERISTICS:

(1) Open Circuit Characteristics of Synchronous Generator:

(Magnetisation Curve).

(2) Short Circuit Characteristics of Synchronous Generator:

(Terminal Voltage vs Current)



 from ur's -- bellapuri saikumar
                          ( www.facebook.com/saikumar544)