Activity :
Research on applications of Marx Generator in various industry.
Objective :
- To wider knowledge on applications of Marx Generator.
- to get the idea of future development of Marx Generator in industries.
Content:
1
BOX SWITCHING OPERATION
Box switching is one of the
application of Marx generator and it is also called as a boxcar switching of a
pockels cell. Four Marx generators are used in this application, two electrodes
of the Pockels cells being connected to a positive pulse generator and another
one is a negative pulse Marx generator. Two generators are having opposite
polarity, in that one of the electrode is first fired to charge the Pockels
cell into one charging polarity. These techniques are used to charge the
two generators, but not trigger them to the pulses of each generator, Because
they needed only partly charged and leak through the Marx resistors which needs
to be compensated by a small bias current through the generator. At the
trailing edge of the boxcar, the two other generators are fired to “reverse”
the cell.
Marx generators are used to provide
high voltage pulses for the testing of insulation of an electrical apparatus
such as large power transformers or Insulators used for supporting power
transmission lines. The voltages applied may exceed two million volts for
high-voltage apparatus of the Marx generators.
2
OPERATION OF LOW JITTER FOR PULSE SYNCHRONIZATION
The low temporal jitter of the
impulse Marx generator may be required for multi source applications or timing
applications. Marx generator is a variable candidate for phased array systems,
low jitter must be reduced to a small fraction of pulse width of 200 ns
to the 1ns impulse signal. The main function of this low jitter to be achieved
for multiple pulse addition circuits such as Gatling systems and bi static
radar systems applications.
Based on the closure of the trigger
switch, the reflected pulse of -1/2 the spark gap-charge voltage and a length
is twice of the charged transmission line propagates toward the spark
gap, as shown in Figure. Arriving at the end of the trigger pin, the pulse
doubles in magnitude, resulting in a potential of minus one-half the charge
voltage. This results in a highly distorted field between the electrodes due to
the presence of the sharp pin at the negative potential.
The low jitter performance is
measured using the three Marx generator system is described. Each Marx
generator is connected to a common trigger circuit, This is a krytron-based
circuit designed to hold off 15KW. These Marx generator is normally connected
to a single output transmission line. We connect temporally because we have to
separate the individual pulses, The trigger lines are connected to each
Marx generator to the trigger circuit that are unique in the same length.
3
GENERATION of UWB SIGNALS
The impulse Marx generator was
tested for its ability to directly generate microwave energy in the form of an
UWB signal. The Marx generator directly drives a rudimentary TEM horn antenna
signal. Generally it measures 100meters from the source, For example an EMCO
3106 antenna was used for radiate measurements. Additional measurements were
made with a crystal detector.
Generation of UWB Signals.
4
SINGLE PULSE SYSTEM WITH BWO
In this application we are using a
narrow band Marx generator, used to drive the cathode of a Russian
made BWO. It was measured in Texas tech university. The max generator directly
groove the cathode and was temporarily aligned with the magnetic field pulse.
An Uncalibrated, b-dot probe was used to monitor the generated
signal as well as the Uncalibrated integrated B-dot probe is used to monitor
the generated signal, then as well as a florescent witness plate.
Now the BWO was designed to
deliver a 35 Hz signal within a 3-4ns. The system is delivered to appear
a 20ns window of microwave energy that was approximated to be 30 MW in peak
power. This power delivers at TM0 mode of the BWO. The BWO delivered a
TM01 mode.
The three Marx generator is
orthogonally connected to the common transition line, And for the purpose of
demonstrating the generator have a common trigger system. A capacitive voltage
probe is placed at the trigger input of Marx generator, and a current viewing
resistor is placed at the output of a common transmission line system. So each
of the generator will be designed to deliver a 140 KW pulse with sub Nano
sec rise time.
The output of the current viewing
resistor demonstrates the system’s ability to generate three district high
voltage pulse, each having an amplitude excess of 125kv range.
The Gatling Marx generator system
was connected to the TEM horn used to earlier in this Marx generated
system. Now we have to take precautions were taken to ensure the antenna did
not break down during the first pulse, so later pulse would be radiated.
5 LIGHTNING
IMPULSE TESTING ON POWER TRANSFORMER
Lighting is a common phenomenon in
transmission lines because of their tall height. This lightning stroke on the line
conductor causes impulse voltage. The terminal equipment of transmission line
such as power transformer then experiences this
lightning impulse voltages. Again during all kind of online switching operation
in the system, there will be switching impulses occur in the network. The
magnitude of the switching impulses may be about 3.5 times the system voltage.
Insulation is one of the most important constituents of a transformer. Any
weakness in the insulation may cause failure of transformer. To ensure the
effectiveness of the insulation system of a transformer, it must confirms the
dielectric test. But the power frequency withstand test alone cannot be
adequate to demonstrate the dielectric strength of a transformer. That is why impulse
test of transformer performed on it. Both lightning impulse test and switching
impulse test are included in this category of testing.
The lightning impulse is a pure
natural phenomenon. So it is very difficult to predict the actual wave shape of
an lightning disturbance. From the data compiled about natural lightning, it
may be concluded that the system disturbance due to natural lightning stroke,
can be represented by three basic wave shapes.
i)
Full wave
ii) Chopped wave
iii) Front of wave
Although the actual lightning
impulse disturbance may not have exactly these three shapes but by defining
these waves one can establish a minimum impulse dielectric strength of a
transformer. If lighting disturbance travels some distance along the
transmission line before it reaches the transformer,
its wave shape may approach to full wave. If during traveling, if flash-over
occurs at any insulator of the transmission line, after the peak of the wave
has been reached, the wave may become in form of chopped wave. If the lightning
stroke directly hits the transformer terminals, the impulse voltage rises rapidly
until it is relieved by a flash over. At the instant of flash - over the voltage suddenly collapses
and may form the front of wave shape.
The effect of these wave forms on the transformer insulation may be different
from each other. We are not going here in detail discussion of what type of
impulse voltage wave forms causes
what type of failure in transformer. But whatever may be the shape of lightning
disturbance voltage wave, all of them
can cause insulation failure in transformer. So lighting impulse test of
transformer is one of the most important type test of transformer.
6 AIRCRAFT
LIGHTNING PROTECTION
Aircraft certification and flight
safety authorities around the world require that aircraft structures and
systems that are critical or essential to the safe flight of an aircraft be protected
from significant lightning-induced damage or upset. These requirements are
fulfilled through a certification plan that details the lightning protection
engineering and shows through
verification testing so that the engineering meets all applicable standards and
regulations.
Lightning can affect avionics
systems in two ways: directly, causing physical damage due to heat or shock,
and indirectly, as a result of earth voltage rises occurring in the aftermath
of a strike. Proper testing to ensure lightning strike protection must take
into account both factors.
- Direct effects — Direct
testing equipment consists of high voltage Marx-type impulse generators
that are capable of producing up to 1.5 million volts, and high-current
generators specially outfitted to produce over 250,000 amperes of current.
- Indirect effects —Earth voltage rises can cause equipment
failure in devices up to a kilometer away from the impact site. For this
reason, it is essential to test sensitive electrical and electronic
components against the indirect effects of a lightning strike.
CONCLUSION
For this week,I have studied about the applications of Marx Generator in various industries. This is important for me to get the idea of added value to my project. I am also looking forward to enhance this project for future development.
