Патент USA US2509869

May 30, 1950
S. E. HEDSTROM
ELECTROMAGNETIC AMPLIFIER
Filed June 19
2,509,864
1946
/
20
[?ve/772W
Patented May 30, 1950
2,509,864
UNITED STATES PATENT OFFICE
2,509,864
ELECTROMAGNETIC AMPLIFIER
Sven Eric lledstriim, Lndvika, Sweden, assignor
to Allmanna Svenska Elektriska Aktiebolaget,
Vastcras, Sweden, :1. Swedish corporation
Application June 19, 1946, Serial No. 677,669
In Sweden June 25, 1945
3 Claims.
1
It is known to amplify a direct current, ?owing
alternatively in diiferent directions, by causing
(Cl. 323-89)
2
current s'aturable reactors, each of which is in
ternally self-magnetized by means of a pair of
it to in?uence two self-magnetized direct current
unidirectional valves I2, 22, respectively, said
saturable reactors polarized in different direc
valves only admitting one half-wave of the al
tions and so connected as to produce the diifer 5 ternating current through each half of the wind
ence between their recti?ed alternating currents.
ing. Each reactor preferably has two cores and
This dilferential current will then be an ampli?ed
two sets of coils, each such core and set of coils
reproduction of the primary in?uencing direct
being, in one possible embodiment, of the type
current as regards magnitude as well as direction.
shown in Fig. 4. Each core and set of coils is
According to the present invention, a consid 10 enclosed in a broken line box in Fig. 1.v Instead
erable increase of the amplification is obtained
of this, an external self-magnetisation may of
in such an ampli?er with the sacri?ce of a small
course be employed. The external primary di
power by causing the di?erential current to in
rect current traverses a pair of windings I3, 23
?uence alsorthe two reactors in the same direc
on each of the reactors. The alternating cur
tion as the external (primary) magnetisation. 15 rents are, in the form shown, recti?ed in sepa
The action will in this way be quite another than
rate recti?ers ll, 24, but the reactors may also
by the also known connection, in which the re
be provided with their own direct current termi
actors are not self-magnetized but only influ
nals by connecting unidirectional valves also be
enced by the differential current in addition to
tween the windings ll, 2| and the lower alter
a polarizing current and the primary direct cur- 20 nating current terminals. The arrangement
rent. In this case the diiferential current opposes
illustrated, including internal recti?ers for the
the external magnetisation in one of the reac
self-magnetisation and external ones producing
tors and co-operates therewith in the other re
the differential current, has however the advan
actor, which makes it necessary that its ampere
tage that the self-magnetisation, in which it is
turns shall not exceed a certain value, in order 25 especially important to keep the leakage current
that the polarity of the reactor shall not be re
of the recti?ers low, can be performed by means
versed. It is also especially important that the
of valves thus dimensioned or selected as to make
differential current, the power of which is . the leakage current particularly low, while the
smaller than the power of each of the component
valves employed for producing the diiferential
currents, is loaded by the smallest possible power, 30 current, in which the leakage current is of in
which is the case if the self-magnetisation is
made independent thereof.
As the ampli?cation characteristic of the sat
ferior importance, may be higher loaded as re
gards voltage or selected of a type having com
paratively higher leakage current. The recti?ed
urable reactor is, as a rule, somewhat curved, the
alternating currents traverse resistances I5, 25
action of the present invention can be further 35 and form a closed circuit, from which the differ
improved by introducing some curvature of the
ential current is tapped in two points 20. Be
characteristic representing the influence of the
tween these points, the amplifying windings I6,
differential current on the reactors. This can be
26 mounted on the reactors according to the
accomplished by means of voltage-dependent
present invention and the load 30, in which the
resistances, either so that a resistance, in which 40 ampli?ed direct current is utilized, are connected
the current rises slower than the voltage, is con
in series.
nected in parallel to the winding influenced by
If the primary direct current ?ows for instance
the differential current, or so that the said wind
from the lower direct current terminal III to the
ing is connected in series with a resistance, in
upper one, it co-operates with the self-magneti
which the current rises more rapidly than the 45 sation in the left reactor, whereby the current of
voltage, and the whole connected in parallel to
this reactor will predominate at the points 20.
the load of the differential current.
The differential current will then further in
Three forms of the invention are illustrated in
crease the action of the left ‘reactor. If the pri
the accompanying drawing, in which Fig. 1 shows
mary direct current instead ?ows from the vupper
the complete diagram of connections for one 50 terminal to the lower one, the right reactor will
form, while Figs. 2 and 3 show modi?cations of
predominate, and the di?’erential current will
a detail of Fig. 1. Fig. 4 shows one of the cores
still increase this action.
and sets of coils associated therewith.
In Fig. 2, only the branching points 20, the
In Fig. 1 the numerals H and 2| designate
load 30, and part of the windings I6, 26 are indi
the alternating currentwindings of two direct 55 cated, while the details which are not shown are
2,509,864
-
4
3
natlng current terminals connected inone, of said
paths in series with the sub-path therein, means
supposed to correspond exactly to Fig. 1. The
load 3!: is connected in parallel to the current
path through the windings It, 26, and the said
forming a current path with the direct current
terminals of said recti?ers in series therein, and
means forming a branch current path connected
to said last path and traversed by the di?erential
current of said recti?ers, said reactors each in
cluding third windings associated with each of
the first and second windings and connected in
current path contains a voltage-dependent re
sistance 3i , the current of which rises more rap
idly than the, voltage. The current in the wind
ings i5, 26 is then better adapted to the curved
characteristic of the reactors, whereby the am
pli?catlon is increased. A similar action is ob
'
tained according to Fig. 3 by connecting a resist 10 said branch current path.
3. An electromagnetic ampli?er comprising
ance 32, in which the current rises slower than
means forming two current paths adapted to be
the voltage, for instance an incandescent lamp
connected to a source of alternating current, a
pair of direct current saturable reactors each in
resistance, in parallel to the windings i6, 29,
which are here connected in series with the load
30, asinFig, l.
'
15 cluding a winding in one of said current paths,
said reactors being self-magnetized and being
polarized in different directions, a source of di
rect current, a second winding in each reactor
means forming two current paths adapted to be
connected to said direct current source, recti
connected to a source of alternating current, a
pair of direct current saturable reactors each in 20 ?ers each having its alternating current termi
nals connected in one of said paths in series
cluding a winding in one of said current paths,
with the reactor winding therein, means forming
said reactors being self-magnetized and being
I claim as my invention:
1. .An electromagnetic ampli?er comprising
polarized in di?erent directions, a source of di
rect current, a second winding in each reactor
connected to said direct current source, recti?ers
each having its alternating current terminals
connected in one of said paths in series with the
reactor winding therein, means forming 9, cur
rent path with the direct current terminals of
said recti?ers in series therein, and means form
ing a branch current path connected to said last
path and traversed by the differential current of
said recti?ers, said reactors each including a third
winding in said branch current path.
2. An electromagnetic ampli?er comprising 35
means forming two current paths adapted to be
connected to a source of alternating current,
means in each of said paths forming two par
allel sub-paths, a pair of direct current saturable
reactors, each reactor including windings one in 40
each of the sub-paths of one of said current
paths, unidirectional valves one in each sub
path in series with the winding therein, said re
actors being polarized in different directions, a
source of direct current, a second pair of wind 45
ings in each reactor associated with the ?rst
windings thereof and connected to said direct
current source, recti?ers each having its alter
a current path with the direct current termi
nals of said rectifiers in series therein, means
forming a branch current path connected to said
last path and traversed by the di?erential cur
rent of said rectifiers, said reactors each includ
ing a third winding connected in said branch
current path, and a voltage dependent resist
ance connected in said branch current path.
SVEN ERIC rmns'mom'.
REFERENCES CITED
The following references are of record in the
file of this patent:
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1,434,346
Name
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Date
Jonas _.a __________ __ Oct. 31, 1922
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_Hedding _________ __ Apr. 30, 1946
‘
Number
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FOREIGN PATENTS
Country
'
Date
Switzerland ______ -_ Oct. 16, 1941