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Патент USA US2136863

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Nov. 15, 1938.
Filed Oct. 9, 1934‘
E'eder/GKC 014/672
Patented Nov. 1-5, 1938 '
Frederick 0. Owen, Fayetteville, N. 0.
Application October 9, 1934, Serial No. 747,607
5 Claims. (Cl. 172--246)
The object of’the invention is to provide a
‘transformer ‘in which the disadvantages due to
its normally low power factor are overcome by
equipping it with a reactance of a character to
materially improve the power factor; to provide
a construction in which the reactance is cut into
and out of circuit, so that its beneficial effects
may be had during load periods in the trans
former without the disadvantage of the absorp
10 tion of energy from the line during periods of
1 idleness; and to provide a construction in which
the operation of cutting the reactance into and
out of circuit is wholly automatic, but dependent
entirely on the presence of a load in the sec
ondary. .
With this object in view, the invention consists
in a construction and combination of parts of
which a preferred embodiment is illustrated in
the accompanying drawing, wherein the ?gure is
a diagrammatic view of the invention.
The transformer illustrated is of the step-down
type, being of the kind ordinarily employed in
electric welding, and being of the magnetic les 1:
age type in which the primary I0 is wound in
three sections on three. different legs of the core
I I. The secondary. llis wound on the remaining
leg of the core, as well as on the diametrically
opposite leg over the intermediate section‘ of the
The primary is energized from a suitable source
and is controlled preferably by the double-pole
single-throw switch it. The two terminals of
the secondary are carried to the load, which, if
the transformer be used‘for welding, for which it
‘is particularly designed, will be dissipated in
maintaining the are necessary to effect the weld;
ing operation.
The normally low power factor inherent in such
a construction of transformer may be materially
improved by the means of a condensive reactance,
of charging current during periods of idleness of
the transformer.
The operation of cutting the reactance into and
out of circuit is made dependent on the trans
former being under load, and to this end a sup- 5
plemental coil I8 is disposed‘in surrounding rela
tion to the core and its terminals are connected
with an electrc-magnet I! which constitutes the
actuating element for the switch. The magnet is
is preferably an element of a stationary yoke 19
member 20, the extremities of which, when the
magnet is energized, become magnetic poles ex
erting a magnetic pull on an armature 2| which
carries the contacts ll.
When there is no load current in the second- 1‘
ary of the transformer, as when the welding op- '
eration is not being performed, if the trans
former be designed for welding, there is prac
tically no magnetic leakage from the core and
hence no energy is present in the supplemental 20
coil l8. Immediately upon a load being imposed
on the secondary, as when the welding operation
is being carried on, the magnetic distortion tak
ing place in the core results in a stray magnetic
field which is effective to generate a current in 26
the coil l8, which becomes effective in the mag
net 18, thereby causing the switch to be operated
and the reactance to be thrown into circuit with
the primary, thus‘ effecting a material improve
ment in the otherwise poor power factor of the 80
apparatus. When thereis no load in the second
ary, as when the welding operation is discontin-f
ued, there exists practically no stray ?eld in the
transformer core and accordingly thereis no cur
rent generated in the coil I! so that the magnet 86
i9 is then deprived of energy, preventing it from
- maintaining-the closed position of the switch,
with the terminals connected to the terminals I!
which then drops to open position, thus cutting
the reactance out of circuit, so that its employ
ment does not represent a loss during idle periods 40
as by the absorption of a charging current.
The invention having been described, what is
claimed as new and useful is:
45 of a double-pole switch which normally assumes
a normally low power factor, a condensive re- 45'
which, in the illustrated embodiment, consists of
capacitors I‘, of which there may be a bank
1. In combination with a transformer having
an open position but which is automatically
moved to closed position. The switch terminals
II, which are complemental to the terminals ii,
are connected across the primary terminals of
actance, an'electrically operated switch for con
necting the reactance in one of the circuits of
the transformer, and a coil for generating switch
the‘ transformer._ When the switch is closed,
therefore, the reactance is thrown directly across
an element of the transformer and generating 50
the primary, but when the switch is open, it is
cut out of circuit. Thus there are provided bene
iicial effects of the reactance without any of the
disadvantages of its use, such as the absorption
actuating current but related only inductively to
switch operating current only when the secondary
is under load. -
2. In combination with a transformer having'
a normally low power factor, a condensive re,
actance, a magnetic switch for connecting the re- ,
actance across the primary, and a coil for ener
connecting the reactance across the primary of
gizing the switch, said coil having such an induc
the transformer, and a supplemental coil ener
gized from the transformer only when the sec
ondary is under load and operatively connected
with the switch to energiae and to actuate the
tion relation to the transformer as to limit it to
generating the switch energizing current only
when the secondary is under load.
3. In combination with a transformer having
a normally low power factor, a condensive re‘
actance, a magnetic switch for connecting the re
actance across the transformer primary, and a
10 supplemental coil for energizing the switch, said
coil being disposed in surrounding relation to the
5. In combination with a transformer having
a normally low power factor, a condensive re
actance, a supplemental coil disposed in sur
rounding relation to the transformer and ren 10
dered active only when the secondary of the trans
transformer but responsive to core leakage in the .former is under load, and a normally open mag
netic switch for connecting the reactance across
latter only when the secondary is under load.
- 4. In combination with a transformer havinl
15 a normally low power factor, a condensive re
actance, a normally open magnetic switch for
the primary of the transformer, said switch be
in: energised from said coil.
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