Improvements in the Construction and Arrangement of Switches for use in connection with Electric Generators, especially applicable to Alternators and their Exciters.
Year: 1892

page_text: Date of Application, 22nd Dec., 1892
Complete Specification Left, 22nd Sept., 1893-Accepted, 28th Oct., 1893
PROVISIONAL SPECIFICATION.
Improvements in the Construction and Arrangement of Switches for
use in connection with Electric Generators, especially applicable
to Alternators and their Exciters.
I, JOHN SMITH RAWORTH, of 112 Belvedere Road, Lambeth, in the County
of Surrey, Engineer, do hereby declare the nature of this invention to be as
follows:-
The object of my invention is to reduce the danger of accidents occurring
either in connecting dynamos with or disconnecting them from the main con-
ductors or omnibus bars of a generating station by means of switches, or in
performing similar operations in connection with the exciting dynamos when such
are used.
My invention is of general application, but is more particularly useful with high
tension alternating currents, with which up to the present time considerable
difficulties have been experienced, owing firstly to the tendency of high tension
alternating currents to form long and dangerous arcs, and secondly to the
inexperience or nervousness of attendants who have at times closed the switches
in the wrong order with disastrous results.
As the application of my invention to alternating current circuits is slightly
more complicated than its application to direct current circuits, I will describe the
arrangement for the former, mentioning such appliances as are not common to
both.
My invention applies to any system where two or more exciters are connected in
parallel for the purpose of exciting several dynamos in parallel. In such cases it is
usual to have a system of main conductors through which the several exciters feed
the several main dynamos and with or from which the various exciters or main
dynamos may be connected or disconnected as circumstances may require.
For facilitating these operations I employ a switch so constructed that it can
only be closed when the difference of potential at the terminals of the exciter is
approximately the same as that in the main exciting conductors and that it will
automatically break the current whenever from any cause the exciter may cease to
transmit current to the said mains.
In constructing this switch I employ two magnets between which is placed an
iron armature carried by the movable arm or rod of the switch; at each extremity.
of its movement it comes actually or nearly into contact with one or other of the
above mentioned magnets. When the switch is open the armature is in contact
with one of the magnets which is differentially wound with a derived circuit or
shunt on the main exciting conductors and with a shunt circuit in the opposite
direction on the leads of the exciter. The switch therefore cannot be closed until
the magnet is neutralised by reason of the difference of potential at the dynamo
being practically equal to or slightly greater than the difference of potential
existing in the main exciting conductors. When this occurs the switch can be
closed by hand or by a weight or spring attached to the lever.
When the switch is closed the armature is nearly in contact with the other
magnet which is series wound so that the whole or a portion of the current
from the exciter passes through it; but if the current from the exciter ceases from
any cause, the magnet releases its hold on the armature and allows the switch to
open by gravity.
This part of my invention is applicable to all continuous current dynamos
arranged to work in parallel, whether they be used as exciters or principal

page_text: For convenience I combine the above described switch with the usual ammeter
and voltmeter in a cast iron pillar which may be placed close to the stop valve or
regulator of the engine or other source of motive power.
Further my invention relates to the, switching arrangements of the principal
generators as follows:-
First. I make the handles of the switches interlocking so that the operations can
be effected! only in the following order :-
Close field switch
Close synchroniser switch (for alternators)
Close main switch
Open synchroniser switch
Close synchronising switch
Open main switch
Open field switch
Open synchroniser switch
}
or vice versa.
This I effect by the use of a star motion similar to that applied to the winding 1
arrangement of Geneva watches or its equivalent. For greater safety I apply a
catch or detent in connection with the main switch, which is not released until the
field current has attained sufficient strength. This is done by a solenoid or magnet
wound in series with the field circuit.
Also for greater safety I employ in connection with the main switch, a solenoid:
or magnet differentially wound in two shunts or derived circuits from the omnibus
bars and from the dynamo leads respectively, so that great resistance to the closing
of the switch is offered when and only when the incoming alternator is not in phase.
with the other or others.
may also combine with the synchroniser switch. a. short circuiting, switch, in
connection with an impedance or choking coil in series with the main circuit. The
object of the said. impedance.coil is to reduce the violence of the synchronising,
effort exerted by the current in the event of the main switch being closed with. the
dynamos out of phase.
I construct the. main switches in a special manner to minimise the risk of the
formation of dangerous arcs in breaking contact. I prefer to use a switch of the.
plunger pattern the contact pieces of which are immersed in water over which
floats a layer of oil. On withdrawing the plunger from the. socket or contact.
pieces the spark or arc is much reduced by the water and effectually extinguished.
by. the oil.
Dated this 22nd day of December 1892:
3
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION..
Improvements in the Construction. and. Arrangement of Switches for
use in connection with Electric Generators, especially applicable
to Alternators and their Exciters..
I, JOHN SMITH RAWORTH of 112 Belvedere Road, Lambeth, in the County of
Surrey, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascer-
tained in and by the following statement:-
The object of my invention is, to reduce the danger of accidents occurring either
in connecting dynamos with or disconnecting them from the main conductors or
omnibus bars of a generating station by means of switches, or in performing similar
operations in connection with the exciting dynamos when such are used.

page_text: My invention is of general application, but is more particularly useful with high
tension alternating currents, with which, up to the present time, considerable
difficulties have been experienced, owing firstly to the tendency of high tension.
alternating currents to form long and dangerous arcs, and secondly to the
inexperience or nervousness of attendants who have at times closed the switches in
the wrong order with disastrous results.
As the application of my invention to alternating current circuits is slightly
more complicated than its application to direct current circuits, I will describe
the arrangement for the former, mentioning such appliances as are not common
to both.
My invention applies to any system where two or more exciters are connected in
parallel for the purpose of exciting several dynamos in parallel. In such cases it
is usual to employ a system of main conductors through which the several exciters
feed the several main dynamos, and with or from which the various exciters or
main dynamos may be connected or disconnected as circumstances may require.
For facilitating these operations I employ a switch so constructed that it will
close when, but not until, the difference of potential at the terminals of the exciter
is approximately the same as that in the main exciting conductors, and that it will
automatically break the circuit of the exciter whenever from any cause the exciter
may cease to transmit current to the said mains.
In the accompanying drawings,
Figs. 1 and 2 are elevations at right angles to each other showing a switch of
this kind. It comprises two solenoids or electro-magnets A B between which is
placed an iron armature C carried by a rod D which constitutes the movable rod
of the switch and to which the movable contact E is secured. At each end of the
movement of this rod, the said armature C comes actually or nearly into contact
with one or other of the above mentioned solenoids The solenoid A with which
the armature is in contact when the switch is open is wound differentially, one set
of coils being in a derived circuit or shunt on the main exciting conductors, and
the other set being in a shunt on the leads of the exciter and wound in the opposite
direction to the first set. Consequently it is not until the action of the solenoid on
the armature C is neutralised by reason of the difference of potential at the
terminals of the dynamo being partially equal to or slightly greater than the
difference of potential existing in the main exciting conductors, that the said
armature C is released to allow of the closing of the switch. When this occurs the
switch can be closed by hand or by a weight or spring attached to the lever. I
prefer however to employ for this purpose the arrangement illustrated in which
F is a weighted lever loosely mounted on a rock shaft G to which at one end is fixed
a disc H having a notch I in which the tooth of a pawl J carried by the lever F
engages. At the other end of the shaft G is a crank whose pin K bears against
the underside of a projection L on the rod D so that when the crank pin is moved
upward it carries the rod with it, whilst when the rod is moved downward it
depresses the pin and turns the crank in the opposite direction. A fixed stop M
is arranged in proximity to pawl J in such a position that it engages with the
tail J' of the said stop when the lever F turns, and consequently disengages the
said pawl from the notch I in the disc H. It will thus be seen that so long as
the armature C is kept down by the attraction of the solenoid A the weighted
lever and connected parts will be maintained in the position shown in Fig. 1 in
which position they are placed or adjusted originally by hand. When however
the armature C is freed from the attraction of the solenoid A, the weighted
lever F partly rotates the disc H and consequently the crank K thereby raising
the rod D and forcing the contact piece or pieces E between the terminal or
terminals E' there being two such terminals in this case marked respectively +
and By the time the contact piece E is in position the tail J¹ of the pawl .J
comes against the stop M and the pawl is disengaged allowing the lever F to fall
by gravity. At this time also the armature C is brought into close proximity to
the solenoid B.

page_text: This solenoid B is series wound, and the current from the exciter, or a portion
thereof, passes through it, thereby serving to keep the armature and connected
parts raised after the lever F has been released. Should however the current
from the exciter cease from any cause, the solenoid B will release its hold on the
armature and allow the switch to open by gravity.
This part of my invention is applicable to all continuous current dynamos
arranged to work in parallel whether they be used as exciters or principal
generators.
5
For convenience I combine the above described switch with the usual ammeter
and voltmeter in a cast iron pillar which may be placed close to the stop valve or 1
regulator of the engine or other source of motive power.
My invention also relates to the switching arrangements of the principal
generators as follows:-
First I make the handles of the switches interlocking so that the operations can
be effected only in the following order :-
Close field switch
:-
Close synchroniser switch (for alternators)
Close main switch
Open synchroniser switch
Close synchronising switch
Open main switch
Open field switch
Open synchroniser switch
}
or vice versa.
This I effect by the use of a star motion similar to that applied to the winding
arrangement of Geneva watches or its equivalent. For greater safety I apply
a catch or detent in connection with the main switch which is not released until 2
the field current has attained sufficient strength. This catch or detent is
controlled by a solenoid or magnet wound in series with the field circuit.
construct the main switch in a special manner to minimise the risk of the
formation of dangerous ares in breaking contact. I prefer to use a switch of
the plunger pattern the socket or contact pieces of which are immersed in water
over which a layer of oil is or may be provided. On withdrawing the plunger
from the socket or contact pieces, the spark or arc is extinguished or much
reduced by the water and effectually extinguished by the oil, if it should extend
through the water.
These parts of my invention are illustrated in the remaining figures of the
accompanying drawings of which
Fig. 3 is a general diagrammatic view partly in section and
Figs. 4 and 5 are detail views.
The
N, O, & P are three switch handles which are interlocked, and of which N
controls the circuit for the synchronising device, O controls the main switch, and P
the exciting circuit for the field magnets of the generator. These are interlocked
respectively by means of the three contiguous stop discs N' O' P', mounted on
their respective spindles or axles. The two outer discs N' and P¹ are formed with
recesses N and P respectively, while the inner wheel O is formed with two
corresponding recesses 03, 0³, arranged diametrically opposite each other.
relative arrangement of the discs is more clearly shown in plan in Fig. 5. The
discs and P¹ have corresponding lateral projections O' and P2 which interlock
when brought into proximity as will be readily understood. To guard against
closing of the main circuit before the proper potential has been reached, an electro-
magnetic locking device is provided which locks the disc O¹, until such time as the
generator is giving the working potential. This locking device comprises a catch Q
adapted to take into a notch O in the disc O' and carried by the armature Q
of a solenoid or electro-magnet. Q. The catch is kept in engagement with the
disc O¹ by a spring or springs Q³ capable of adjustment, and whose force is so

page_text: regulated that when the potential reaches the proper degree, the armature is
attracted and the catch is withdrawn, thereby permitting the disc O' and the
handle connected therewith to be operated when unlocked by the disc N¹
and P¹.
The main switch proper comprises a pair of plugs R adapted to enter spring
fingers or sockets S, and carried by rods R' which work in cylinders T¹ secured
each upon the upper part of a case or cell T of insulating material. The rods R¹
are secured to pistons R* formed of metal gauze stampings or otherwise suitably
arranged to make efficient electrical contact with the inner walls of the cylinders T
The said plugs are operated from the handle O, through the medium of rods R
which pass through the upper ends of the cylinders T and are secured to a cross
bar U of insulating material which is carried by a rod V mounted between suitable
rollers or guides V₁ and connected at its lower end by means of a connecting rod V2
with a crank pin O' on the disc O'. By this means when the handle is turned
in one direction the plugs R are brought into proper contact with the spring
fingers or sockets S and the main circuit is completed through the said fingers or
sockets and plugs, the rods R' and the walls of the cylinders T¹, the main leads
terminating at the said cylinders and fingers. By a movement of the handle O in
the opposite direction the circuit is of course opened.
Undue sparking in opening the circuit is prevented by partly filling each
cell T with water W and oil W', the spark or arc produced on breaking con-
tact, if sufficiently powerful to pass through the water being extinguished by
the oil above it.
A special switch may be provided for closing the exciting circuit, comprising
a bell crank switch lever X, spring contact fingers X' between which the free
end of the switch lever X can pass, and auxiliary carbon contacts X'X' for
preventing sparking between X and X'. The movable carbon contact is carried
by a lever X3 pivoted coaxially with the lever X and provided with a spring X
which tends to pull the carbon contacts together. The lower arm of the switch
lever X is connected by a rod P³ with a crank pin on the disc P¹ whereby it
is operated. In its turn this switch lever X actuates the lever X' of the
auxiliary contact, by means of a projection or heel X which bears against the
lower arm of the said lever X3 as shown. The size of the projection or heel
and the range of movement of the parts is so arranged that there is a certain
amount of lost motion between X and X so that the auxiliary contacts X'X'
will be closed by the action of the spring X* before X and X' come into
contact, and will remain in contact, or at least in arcing distance, until X and X'
have passed out of contact.
In the case of the handle N a spring N³ is connected to a pin on the disc N¹
in order to give a quick closure of the switch connected therewith.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. For connecting and disconnecting a dynamo, working in parallel with
another dynamo or dynamos, to and from the mains, a switch in which the
movable contact of the switch is controlled by two solenoids or electro magnets,
one of which is arranged to be placed in the circuit of the switch when the
same is closed, and the other of which is wound differentially with two sets of
coils of which one set is in a shunt between the said mains and the other set
is placed in a shunt circuit between the terminals of the said dynamo and is
wound in an opposite direction to the other, the arrangement being such that
the switch cannot be closed until the difference of potential between the terminals
of the dynamo is equal, or approximately so, to that between the said mains,
and that upon the said dynamo ceasing to supply current, the switch will
automatically disconnect it from the said mains substantially as herein described.
2. My improved switch for automatically connecting and disconnecting a

page_text: dynamo that works in parallel with another dyuamo or dynamos to and from
electric mains, constructed, arranged, and operating substantially as hereinbefore
described with reference to and shewn in Figs. 1 and 2 of the accompanying
drawings.
3. A switching arrangement for use with electrical generators working in
parallel in which the handles of separate switches controlling independent circuits
are interlocked with each other in such a manner that the switches or some of
them can only be operated in a certain predetermined order or sequence sub-
stantially as herein described for the purpose specified.
4. A switching arrangement of the kind referred to in the preceding claim in
which the several switch-handles are provided with discs having cut-away portions
after the manner of Geneva stops and arranged to interlock with each other
substantially as hereinbefore described with reference to and shown in Figs. 3, 4
and 5 of the drawing annexed for the purpose specified.
5. A switch wherein in order to prevent injurious sparking, the fixed contact
portion of the switch is immersed in water above which floats a layer of oil
substantially as and for the purpose hereinbefore described.
6. The improved switching arrangement shown in and described with reference
to Figs. 3, 4 and 5 of the drawing annexed and comprising the switch handles
with interlocking discs the electro-magnet catch or detent for the main switch
handle and the main circuit switch with the fixed contacts immersed in water,
whether or not oil be placed above such water, as set forth.
Dated this 22nd day of September 1893.
W. LLOYD WISE,
Per W. Cross,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.