relation of PF, MVAR, voltage, kV
relation of PF, MVAR, voltage, kV
(OP)
good afternoon all..
can somebody explain why:
- inceasing voltage of generator makes power factor decreases (lagging condition), MVAR decreases, and kV from generatot decreases.
and vice versa.
any idea would be appreciated... thank you
can somebody explain why:
- inceasing voltage of generator makes power factor decreases (lagging condition), MVAR decreases, and kV from generatot decreases.
and vice versa.
any idea would be appreciated... thank you






RE: relation of PF, MVAR, voltage, kV
- what is PF in capacitive and inductive, or lagging and leading.
- we have one turbine is running on PF positive, and other is running on PF negative. why this system can work?
-what makes generator to have PF negative and positive.
thank you very much
RE: relation of PF, MVAR, voltage, kV
I'd suggest finding a basic text on generator concepts - the Electrical Engineers Handbook would be a good starting point.
Increasing excitation to generator increases the output voltage of the generator and causes it to create more VARs. A generator that is producing vars is operating at a lagging pf. A generator that is consuming vars is operating at a leading power factor.
Generator voltage and power factor is controlled by the amount of field excitation current.
RE: relation of PF, MVAR, voltage, kV
Check this thread out;
thread238-217958: Reactive power
Bill
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"Why not the best?"
Jimmy Carter
RE: relation of PF, MVAR, voltage, kV
RE: relation of PF, MVAR, voltage, kV
In addition, the power of the generator is fixed, determined by the machine turning the generator (the "prime mover"). Only the magnetization current can be controlled. It determines the magnitude of the voltage induced in the stator windings. The phase of the induced voltage cannot be independently controlled. The induced voltage is E cos(fii) + jE sin(fii), where E is the magnitude of the induced voltage and fii is the phase angle.
The current in the stator winding is I = (E cos(fii) + jE sin(fii) -U) / jX , where X is the generator reactance. It is assumed that the resistance is so small that it can be neglected, and that the windings are connected in a wye. The complex power of the generator is equal to the product of the voltage times the complex conjugate of the current, multiplied by three, because of the three phases, S = 3UI*. The real power is the real part of the complex power, P = Re(S) = 3 U E sin(fii)/X.
When the magnetization current is increased, the magnitude of the induced voltage E increases. But because the power is fixed, the phase angle fii must change so that the product E sin(fii) stays constant. Because the induced voltage changes, the current (phase and magnitude) will also change. The reactive power and the power factor can thus be adjusted in this way by changing the magnetization current.
The interesting part is that sin(180deg - fii) = sin(fii), so that the same power can be obtained with two different phase angles, in principle, at least. I do not know, how this is achieved in practice. Maybe someone can explain this?