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Патент USA US3092783

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June 4, 1963
Filed March so, 1959
x .
BY MW m,’
Patented June 4, 1963
trode connection to either a source terminal or a load
terminal. The recti?ers associated with each gate wind
Company, a corporation of New York
ing need not be matched in characteristics, as might be
expected when recti?ers are normally connected in paral
William R. Miller, Erie, Pa., assignor to General Electric
lel, so that when the voltage across the recti?ers is neces
sarily equal, there is a proper division of load current
Filed Mar. 30, 1959, Ser. No. 802,802
1 Claim. (Cl. 323-89)
through such parallel recti?ers. In such parallel recti?er
This invention relates to a magnetic ampli?er adapted
arrangements one or more recti?ers, if all are not ac
to supply a direct current load, through gate windings,
curately matched, may carry several times the current of
from an alternating current source. Each gate winding 10 the others and therefore be seriously overloaded.
comprises a plurality of gate winding legs. A recti?er
Since individual diodes vary in their forward voltage
is in series with each winding leg and all of the gate wind
characteristics, current distribution between parallel con
ing legs of each gate winding are arranged in parallel on
nected diodes may vary widely unless the diodes are
a saturable core. By this arrangement, the gate winding
closely matched in these characteristics. For example,
legs of each gate winding cooperate to ‘distribute and 15 a silicon diode may have a threshold voltage energy level
equalize the load on the recti?ers even though the indi
of .5 to .6 volt drop after which the current therethrough
vidual recti?ers may have characteristics which do not
increases almost asymptotically with voltage and only a
match so that in the absence of the equalizing effect of
small percentage of the threshold voltage drop is due to
the gate windings, one of the recti?ers might carry several
the forward resistance of the diode. Furthermore, diode
times the current of the other.
characteristics are changeable with age, temperature, and
In the drawing, the single FIGURE is a circuit diagram
other conditions so that even diodes which have originally
of a magnetic ampli?er embodying the invention.
been matched to conduct substantially the same forward
In the ampli?er, alternating current from a polyphase
current at equal applied voltages may become unbalanced
power supply, not shown, is applied to alternating cur
in their forward voltage-current characteristic after a short
rent input terminals 1a, lb and 11c and is converted into 25 period of operation. However, because of the parallel
a direct current voltage of variably controlled magnitude
connection of the gate winding legs in each gate winding,
at output terminals 2. The conversion is effected by satu
the current through the recti?ers is equally distributed so
rable core reactors 3a, 3b, 30 respectively and associated
that individual recti?ers in the group are not overloaded.
circuitry. The reactors are arranged in each pulse of the
The uniform distribution of current through the recti?ers
power supply which might be supplied by auto transform
results from the substantially equal resistance of the gate
ers 4a, 4b, 4c. The magnitude of the direct current volt
Winding legs in each gate winding which is substantially
age is controlled by the level of magnetic ?ux preset in the
greater than the forward resistance component of its
reactor cores by control windings 5a, 5b, 5c, 6a, 6b, 6c fed
associated recti?er voltage drop. Not only does this ar
from a control voltage 7. Each control winding is arranged
rangement result in uniform distribution of the current
to preset the level of magnetic ?ux in an associated satura
through the recti?ers, but it also blocks circulating cur
ble magnetic core ‘7a, 7b, 7c, ta, "8b, 80, respectively, and
rents between gate windings in the group due to slight
thereby to control the impedance of the gate windings
differences in the windings. The load distributing func
mounted on each core.
Referring speci?cally to the re
tion and the other advantages are obtained without the
actor 3a, there is a four-legged gate winding GA com
addition of any parts to the magnetic ampli?er, and with
prising gate winding legs 9a, 10a, Ila, 12a on the core 40 out the addition of load equalizing devices such as resist
7a controlled by the control winding 5a and there is a
ances in series with the paralleled recti?ers.
four-legged winding GB comprising gate ‘winding legs 13a‘,
What is claimed as new is:
14a, 15a, ‘16a on the core ‘8a controlled by the control
A magnetic ampli?er for supplying direct current elec
winding 6a. The gate winding legs 9a, Ida, 11a, 12a are
trical energy of variably controlled magnitude to a load
respectively connected to the positive side of a load, not 45 from an alternating current source comprising: a saturable
shown, across terminals 2 through recti?ers 17a, 18a, 19a,
magnetic core, a gate winding on said core serially con
20a, respectively, all having a common cathode connec
nected between an alternating current input terminal and
a direct current output terminal; said gate winding com
tion. The recti?ers ‘17114011 ?re during the positive half
cycle of the voltage supplied from terminal la through
prising a plurality of similarly poled gate winding legs of
substantially equal resistance value, a rectifying element
transformer 4a and supply a voltage to the load of a mag
nitude dependent upon the current in the control winding
in series circuit with each of said gate winding legs, all
of said rectifying elements being poled in the same direc
tion with respect to said terminals, the resistance of each
5a. The gate winding GB comprising gate winding legs
13a, 14a, ‘15a, 16a is connected to the negative side of
the load across terminals 2 through recti?ers 21a, 22a,
23a, 24a respectively, which ?re during the negative half
cycle of the voltage supplied from transformer 4a and
of said gate winding legs being substantially greater than
55 the ‘forward resistance of its associated series connected
rectifying element; each of the rectifying element-gate
supply to the load \2 a voltage of magnitude controlled
winding leg series circuits being arranged in parallel to
by the control winding 6a. The reactors 3b and 3c are
form said gate winding, the substantially equal resistance
similarly connected and corresponding parts are indicated
of said winding legs substantially equally distributing the
by the same reference numerals with the subscripts b and 60 load current between the recti?ers of said gate winding;
c. There is a de?nite and substantially linear relationship
and a control winding on said core arranged to conduct a
between the magnitude of the direct current voltage at
direct current therethrough to control the magnetic flux
the output terminals e and the control voltage from
density in said core to thereby control the magnitude of
source 7 supplying the control winding ampere-turns ‘for
65 the direct current electrical energy supplied to the load.
the saturable magnetic cores 7a~8c.
From the foregoing, it appears that on each of the cores
References Cited in the ?le of this patent
711-80 there is a gate winding GA-GF, respectively,
each comprising a plurality of gate winding legs. In series
with each gate winding leg is a recti?er, the recti?ers being
similarly poled and all having a mutually common elec 7 O
Burton et al ___________ __ Mar. 23, 1954
Bingham _____________ __ June 16, 1959‘
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