2. INTRODUCTION
• Flux Compression Generators (FCGs) are defined to be devices
that convert the chemical energy of high explosives into
electromagnetic energy by using the explosive to mechanically
compress a magnetic field complety enclosed within a metallic
boundary.
• They utilise a tree-step energy conversion process. chemical
,kinetic and electrical.
• Two main application for FCGs
1)field generator-as as source of intense magnetic field
sometimes referred to as Type 1,Mark 1,MC-1,or MK-1
generators.
2)current generator-as a source electrical power sometimes
referred to as Type 11,Mark 11,MC -11 or MK-11 generators.
3. INTRODUCTION
• FCG can be used only once as a pulsed power supply because the
device is physically destroyed during operation. FCG package
that could be easily carried by a person can produce pulses in
the millions of amperes and tens of tera watts.They require a
starting current pulse to operate, usually supplied by capacitors.
• Flux compression generators are popular as power sources for
electronic warfare devices known as transient electromagnetic
devices that generate an electromagnetic pulse without the
costs and side effects of a nuclear weapon.
• They also can be used to accelerate objects to extreme
velocities and compress objects to very high pressures and
densities; this gives them a role as a physics research tool.
• The first work on these generators was conducted by the
VNIIEF center for nuclear research in Sarov in the U.S.S.R. at
the beginning of the 1950s followed by Los Alamos National
Laboratory in the United States.
4. HISTORY
• At the start of the 1950s, the need
for very short and powerful
electrical pulses became evident to
Soviet scientists conducting nuclear
fusion research.
• The Marx generator, which stores
energy in capacitors, was the only
device capable at the time of
producing such high power pulses.
• The prohibitive cost of the
capacitors required to obtain the
desired power motivated the search
for a more economical device.
• The first magneto-explosive
generators, which followed from the
ideas of Andrei Sakharov, were
designed to fill this role.
C. M. (Max) Fowler
Andrei Sakharov,
5. HISTORY
Table 1 Magnetic field (flux density) energy and current which have been
reported as acheved by the different countries
8. TYPE OF FC GENERATORS
• The shape of these conductors can take on different forms
including planar,cylindrical,toroidal and spherical.The shape of
their conductors and include.
plate generators
strip generators
bellows generators
coaxial (cylindrical) generators
spiral (helical) generators
disk generartors
loop generators
spherical generators
9. TYPE OF GENERATOR
Basic flux compression generator schemes. (a) Disk
generator (before detonation). (b) Coaxial generator. (c) Parallel
plate generator. (d) Spiral generator all during operation. Arrows
indicate current flow in conductors
10. PRINCIPLES OF FUNCTION
• Magneto-explosive generators use a technique called "magnetic
flux compression".
• The technique is made possible when the time scales over which
the device operates are sufficiently brief that resistive current
loss is negligible, and the magnetic flux on any surface
surrounded by a conductor (copper wire, for example) remains
constant, even though the size and shape of the surface may
change.
• This flux conservation can be demonstrated from Maxwell's
equations.
• The most intuitive explanation of this conservation of enclosed
flux follows from the principle that any change in an
electromagnetic system provokes an effect in order to oppose
the change.
11. PRINCIPLES OF FUNCTION
• This flux conservation can be demonstrated from Maxwell's
equations. The most intuitive explanation of this conservation of
enclosed flux follows from the principle that any change in an
electromagnetic system provokes an effect in order to oppose
the change.
• For this reason, reducing the area of the surface enclosed by a
conductor, which would reduce the magnetic flux, results in the
induction of current in the electrical conductor, which tends to
return the enclosed flux to its original value.
• In magneto-explosive generators, this phenomenon is obtained
by various techniques which depend on powerful explosives.
• The compression process allows the chemical energy of the
explosives to be (partially) transformed into the energy of an
intense magnetic field surrounded by a correspondingly large
electric current.
12. PRINCIPLES OF FUNCTION
• For a constant intensity
magnetic field of magnitude
B traversing a surface S, the
flux Φ is equal to B × S.
13. Elementary description of flux compression
• An external magnetic field
(blue lines) threads a closed
ring made of a perfect
conductor (with zero
resistance).
• The nine field lines represent
the magnetic flux threading
the ring.
Fig. 1: Original magnetic field lines.
14. Elementary description of flux compression
• After the ring's diameter is
reduced, the magnetic flux
threading the ring,
represented by five field
lines, is reduced by the same
ratio as the area of the ring.
• The variation of the
magnetic flux induces a
current in the ring (red
arrows), which in turn
creates a new magnetic field,
so that the total flux in the
interior of the ring is
maintained (four green field
lines added to the five blue
lines give the original nine
field lines). Fig. 2: Configuration after the ring's
diameter has been reduced.
15. Elementary description of flux compression
• By adding together the
external magnetic field and
the induced field.
• The final configuration after
compression can be obtained.
• The total magnetic flux
through the ring has been
conserved (even though the
distribution of the magnetic
flux has been modified), and
a current has been created in
the conductive ring
Fig. 3: Magnetic field lines after
compression.
16. THE FUNDAMENTAL CONCEPTS
• Flux compression in the ideal
case relies on Faraday’s law of
flux conservation.
• This is best demonstrated by
the diagram shown in figure 1: if
the area changes the flux
density BF must increase.
• This can be rewritten in terms
of the current and inductance of
the generator shown in equation
3 .
• In order to obtain a high
magnetic field the moving liner
should have as high a velocity as
possible to prevent the
dissipation of the flux through
the liner therefore causing
losses in the system.
.
17. THE FUNDAMENTAL CONCEPTS
• For a high current output there should be a large initial
inductance of the system and the final inductance should be as
low as possible.
• The final inductance includes the load which in some cases
requires the generator to be coupled to the load via a
transformer.
• A lot of work performed with FCGs requires the calculation of
the mutual inductances of the generator.
18. THE FUNDAMENTAL CONCEPTS
• The most common method
used for these calculations is
by using standard elliptic
integrals K(k) and E(k).
• The energy component of the
system comes from two main
sources, these are defined in
equation 4 & 5.
• The energy equations are
written for a cylindrical
system. The first is the
initial energy in the magnetic
field produced either by
permanent magnets or by a
capacitor bank and coil.
19. • Spiral generators were principally conceived to deliver an
intense current to a load situated at a safe distance.
• They are frequently used as the first stage of a multi-stage
generator, with the exit current used to generate a very intense
magnetic field in a second generator.
• A spiral generator has a long metal armature that is packed with
high explosive and placed within a solenoid.
SPIRAL GENERATORS
20. • As the capacitor bank discharges, the current generates a
magnetic field in the space between the solenoid and the
armature.
• The load switch is initially in the closed position, preventing the
current from flowing through the load.
SPIRAL GENERATORS
21. SPIRAL GENERATORS
• The explosive is detonated at one end, and the armature
expands like inflating a long balloon.
• The volume between the solenoid and the armature decreases in
both the radial and longitudinal directions.
• This causes the magnetic flux to be compressed.
• Flux conservation results in an enhanced magnetic field, which
induces a large current in the remaining loops of the solenoid.
22. • At peak flux compression, the load switch is opened, and a
greatly enhanced current is delivered to the load.
SPIRAL GENERATORS
23. • The generator is particularly interesting for the production of
intense currents, up to 100 MA, as well as a very high energy
magnetic field, as up to 20% of the explosive energy can be
converted to magnetic energy, and the field strength can attain
2 × 106 gauss (200 T).
• The generators work because high explosives are detonated, and
therefore, the entire experiment must be completed in
substantially less than a millisecond, after which time the
generator and most of the experimental apparatus is completely
destroyed.
SPIRAL GENERATORS
24. COAXIAL GENERATOR
• Generator of this type are,also called cylindrical Flux
Compression Generator or,more simply coaxial generator.
• The basic generator components include the stator ,the outer
cyclinder and the armature,the explosive loaded inner cyclinder.
• The load coil pictured is annular or doughnut-shape.
• Initial current is supplied by a capacitor bank ,or commonly,by
another FCG,through the annular input slot at the left.
25. COAXIAL GENERATOR
• Arrows show that the
current flows along the
outside cyclinder,through
the load coil and back
through the armature.
• Magnetic field lines
B,indicated by circles and
crosses,are circular
tangential.
• They encircle the armature
and are restricted
essentially to the annular
space between the stator
and the armature and to the
coil.
26. COAXIAL GENERATOR
• Detonation of the armature explosive is again timed to close the
input current slot at such time that maximum current or flux is
in the system.As the detonation proceeds.
• The armature expands into a conical front which moves at the
detonation velocity.
27. COAXIAL GENERATOR
• The top sketch shows a variant of this class of
generator.Here,the central cyclinder plays te role of stator of
such while the outer cyclinder becomes the armature.
• These generators have low impedance ,but are extremely
rugged,can carry very large current and are quite efficient in
conversing flux.
• They are frenquenly built as an extension of spiral generator
,whose armature has been extended in lenght to power the
coaxial section.
• It common to find that this stage of such a multi stage
generator accounts for much of their overall again.
• In some cases,the stators have been especially contoured to
approximately match the armature expansion angle so that
closure in this last section is almost simultaneous near burnout
to increase its effective impedance
28. COAXIAL GENERATOR
• The below photograph shows a series of increasingly large
helical or spiral generators boosting a final output coaxial
generator.
• The lower photgraph shows a coaxial generator with a spiral
booster generator
29. Summary of generator Classes
• The various classes of FCG all operate on the same principle,yet
each has its own unique set of capabilities.
• Coaxial Generator
• Have low gain
• Can generate very large currents and energies in low inductance load.
• Spiral Generator
• Have high current and energy gains
• often require power conditioning.
• Are widely used as a booster for other generator.
,
30. TYPICAL AREA OF USE
• The following lists are past and current areas that flux
compression generators are used for.
• Historical uses:
• Charged particle beam diodes
• Imploding plasmas
• Large collection of defence .
• Modern day uses:
• Biological samples
• Environmental
• Biomedical
• Hydrodynamics programs and high magnetic field research
• Exploration for oil and minerals
• Landmine detection
32. QUESTION
1.What is Flux Compression Generators?
2.Name the Basic component of
generators?
3.Explain Faraday’s law of flux
conservation ?
4.Why the generator and most of the
experimental apparatus is completely
destroyed after experiment done?
33. 1. Flux Compression Generators (FCGs) are defined to be devices that convert the
chemical energy of high explosives into electromagnetic energy by using the
explosive to mechanically compress a magnetic field complety enclosed within a
metallic boundary.
2. stator winding,armature,explosive charge and intiation point.
3. ifthe area changes the flux density BF must increase.
4. because used high explosive elements like TNT.
