Improved Automatic Electromagnetic Interrupter for Protecting Electrical Installations.
Year: 1895

page_text: Date of Application, 27th Nov., 1895
Complete Specification Left, 27th Aug., 1896-Accepted, 24th Oct., 1896
PROVISIONAL SPECIFICATION.
[Communicated from abroad by COMPAGNIE POUR LA FABRICATION DES
COMPTEURS ET MATERIEL D'USINES À GAZ, of 29 Rue Claude Villefaux,
Paris, France.]
Improved Automatic Electromagnetic Interrupter for Protecting
Electrical Installations.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery
Lane, in the County of London, Consulting Engineer, and Chartered Patent
Agent, do hereby declare the nature of this invention to be as follows:-
As is known, the short-circuits which are accidentally produced in electric
installations cause great inconvenience. They subject electric lighting apparatus
to detrimental electrical and mechanical shocks; they cause a useless consumption
of energy; they render useless for a considerable time the part of the installation
where the short-circuiting occurs and lastly, the passage even during a very
limited time, of an intense current has a very hurtful effect upon delicate electro
magnetic apparatus, such as the measuring apparatus, or counters, which contain
magnets or iron parts.
The lead fuses hitherto employed do not obviate this inconvenience, as they
do not at all limit the maximum intensity of the current passing at the moment
of short circuiting. They only have the effect of breaking the circuit a short time
after the passing of the intense current. The same is the case with respect to the
various automatic electromagnetic interrupters now employed.
The present invention has for its object the construction of a new form of
interrupter which has the effect of combining a very short duration of interruption
with a very great self induction, so that, according to a well known law, the
circuit will be broken when the current has attained only a predetermined fraction
of the total value which it would attain without the use of the interrupter. No
matter how the short-circuiting is brought about, the apparatus does not allow the
current to pass a predetermined limit; it is therefore an interrupter with maximum
of current. This apparatus will advantageously replace the lead fuses (which may
however be left as a double security) in the sense that after having operated in
breaking the circuit where an accident has occurred, it is immediately ready to
operate again in simply setting its switch lever. If it be regulated for the same
limit of current as the lead fuses, it will break the circuit well before the fuse can
melt, so that the effect of the short circuit on the installation will be very greatly
diminished.
The apparatus is so adjusted that its action will take place on the passing
of a current slightly greater than the maximum current of the installation to
be protected. At the moment of short circuiting, the current instead of increasing
almost instantaneously to the value determined by the electromagnetic force and
the resistance, will increase gradually; as soon as it has attained the value
determined by the regulation, it will actuate the disengaging mechanism; the
current will continue to increase during the time necessary for the displacement of
the parts of the interrupter, but without attaining the limit value.
By suitably proportioning the self-induction to the time unavoidably necessary.
for the movement of the parts of the interrupter, the maximum current can be
reduced to a predetermined fraction of the limit current.

page_text: The ordinary interrupters cannot produce this limitation because the self
induction which they can present is much too feeble relatively to the time lost,
between the moment of starting the mechanism and that when the circuit is
broken.
The apparatus can be constructed in a variety of ways for carrying out the
above described principle of action.
The following is an arrangement which has proved advantageous.
Within a cylindrical casing, preferably of cast iron, is a comparatively large
core of soft iron or cast steel on which is coiled a wire included in the circuit to be
protected. The core has a central hole, in the upper end of which slides a plug of
soft iron that is pressed upward by an adjustable helical spring. The upper end
of the plug has two upward projecting pins that ordinarily take into two recesses
in the lower end of a stem carried by a head-piece fixed on the top of the electro-
magnet casing, and containing a cavity in which is a strong spiral spring, the inner
end of which is fixed to the cylindrical stem, so as to tend to rotate it. On the
upper end of the stem is fixed a crosshead of conducting metal, which, when the
apparatus is in the normal condition, presses with each end against a contact spring
connected to one of the screw terminals to which the circuit wire is attached, so
that the crosshead in this position, in making contact with the two springs closes
the circuit to be protected. The crosshead is ordinarily held in this position by
the before mentioned two pins engaging with the recesses in the lower end of the
stem fixed to the crosshead, and when in that position, the spiral spring has a
considerable tension upon it, tending to move the crosshead away from the spring
contacts. When a current of predetermined maximum strength is passing through
the circuit and electromagnet coil, the downward attractiou exercised by the core
upon the soft iron plug is not sufficient to overcome the upward pressure exerted
upon the latter by the helical spring, and the circuit is consequently maintained
closed.
the
As soon however as such maximum strength of current is exceeded, owing to
short circuiting in the installation, the consequent increase in the attractive force
of the electromagnet due to its considerable self-induction will cause the soft iron
plug to be drawn down against the action of the helical spring, thereby releasing
upper stem from its pins, and the stem will consequently be rapidly rotated by
its spiral spring so as to bring it out of contact with the terminal springs, thereby
breaking the circuit, and this, owing to the great self induction of the electro
magnet, will take place before the strength of the current has increased sufficiently
to exceed a predetermined fractional amount of the total strength to which it
would otherwise be capable of rising.
Dated this 27th day of November 1895.
ABEL & IMRAY,
Agents for the Applicant.
Improved Automatic Electromagnetic Interrupter for Protecting
Electrical Installations.
I, CHARLES DENTON ABEL, of No. 28 Southampton Buildings, Chancery Lane,
in the County of London, Consulting Engineer, and Chartered Patent Agent, do
hereby declare the nature of this invention and in what mauner the same is to be
performed to be particularly described and ascertained in and by the following
statement :-
As is known, the short-circuits which are accidentally produced in electric
installations cause great inconvenience. They subject electric lighting apparatus

page_text: to detrimental electrical and mechanical shocks; they cause a useless consumption
of energy; they render useless for a cousiderable time the part of the installation
where the short-circuiting occurs and lastly, the passage, even during a very
limited time, of an intense current has a very hurtful effect upon delicate electro-
magnetic apparatus such as the measuring apparatus, or counters, which contain
magnets or iron parts.
The lead fuses hitherto employed do not obviate this inconvenience, as they do
not at all limit the maximum intensity of the current passing at the moment of
short circuiting. They only have the effect of breaking the circuit a short time.
after the passing of the intense current.
The same is the case with respect to the various automatic electromagnetic
interrupters now employed.
The present invention has for its object the construction of a new form of
interrupter which has the effect of combining a very short duration of interruption
with a very great self induction, so that, according to a well known law, the circuit
is broken when the current has attained only a predetermined fraction of the total
value which it would attain without the use of the interrupter. No matter how the
short-circuiting is brought about, the apparatus does not allow the current to pass
a predetermined limit, it is therefore an interrupter at maximum of current.
This apparatus will advantageously replace the lead fuses (which may however
be left as a double security) in the sense, that after having operated in breaking
the circuit where an accident has occurred, it is immediately ready to operate again
in simply setting its switch lever.
If it be regulated for the same limit of current as the lead fuses, it will break
the circuit well before the fuse can melt, so that the effect of the short circuit on
the installation will be very greatly diminished.
The apparatus is so adjusted that its action will take place on the passing of a
current slightly greater than the maximum current of the installation to be.
protected. At the moment of short circuiting, the current instead of increasing
almost instantaneously to the value determined by the electromagnetic force and
the resistance, will increase gradually; as soon as it has attained the value.
determined by the regulation, it will actuate the disengaging mechanism; the
current will continue to increase during the time necessary for the displacement of:
the parts of the interrupter, but without attaining the limit value.
By suitably proportioning the self induction to the time unavoidably necessary
for the movement of the parts of the interrupter, the maximum current can be
reduced to a predetermined fraction of the limit current.
The ordinary interrupters cannot produce this limitation because the self
induction which they can present is much too feeble relatively to the time lost,
between the moment of starting the mechanism and that when the circuit is
broken.
The apparatus can be constructed in a variety of ways for carrying out the
above described principle of action.
An arrangement of the apparatus which has proved advantageous is shewn by
the accompanying drawings,
Fig. 1 being a section, Fig. 2 a plan and Figs. 3, 4 and 5 shewing details.
Within a cylindrical casing A preferably of cast iron, is a comparatively large
core B of soft iron or cast steel on which is coiled a wire C forming part of the
circuit to be protected and such as practically to saturate the core by the instan
taneous maxiinum current which may be attained.
D is a piece arranged to oscillate about the centre and carrying a spring
contact E bearing against the contact I which is connected through the coil C with
a spring contact 2. Two other contacts 1 and 2¹ can become connected by the
block F which is inserted at the right moment between the springs G and H
attached to 1' and 2¹.
A projection a from the plate I which is attached to the handle K and carries

page_text: the block F gives motion to D in the one direction or the other by bearing against
the lip bor b. A spring L always urges the contact E away from 1.
A roller c carried by D when the circuit is closed, has its end engaged in a
notch d (see Fig. 3) formed in the edge of a plate P which is the armature of the
electro magnet and is always urged upwards by the spring f. For closing the circuit,
the handle K is moved to the left turning D and causing c to roll along the edge
of P until it becomes engaged in the notch d, the springs E are by this movement
brought to bear on 1.
The handle is then moved to the right pushing the block F in between the
springs G and H, but not moving back E as there is free space for a to move
between band .
Thus the circuit is closed through 1, contact E, coil C, 2, 21, H, G and 11.
When the current is of too great intensity, the attraction of core B overcomes
the spring drawing down P and so disengaging c from the notch d, and releasing D
which is drawn back by the spring L breaking the contact at 1 and so opening
the circuit. Besides the spring contact E there is a carbon contact m which being
the last to leave 1 is subject to the spark, and when damaged can be readily
replaced. By depressing an external knob the plate P can be made to release c
from its notch d thus causing the opening of the circuit.
To prevent lateral movement of P it is connected to B by a spring r as shewn
in Figs. 4 and 5.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. An automatic interrupter of excessive electrical current, wherein the
magnetic force resulting from the action of the current effects a sudden opening of
circuit.
2. The combination of an interrupter such as is above referred to with electrical
instruments or installations for the purpose of protecting them from the effects of
excessive currents.
3. The construction of interrupter substantially as described with reference to
the drawings.
Dated this 27th day of August 1896.
ABEL & IMRAY,
Agents for the Applicant.