Improvements relating to Induction Coils or Transformers, chiefly designed for use in Welding or otherwise Working Metal by Electricity.
Year: 1890

page_text: Date of Application, 19th Aug., 1890-Accepted, 11th Oct., 1890
[Communicated from abroad by Professor ELIHU THOMSON, of Lynn, Massachusetts,
United States of America, Electrician.]
Improvements relating to Induction Coils or Transformers, chiefly
designed for use in Welding or otherwise Working Metal by
Electricity.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, do hereby declare the nature
of this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
My invention relates particularly to that class of induction coils or transformers
in which the secondary circuit is adapted to develope a current only of a very low
potential as is the case with converters or transformers constructed for electric welding
or other metal working operations. In this class of apparatus I have found that
frequently a rupture of the insulation of the primary. circuit of the apparatus takes
place, and I have ascertained that such rupture is ordinarily due not to any change
of electrical condition in the circuit supplying the primary but to a sudden rupture of
the circuit for. the secondary current arising from a melting down of the work and a
rupture of the circuit at such point. I have also ascertained that the destruction
of the insulation of the primary is largely due to the fact that the current of the
secondary is so low in tension as to be incapable of maintaining itself even for an
instant at the point of break in the work, the result being that no arc can follow the
rupture and prolong the current and consequently there is developed in the primary
coil of the apparatus an extra or induction discharge current of great potential which
breaks through the insulation of the primary coils.
My invention consists in removing the danger to the primary from a melting down
of the work in the secondary circuit, by placing an induction discharge protector
across the terminals of the primary and adapted to provide a path for the high tension
induction discharge while maintaining an insulation which will prevent a shunting of
the ordinary currents passing through the primary of the coil for the purpose of
setting up the low tension currents in the secondary. Such discharge protector
consists essentially of two electrodes or contacts brought into close proximity but
normally separated from one another by a thin layer of air or film of insulating
material which furnishes a sufficient obstacle to the flow of the ordinary currents on
the circuit.but provides a path for the high potential discharge current inasmuch as it
is a path of comparatively little self induction so that such induction current passes
by it in preference to passing over the general circuit or across and through the
insulation of the coil.
My invention consists further in the combination with the induction discharge pro-
tector placed across the terminals of the primary circuit, of a circuit breaker of any desired
character for the current of any are following the discharge across the protector. This
part of my invention is applicable to any electric apparatus or electro-magnetic coils.
placed in the circuit from any generator and provided with an induction discharge pro-
tector across its terminals for the high potential extra current developed in the magnetic
coils or apparatus. The arc which follows the passage of the discharge current across
or through the discharge protector is produced by the current from the generator
supplying the magnetic coils or other apparatus, and obviously requires to be
removed in order that damage to the protector or generator may be obviated.
The circuit breaker or device for breaking the current by which any arc is maintained
through the protector may be of any desired character, and I include under such term
not only a magnet the field of which acts to blow out or disrupt the arc itself but also

page_text: a device placed in the circuit and adapted to fuse by the abnormal current which
maintains the arc and also electric contacts movable with relation to one another and
included in the normal circuit but adapted to be separated for the purpose of inter-
rupting the current which maintains the arc, or any other device which is adapted
to produce a cessation in the flow of the current through or over the protector
producing the arc.
In the accompanying drawings,
Fig. 1, is a diagramatic view showing an arrangement of apparatus embodying
my invention,
1
Figs. 2, 3, 4 and 5, illustrate forms of devices which may be employed in carrying
out my invention.
S, indicates the secondary circuit or coil of a converter and P, the primary thereof.
The secondary S is of large gauge or few convolutions and is adapted to supply a
current of low potential to welding or metal working apparatus in which a piece or
pieces of metal are heated by such low potential current. The primary P, of such
converter carries a current of comparatively high potential supplied thereto over a
main M, from any suitable generator, preferably an alternating current generator.
The form of induction discharge protector shown in Fig. 1, consists simply of two
electrodes or pieces of metal A, B, presented to one another but separated by a small
air space. The protector is included in a short branch circuit between the terminals
of the coil P. By short circuit I mean one which possesses comparatively little self
induction to the passage of a high potential current. In the circuit with the induction
protector is shown a fuse C.
In the operation of welding apparatus it is the ordinary practice to employ a
secondary current insufficient to maintain an arc. When, therefore, the secondary
circuit is interrupted, or ceases, an exceedingly high potential current is developed in
the primary P, which, if it were obliged to circulate over the main line M, wherein
it would meet, considerable self-induction might in preference break through the
insulation on the primary P, thus destroying the same. By means of the protector A, B,
however, a comparatively free path is afforded for such current of self induction and
it passes and dissipates itself over the circuit including the electrode A, B, and fuse C.
The passage of the high potential current at A, B, however, establishes a circuit for
the current supplied over the line M, from a generator and an arc is immediately
established across the electrodes A, B. The current which maintains such arc, however,
being of comparatively large volume and the fuse C, being properly adjusted to such
current, said fuse will immediately rupture and will thus interrupt or break the
current which maintains the are thereby preventing damage to the apparatus.
In Fig. 2, the narrow space across which the arc is formed is shown as in the field
of an electro magnet E, which is in the circuit traversed by the arc and which by
its magnetic field interrupts or breaks the circuit of the current maintaining the arc
at the arc itself.
In the form of protector shown in Fig. 3, electrodes A, B, are separated by a film m
of some insulating material such as mica, but which cannot withstand the high
potentials established at the electrodes A, B, on the development of the extra or discharge
current in the coils P. Such film, however, is sufficient to prevent the passage of the
ordinary current on the main M, through the branch around the coils P, just as the
air film does in Figs. 1 and 2. In Fig. 3, the circuit breaker is a fuse C.
In Fig. 4, the circuit breaker consists of two contacts G, H, normally held in
connection by a suitable spring applied to the lever K, supporting one of them. The
electro magnet E, is included in the circuit with the protector and such contacts, and
has an armature which is attached to the lever K. When the circuit is established
through the protector before explained the magnet E, becoming energized, draws
contact H, away from G, and thereby breaks the circuit for the current which forms
the arc and causes the same to be put out.
In the modification indicated in Fig. 5, the electro magnet E, has an armature
lever K, which carries one of the electrodes A, B. On establishment of the circuit

page_text: and the formation of an are the current which produces such arc energizes the magnet
and draws the electrode B, away from A, to such an extent as to break the circuit for
the arc maintaining current.
Other ways will readily suggest themselves to electricians of interrupting or
breaking the circuit for the current of the generator when it finds a path over the
discharge protector and through the main M.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, as communicated to me by
my foreign correspondent I declare that what I claim is :--
1. The combination with a transformer or converter for electric welding or other
metal working operations, or for other purposes, of an induction discharge protector
in a short circuit between the terminals of the primary whereby on rupture of the
secondary circuit damage to the primary may be prevented.
2. The combination with magnet coils placed on an electric circuit and traversed by
current from any suitable source, of an induction discharge protector consisting of
electrodes normally separated by a narrow insulating space but connected respectively
to opposite sides or terminals of such coil directly so as to form a short circuit path
for any inductive electric discharge current produced in the coils themselves, and a
circuit breaker for rupturing the circuit of any are following such induction discharge
from the coils and maintained by the electric current flowing over the main line.
Dated this 26th day of June 1890
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.