21-04-2014, 12:55 PM
SYNCHRONOUS GENERATOR- CAPBILITY CURVE
SYNCHRONOUS GENERATOR.ppt (Size: 263.5 KB / Downloads: 126)
SYNCHRONOUS GENERATOR
P=3 VφIA cosθ = 3 Vφ / Xs (Xs IA cosθ)
Q= 3 VφIA sinθ = 3 Vφ / Xs (Xs IA sinθ)
On voltage phasor diagram, origin of phasor diagram is at –Vφ on horizontal axis, so origin on power diagram is:
Q = 3Vφ /Xs (-Vφ)=-3Vφ^2/Xs
Field current ~ machine’s flux & flux ~ EA=kφω
Length corresponding to EA on power diagram:
DE=- 3 EA Vφ / Xs
IA ~ Xs IA , and length corresponding to XsIA on power diagram is 3 Vφ IA
Any point lies within both circles is a safe operating point for generator
However, the R.H.S. of Q axis means generator
Also maximum prime-mover power & static stability limit should be considered
SYNCHRONOUS GENERATOR
Capability Curve EXAMPLE
A 480, 50 Hz, Y connected, six-pole syn. Gen. is rated at 50 kVA at 0.8 PF lagging. It has a synchronous reactance of 1.0 Ω per phase
Assume generator connected to steam turbine capable of supplying up to 45 kW. The friction and windage losses are 1.5 kW, and core losses are 1.0 kW
(a) sketch capability curve for this generator, including prime mover power limit
(b)can this generator supply a line current of 56 A at 0.7 PF lagging? Why or why not
© what is the maximum amount of reactive power this generator can produce
(d) If generator supplies 30 kW of real power, what is maximum amount of reactive power that can be simultaneously supplied?