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Патент USA US3054949

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Sept 18, 1962
Filed Dec. 24, 1958
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United States PatentO??ce
Patented Sept. 18, 1962
Since the transformers inherently regulate for input volt
age deviation, there can ‘exist considerable phase unbal
ance which is attenuated by the regulating action. Tests
Leon J. Thompson, Poughkeepsie, N.Y., assignor to Inter
have shown that less than 5% peak to peak ripple is
national Business Machines Corporation, New York,
Or possible without capacitors as compared to approximately
N.Y., a corporation of New York
15% ripple in a conventional supply (i.e. a three phase
Filed Dec. 24, 1953, Ser. No. 782,812
recti?ed supply with sine output and no capacitor). Since
1 Claim. (Cl. 321-16)
the wave form is substantially ?at topped, the peak rec
The invention relates to eiectrical converting means and
ti?er currents are reduced which results in better recti
more particularly to means for producing a substantially 10 ?er operation. As representative of the constant voltage
smooth ‘direct current power supply derived from a three
type of transformer, reference may be made to the ex
phase alternating current source through three constant
voltage transformers connected in parallel with diode
recti?cation and without the use of the usual smoothing
output capacitor.
pired Patent 2,143,745.
Reference to vFIGURE 1 shows that the three phases
of the A.C. input are wired to the three primary wind
15 ings A, B and C of three constant voltage transformers
An object of the invention is to provide an improved
DC. power supply by the use of a plurality of ferro
resonant transformers through which an alternating cur
rent is commutated.
Another object of the invention is the provision of a 20
direct current supply which has very little ripple through
the use of a plurality of constant voltage transformer
secondaries connected in parallel through full wave recti
CV'lll, CVT2 and CVT3. The secondary windings A’,
B’ and C’ of the same transformers are connected in
parallel with the usual resonating capacitors 21, 22 ‘and
23 and are tapped centrally with connections to sepa
rate recti?ers 31, 33 and 35 leading to one of the out~
put leads 40 extending to the load RL which is ener
gized by the direct current output.
The secondary wind
ings are tapped further at an intermediate point to pro
vide separable connections to the other output lead wire
A further object of the invention is the elimination of 25 all which is connected to the other side of the load
relatively large ?lter capacitors in electrical converting
RL. A series of right end connections are made to the
secondary transformer coils A’, B’ and C’. Such at
A still further object of the invention is to put to novel
tachments are at the ‘ends of the secondaries and are
use the square wave outputs of a plurality of ferroresonant
connected to one side of three other recti?ers 32, 34 and
transformers which are energized from a plural phased 30 36, the other sides of \which are separately connected to
power source.
the output lead ‘40.
Other objects of the invention will be pointed out in
Although the connections from the transformer sec
the following description and claim. and illustrated in the
ondaries to the recti?ers 31, 33 and 35 are shown schemat
accompanying drawings, which disclose, by way of ex
ically as made at the center, this is not necessarily the
ample, the principle of the ‘invention and the best mode, 35 electrical center of the winding. The number of turns
which has been contemplated, of applying that princi
between these connections which connect recti?ers 31,
33 and 35, and 32, v34, 36, determine the desired output
'In the drawings:
voltage of the system. It is the taps which are connected
FIGURE 1 shows the circuit connections for connect
between said connections and which are tied together to
ing a three phase A.C. input to three constant voltage 40 the bottom end of the load resistance RL, which are
transformer and recti?er connections in parallel to sup
truly centrally located. ‘In practice, it may be desirable
ply direct current to a load across the output lines.
to connect the resonating capacitors to any of the taps
FIGURE 2 shows the unrecti?ed but ?at topped output
shown or as rearranged. It is also possible that there
of the three transformers.
should be two or more secondary windings. One of such
FIGURE 3 shows the recti?ed and related output of 45 windings would be connected to the resonating capacitor,
the three waveforms which are combined for an im
and another winding would be center tapped and used
proved resultant.
as the output.
FIGURE 4 shows the combined result of the three
Each ferroresonant transformer may actually be built
on two physically separate cores, the one being the linear
phase recti?ed outputs showing the overlapping proper
ties of the waveforms which result in a low degree of 50 inductance element, and the other the non-linear induc
tive element, across which the resonant capacitor is con
The invention deals with means for providing a regu
nected, and in which the output winding is placed.
lated DC. power supply with low ripple. A high purity
Taking the ?rst transformer CVTl as an example, it
DC. is produced from a three phase A.C. source such
will be noted that the square wave A.C. input to the
as could be used for computer systems. The design ap 55 two recti?ers 31 and 32 is fully recti?ed and will appear
proaches the ideal system of rectifying square waves and
as shown at the top of FIGURE 3 after being treated be
ripple in the output voltage.
applying the recti?ed square wave to a common load to
yond the preliminary transformer output showing as
given at the top of FIGURE 2. When all three trans
former outputs are considered, it will be realized that
frequency ?lter.
60 before recti?cation they appear as shown in FIGURE 2
Although illustrated in connection with a three phase
with a form of commutating spacing due to the phas
A.C. source, it is apparent that two phase, six phase,
ing of the three phase input. Then too, after recti?ca~
or other varieties of multi-phase input may be employed
tion, the three output wave formations of the three trans
and the same novel advantages derived therefrom.
produce D.C. without ripple while eliminating the usual
comparatively large smoothing capacitors or other low
The system is based on the use of ferroresonant trans
formers (also known as constant voltage transformers,
voltage stabilizing transformers, etc.) which are operat
ed at high flux densities (overexcited) to produce approxi
mately square waves or ?at topped waves. Three such
transformers excited by a three phase power source and
are connected full wave recti?er connections so that cur
rent commutation takes place to produce a DC. output.
formers and associated recti?ers will appear as shown in
FIGURE 3 with all depressions between Waves mainly
compensated for by the overlap of the waveforms. In
FIGURE 4 it is shown that the resulting ripple from the
combined effects of the wave formations in FIGURE 3 is
such that the extent of ripple is no more than 5% and
a great deal better than expected.
Regarding the particular values used for an example of
the power supply of the present invention, it may be noted
that the particular kind of constant voltage transformer
used for one example is designated as GE 9T91Yl047.
Associated with such transformers, as designated by ref
pedance. It is at this point that the wave form ?attens out
and appears ?at topped.
A somewhat similar explanation seems to apply relative
to the present invention except that the voltage across the
erence numerals 21, 22 and 23 in FIGURE 1, are capaci
recti?er in its back-biased condition is that voltage pro
tors which could be GE Pyranol 21F432, rated as 6
microfarads, 660 v. A.C., 60 cycle. When three such trans
duced by previously conducting recti?ers of different
phases rather than the output of the usual capacitor.
formers are connected as shown to a source of supply hav
This process may be referred to as a commutating load
ing a frequency of 60 cycles and voltage of 210, the out
which implies that the load commutates between recti?ers
put may be expected to be maintained so as to vary no 10 and phases by a form of switching action and is responsi
more than 5% when operating at 32 volts and a. current
ble for the unusual ?atness and usefulness of the trans
demand of 11.5 amperes. The particular recti?ers or di
former output wave forms.
odes 31—36 suitable for use in the particular example men
While there have been shown and described and pointed
tioned may be identi?ed as a germanium recti?er GE
out the fundamental novel features of the invention as
applied to a preferred embodiment, it will be understood
It is known that when a ferroresonant transformer feeds
that various omissions and substitutions and changes in the
a recti?er system having a capacitor ?lter as ordinarily
form and details of the device illustrated and in its op
used for a D.C. power supply, certain complicated results
erations may be made by those skilled in the art without
are produced which are difficult to explain. One of the
departing from the spirit of the invention. It is the in
major results is that the output waveshapes from the trans
tention, therefore, to be limited only as indicated by the
former changes and becomes ?at topped and appears trap
scope of the following claim.
ezoidal in form. This result is used to advantage in a rec
What is claimed is:
ti?er-capacitor power supply because the effect is to re
In a constant voltage electrical power supply: a source
duce the peak currents over that which would be obtained
of multi-phase alternating current supply; a plurality of
if the waveform were sinusoidal. The result is less output
constant voltage transformers, each having a primary
ripple and, in addition, since the peak currents are smaller,
the recti?er can be operated less conservatively. It is also
known that the ?at topped or squareness of the wave can
be accentuated by increasing the excitation of the trans
former. These properties and results are derived from
winding and a secondary winding, said transformers being
of the type which produce a substantially ?at topped volt
age wave shape across the secondary thereof, the wave
shapes across all of said secondaries being of substantially
the same amplitude, each transformer being connected to
the inherent characteristics of non-linear ferromagnetic
a different phase of said supply through its primary wind
operations. In the present instance, it is proposed to use
ing; a pair of tapped output connections on each said sec
such characteristics in a new and useful way.
ondary winding; a plurality of recti?ers, one associated
The present invention is concerned primarily with the
with each of said output connections, each having a ter
fact that the square wave output operation can be obtained
minal of ?rst polarity and a terminal of second polarity,
and synthetized without the use of the usual capacitor ?l
each said recti?er being connected at its terminal of ?rst
ter. This is accomplished by the use of a succession of
polarity to its associated tapped output connection; a
pulses obtained from several phases of a multi-phase
center tap on each of said secondary windings at the elec
power system which feed into a particular recti?er, wave
trical center portion of said secondary winding between
forms similar to those which would appear ordinarily with 40 said tapped output connections; a pair of output leads, one
a capacitor in an intermediate position.
of said leads being connected to each of said recti?ers at
Ordinarily the output wave form of a ferroresonant
the terminal of second polarity of said recti?er and the
transformer with a recti?er and capacitive load is depend
other of said leads being connected to each of said center
ent on the commutative characteristic which exists in
taps, to provide full wave recti?cation; whereby said out
herently. Assuming a stable circuit with a capacitive load,
put leads connect said secondary windings in parallel to
wherein the capacitor is large enough to sustain a voltage
produce a substantially smooth direct current output.
near peak value, as is usually the case in a power supply,
References Cited in the ?le of this patent
if the circuit is examined when the transformer output
voltage is rising from zero, it is found that at such a time
and until such time as the instantaneous output voltage is
Fortescue _____________ __ Nov. 2,
equal to the instantaneous voltage on the capacitor, the
Jansson ______________ .. May 19,
recti?er is back-biased or cut-01f and the transformer is
Sola ________________ __ Jan. 10,
operated in what is essentially a non-loaded condition.
Sola _________________ __ Nov. 9,
It is not until the instantaneous transformer voltage is
Sola _________________ __ July 3,
greater than the capacitor voltage that the recti?er will con
duct in its forward direction and when it does, in the case
of a capacitor, the circuit suddenly becomes a low im
Great Britain _________ __ Nov. 28,
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