System of Electric Distribution for Combined Lighting and Traction Plants.
Year: 1896

page_text: Date of Application, 16th Dec., 1896
Complete Specification Left. 10th Sept. 1897-Accepted. 6th Nov. 1897
PROVISIONAL SPECIFICATION.
A System of Electric Distribution for Combined Lighting and
Traction Plants.
We, ALEXANDER BEWICKE BLACKBURN, Manager of the Electric Construction
Company Limited of Wolverhampton and WILFRID L. SPENCE of Dunluce
Tettenhall Road Wolverhampton aforesaid, Civil Engineer, do hereby declare the
nature of this invention to be as follows:-
This Invention has for its object to effect the simultaneous distribution of
electricity from generating plant common to both lighting and traction systems
and it is designed to provide adequate means for the regulation of the current of
either of these systems without interference with the other of them.
It consists in the combination with generators earthed on one pole by the return
Railway circuit, of a two wire lighting net work correspondingly earthed (or
having the like pole at earth potential) and fed through reducing transformers at
a pressure appreciably less than that available for the Railway and preferably
about one half of the same.
The reducing transformers should be of the variable-ratio type with a normal
transformation of about one to one. The lighting circuit will be tapped on the
one side at the earthed pole and on the other at the junction between the two
armatures of the reducer.
In those cases where either the Railway or the lighting circuits extend beyond
the limits of economical feeding, the former direct and the latter by reduction as
set forth, the generators are arranged to give by means of two armatures in series
twice the normal railway pressure, which then becomes the standard for all long
feeders, both railway and lighting.
Outlying circuits of the former are fed by reducers, which may, or may not, be
of the variable ratio type, and the remote lighting net works are supplied by
complete transformation so that the distribution can be on a three-wire system
electrically separate from the others. This enables a higher pressure to be used
and the middle wire to be earthed if necessary.
The system is clearly illustrated by the following example.
The generators in this example are presumed each to have a double wound
armature and two 500 volt commutators connected in series. The negative pole
is earthed by connection to the Railway return circuit and local trolley wires are
fed at 500 volts direct from the first positive brush.
All lighting, within a radius of say 1½ miles, is carried out on a two-wire
system with earthed negative, and say 220 to 250 volt lamps, current being tapped
from the 500 volt generator brush and reduced in one-to-one variable ratio trans-
formers. For the outlying districts, the 1000 volt pressure from the second positive
brush is used. Current is conveyed by suitable feeders to sub-stations in which
one-to-one transformers reduce it to 500 volts for the trolley wires. The lighting
demand is met by current entirely transformed from 1000 volts to the lamp pressure

page_text: or to twice this in the case of a three-wire system, suitable balancing machines
being employed to equalise the load on the positive and negative circuits.
By the use of this combination of apparatus all generators can be of the same
type and may be interchangeable and those in operation may be coupled in parallel
and simultaneously feed both local and outlying railway and lighting circuits.
The reducing transformers, while of a size corresponding to only one half the
demand, have an extremely high efficiency of conversion. Thus for 100 Kilo-
watts, demand a reducing transformer with one-to-one ratio only carries 50 Kilo-
watts on each winding its efficiency may be 93 per cent. but as only one half the
consumption is transformed the efficiency of reduction is 93 or over 96 per cent.
The local lighting circuits, although only two-wire at 220, 230, 240, or 250 volts,
are fed at the same pressure as a three-wire system and will therefore cover an
equal area.
The use of a concentric system of wiring on consumer's premises does away with
the objection of an earthed negative pole and puts them on the same basis as if the
distribution were three-wires with carthed neutral. The variable-ratio reducing
transformers may be compound wound, as described in the Specification of Letters
Patent No. 24296 of 1895, granted to us, or controlled by hand as set forth in the
Specification of Letters Patent No. 11153 of 1895 granted to us.
For the suburban lighting circuits, which will have a much smaller density of
lamp connections, a three-wire system of distribution becomes very desirable, and
in order to secure this as well as for the additional safety gained, the current should
be entirely transformed and not merely reduced from the 1000 volt feeders. By
this means the neutral wire may be earthed and very considerable distances may be
covered from each sub-station.
The use of variable-ratio reducers and transformers for the lighting services
will enable the station pressure to be varied to correspond with the traction demand
without affecting the constancy of pressure on the lamp circuits. Or the converse
arrangement may be employed if the consumption for lighting purposes be the
greater.
In any case, storage battery auxiliaries may be used for either service, or for
both. Instead of a booster for charging them from the corresponding circuit, the
variable-ratio reducer may be used taking current from the circuit of higher
pressure. Thus for the 250 volt lighting battery, current may be taken from the
500 volt Trolley wires, for the 500 volt three-wire lighting and for the traction
batteries it can be taken from the 1000 volt feeders...
1 TY
1000
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.
A System of Electric Distribution for Combined Lighting and
Traction Plants.
We, ALEXANDER BEWICKE BLACKBURN Manager of the Electric Construction
Company Limited of Wolverhampton and WILFRID L. SPENCE of Dunluce,
Tettenhall Road Wolverhampton aforesaid, Civil Engineer, do hereby declare the 4
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 has for its object to effect the simultaneous distribution of
electricity from generating plant common to both lighting and traction systems

page_text: and it is designed to provide adequate means for the regulation of the current of
either of these systems without interference with the other of them.
It consists in the combination with generators earthed on one pole by the return
railway or traction circuit of a two-wire lighting network correspondingly earthed,
(or having the like pole at earth potential), and fed through reducing transformers
at a pressure appreciably less than that available for the railway or traction, circuit,
and preferably about one half of the same.
The reducing transformers should be of the variable-ratio type, with a normal
transformation of about one to one. The lighting circuit is tapped on the one side
at the earthed pole, and on the other, at the junction between the two armatures
of the reducer.
In those cases where either the railway, or traction circuit, or the lighting
circuit, extends beyond the limits of economical feeding, the former direct and the
latter by reduction as set forth, the generators are arranged to give, by means of
two armatures in series, twice the normal railway or traction pressure, which then
becomes the standard for all long feeders: both railway or traction, and lighting.
Outlying circuits of the former are fed by reducers, which may, or may not,
le of the variable-ratio type, and the remote lighting networks are supplied by
complete transformation, so that the distribution can be on a three-wire system
electrically separate from the others. This enables a higher pressure to be used,
and the middle wire to be earthed, if necessary.
The system is clearly illustrated by the following example:-
The generators in this example, are presumed each, to have a double wound
armature, and two 500 volt commutators connected in series. The negative pole
is earthed by connection to the railway return circuit, and local trolley wires are
fed at 500 volts direct from the first positive brush.
All lighting, within a radius of say 1 miles, is carried out on a two wire system
with earthed negative, and say 220 to 250 volt lamps; current being tapped from
the 500 volt generator brush, and reduced in one-to-one variable ratio transformers.
For the outlying districts the 1000 volt pressure from the second positive brush
is used. Current is conveyed by suitable feeders to sub-stations in which one-to-
one transformers reduce it to 500 volts for the trolley wires. The lighting demand
is met by current entirely transformed from 1000 volts to the lamp pressure, or to
twice this in the case of a three-wire system, suitable balancing machines being
employed to equalize the load on the positive and negative circuits.
By the use of this combination of apparatus all generators can be of the same
type, and may be interchangeable, and those in operation may be coupled in
parallel and simultaneously feed hoth local and outlying railway or traction and
lighting circuits.
The reducing transformers, while of a size corresponding to only one half the
demand, have an extremely high efficiency of conversion. Thus for 100 Kilo-watts
demand, a reducing transformer with one-to-one ratin only carries 50 Kilo-watts
on each winding, its efficiency may be 93 per cent. but, as only one half the con-
sumption is transformed, the efficiency of reduction is 0.98 or over 96 per cent.
The local lighting circuits, although only two wire, at 220, 230, 240, or 250 volts,
are fed at the same pressure. as a three-wire system and will therefore cover an
equal area.
The variable-ratio reducing transformers may be compound wound, as described
in the Specification of Letters Patent No. 24296 of 1895, granted to us, or he
controlled by hand, as set forth in the Specification of Letters Patent No. 11153
of 1895, granted to us.
For the suburban lighting, circuits, which will have a much smaller density of
lamp connections, a three-wire system of distribution becomes very desirable, and
in order to secure this, as well as for the additional safety gained, the current
should be entirely transformed and not merely reduced from the 1000 volt feeders.
By this means the neutral wire may be earthed and very considerable distances
may be covered from each sub-station.

page_text: The use of variable-ratio reducers and transformers for the lighting services.
will enable the station pressure to be varied to correspond with the traction
demand without affecting the constancy of pressure on the lamp circuits. Or the
converse arrangement may be employed if the consumption for lighting purposes
be the greater.
In any case, storage battery auxiliaries may be used for either service, or for
both.
Instead of a booster for charging the batteries from the corresponding circuit, a
variable-ratio reducer may be used, taking current from the circuit of higher
pressure. Thus for the 250 volt lighting battery, current may be taken from the
500 volt trolley wires, for the 500 volt three-wire lighting batteries; and for the
traction batteries current can be taken from the 1000 volt feeders.
In order that the invention may be clearly understood we will describe with
reference to the accompanying drawings some arrangements according thereto.
Figure 1 relates to the simpler case where a pressure of say from 500 to 550 volts
is sufficient for the whole railway or traction service. G is the common generator,
or it may be taken as the bus bars from which both the lighting and the traction
circuits are supplied. The negative pole, say, is earthed at E, and the positive pole
is connected through the feeder, T. F. to the trolley wire T. W. A battery B',
may be used to equalizo the load. Two sets of lighting circuits at 250 volts, fed,
through reducing transformers, R 1, and R2, are shewn. These circuits may be
considered as local and distant networks respectively and they are treated alike.
The lamp voltage on these may be chosen at rather less than one half of the normal
traction pressure, so that the reducers may have a ratio of about one to one while
allowing for small losses in the feeders. Variations of the supply pressure are
compensated by corresponding alterations in the strength of the auxiliary field
magnet of the transformers in accordance with the Specifications of the aforesaid
Letters Patent, or otherwise by the use of resistance regulation. As all lighting
feeders are at the full traction pressure of 500 to 550 volts, very considerable
distances can be reached without undue loss. For instance a 230 volt lighting
network, on which the greatest pressure is 3 per cent. high, can be supplied by
means of reducing transformers (with a maximum drop of 24 per cent) through
feeders carrying 750 amperes per square inch of section at a distance of one mile
from the station, the trolley wires being at 545 volts. Assuming uniform distri-
bution of connections on the lighting network, and an initial density of 1000
amperes per square inch, a further distance of 550 yards can be reached without
exceeding the permissable 3 per cent variation of pressure at the consumers
terminals. The total efficiency of supply in this case would be 82 per cent. at full
lond.
Figure 2 shews the case of a high pressure supply (at say from 1000 to 1100
volts) for the outlying districts while retaining the direct supply at low pressure
for the nearer arcas as before.
+
+
The generator, G, is wound with two circuits, which are connected in series each
yielding current at from 500 to 550 volts. The negative pole is earthed, and, from
the first positive brush, + the lighting and traction supplies are taken as before.
For supply to considerable distance, such as to suburbs, the second positive brush
marked
at 1100 volts is used. The trolley wire T. W. being fed through a
feeder. STF at 1100 volts, and a reducing transformer R2, exactly as is the
lighting service in Figure 1. The lighting area shewn at the right hand lower
corner of Figure 2, heing assumed as a residential or suburban area, will have
fewer lamps connected, per yard of cable laid, than will the Town area, and it
therefore becomes desirable to adopt a higher pressure and to distribute on the
three-wire system. This can be done by complete transformation in the usual way
as shewn at T, or by reduction in accordance with this invention, but this latter
method is not considered advantageous when the electromotive force on the high
tension circuit greatly exceeds 500 volts above, or below, the earth potential. It

page_text: is, however, obviously desirable to use the apparatus and organisation of circuits
according to this invention for the supply of lighting circuits when the traction
circuits are worked at about 1000 volts on the outers of a three-wire system with
the neutral at earth potential. Each side of the system is, in this case, to be
treated as a separate two-wire distribution. The positive traction bus bar at.
550 volts or thereabouts above earth will feed, by reduction, a two-wire lighting
network whose negative will be at earth potential, and similarly the negative
traction bus bar, at a like pressure below earth, will feed,' by reduction, a second
two-wire lighting network whose positive will be at earth potential, the earthed
negative of the one circuit, being connected to the earthed positive of the other the
advantages of a three-wire distribution for lighting purposes are at once obtained.
It would be preferable where this arrangement is employed to use single.arma-
ture dynamos of, say, 1000, to 1100, volts pressure instead of the double wound
generators shewn at G in Figure 2, and to make the earth connection solely by
means of the balancing transformers which will be necessary to equalize the
positive and negative circuit traction loads.
A storage battery is shewn in connection with each service at B1, B2, B3, in
Figures 1 and 2 and this is considered desirable. The batteries may be controlled
in the usual way by means of a booster for charging only, in which case it will
have to give about 35 per cent. of the normal circuit pressure; or the said batteries
can be used in connection with a booster both for charging and discharging, in
which case the booster need only have about one-half of the previous capacity,
giving 15 per cent. of the circuit pressure, but capable of carrying the discharge
current; or according to this invention, a reducing transformer can be used taking
current from a circuit at higher voltage. Figure 3 shews one arrangement as
applied to the battery B2, Figure 1. In this case the charging reducer will be
of rather larger size than the booster first above named, in the ratio of about 1
to 1, but there is the advantage that the battery charging current does not have
to go through the lighting reducer R, and, further, that if the charging reducer C, R,
be of the variable-ratio type, it is also available for direct lighting purposes when
not required for charging. Switches and other accessories are omitted from all the
figures for the sake of clearness. Their application is well understood, and needs
no particular description or illustration.
Having now particularly described and ascertained the nature of our said
Invention and in what manner the same is to be performed we declare that what
we claim is:-
1. In combination an electric generator or a source of electric supply or a set of
electric terminals earthed on one pole by connection to a traction circuit, a two-
wire lighting system correspondingly earthed, or having the like pole at earth
potential, and a reducing transformer for supplying the lighting circuit with
current derived from the traction generator, and at about one-half the pressure of
the same substantially as hereinbefore described.
2. In connection with a three-wire system of distribution for electric traction,
purposes earthed on the neutral wire, the combination of two two-wire lighting
networks, separately fed, through reducing transformers, with current derived
from opposite sides of the three-wire traction circuit to form a three-wire lighting
network, substantially as herein before described.
3. The combination with an electric generator having two armature windings
and commutators connected in series, as a means of supply of current at two
pressures one approximately double the other, of local traction and lighting circuits
supplied at the lower pressure as in the preceding Claim and remote circuits
supplied at the higher pressure, by reduction, for traction, and by complete trans-
formation for lighting, substantially as herein before described.
4. In a system of electric distribution at two different pressures, the use of a
reducing transformer to charge a battery with current derived from a circuit of

page_text: higher voltage than that to which the battery is normally connected, substantially
as hereinbefore described.
5. For the distribution of electricity for combined lighting and traction purposes
the arrangements of circuits and their adjuncts substantially as hereinbefore
. described or as herein before described and illustrated in the accompanying
drawings.
loted this 9th day of Santambor 1807
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, W.C.