Improvements in Magnetic Cut-outs.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improvements in Magnetic Cut-outs.
I, LEONARD ANDREWS, of 20 South Terrace, Hastings, Electrical Engineer,
do hereby declare the nature of this invention to be as follows:-
The object of my invention is 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.
It is well known that with the fusible wire and magnetic cut-outs now in use for
this purpose it often happens that the generators which are not disabled get dis-
connected from the circuits before the faulty one since the others have to supply
the current for the mains in addition to that required to cause the disabled one's
cut-out to act. To overcome this difficulty, I take any form of series magnetic
cut-out now in use and wind upon the actuating solenoid, a shunt winding, which
is connected directly across the omnibus bars supplying the mains, or in any other
manner, provided that the variations in phase of the current passing through the
shunt shall always correspond with that of the current in the mains, preferably in
the case of high tension alternating currents across the secondary of any transformer
connected to the said omnibus bars.
The shunt winding is so connected that the current passing through it will be
in an opposite direction to the current from the generator to which it is connected,
provided that the said generator is supplying current to the mains, consequently
there will be little or no pull upon its core or plunger, but in the event of any
failure in the generators supply causing it to receive energy from the supply mains,
the current in the series and shunt windings on the solenoid will go in the same
direction, and consequently will assist each other to pull in the plunger, thus
releasing the weight, or other arrangement employed for controlling the cut-out.
1
1005
H. GARDNER,
Patent Agent, 166 Fleet Street, London,
Agent for the said Leonard Andrews.
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:-
The object of my invention is to provide a reliable cut-out for disconnecting
from the omnibus bars any one of a series of high tension electric generators
working in parallel to supply current through a common system of mains in the

page_text: 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.
It is well known that with the fusible wire and magnetic cut-outs now in use for
this purpose, it often happens that the generators which are not disabled get dis-
connected from the circuits before the faulty one, since the others have to supply
the current for the mains in addition to that required to cause the disabled one's
cut-out to act. To overcome this difficulty, I take any form of series magnetic
cut-out now in use and wind upon the actuating solenoid, a shunt winding, which
is connected directly across the omnibus bars supplying the mains, or in any other
manner, provided that the variations in phase of the current passing through the
shunt shall always correspond with that of the current in the mains, preferably,
across the secondary of any transformer connected to the said omnibus bars.
The shunt winding is so connected that the current passing through it will be i
an opposite direction to the current through the series winding from the generator
to which it is connected, provided that the said generator is supplying current to
the mains, consequently there will be little or no pull upon its core, but in the
event of any failure in the generator's supply causing it to receive energy from the
supply mains the current in the series and shunt windings on the solenoid will be
in the same direction, and consequently will assist each other to pull in the core,
thus releasing the weight or other arrangement employed for controlling the
cut-out.
My invention will be understood upon reference to the accompanying diagram
in which A is a compound wound solenoid, the winding B of which is in series
with an alternator C.
A shunt winding D is wound upon the solenoid which is directly connecte
across the omnibus bars H, H, supplying the mains. I prefer to attach the shunt
winding across the secondary of any transformer connected with the omnibus bars.
The shunt D is arranged so that the current passes through it in the opposite
direction to that passing through the series B from the generator C as indicated
by the arrow heads in the diagram a.
By causing the current in the shunt winding D of the solenoid to flow in an
opposite direction to that in the series it follows one tends to neutralize the
magnetic effect of the other, so long therefore as the current is flowing in opposite
directions in the solenoid (as would be the case when the alternator to which it
is connected is generating current and is in proper phase) there will be little or no
pull upon the core G, but in the event of the failure of the generator C causing
it to receive energy from the omnibus bars H, H, then the current will tend to
flow in the same direction through, both windings, the joint magnetic effect being
sufficient to pull the core and by overbalancing the catch I to release the weighted
lever J which hitherto has been held in position by said catch.
The weighted lever is pivoted upon, the centre K and works in the slots L
cut in the drum that carries a short circuiting plug M, so that when said lever J
drops to the position shown in dotted lines its accumulated force while travelling
through the slot L is sufficient for it to (on striking the opposite sides of said
slot) rotate the drum and withdraw the plug M thus disconnecting the alternator C
from the omnibus bars H, H, until the weighted lever J is re-set by turning the
handle N upwards when the spring P (which also acts as a check to the falling
weighted lever) will draw upon the chain Q and pull the weighted lever J up until
it engages behind the catch I.
By the foregoing arrangement a switch is provided which will act automatically
to disconnect the generator in the event of a return current tending to enter the
generator; or through an abnormally high forward current as in the case of a
short circuit.
It is to be understood that the accompanying drawing is, simply a diagram to
explain the connections and direction of the current's flow and is in no way intende
to represent the actual construction of the parts, and although solenoids only are

page_text: referred to I may without departing from my invention use one or more compound
electro magnets. Or I may put an additional winding on the solenoid and employ
the currents induced in same to release a magnetic catch or melt a fusible wire
holding the weight in position, also other methods depending upon the arrangement
of windings described.
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 :-
The use in connection with alternating current electric generators and trans-
formers coupled in parallel, of a compound wound magnetic device having the
thick winding connected in series with an alternator or transformer supplying
current to a pair of omnibus bars, and having a thin coil connected either directly
across the omnibus bars, or across the secondary of a transformer excited by the
said omnibus bars, the direction of the current in the two windings relatively to
each other being such that so long as the current in the generator is pulsating
synchronously and in phase with the current in the omnibus bars, the combined
magnetic effects of the two windings will produce little or no magnetism, but
which when pulsating in opposite phase will combine to disconnect the generator
from the main circuit, as described.
TL 10
1
1002
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.