about PQ curves on syncronous generators

[181273]

hello, I got an 1300 KVA syncronous generator, and I want to work with it.. on the range of 0,95 capacitive and 0,95 inductive... but i need to know the capacitive curve ¿ pq curve? ... I wanna know if i could do it with simple method knowing the saturation curve, 0 volts to full volts on the saturation area..... and the reactances... please somebody that could help me...
sorry for my badly english,, and I really love this forum

 

[aolalde]

The limits to operate a synchronous generator are thermal and synchronous stability.
The thermal limit is imposed by the heat developed in the windings ( i^2*R) when the current is increased. The stator will see the line current and the field (normally the rotor) the excitation current. The synchronous stability is lost when the torque imposed in the rotor shaft breaks the magnetic link produced by the flux field intensity.

The generator manufacturer provides the “Capability Curves” or power factor operational limits. When the curves are missing, the name-plate data can give you lead information of your generator. Look for the “full load current” or nominal current, which is the maximum that the stator winding can handle without thermal degradation. Look for the “Power Factor” if that is 0.80 you have almost certainty that it will operate at 0.95 PF at full load current without problem. If the nameplate has PF= 1.0, probably you need to reduce the load current to 95% at PF= 0.95 leading due to the field current and while lagging due to field weakening limits. At PF=1.0 load the current is the 100% or nominal.
A last check is for the duty rating. If it shows “continuous duty” it could work 24 hours per day but “standby” has limited hours at full load.

 

[waross]

The KVA rating applies to the generator capabilities.
The KW rating is determined by the primemover capabilities.
A 1000 KVA set may be a 1000 KW set if the prime mover has sufficient power to produce 1000 KW.
This set would normally be rated at 0.8 PF and the prime mover would supply enough power to produce 800 KW.\
respectfully

 

[181273]

thanks for your help, but my questions is about the stability side of the curve, I know, or I remember to study long time ago, that the syncronous machine start to be into unestability when the diference of the rotor and stator vector is more than 90º, but usually I heard about use 60º... of diference.... What´s the good valium when you haven´t got availiable the PQ curves... how long I can go into the under excited side.??
thank in advance.