Improvements in Magnetic Cut-outs.
Year: 1896

page_text: Date of Application, 6th Aug., 1896
Complete Specification Left, 6th May, 1897-Accepted, 12th June, 1897
PROVISIONAL SPECIE
TION.
Improvements in Magnetic Cut-outs.
I, LEONARD ANDREWS, of 20 South Terrace, Hastings, Electrical Engineer
do hereby declare the nature of my said invention to be as follows:-
This invention relates to certain improvements on an invention previously
patented by me under the number 671 A.D. 1895 in which the object was to
provide a reliable cut-out for disconnecting from the omnibus bars any one of a
series of electric generators working in parallel to supply current through
a common system of mains in the event of the said generator becoming disabled
through the failure of the exciting current, a short circuit in the armature, or from
any other cause which shall tend to render it unable to maintain its customary
difference of potential at its terminals.
The present invention is for precisely the same purpose as the previous one
above referred to.
In practice it has been found the former arrangement would cut out with an
excess current or in the event of the shunt current becoming interrupted and this
is found to be undesirable.
In the new arrangement the normal position of the core is the centre of the coil,
and whatever the series current may rise to, that alone will not tend to move it.
I wind the shunt in two directions, half at. top and half at bottom, so that when
the machine is doing its work, the top winding will be helping the series and the
bottom winding opposing it, thus producing a field at the top only. Should the
series become reversed the field will be produced at the bottom and the switch will
cut out.
Dvd
1002
Improvements in Magnetic Cut-outs.
I, LEONARD ANDREWS, of 20 South Terrace, Hastings, Electrical Engineer,
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 certain improvements on an invention previously
patented by me under the number 671 of A.D. 1895 in which the object was to
provide a reliable cut-out for disconnecting from the omnibus bars any one of a
series of electric generators working in parallel to supply current through a common

page_text: system of mains in the event of the said generator becoming disabled through the-
failure of the exciting current, a short circuit in the armature or from any other
cause which shall tend to render it unable to maintain its customary difference of
potential at its terminals,
The present invention is for the same purpose as the previous one above referred
to. In practice it has been found the former arrangement would cut out with an
excess current, or in event of the shunt current becoming interrupted, and this is
found to be undesirable.
In the new arrangement, the normal position of the core is the centre of the coil
and whatever the series current may rise to that alone will not tend to move it.
My invention and the manner of carrying the same into practice will be fully
understood upon referring to the accompanying diagram which illustrates the
principle of the winding and general arrangement of the connections. As will be
seen the compound wound solenoid A is connected up practically as described in
my previous patent, the difference being that the shunt B is wound half in one
direction, as B', and half in the opposite direction, as B, and the normal position
of the core C is exactly in the centre of the coil.
Now suppose that the arrow heads represent the direction of the current through
all parts of the system at a particular moment when the machines on the bars are
generating current, then it will be seen that the direction of the current in the
shunt winding B' of the solenoid A. is opposite to that in the series D at the top
balf of said solenoid but in the bottom half both of the currents are flowing in
the same direction. The result is that the two windings neutralise each other at
the top but assist each other to produce a magnetic field at the bottom, the tendency
of which is to hold the core C and catch E down, and by this means making it
impossible for the cut out operating weight arm F to be released. Should however
the generator become disabled the direction of the shunt remains the same but the
series become reversed.
The shunt winding B' now opposes the series in the bottom half of the solenoid A
and helps it at the top, thus producing a magnetic field above the centre of the
solenoid A and causes the core C to spring up and litt the catch F supporting the
weighted arm E, which becoming released falls with accelerating force upon
the switch G which is thus opened to disconnect the faulty machine from the
.general supply.
The switch and weight can be reset by moving the lever H down to the dotted
line position.
The shunt circuit may be excited directly across the omnibus bars G', H', or
across the secondary of a transformer excited by the bars as desired. It is obvious
that the shunt current by itself will not have any effect upon the core C because
the two halves being wound in opposite directions will neutralise each other.
Again, the series winding alone will tend to hold the core in the centre of the coil
but as that is its normal position it will not be moved.
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. The use in connection with alternating current generators and transformers
of a compound wound magnetic device such as a solenoid with central core and
the thick winding of which is connected in series with an alternator or transformer
supplying current to the omuibus bars and having a thin coil wound in reverse
directions at the top and bottom of the solenoid and connected either directly
across the omnibus bars or across the secondary of a transformer excited by said
bars, all arranged substantially as shown in the diagram, and operating in the
manner and for the purpose described.
2. The combination of a compound wound magnetic device such as a solenoid
having the shunt circuit wound in reverse directions on the top and bottom thereof

page_text: respectively with a core, the normal position of which is in the centre of said.
solenoid, and a catch, weighted arm, switch, and lever, such as F, E, G, and H.
respectively, all operating in the manner set forth.
H. GARDNER,
Patent Agent, 166 Fleet Street, London,.
Agent for the said Leonard Andrews.
H. GARDNER,
Patent Agent, 166 Fleet Street, London,.
Agent for the said Leonard Andrews.