Page 206 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Output of P/mover = Input of the generator
= generator output + losses
= 39000 W + 3100 W
= 42.1 KW

• Mechanical efficiency?
E. power developed in armature
Mech. Efficiency
Mechanical power input
Power developed in arm. = Gen-input – Stray losses
= 42.1 KW – 900 W
= 41.2 KW{EgIa = 41.2 KW}
Generator input = output of prime mover
= 42.1 KW
Mech. Efficiency = 41.2 KW x 100 / 42.1 KW Electrical efficiency?
Elect. Efficiency = V I /EgIa
L
= V I / (Gen-input – Stray losses)
L
= V I /EgIa
L
= 39000 x 100 / 41200
= 94.66 %
Commercial efficiency = Elect. power output
Mech. power input
= V I / Mech-IP
L
= 39000 x100 /42100
= 92.64 %
Armature reaction
Few terms first;

GNA- Midway b/w opposite adjacent poles and right angle to center line of poles

MNA-Perpendicular to lines of force
Brush placing axis -Least spark
LPT -End of pole tip which first contact armature in DOR
TPT -End of pole tip which comes in contact later with armature in DOR

LPT
• End of pole tip which first contact armature in DOR

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CITS : Power - Electrician & Wireman - Lesson 30-37