Improvements in Circuit Breakers for Three Wire Electricity Distribution Systems.
Year: 1898

page_text: Date of Application, 20th Sept., 1898-Accepted, 7th Jan., 1899
COMPLETE SPECIFICATION.
Improvements in Circuit Breakers for Three Wire Electricity
Distribution Systems.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of this
invention (which has been communicated to us from abroad by Edward M.
Hewlett, residing at Schenectady, State of New York, United States of America,
Electrical Engineer), and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
on
The present invention relates to an adaption of circuit-breaking apparatus to
the well known three wire electric distribution system, by which a "ground
one side or the other will operate the main circuit-breaker at the station.
In many three wire installations the neutral is grounded, and with this arrange-
ment only one circuit-breaker is as a rule employed in the station. If therefore
a ground occurs on either side of the system, the lamps or equivalent translating
devices will be burned out by excess of current. To obviate this, the present
invention has been devised, which consists, in addition to the ordinary circuit
breaker of the station, of a device like a relay magnet, having differential coils
included in the two sides of the three-wire system, and designed by the attraction
of its armature to close a circuit across the outside mains including an auxiliary
coil upon the circuit breaker, which will trip its latch and so open the circuit.
The accompanying drawings show the invention, Fig. 1 being a diagram of the
circuits; Fig. 2 a mechanical view with the circuits shown in dotted lines, and
Fig. 3 a side elevation of the two coils upon the circuit-breaker.
The mechanical embodiment of the invention will first be described, and there-
fore reference is first made to Fig. 2. In this figure, the circuit-breaker CB is
one of well-known type, embracing a bridging contact m connecting the two
terminals n, n'. This is the main circuit. A shunt to these terminals is indicated
in dotted lines in the upper part of the figure. This shunt is provided with
circuit breaking-contacts and the usual arc-disrupting means. A toggle lever P
is provided for closing the circuit, and a detent o engages with the pawl or trip O
connected to the armature K, operated by the coils D, D' in a way presently to
be pointed out. The spring P₁ serves to open the circuit when the pawl or latch O
is tripped. On the left in Fig. 2 is shown the relay device, comprising coils d, d'
wound differentially, acting to pull down the armature E¹, with which is con-
nected a bridging terminal E held away from the terminals H, H by the spring F,
and which, when drawn down by the armature, completes a circuit through the
coil D' upon the circuit-breaker.
In Fig. 3 is shown the arrangement of the coils, the coil D being the ordinary
series coil designed to operate on overload, the coil D¹ a shunt coil in circuit with
the relay device for operating the circuit-breaker under the peculiar conditions
set out in the statement of invention.
The circuits of the device are illustrated in Fig. 1, where the same reference
In Fig. 1A is
letters refer to the same parts as in the mechanical embodiment

page_text: the generator, and B, C are compensating dynamos for dividing the voltage of
the main generator in the way adapted to three-wire system. Of course the
generator might be omitted, and the dynamos B C represent a suitable divided
source of electro-motive force, without effecting the essence of the invention, this
modification being one readily understood by engineers. With either form of
the invention, a, b, c are the mains, positive, negative and neutral, the neutral
main being grounded at G. Leads from these mains are shown as a¹, b, c¹,
between which are coupled differential windings d, d of the relay device.
D, D are the series and shunt coils upon the circuit breaker CB. The differential
coils d, are substantially equal in effect so that the relay is normally not
operated by them, the bridging contact E being held out of contact with the
terminals H.
The operation of the apparatus is as follows: the main being grounded, and
the distribution of current proceeding in the usual way, if a ground occurs (on
the main c for instance) there will be no difference of potential across the terminals
of the coil connected between these mains; if the grounds were some distance
apart, there might be a slight difference of potential, but practically no current
would flow in this coil. The coil d therefore would energize the core of the relay
device, pulling down the armature and contact E, closing the circuit across the
terminals H. Current would then flow by the lead a through these terminals
around the shunt coil D¹ of the circuit-breaker to the grounded main c, and the
coil will then open the circuit-breaker. A similar action would take place should
the main a become grounded. While the general arrangement of the circuit-
breaker shown in the present application forms no part of the invention, it is
considered to be new in the present instance to apply to a circuit-breaker a main
coil and a shunt coil operated by different circuits to open the main circuit of the
station, or of any particular dynamo, under different conditions. It will be
readily perceived that the broader aspect of the invention is capable of many
useful applications, all of which could not be easily outlined in a single speci-
fication. It would be possible, as one example, to close the circuit of the coil D¹
by hand from different parts of the station so that in the event of any accident,
the main circuit could be at once opened.
Having now particularly described and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same is
to be performed, we declare that what we claim is:-
1. A circuit breaking device for a three-wire electric distribution system, com-
prising a main switch designed to act upon the circuit of a given dynamo, and a
relay device connected across and to each of the outside mains of the three-wire
system and in circuit with a coil upon the main switch, the relay device provided
with contacts closing the circuit of a coil on the main switch on excess of load
in either side of the three wire system.
2. A circuit breaking apparatus for use in a three-wire electric distribution
system, comprising a main switch having a plurality of coils, and a relay having
differentially wound coils connected in the two sides of the three-wire system,
with a circuit controlled by the relay including one of the coils upon the circuit-
-breaker.
3. In combination with an actuating coil upon a circuit-breaker in the main
circuit of the station, a relay magnet having differentially wound coils connected
respectively in the two sides of a three wire system, and a circuit aeross the
outside mains of the three wire system, including a shunt coil upon the circuit-
breaker and controlled by the relay magnet.
4. A circuit-breaker comprising a series coil opening the switch upon a definite
overload, another normally idle coil also arranged to open the circuit when
energized, a circuit including the second coil with a source of current, and a relay
device for opening and closing the exterior circuit.
5. The combination with a series or overload coil and the trip of a circuit-

page_text: breaker, of an additional or auxiliary coil also acting to open the circuit, and
included in another circuit controlled by a relay device.
6. The combination with a series coil carrying the main current and the trip
of a circuit-breaker, of a shunt coil acting to open the circuit and controlled by
exterior contacts.
7. The combination with a series or overload coil and the trip of a circuit-
breaker, of an additional coil acting to open the circuit and controlled by an
exterior circuit.
Dated : 2011. 1
1000