Question

Prime-mover control of a generator is responsible for a

significant change in ___________, whereas excitation control

significantly changes __________.

Short answer

Real power and reactive power.

Step-by-step solution

Determine the formula of real power and reactive power.  

Write the formula of real power.

$\mathbf{P}\mathbf{=}\mathbf{ReS}\mathbf{=}\frac{{\mathbf{V}}_{\mathbf{t}}{\mathbf{E}}_{\mathbf{g}}}{{\mathbf{X}}_{\mathbf{g}}}\mathbf{sin\delta }\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\dots \dots \left(1\right)\mathbf{}\mathbf{}\mathbf{}\mathbf{}$

Here, ${\mathbf{V}}_{\mathbf{t}}$is generator terminal voltage,${\mathbf{E}}_{\mathbf{g}}$is excitation voltage,${\mathbf{X}}_{\mathbf{g}}$is positive-

sequence synchronous reactance and$\mathbf{\delta }$is power angle.

Write the formula of reactive power.

role="math" localid="1655203396910" $\mathbf{Q}\mathbf{=}\mathbf{Im}\mathbf{}\mathbf{S}\mathbf{=}\frac{{\mathbf{V}}_{\mathbf{t}}}{{\mathbf{X}}_{\mathbf{g}}}\mathbf{(}{\mathbf{E}}_{\mathbf{g}}\mathbf{cos\delta }\mathbf{-}{\mathbf{V}}_{\mathbf{t}}\mathbf{)}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\mathbf{}\dots \dots \left(2\right)\mathbf{}$

Here,${\mathbf{V}}_{\mathbf{t}}$is generator terminal voltage,${\mathbf{E}}_{\mathbf{g}}$is excitation voltage,${\mathbf{X}}_{\mathbf{g}}$is positive

sequence synchronous reactance and $\mathrm{\delta }$is power angle.

Determine the Prime-mover control of a generator in real and reactive power.

Prime-mover control of a generator is responsible for a significant change due

to:

(a) From an operational standpoint of view when the prime mover increases

the power input to the generator while the excitation voltage is held constant,

the rotor speed increases.

(b) As the rotor speed increases, the power angle $\delta$also increases when $\delta$is less than${15}^{\circ }$angle, causing an increase in generator real power output P .

(c) As the rotor speed increases, the power angle decrease when $\delta$is

greater than${15}^{\circ }$angle, causing a decrease in generator reactive power

output Q.

Hence, real and reactive power are the significantly change of excitation

control of prime mover of generator.