Articles
Excitation Principle of Synchronous Generator
by Starlight Generator dieselgeneratortechThe excitation system supplies
the DC power supply of the excitation winding of the synchronous generator. The
effect of the excitation system on the synchronous generator can be reflected
from the following aspects.
1. Adjust the excitation can
maintain voltage stability.
2. It can make each unit between
the reactive power reasonable distribution.
3. By adopting perfect excitation
system and its automatic adjusting device, the transmission power limit can be
raised and the range of static stable operation can be enlarged.
4. In the event of short circuit,
forced excitation is helpful to improve dynamic stability.
What is the
structure and principle of constant voltage excitation system for synchronous
generator.
The excitation system of
synchronous generator with AC exciter and rectified by rotary rectifier is
called brushless synchronous generator excitation system in modern times. Below
will introduce the structure and principle of the constant voltage excitation
system of the next synchronous generator.
The motor
adopts the capacitor phase shift phase compound excitation device.
A secondary coil is installed in
the stator of the generator for special excitation. The generator stator
sub-coil is used as the excitation current after rectifying, and AC induced by
the exciter is rectified to DC through the rotary collator and fed into the
generator as the excitation current.
The AC side current component of
the rectifier is provided by the current transformer CT in the neutral cabinet,
while the voltage component is provided by the secondary coil through the
capacitor in the excitation block, and then synthesized by rectifier, exciter,
rectifier and generator to form the excitation current.
When the load current or power
factor COS is changed, the magnitude of the excitation current s changed by
changing the current component or the voltage component to achieve the purpose
of voltage regulation. When starting, DC is directly supplied by BWA (B\ C\ D).
After rectifier, DC is like AC excitation, and DC passing through rectifier
will not be affected.
Automatic
voltage regulator
The automatic voltage regulator,
matches the brushless three phase AC synchronous generator, through which the
excitation current of the exciter is controlled, and then the excitation
current of the generator is controlled, so that the output voltage of the
generator is constant.
Regulation
principle of automatic voltage regulator
When the main generator voltage
decreases, the voltage output of the voltage measurement circuit through the
voltage transformer PT decreases and the pulse width of the pulse width
modulation voltage output voltage increases. The excitation current of the
power amplifier tube with long turn-on time increases and the magnetic field of
the main generator increases, which makes the output voltage of the generator
rise again and stabilize at the original setting valve. Vice versa, so that the
generator output voltage back down, stable in the original set value.
The function characteristics of
forced excitation of diesel generator set and points for attention.
In the process of application of
diesel generator set, some users will force excitation to diesel generator set.
So what is forced excitation? What factors limit the forced excitation time?
Why should
the generator set be excited?
In order to improve the stability
of diesel generator set operation system, the voltage can quickly return fault
is removed, and when the voltage drops to a certain value. The excitation of
the generator can be increased immediately, so the generator should be forced
to excite.
What factors
limit the forced excitation time?
The action of line excitation is
to connect the magnetic field adjustment resistance of the exciter loop by the
relay automatically, or the excitation device of the generator set to adjust
the exciter automatically and quickly so that the exciter works under the
maximum voltage. Supply generator sets with sufficient excitation current.
The forced excitation of a
generator can play its due role when the forced excitation multiple is higher,
the excitation voltage rises faster, and the forced excitation time is
sufficient. Therefore, when the excitation of the generator is increased to the
maximum due to the forced excitation. No interference with the forced
excitation shall be made within one minute, and immediately after one minute
measures shall be taken to reduce the stator and rotor currents of the
generator to the normal allowable values.
What should
we pay attention to after the forced excitation action?
After forced excitation, if not
returned, the magnetic field resistance will be connected for a long time, and
the rotor will suffer high voltage and be damaged when the generator is in
normal operation.
It can be seen that if you do not return, you will do more harm to the diesel generator set. Therefore, it is suggested that according to the operation condition of diesel generator set, under the premise of ensuring normal operation, the forced excitation device that does not return can be excised, the reason can be found out, and then put into operation after troubleshooting.
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About Starlight Generator 
dieselgeneratortech
191 connections, 3 recommendations, 673 honor points.Joined APSense since, April 16th, 2017, From Guangxi, China.
Created on Nov 18th 2018 20:22. Viewed 383 times.
