MAGNETIC AND DIELECTRIC AMPLIFIERS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-04861A000400030005-1
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 16
• Document Creation Date: December 20, 2016
• Document Release Date: June 6, 2006
• Sequence Number: 5
• Publication Date: August 1, 1955
• Content Type: REPORT

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or Release
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MAGNETIC AND, DLEL. ~TRIC AMPLIFIERS.
y
I
H. Braun
VDI Zeitschrift 95 (1953) 335 340
(From German)
August, 1955
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Manetic: and Dielectric Amplifiers
H. Braun
VDI Zeitschrift 95 (1953..) 33.5-3??O.y
From German
The most modern types of electrical amplifiers are
magnetic and dielectric amplifiers, which as variable impedances
are inserted in front of the existing load resistance.
In the magnetic amplifier the permeability is changed by
d.c. pre magnetization of the iron core and in the
dielectric amplifier the dielectric constant is changed
by d.c. biassing of the dielectric of a condenser.
While magnetic amplifiers are chiefly suitable for the
amplification of direct currents and of very low-frequency
currents, capacitative amplifiers are used at high
frequency voltages. Magnotic amplifiers have already
won for themselves a wide field of application in general
electro-technology and in regulating techniques; dielec-
tric amplifiers, on the other hand, are in the early stages
of development. There are very many characteristics
which the two typos of amplifier exhibit in common due to
their non-linear behaviour. The magnetic amplifier,
being a durable structural element, has replaced the
electronic valve and the relay in many circuits and - in
combination with metal rectifiers - the rotary amplifier
also. Naturally, its relatively long response time
sets limits to its application.
The design and development engineer is frequently faced with
the problem of amplification for the purpose of power gain.
This problem occurs most frequently in the sphere of control
and regulation techniques because here the measurement output
available is generally so small that it will not actuate
the regulating member directly; hence, no solution is possible
without the use of amplifiers. This amplifier must convert the
given input into an output - as f'ar as possible without distortion
by making use of an auxiliary source of energy (Figure 1). The
efficiency of the amplifier 7Z = GA`GH plays only a minor part in the
present problem because, as a. rule, the auxiliary quantity
constitutes only a fraction of the total energy available.
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11 According to the nature of the problem to be solved
different types of amplifiers can be employed either singly or
in combination.
N,cl?ancal, _amTl c s. The lever,block and pulley,
inclined plane and screw are the oldest types of mechanical
amplifiers. They amplify power not energy, an example of
a mechanical amplifier of energy would be a heat engine in
which the applied heat energy would be the operating medium.
The input quantity would be the mechanical actuation of a
valve or throttle while the output would be the power
delivered by the engine.
Iydraulic amplifiers. - e. g. hydraulic presses - are
also power amplifiers light pressure of the hand on the valve
produces greater power. Other examples of hydraulic amplifiers
are hydraulic brakes on vehicles, which amplify the pressure
of the foot and also oil control of machine tools. The
operating medium mostly used is electrical energy which
activates the oil pressure pump by means of a motor. Pneumatic
amplifiers operate similarly to the hydraulic type except
that the medium is air and not oil. The advantage of
pneumatic control over hydraulic amplifiers lies in the
shorter response period.
Electrical amplifiers are most widely used in general
technology because with them it is relatively simple to
convert and amplify energies. There is also an additional
and considerable advantage with electrical amplifiers in,
that almost all measurable non-electrical quantities can be
reproduced as electrical quantities and thus made capable of
amplif ication.
Currents, voltages, and power can be selectively amplified.
The process can be carried out in rotary and electromechanical
amplifiers, in electronic amplifiers, and also in magnetic and
dielectric amplifiers. These are known as continuous
amplifiers. In addition there are the intermittent types
of amplifier, (two-point amplifiers).
Electrical amplifiers, The most simple form of rotary
amplifier machine amplifier) is exemplified by the separately
excited LC generator (Figure 2). This type has been known
since the beginning of electrotechnology; the power is
amplified 10 to 50 times according to the size of the generator.
By connecting two generators in tandem - for example the
auxiliary exciter and the exciter of a turbogenerator installation-
it is possible to increase the amplification of power to very
high values. The machine amplifier has reached a special stage
in the Leonard generators in which the dynamo drives a motor with
a speed which can be varied at will. The most recent form of
the machine amplifier is the transverse field machine
(amplidyne) which is being used to an increasing extent in the
techniques of speed control and regulation.
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Electromechanical amplifiers are employed in the form of
drum regulators, vibration regulators (Tirrill regulators) and
carbon pile voltage regulators.
Electronic amplifiers are chiefly electronic valves and.
gas-filled tubes which since the discovery of the control grid
have been used to the widest extent - one has only to
remember the millions of wireless sets - in electrotechnology.
By controlling the valve with a grid potential (Figures 3 and 4)
it is possible to vary the magnitude of the output without
inertia. Electronic amplifiers can be voltage or current
amplifiers. The control of larger powers is principally the
function of.thyratrons and grid-controlled mercury vapour
rectifiers (Figure 4).
Inetic amplifiers _ __(Figure also called amplistats or
transductors operate with d.c, magnetic biassed reactors.
In this type the inductive resistance of a saturable reactor is
varied. Their chief function is that of current amplification;
the output current is generally an alternating current but by
connecting a metal rectifier to the output, this can be
converted into direct current.
Dielectric a~Rli_fier_s.* (Figure 6), in common with the
magnetic amplifiers, depend on variation of impedance.
This impedance, in the capacitative amplifiers, is a biassed
condenser with a non-linear capacity curve. They are used
principally as voltage amplifiers for the higher frequencies.
'Intermittent amplifiers have been known for many years in
the sphere of control as relays and protective devices. Of
course, as amplifiers they have the distinct disadvantage
that they can only be adjusted in two positions: they can
only be open (GA = 0) or closed (GA is a maximum).
netic Amplifiers
Fundamental Princi2les
If it is required to vary the current in a load resistance
connected to a constant voltage, the usual procedure is to
connect a variable resistance in front of the load resistance
Rqq. This is sometimes accompanied however by considerable
p~wer consumption in the regulating resistance; moreover the
control of fairly high current intensities creates difficulties
because as the current intensity increases the sliding contacts
are subjected to stresses which become increasingly difficult to
withstand. In A.C. circuits the solution of the problem is made
easier by the fact that the variable resistance is generally a low loss
A.C. impedance. In the magnetic amplifier the variable impedance is
inductive and is calculated from:
Z = wL = 2itf kp = c ons t p . . . . . . . . (1 )
The technical world has as yet no unform expression for an
amplifier with variable dielectric; the term capacitative
amplifier is also frequently met with.
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where: Z is the A.C. impedance, w the supply frequency, L
the inductance,f the frequency of the alternating voltage,
k the form factor of the inductivity, and u the permeability
of the core.
The impedance is thus in direct proportion to the
permeability; the process is based on the fact that, by A.C.
polarization, the permeability can be reduced from its
initial basic value [2,)+,5,9,10] **
In its simplest form the magnetic amplifier consists of
a saturable iron core with two windings; the normal A.C.
winding power section) and, wound over this, the ,a.C. control
winding control section). In Figure 5 these two windings
are shown separately, side by side. In practice such a
biassed reactor has to be fitted with a non-saturable
reactor for the A.C. control circuit ( as in Figure 5) in
order to suppress the voltages induced in the D.C. winding from
the A.C. winding due to the transformer effect. The
magnetization produced in the biassed reactor will then be
determined by the steady D.C. control current.
In Figure 7 all the terms used in the following formulae
for voltages, currents, etc. of the magnetic amplifier have
been assembled so'that the general terms (G ...) in Figure 5
can be transposed immediately into the usuaFY practical nomen-
clature ( ...)* . Using Figure 7 an explanation will now be
given of t& electrical processes in the magnetic amplifier.
Let it first be assumed that no D.C. is flowing in the control
winding (iE = 0) and that RA = 0. If the magnetization curve
of the saturable coil has the form illustrated in Figure 8
(transformer sheet IV), the sinusoidal potential U across the
reactor develops a current iA which is also sinusoidal, since
the magnetization curve is practically linear in this zone.
If a direct current iE flows through the control winding
the working point Al of the alternating potential is shifted
from the zero point of the magnetization curve to the working-
point A2 (Figure 9). By this shifting of the working point
from A 1 to A2 a section of the magnetization curve is reached
where it is no longer linear. The current-time area of the
current which now develops (A), i.e. the enclosed area in
the diagram, is larger than in the case of magnetic bias.
A similar process can be found in the case of electronic valves
where the valve characteristic a = f(Ua) depends on the grid
potential.
* The circuit symbols for magnetic amplifiers have not yet been
standardised. The control coils are often drawn at right
angles to the A.C. windings.
* * For references .see end.
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If the D.C. polarization is increased still more and the
working point A3 is reached (Figure 10) the positive
alternating potential amplitude enters the zone of
saturation and an alternating current develops which has an
effective value markedly greater than without magnetic bias.
The essential characteristic of a magnetic amplifier is it's
non-linearity.
Examination of Figure 10 might indicate that some
rectification of the alternating current had set in, since
the current no longer produces equal areas about the zero
line. This does not happen, however, because in reality,
with A.C. excitation the magnetization curve forms a
hysteresis loop; for purposes of simplification this has not
been shown. If the alternating potential is reflected at
this hysteresis loop the working point A3 moves further down,
causing the current to become symmetrical about the zero
line and also, in this case, to fulfil the condition for
alternating current
f iat=0.
From the magnetization curve of the core material it
is easy to derive by differentiation the function ? = f(iE),
since ? = dB/dH . Of course this differential does not
apply quite strictly in the transition zone in the case of
small control currents Y
Figure 11 shows the course of the
permeability and hence also of the reactor inductivity L in
relation to the bias current iE . The steeper the initial
slope of the magnetization curve and the more definite the
saturation hump, the more effective is the.. operation of a
magnetically biassed choking coil. For this reason core
materials having almost rectangular magnetisation curves
hysteresis loops are eruployed for high performance magnetic
amplifiers.
Starting with the basic pattern of the biassed reactor,
use has already been made of the single-phase magnetic
amplifier because the simple biassed reactor had the
definite drawback that the control circuit had to be provided
with a reactor and the resulting alternating current was not
symmetrical about the zero line. These drawbacks are removed
by a magnetic amplifier with two A.C. windings, (Figures 12-14).
Figure 12 shows a normal iron-clad core in which each outer leg
is wound with an A.C. winding. These two A.C. windings are
in parallel and lie in series with the load resistance RA.
,The applied alternating voltage E induces thefluxes and
1 A
in the outer legs. In the middle leg the two fluxes are
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opposed to each other in direction and, since they are equal
in magnitude, cancel out. Thus, in the winding on the middle
leg, no alternating potential can be induced on the fundamental
wave.. Since the two A.C. windings are in parallel, the
harmonics which develop are also suppressed. There is no
need, therefore, in this magnetic amplifier, for a smoothing
choke in the D.C.-control circuit; and the output current is
symmetrical about the zero line. The best core material
for such a lamination is dynamo sheet iron because, owing
to the dissipation at the intersections of the laminations
the magnetization curve for high-grade core laminations is
not distinctly rectangular. On the other hand, for fairly
high duty, it is best 'to use the transformer construction of
the ideal type, i.e. an annular core, so that there is practically
no dissipation. In this case a circuit like the one shown
in Figure 13 is employed. The magnetic fluxes cl :L and ~) a
are again so directed that the induced fundamental waves cancel
out in the control winding. The core materials used here
are highly permeable annular sheets having permeability values
up to 1000000. The circular core amplifiers are more expensive
than iron-clad core amplifiers, of course, because owing to
the difficulty of the ring winding process the proportion of
costs for wages is about twice that for materials, while it is
roughly the other way about for amplifiers with transformer
laminations.
Figure 14 shows types of single-phase magnetic amplifiers.
In contrast to the arrangement described above with one core the
middle leg of each core of the left hand amplifier (with two
iron-clad cores M 102b) is wound with an A.C. winding ("a" in
Figure 14), while the common control winding surrounds both
cores. The annular-core amplifier('b, Figure 14) has two
cores made of the material 5000 Z * . To simplify production
of two cores which each have an A.C. winding are surrounded
theone control winding, an arrangement frequently met with in
practice. Single-phase magnetic amplifiers with dynamo
laminations are produced commercially up to about 4 kVA,
and with high permeability annular cores up to about 400 VA
rated capacity.
If the powers which has to be controlled is higher
than these it is advisable to use three-phase, magnetic
amplifiers because of the more uniform mains loading. This
can be done either by the suitable connection of three single-
phase magnetic amplifiers or specially constructed three-phase
amplifiers can be used (of. e.g. Figure 18). This is built up
from three single cores currounded by a common control
winding. These large amplifiers are constructed on the same
lines as ordinary transformers.
* 5,000 Z a core-material produced by the Vacuumschmelze A.G.
Hanau, is a nickel-iron alloy of high permeability. In these
annular cores the core is coiled like ribbon. Other materials
for magnetic ring-core amplifiers are Mu metal, Permalloy C.
and Hype= 50.
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-7-
The magnetic amplifier is essentially an A.C. amplifier
which is controlled by direct current. However, if D.C. is
required in the output circuit, the alternating output
current can be converted into direct current by the insertion
of a full-wave rectifier circuit arrangment of metal
rectifiers. The current amplification rate is obtained from
the ratio of the arithmetic mean of the D.C. output to
the required control current; it can amount to 1 : 330.
On the other hand the factor NA/NEis the power amplification
rate which, in the case of magnetic ono-stage amplifiers may
reach 100,000. It is possible, by series connection of
magnetic amplifiers, to increase the amplification very
considerably; the total amplification is obtained from the
product of the single amplification rates.
As with all amplifiers the degree of amplification can be
substantially increased by feedback coupling. Since the
magnetic amplifier is a current amplifier, this feedback.
must be a current feedback, i.e. the output current is. led
back to the amplifier, after rectification by a separate
feedback winding, so that an auxiliary bias magnetization is
produced, which is dependent upon the output current. Very
high degrees of amplification can be achieved by this means.
Since, in contrast to the electronic amplifiers, every
magnetic circuit has a natural inertia - the magnetic field
has to be built up and to die away - a response time is
associated with magnetic amplifiers and this can be measured.
The response time is the time required, if there is a sudden
change of control current from zero up to the maximum value,
to change the output current from 10 jo to 90?c of its maximum;
it is roughly proportional to the currant amplification rate
and inversely proportional to the supply frequency. The
response time can amount to some seconds in the case of the
amplification rates mentioned above, but it usually fluctuates
between 0.05 and 0,3 seconds with a supply frequency of
50 c.p.s. If several amplifiers are connected in series
the response times are added together but the amplification
rates are multiplied; it is therefore possible to reduce
the response times by arpropriate circuits. Another
possibility for reducing the response time is the employment
of high-resistance control circuits and also the application
of higher supply frequencies.
In making calculations for magnetic amplifiers an important
fact is that amplifiers which are not back-coupled behave
like current transformers, i.e.,,the current flow in the
control and power sections are equal. Of course in this
case the arithmetic mean of the current has to be substituted
for the power section. It appears, that the current
amplification rate of an amplifier .without feedback coupling is
dependent only upon the transformation ratio of the number of
turns (control windier to A. c. winding); for this reason it
can be calculated exactly-in advance,
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Applications
One of the most important fields of application for
magnetic amplifiers is in the technology of speed control.
The ideal variable speed electric motor is the D.C. shunt-
wound motor, the speed of which can be controlled from zero
up to the maximum by varying the armature voltage, In
addition the rotation speed can be raised still further by
reducing the field strength (where the torque is fairly small).
If a magnetic amplifier connected to an A.C. mains sufflies
the armature of a D.C. shunt-wound motor through half-wave
rectifiers - a combination often referred to as "reactor
regulated drive"[7jth~ armature voltage of the motor and hence
also. its rotation sp,;ed can be varied very simply by magnetic
bias of the magnetic amplifier. This control by the amplifier
is not enough by itself, because, owing to the drop in
potential in the reactor, half wave rectifier, and armature,
there is a pronounced reduction in rotation speed with load,
i.e. as the torque of the motor increases. The rotation
speed must therefore be regulated, i.e. the rotation must be
measured and compared with a constant theoretical value.
The difference between the theoretical and actual values acts
on the amplifier as an increase in the armature voltage when
the load increases. In the case of high performance speed
regulators the actual value is obtained by means of a tachometer-
dynamo, the output voltage of which is in proportion to the
rotation speed. On the other hand, if a drop in speed of
several per cent between no-load and full-load conditions is
permissible a circuit, such as that shown in Figure 15 is
employed. The magnetic amplifier - with economy feedback
connected for self-saturation and with D.C. output ccrmected
to a converted Graetz-circuit - is loaded by the armature
of a D.C. shunt-~iound motor. The armature voltage Uactual -
which is approximately proportional to the rotation speed -
is compared with an adjusted D.C. voltage U hhear. If, as
the result of increased load, the speed of -Ihe motor is
reduced, there is also a drop in the terminal voltage of the
motor. The difference between the two voltages Utheor and
U act. generates a current through the bias winding 'c' of the
magnetic amplifier; this current is such that the armature
voltage of the motor is increased until the equality of the
voltages Utheor. and Uact. has been restored. Since, however,
the rotation speed of the motor is not directly proportional
to the armature voltage, because the decrease in speed
consequent upon the drop in armature voltage is still effective,
the voltage drop is compounded with the aid of the reaction
winding 'd' (Figure 15). If there is constant field excitation
of the motor this circuit permits a speed variation of 1 ; 25
where amplifiers with dynamo laminations are employed. For
small motor powers annular core amplifiers with highly permeable
sheet iron are used and in this case the adjustable speed. range
can be brought up to I : 100.
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The rotation speed curves n = f(M ) for the reactor coupled
speed regulator can be seen in Figure '6. For comparison with
the regulated curves 'b' the dotted lines show the rotation
speed curves 'a' for a controlled D.C. shunt-wound motor
connected directly to the D.C. mains. Normally such a motor
has a speed range of only about 1 : 10 because, owing to the
natural 10/o speed drop between no-load and full-load, it would
stop if it ran at an adjusted speed of 10/ of the nominal value
below full-load. These limits can be substantially widened
by regulation through a magnetic amplifier.
Reactor-coupled speed regulators with single-phase connection
to the A.C. mains supply are produced for motor outputs up to
2 kW; and with three-phase A.C. connection up to 8 kW.
These regulators have proved very satisfactory for machine tools,
testing machines, and in fuel regulation for power station
steam generators. They have also been used with good results for
small servo-motors.
At higher outputs, magnetic amplifiers, in combination
with half -wave rectifiers, have begun to be used for the field
excitation of motors and generators. Thus, for example, the
auxiliary exciter of a turbo-generator inutallation can be used
more econo iically if a magnetic amplifier is fitted. If a
magnetic amplifier is employed for field excitation in a rolling-
mill motor the field voltage can be varied with low regulation
consumption.
For voltage regulation in small and medium threvhase
current generators 161 magnetic amplifiers are installed as
contactless regulators. These voltage regulators with
magnetic amplifiers arc distinguished - in contrast to vibrating
regulators - by the fact that they are not sensitive to position
or vibration, particularly in non-stationary generating plant.
The potential of the three-phase current generator is kept
constant at t1%, independent of the load and the power factor.
Rectifier technology offers a wide field of application for
magnetic amplifiers [i ] where they are used as regulators and
variable-gain amplifiers. Rectifiers regulated by means of
magnetic ,_-juplifiers are especially useful in low-performance
operations where the regulation required does not make such
great demands. Charging rectifiers with magnetic amplifier
regulation are used especially for l-_rge storage batteries on
the rail motor cars of, the German Federal Railways; with these it
is possible to charge the lead storage batteries without
electronic tubes and relays on an economic scale. In addition
by means of rectifiers with magnetic rcgulatinL~ amplifiers, the
batteries can be charged again without trouble on the principle
of three-stage charging, when the driving current has discharged
them completely.
Magnetic amplifiers can be employed as inductive series
resistances for thermostatically regulated heating of fairly small
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industrial resistance furnaces (Figures 17 and 18). The
tem1D rature is measured by a thereto-element or resistance
thermometer and then converted into a proportionate current
(actual value of the temperature). This temperature is
compared with a theoretical value for the temperature and the
difference bctvwreen the two currents is fed to a magnetic
preamplifier as a D. C. control current. this preamplifier
is necessary as it is not possible to control the power
amplifier with the smal amount of energy v_ it :.ble. The output
current from the preamplifier then flows into the three- kr _se
power amplifier as a control current.
Illumination is one of the latest fields in which magnetic
amplifiers h ve been used. Here they operate as compensating
resistances for filament lamps and fluorescent tubes and make
it possible to vary the luminous intensit- of these light
sources. This can simplify many ~-)roblcs s of li?' hting;; for
instance the control elements for 200 fill-inent l^~mps in a
theatre can be accommodated on a switch panel only 2 m2 in size.
The electrician can therefore control the individual leap
circuits with ease and certainty by adjusting small variable
resistances.
In the technology of teleconununicationLmeasurir control
and r ulation [8] low power magnetic amplifiers have been used
for about 15 years. Even though there has been no success from
attempts to amplify telephone alternating currents by magnetic
means - if there were, overseas telephony by cables woula be
possible - A.D.C. transformer developed by Kramer [3] has
nevertheless been in use for D.C. measuring techniques for a-
long time; these are produced up to a transformation ratio of
I : 80,000 with an output current of 5A with a class accuracy of
? 0.5%. These D.C. transformers have the same electrical
construction as magnetic amplifiers with series-connection of
the A.C. windings, The only difference between them is the
transformation ratio. rthile the amplifiers amplif1 currents,
D.C. transformers transform large currents into small cries. For
this reason D.C. transformers mostly have only one control
,grinding in the form of a bar pushed through the coils and
carrying the current to be measured. Magnetic amplifiers are
also ~in common use for controlling ma.a-gnetic powder couplings,
as amplifiers for photoelectric cells, and as magnetic current
stabilizers for regulating purposes.
The largest magnetic ;amplifier units are those designed for
ions;-distance circuits. Units of up to 50 MVA are to be
installed alongsiue the big long-d ct once lines, so as to
compensate the capacitative idle current of the lines. The
compensation is automatically regulated by a grid-controlled
rectifier which sup?lies the biassing current.
Dielectric -plifiers
The dielectric amplifier resembles the magnetic amplifier
in that, e ,s a (capacitative) comipensatin ; resistance it is
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controlled by way of a D.C. voltage (connected to the
condenser); here, too, an alternating voltage is employed
as an auxiliary cjuantity. The control effect is based on
variation of the dielectric constants s by the control voltage.
Figure 19 illustrL_tes this. In the Base of some dielectric
substances hysteresis curves are obtained which are very
similar to those for magnetic substances [11]. Thus,
although there is no iron present here, a so-called fcrro-
electric effect is spoken of, in a similar way to that used
in fcrro-magnetism. This ferro-electric offact is due to the
alignment of electric dipoles of ionized atoms in non-magnetic,
crystalline substances.
The d.iclcctrics used arc barium titan.ate and some
combinations of strontium titanates with barium titanatoz and
also combinations of barium -and load zirco aces. Unfortunately
the dielectric constants of these substances ?re strongly
affected by temperature so that a new dielectric is needed
for each temperature range. A certain dogree?of temperature
compensation can only be achieved by comb ion of
various dielectrics. The dielectric substances, like the''
magnetic ones, h ve a Curie point, the temperature of which is,
lo;-er. ~re__test amplification lies in the
The hov~r;:v~-:r, much 1~1~
vicinity of the Curie point; it is specially important
therefore to keep the dielectric at this temperature. For this reason
the temperature of dielectric amplifiers is often regulated
therrilostatic filly. The non-linear dielectric of the condenser
acts as the tcmper^.tive sensitive member of the thermostat.
Such an arrangement is not necessary in the case of magnetic
amplifiers.
Figure 20 shoves the typical circuit of a dielectric
amplifier. Two non-linear and two linear condensers are
connected to form a bridge. The control potential is
connected in one diagonal arm of this bridge and the supply
potenti al with the to _d resin tance RA in the other. The
linear cone cnsers have the function of rendering the circuit
syulmetrica.1; naturally the, reduce the aunplific Gp > GE~ The numbers of the
terminals have tie sale significance in the
subsequent figures.
Fig.2: Basic circuit of the machine amplifier
(separately excited D.C. generator).
6`6H -6
Fig.3: Electroair amplifier Fig.4: Thyratron or Mercury
Vapour Rectifier
Figs. 3 and 4: Basic circuit for amplifiers with charge
carriers. GE grid voltage. GH anode rpltage.
GA output power across the working resistance RA.
Fig-6: Cbrpacitative amplifier.
GE control voltage
91 Cx alternating voltage
A output voltage across the
output resistance RA.
Figs. 5 and 6: Basic circuits of amplifiers based on variation
of an A.C. resistance.
Oa field potential
ON energy of rotation
OA terminal Voltage.
LN
Fig.5: Magnetic amplifier.
GE control current
Gu alternating voltage
G'A` output current in the
working resistance RA.
a - choke for suppression of
A.C. voltage induced by GA.
B source of alternating voltage
lA output A.C.
iB control D.C.
RA working resistance (load)
U alternating voltage across the choke coil.
Fig.7: Carrents and voltages in the magnetic amplifier
shown in Fig. S.
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 Approved For Release 2007/10/23: CIA-RDP78-04861A000400030005-1
Fisld- Field- Pield-
t
e
ren+th strength strength
CCC+/
/
Fig-10
Fig.8: Formation of a sinusoidal current IA
Control current I F - 0.
Be characteristiE curve B - f(H) is rectilinear in
the section under consideration (working point A1).
Be working point can (by reversing the polarity of
Ig) be transposed to the negative branch of the curve;
this also applies to Figs. 9 and 10:
Fig.9: Formation of an amplified, somewhat distorted
current t . The control current iE is no longer
zero. rorking point A2 is already in the non-linear
section of the curve.
Fig.10: Formation of a consideraDly amplified and
distorted current i . The control current iFF is
large and carries t1fe working point A3 into the
pronounced bend of the curve.
Figs. 8 to 10: Method of operation of the magnetic
amplifier. 1 Vs/s2 - 10-4 Vs/cm2 - 10, 000 G;
I Alm - 10-2 A/cm.
Ftg.11: Relation of the
be self tndu tiog Le toe
the control current iE.
Iron-clad core
Figs. 12 and 13: Construction design of amplifiers with
iron-clad and annular cores.
Below: Q+alitative behaviour of the current i
function of time t. A as a
it1 and 5 magnetic fluxes.
11 + 12 - 1A partial currents.
Fi9.14: 300 VA commerical type amplifiers
a - iron-clad core of transformer laminations
IV, yvax - 250.
b - ring-core of highly permeable sheet,
mum - 100, 000.
Figs. 12 to 14. Single-phase magnetic amplifiers.
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 Approved For Release 2007/10/23: CIA-RDP78-04861A000400030005-1
ppl, (potential divider)
itegnetlc amplifier with
food- bck coupling and
8.C. out t.
c control Coll.
d - compounding (feed-back)
e ? D.C. shunt-wound motor.
I
a
function of the n torque Md in
f
a D.C. shunt-wound motor.
st V-70, %I Torque '-d
J
Desired temp; rsturel
(adjustable)
D.C. D.C. J Power
~? _ -P~e- - maplifier
amplifier
p
t em
o
temperature
Temperature I Furnace
l+u to --
Fig.17: Circuit diagram of a magnetic amplifier
for regulating.an electrical industrial resistance
furnace.
Heavy lines - three phase mains.
Light lines - alternating or direct circuits.
a - characteristic curves for the
motor without speed regulation-
b - the seal with a regulation circuit
as shown in Fig?13.
F4g?l8: 16 IVA three-phase magnetic
amplifier (see Fig.171.
_j Electrical R mid s aigapccitasirecircui fier diagram of
Fig.19: Dielectric constant E of barium
titanats (11 as a function of
curveaenser
characteristic the
field
Approved For Release 2007/10/23: CIA-RDP78-04861A000400030005-1