Improvements in and relating to Electric Induction-coils or Transformers.
Year: 1889

page_text: [Communicated from abroad by ELIHU THOMSON, of Lynn, Massachusetts, United
States of America, Electrical Engineer.]
Improvements in and relating to Electric Induction-coils or
Transformers.
1, HENRY HARRIS LAKE,, of the firm of Haseltine Lake & Co. Patent Agents,
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 :-
This invention relates to electrical apparatus in which two coils or circuits are
placed in inductive relation to one another, one of the said coils or circuits being
traversed by, alternating or otherwise varying currents from any desired source.
The object of the said invention is to regulate or adjust the current made to flow
in the second of the two coils by the alternating currents in the first. The inven
tion is especially applicable to that class of apparatus known as induction coils or
transformers and can be used for obtaining a current from the secondary which differs
radically in properties or character from that from which the primary draws its
supply.
Thus if the primary coil of a converter be attached to a constant potential
circuit as a branch, the current which may be obtained in the secondary circuit
may, instead of being approximately of constant potential like the primary, be of
approximately constant strength or volume of flow regardless of a wide range of
differences of resistance interposed in such secondary circuit. Or, again; an electro..
motive force or potential which diminishes as the current strength. increases may
obtained from the secondary, as when resistance is gradually taken out of the
secondary circuit.
he
The said-invention is particularly applicable to the running of are lamps by induc-
tion from constant potential mains without the use of resistances in circuit with the
ares for limiting the current which they receive, since, by the use of this invention any
increase in the secondary may be made to produce a fall of electro motive force

page_text: given out by the secondary coil feeding the are.
Were this not the case, or were
the electro motivo force maintained, the current flowing to the are lamps would be
unstable and the lamps would be very irregular in action, owing to the fact that as
the current in the are increases the resistance of the arc falls which would with
constant potential bring about further current increase and so on.
By the present invention if the current is to be ten amperes for the arcs it cannot
rise much above that amount no matter whether the carbons in the are are apart or
near together, or in actual contact.
The said invention also enables the operation of a number of incandescent lamps,
or other translating devices, in series from the secondary coil of a transformer and
permit the shunting without resistance of one or more of the lamps while the current
in the circuit of the remainder is substantially unchanged. In fact by proper modi-
fications in the manner of carrying out the invention, the primary coil being on
constant potential, the secondary coil may be short circuited and retain only the
normal or a slightly increased current. I am not aware that this has ever been done
before.
The invention consists essentially in a novel method of adjusting, regulating or
determining the current or potential in the secondary of two coils or circuits placed
in inductive relation by developing alternating magnetism through the action of the
current in each or either of said circuits, in a suitable iron core, and variably closing
the magnetic circuit of said core through a path independent, in whole or in part, of
the magnetic circuit for the magnetism developed by the other coil or circuit.
The variable closure of the magnetic circuit may be produced by any desired
means, but is preferably automatic and is produced by the direct action of the lines of
magnetic force themselves in concentrating or focussing themselves in or across a
narrow non magnetic space or septum forming a partial break in what would otherwise be
a perfectly closed magnetic circuit or path for the magnetism developed by the current
of the coil or circuit in question. The variable closure may however be produced in
other ways without departing from the invention, as will presently appear.
The magnotic circuit for magnetism so developed by one of said coils or circuits
may be that either of the primary or the secondary, or as will be evident, the
magnetic circuits developed by the current flowing through both coils or circuits may
be partially and variably closed at once. In any case however there should be an
opportunity for a magnetic circuit for each coil or circuit which shall be independent
in whole or in part of that developed by the other, that is to say, each magnetic circuit
may have a path entirely independent at all points, of that for the other, or each may
include a part of the path of the other, such common part being in ordinary cases
the part where the higher magnetic resistance resides and where the variations in the
magnotic closure are produced.
The invention consists also in a novel construction of a transformer the object of which
is to give the transformer itself a self regulating character resulting in an automatic
adjustment or regulation of the current or potential in the secondary when the
resistance or current in the same varies.
To this end the invention consists in providing the core upon which the primary and
secondary coils of the transformer are wound, with an extension or extensions in the
nature of carriers of magnetism arranged to form a magnetic shunt as it were of
determinate or set value for the magnetism threading the coils, as hereinafter
described.
The said invention also consists in certain improved details of construction hereinafter
described.
In the accompanying drawings :-
:-
Figure 1 is a diagram illustrating circuits and apparatus by which the invention
may be carried out.
Figure 2, is a plan view of the apparatus shown in Figure 1.
Figures 3, 4 and 5 show another form of induction coil or converter that may be
used.
Figure 6, illustrates a modification in the devices for carrying out the invention.

page_text: Figures 7 and 8, show in partial side view and in perspective, other devices that
be employed.
Figure 9, shows in side view a part of a similar device.
may
Figures 10, 11, 12 and 13 illustrate other modifications in the form of devices, and
in the manner of applying the invention.
Figures 14, 15 and 16 illustrate some of the uses of my invention.
Figure 17, is a diagram illustrating the elementary principle of my invention.
Figure 18 shows a further modification in the manner of applying my invention.
Figure 19 is a diagram of current and potential.
Figure 20 illustrates a device that may be employed for producing variations in
the closure of the magnetic circuit or for adjusting the action of the apparatus.
In the various Figures of the drawings a and indicate alternating current
mains having a constant, or approximately constant difference of potential, and P, a
coil in the circuit between said mains.
S, is a coil of suitable number of turns according to the potential to be derived
therefrom, in inductive relation to the coil or circuit between a and b, which coil S,
forms a part of a local circuit and applies thereto currents inductively set up by the
currents in the circuit from a to b.
The coils P and S, are preferably wound on the same continuous or endless,
laminated or other core I, and the number of turns in P or in any coil in circuit
with it, as P1, is such that having reference to the potential of a, very little current
will pass in P, when the circuit of S is open.
Referring first to Figure 17, P indicates an additional coil wound on a suitable
iron core 1, laminated or otherwise, and in which core the currents flowing from a
to b, as an alternating or otherwise varying current, will obviously produce an
alternating magnetism, and if the core of said coil were continued around so as to be
endless there would be a magnetic circuit entirely closed and a maximum of reactive
effect in the coil P', opposing the passage of current from a to b.
Instead however of making the magnetic circuit completely closed, I provide the
core I, with projections e, e', which are brought rather closely together with, how-
ever, a determinate air space between them forming a partial break in the closure of
the magnetic circuit for the magnetism developed by the current flowing from a
to b. The width of the space may in some cases be quite narrow and in others the
projections c,el,may be well separated. The space forms an air or magnetic resistance to
the closure of the magnetic circuit for coils P and as will be obvious the more
perfect the closure of the magnetic circuit for coils P¹ of this variable point the
greater will be the reaction upon the currents flowing from a to b, through coils P¹.
During normal flow of currents from a tob, there is a definite degree of closure of
the magnetic circuit at K, dependent upon the width of the space and the number of
magnetic lines of force which, with the given strength of magnetism, in the core
of 1', may force themselves across the space. If there is any tendency to increase
in the magnetism of the core of P', the lines of force concentrate or mass themselves
together in the space across K and become less diffused. By this means the degree
of closure of the magnetic circuit of the core is increased and the reaction in coils P
increased. This variation of partial magnetic closure or variation of magnetic
resistance obviously takes place independently of the magnetic circuit formed by the
core threading the coils S.
Leaving out of consideration the coil S', in the circuit of S, the operation in
regulating or adjusting the current in the circuit of secondary S, is as follows:-
When there is a tendency to increase of current in the circuit of S, due to decrease
of resistance, there is an attendant decrease in the counter-electro motive force of
the primary coil P, as is well understood, and there would hence be a tendency to
increase of flow in the coil P. But with an increase of flow in the coils of P there
is also an increase in the coils of P and an increase in the number of lines of
magnetism which pass over the magnetic resistance at K, is produced. Inasmuch
as the reaction of the coil P¹ depends upon the amount of magnetic disturbance set
up in its core or the number of lines passing from c to e¹, it is obvious that the

page_text: currents flowing from a to b, will meet an increased self inductive reaction, and the
current on the secondary circuit S, will be cut down.
As the rate of variation of closure at K, may be varied by any desired means, and
may in fact be determined automatically by the width of the space K, as well as
by the means to be described, it is obvious that the regulation or the adjustment of
current in the circuit of $, may be of any desired nature. The prime object of the
invention is, however, to secure a practically constant current in said circuit, and
the width of the gap K, is made such as to produce as near as may be that effect.
The regulation of the current or potential in the secondary circuit might also be
produced by variably closing a magnetic circuit developed by the second current,
and independently of the magnetic circuit of the primary current. Thus as indicated
at S¹, the secondary current may pass through a coil which shall set up magnetic
effects in a core having a partial closure of variable amount at K.
In this case the same effect of a reduction in the current or potential of the
secondary is produced by the variation in inductive roaction at the coil S¹,
secured by variably closing magnetic circuit of the core of $1 at at K.
The effects produced by the variation of magnetic closure of the core excited by
the secondary current might obviously be used alone or in conjunction with similar
effects produced in the primary as at P.
Instead of varying the magnetic closure of a core surrounded by a separate coil, I
may, as shown in Figure 1, and other figures, variably close the magnetic circuit for
the portions of core of the coils P, S, themselves, each portion of core having its
magnetism closed without passing through the other portion. This is accomplished
by means of projections or magnetic carriers e, c', extending from some part of the
iron core or circuit which threads both the primary and secondary coils, said projec-
tions being separated from one another by a space K, forming a magnetic resistance
similar to the space K, of Figure 17. By means of the variable magnetic resistance
formed at K, the magnetism developed in the portion of core surrounded by the coil P,
is variably closed. In fact such magnetism can work, as it were, through two
magnetic circuits, one including the space or resistance K, and the other including
the portion of core passing through the coil S.
The magnetic lines developed by the core or coil P, which pass through the air
space at K, and escape the coil S, produce wholly self-inductive effects resulting in
an opposition to the flow of the primary currents, while all the lines developed by the
coil P, which pass through the axis of the coil S, result as usual in the production of
secondary currents.
It will be readily seen that, as before described, any tendency to increase of the
current flowing in coil P, resulting from a lowering of the resistance in the circuit
of S, will be at once followed by the development of increased magnetization of the
portion of core in coil P, and by the formation of increased magnetic lines across the
air space, while at the same time self induction of the coil S, itself, will undergo an
increase owing to the fact that a path of variable closure for the magnetism in said
core is likewise formed across the space K. In fact the effect of a slight increase of
current in the coil S, would be to beat back the lines of force tending to pass through
its coils, from the coil P, and cause them to be shunted across the space K.
The result of all this is that the varying resistance in the circuit of the secondary S,
would receive a current which tends to be limited in strength and to be self-
regulated through the provision of the variable magnetic resistance formed at the
point K, on partial closure of the magnetic circuit for the cores of the coils. As will
be observed the effect and principle of operation are much the same as before
explained in connection with Figure 17, excepting that the partially closed path here
permits the added effect due to the beating back of the inducing magnetism in S,
and in effect results in a shunting from S, of the magnetism developed by coil P.
In the Figures 1 and 2, I have shown one form of my new construction of
transformer having a self regulating character. A, represents an are lamp, or a series
of arc lamps, fed with constant current from the secondary P, although the primary
coil S, is subject to constant potentials: The coils organized as shown in Figure 1, if

page_text: the distance between the projections e, e¹ be properly determined, will have the peculiar
property of producing in the secondary coil S, a droop or fall of electro-motive force
when the resistance is cut out of the circuit, and this fall may be made nearly pro-
portionate to the fall of the resistance, or diminishing resistance, in such circuit. The
space K, might be filled in whole or in part with solid or liquid substance such as
wood, paper, slate etc.
The partial closure of the magnetic circuit of the core I, may be produced outside
of both coils P, S, instead of between them as indicated in Figure 3, or a partial
magnetic closure may be provided at two points K, K, as indicated in Figure 4. In
the case of the arrangement shown in Figure 3, the coils P and S, might be inter-
changed in position on the core 1, 1. The core 1, might also take the form indicated
in Figure 5, without changing the essential character of the action.
The current or potential in the secondary might be regulated or adjusted in
accordance with changes therein by moving, by hand or by any mechanism, the pro-
jections e, e¹, towards one another, as by a screw W, shown in Figure 6, such screw
being operated by hand, or by applied means, so as to vary the magnetic closure at K,
in accordance with the effects desired in the secondary circuit. The nearer the pro-
jections e, e¹, are brought together the smaller will be the current given out in the
secondary S, and vice versa. The distance between the projections affects but little
the potential of coil S, on' open circuit, but when the coil is put to work its possible
current becomes limited in accordance with the distance between e, e¹:
Instead of operating the screw W, to regulate the current in the secondary coil in
accordance with changes of resistance in the same, said screw may be employed
simply to set the projections e, e¹, in definite relation to each other leaving the opera-
tions of the closure of the magnetic circuit at its resisting portion K, to be effected
in the manner already described by the bunching or increasing of the number of
lines of magnetic force passing across the space when the current increases in the
coil P, or in S.
The variation of closure of the magnetic circuit of the core may be effected by
still other means, as for instance by varying by hand or by other mechanism, or by a
self adjusting action, the insertion of a conductor such as a copper plate K' Figure 7,
in the magnetic field or lines of magnetic force through which the magnetism of the
core is closed upon itself. The conductor K, Figure 7, when fully inserted in the
air space between e, e¹, cuts off still further the passage of magnetism across from
one projection to the other through the setting up, by induction, in said conductor, of
strong currents of high self induction which oppose the magnetic effects. The action is
virtually to increase the magnetic resistance at this point. By drawing out the con-
ducting plate the amount of the current induction in the space is lessened and the
closure of the magnetic circuit of the core is improved with the effect of heightening
the self-inductive or reactive effects in the circuit of the current which excites the
core.
To make the action of the conductor K', automatic or self adjusting it may be
hung on a movable support, such as a lever L, and be permitted to come part way
between the projections e, e¹, as shown. When the current is flowing in the coils P,
the plate will tend to be repelled from the space. The spring Z, may be employed to
partially counterbalance the weight of the piece K. This device will still further
perfect the automatic action of the apparatus in delivering a constant current to the
coil S.
In Figure 9, the conductor K, is shown as a hollow frame of copper, or other good
conductor partially counterbalanced by a weight Z. This device being set so that
when current is passing in the coil P, it will be balanced in a position partly within
the space K, as in Figure 8. The secondary coil S, being at the same time in circuit
with its normal resistance, an action as follows will be produced.
If the resistance be partly cut off there will generally be a slight increase of current
in the coil.
The frame K', is thereby repelled outward from the slot and will compensate for
such increase, since a movement of K', outward, will result in a diminished current

page_text: in the coil S, under any conditions. The apparatus by suitable balancing can thus
be made accurately self adjustable, so that a constant strength of current, or an average
constant strength, is produced in the coil S, unless the resistance interposed exceeds
its proper limits..
Where the current to be obtained is to have properties between those due to
constant potential average and constant current average, the modification Figure 10,
may be adopted. One coil S', or part of the secondary winding is near the coil P,
or adjacent thereto, (or under or overlying the same) and the other part of the
secondary is, as at S, removed therefrom on the same core. In this case the terminals
of the secondary coils in series will deliver neither constant potentials nor constant
current, but if the resistance in the secondary be diminished the current will increase
but at a less rate than constant potential would give so that a limited current of
moderate strength flows even on short circuit.
Figure 11 shows a form of induction coil or converter having a self regulating
character like that of Figure 1. Between each primary coil and secondary the iron
of the core is extended inward to approach similar projections upon other points of
the core. The projections at their ends are separated by small spaces similar to the
spaces K, and over such space the variable closure of the magnetic lines from the
portions of core including the coils P'and S, is formed.
In Figure 12, the core itself is made as an interior ring wound with coils P, S, and
has an exterior ring closely enveloping it which outer ring may be joined to the
inner one between the alternate coils as shown. The variable closure of the magnetic
circuit occurs at the points e, e¹.
Figure 13, shows a form of core differing from that of Figure 1, only in outline.
To construct this form the core may be formed in two parts joined on the dividing
line X X.
Instead of employing the device shown in Figure 6, for varying the magnetic
closure, an arrangement such as shown in Figure 20, may be used, where the one
part c, slides to and from the other part in suitable guides formed in the magnetic
core [.
This movement may be used to primarily regulate the flow of current in the
secondary S, in obedience to changes in resistance, or the part may be set or adjusted
and left in position, the variable closure being then dependent solely upon the
number of fines of force which are concentrated across the space between the
projections e, e¹.
Figure 14, illustrates the application of the invention to the running of a series of
incandescent lights or other working resistance from the secondary coil S, the coil 1,
being connected with the constant potential alternating mains a, b. When the
adjustments are properly made one or even all the lights L, L, may be shunted by
switches of no resistance, and the current in the circuit of S, will be substantially
unchanged in amount i.c., the potential of the coil S, is self adjusting to the resistance
in the circuit unless the latter be too great.
Figure 15, shows how a wire L, may be maintained at a uniform temperature while
its length in circuits may be greatly varied, owing to constant current strength
obtained, notwithstanding constant potentials at a, b. For are light work, or for
electric furnaces or heating, as in Figure 16, my invention permits distribution at
constant potential to the coils and feeding to the work as at A', currents of constant
volume, or, as before indicated, of a volume much less increasing than in the ratio of
constant potential over the resistance in circuit.
It is not to be understood that with all the arrangements described there is an
absolute adjustment of the potential on the secondary so that an absolutely constant
current is obtained despite variations of resistance, and Figure 17 is intended only to
illustrate the principle of my invention in so far as it shows how diminution of
potential may be obtained automatically with a diminution in the resistance. In that
Figure, as in the arrangement shown in Figure 10, the current will increase but at
a less rate than constant potential would give but there would be an adjustment
which would prevent an abnormal rise of current in the secondary.
The introduction-of either coil S or S', as in Figure 17, will cause a rapid fall of

page_text: available potential at A, when the resistance diminishes, while at the same time the
lines a, b, are of constant difference of potential.
Figure 18, illustrates a modified arrangement resembling in some respects
Figure 10, and in others Figure 17. An ordinary induction coil P, S, with closed
magnetic core has in each of its circuits a coil P', or S¹, placed on a core and
combined after the manner of the coils P, S, Figure 1. By the variation of
magnetic closure of the cores, or portions of core of coils P1, S1, at K, a regula-
tion of current on the secondary circuit of S, S', of any desired character, according
to the character of adjustment, may be obtained.
Figure 19, shows the curve which may be called the characteristic curve of the
secondary currents in such a coil as Figure 1, the verticals or ordinates representing
the electro motive forces evolved, and the horizontals or abscissas the current strengths
corresponding thereto. At electro motive forces below 100, as marked the curve is
almost a vertical line, showing that a constant current is evolved at any resistance
below that corresponding to a potential of 100. The dotted curve represents the case
of drooping or falling potential with increase of current such as is obtained with the
special devices shown in Figures 10, 17 and 18.
Having now particularly described and, ascertained the nature of the said
invention 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 :-
First. The herein described method of adjusting, regulating or determining the
current or potential in the secondary of two coils or circuits placed in inductive rela-
tion, consisting in developing alternating magnetism through the action of the current
in each or either of said circuits in a suitable iron core and variably closing the
magnetic circuit of said core through a path independent, in whole or in part, of the
core or portion of core in which magnetism is developed by the other coil or
circuit.
Second. The herein described method of obtaining a substantially constant current
in the variable resistance circuit of a transformer fed from a constant potential source,
consisting in shunting the magnetism threading the two coils of the transformer in
variable amount as and for the purpose described.
Third. An induction coil or converter having an endless iron core or magnetic
circuit on which the primary and secondary coils are disposed at different points, and
having parts or extensions of said core brought into determinate magnetic inductive
proximity to form a partially closed magnetic circuit over the iron core and through
the coils.
Fourth. The combination with an induction coil or converter, of a partially
closed magnetic circuit excited by the current in each or either of the electric
circuits and a conducting plate movably suspended in a gap in such magnetic circuit
as and for the purpose described.
Dated this and dave of Amil 108