An Improved Method of Actuating Electrically-propelled Tramcars.
Year: 1891

page_text: Date of Application, 11th Sept., 1891
Complete Specification Left, 10th June, 1892-Accepted, 3rd Sept.. 1892
PROVISIONAL SPECIFICATION.
An Improved Method of Actuating Electrically-propelled Tramcars.
I, WILFRID SWANWICK BOULT, of 60 Castle Street, Liverpool, in the County
of Lancaster, Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to the utilization of alternating currents of electricity in
maius laid in completely covered-in culverts, the energy being transferred to the
mechanism on the tram-car in the form of magnetism instead of directly as current
electricity and afterwards manifesting itself in the form of current available for
actuating the motor hereinafter described, or other suitable motor.
The transference of energy from the culvert is accomplished by means of a
divided transformer, one half of which, consisting of the primary or inducing coil
and its core, mounted on a trolley, travels along the culvert containing the main or
mains supplying it with current, and the other half, consisting of the secondary
coil and its core, is carried by the tram-car. The primary half of the transformer
may be hauled along the culvert solely through the magnetism between this and the
secondary half, or special auxiliary magnets, or a motor on the trolley, may be
used, as found necessary or desirable.
This arrangement permits of the use of high-pressure mains throughout the system
of tram-lines, and precludes all chance of accidents through shocks to persons or
animals on the roads traversed.
It is much to be desired that the tram-car motor should be self-starting when the
current is turned on otherwise it will have to be kept continually running, and
connection with the driving wheels be made through some kind of clutch gear.
The motor included in this invention is capable of self-starting, and may best be
described as of bi-uni-polar construction. A core, made by preference of a bundle
of varnished iron wires, arranged and shaped as in the well-known "Hedgehog'
transformer, wound with a few turns of conducting wire or rod of large section,
forms the field-magnet. The shaft of the motor passes down the centre of the
field-magnet-core and carries at each end a cup-shaped armature enclosing the
expanded end of the magnet. The cupped armatures are preferably split radially
(or formed with radially conducting wires or bars) for the purpose of preventing.
eddy currents and condensing the motive-current into definite paths. Currents,
which in practice must be of great volume or intensity and low pressure, passing
through these armatures more or less in phase with the alternating magnetic field
emanating from the field magnets cause rotation of the armatures in the same
manner as if continuous currents were employed. By the construction adopted, viz.,
the small amount of iron in the field magnet, (and that divided into thin insulated
wires), and the small number of turns in the winding, the desired synchronism of
phase is sufficiently approximated. If found desirable, the magnetic circuit may be
completed through an outside casing of laminated or otherwise divided iron.
It is not essential to have an armature at each end of the field-magnet, one being
able to act alone; and it is possible to arrange more than one at each end, so that
the motive current may interact with the field more than once, as in the case of
coiled armatures, but, to avoid the use of a commutator, the machine is so made
that, if used as a generator instead of a motor, a continuous current in the armature
is produced.
For varying the torque as required, any of the well-known methods used in
other motors may be employed. As this motor will require a very large current (at
very low pressure), it will generally be necessary to supply it from a transformer.in

page_text: close proximity. For convenience, this may be fixed upon the same bed-plate as
the motor.
It is not essential that this particular motor should be used in connection with
the divided transformer, the duty of such transformer being merely to transfer
energy from the buried mains to the movable motor, lamps, etcetera above, though
it may be also utilized at the same time for the ordinary purpose of a transformer.
Any alternating or pulsating current motor otherwise suitable is workable in
connection with the divided transformer, whether multiphase (or rotary) or single
current.
Dated this 10th day of Santambor 1901
WILFRID S. BOULT.
COMPLETE SPECIFICATION.
An Improved Method of Actuating Electrically-propelled Tramcars.
I, WILFRID SWANWICK BOULT, of 60 Castle Street, Liverpool, in the County
of Lancaster, 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 the utilization of alternating currents of electricity in
mains laid in completely covered-in culverts; the energy being transferred to the
mechanism on the tram-car in the form of magnetism, instead of directly as current
electricity, and afterwards manifesting itself in the form of current available for
actuating the motor hereinafter described, or other suitable motor. The trans-
ference of energy from the culvert is accomplished by means of a divided
transformer, one portion of which, consisting of the primary or inducing coil and its
core, mounted on a trolley, travels along the culvert containing the main. or mains
supplying it with current, and the other half, consisting of the secondary coil and
its core, is carried by the tram-car. The primary half of the transformer may be
hauled along the culvert solely through the magnetism between this and the
secondary half, or special auxiliary magnets or a motor on the trolley may be used
as found necessary or desirable; or the transformer-trolley may be pushed along by
an independent motor-trolley.
This arrangement permits of the use of high-pressure mains throughout the
system of tram-lines, and precludes all chance of accidents through shocks. to
persons or animals on the roads traversed.
The method of carrying out this invention practically is shown in the accom-
panying drawing.
Fig. 1. is a longitudinal vertical section through the closed culvert, showing
the divided transformer and trolley, &c. in elevation, and Fig. 2 is a transverse
section.
In these figures, A. is the subway; B, B, are insulated trolley rails acting as the
high-pressure conductors or mains; C, the trolley; D, D, the trolley wheels,
which, suitably mounted and insulated, act as collectors for the current
energising E, the primary half of the transformer; F, a laminated cover to the
subway, formed of alternate plates of iron and some other material, for instance
wood, thus providing a ready path for the magnetic lines of force vertically
between the two halves of the transformer, but not horizontally between the
two ends of each coil; G the secondary half of the transformer, carried by
the tram-car.
Instead of using the trolley-rails as main conductors, special insulated conductors
may be independently laid, and supply current to the primary coil through special
brushes or collectors carried by the trolley.
With a view to preventing magnetic leakage between the two ends of the
primary coil,, I prefer that this shall extend as nearly as possible along the whole
length of its core, being turned up at the ends close under the laminated cover of

page_text: the subway, as shown at e, e, on the drawing. As a further means of preventing
leakage and causing lines of force to be projected into the secondary core (and
therefore to cut the secondary coil, and improve the efficiency of the apparatus), I
make the core in the secondary coil of larger cross section than that in the primary
coil, and form it with enlarged ends or pole-pieces as shown at g, g, reaching nearer
together than those of the primary core. I also prefer that the secondary coil shall
be shorter than the primary coil.
If the motor on the car is of the "synchronising" type,-keeping in step with
the generator supplying the mains, it will be necessary to keep it continually
running, (or have some special starting apparatus), and connect it when desired with
the driving gear through some kind of clutch or gearing.
To avoid the necessity for such apparatus or gearing, a self-starting motor must
be used. I employ a uni-polar machine: a special uni-polar machine for this purpose
is shown in Figs. 3. and 4. where Fig. 3 is a longitudinal section and Fig. 4 a
transverse section on line W, X.
A is the field-magnet core, inade by preference of a bundle of varnished iron wires
arranged and shaped as in the well-known "Hedgehog" transformer wound with
a few turns of insulated conductor, B, of large cross section.
:
a, is a tube on which the core is built, having attached to it the webs or
distance-pieces b, b. e is a tube preferably of some insulating and non conducting
material such as vulcanized fibre, (or a serving of string or other substance), for
binding the loose wires of the core together. , d, are stays or ties for preventing
rotation of the core. The shaft C of the motor passes down the centre of the field-
magnet core, and carries at each end a cup-shaped armature, D or E, enclosing the
expanded end of the magnet core A. D and E show alternative modes of construction
for different machines.
The armature D is of a form suitable for passing the actuating current through
once only, and consists of a simple metallic basin (or basin-shaped cage formed of
bars or conductors all in parallel) the current passing in at the botton through a
brush (or brushes), D 1, and out at the rim through brushes D2, or the reverse
way through. To prevent eddy currents, due to the alternating magnetic field, the
armature, D, and contact rings, and all other metal in any way forming a circuit
round the field magnet, should when possible be split radially, the edges of the
metal being separated by air or other insulating material.
The armature E is constructed of several, (in the drawing, four), separately
insulated sectors through all of which the current passes in succession or series;
thus interacting with the magnetic field as many times as there are sectors, instead
of once only as in the case of D. 1, 2, 3, 4, are insulated metal rings mounted on
the shaft C and in electric connection respectively with the four arinature
sectors. I, I, III, are three fixed insulated metal rings connected by insulated
conductors, as shown by dotted lines, to rings 2, 3, 4, respectively. IV is a similar
ring in electric connection with the energising magnet coils B. G, G, are brushes
bearing on collecting rings as shown. Current entering ring 1, through a brush G,
passes through the first armature sector, ring I, ring 2, second sector, ring II, ring 3.
and so on to ring IV and the field coils as arranged, and then to a second armature E
on the other end of the field-magnet in the position occupied in the drawing by the
arinature D. This machine may be shunt, series, or compound wound as required.
Alternating currents in these machines, which in practice must be of very great
volume or intensity and low pressure, passing through the armatures as explained,
more or less in phase with the alternating magnetic field emanating from the field-
magnets, cause rotation of the armatures in the same way as if continuous currents
were employed.
By the use of very heavy currents and correspondingly few turns of conductor
in both field-coils and armature, self-induction is to a great extent prevented.
In the case of large machines, the uneconomical effect of using solid conductors of
large diameter may be modified by making the conductors as much as possible of a
thin broad section.

page_text: To complete the magnetic circuit of the field-magnets, an iron return H
(laminated or divided) may be provided. It is shown in the drawing as an iron
cage formed of rods held by suspenders J which also clamp and suspend the
field coils. The suspenders J have insulated joints at j, j.
K is a pulley or gear-wheel for transmitting the power of the motor. L, L are
hangers, attached to the under-frame of the tram-car, a common bed-plate, or other
support in which the motor shaft is journalled at 1, 1. Additional or substituting
bearings may be fixed in the tube C as at m; and, generally, the designs of the
different parts of the motor may be modified to suit different cases.
It is not essential to have au armature at each end of the field-magnet; one being
able to act alone.
For varying the torque or speed of this motor, any suitable well-known methods
used in other motors may be adopted.
The use of the motor here described is not essential in connection with the divided
transformer, which may be arranged to deliver current to any suitable motor.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is:
1. In electric tram or railway traction, a divided transformer having the primary
coil with iron core travelling along a closed conduit or subway containing bare
conductors supplying the primary coil through brushes or collectors with an
alternating or pulsating electric current, and the secondary coil and core carried
by the tram- or railway-car outside the conduit, substantially as described, and
illustrated in the accompanying drawings.
2. In electric tram or railway traction, the carriage of the primary portion of a
divided transformer, such as described in claiming clause Number 1 above, on a
truck or trolley running on rails, substantially as described, and illustrated in the
accompanying drawings.
3. In electric tram or railway traction, the use of the magnetic attraction between
the two portions of a divided transformer for hauling the primary portion along a
conduit or subway by moving the outside or secondary portion, substantially as
described, and illustrated in the accompanying drawings.
4. In electric tram or railway traction, the formation of the secondary core
of a divided transformer of larger cross section than the primary core, for the
purpose specified.
5. In electric tram or railway traction the formation of the ends of the secondary
core of a divided transformer, so as to extend closer together than those of the
primary core, substantially as described, and illustrated in the accompanying
drawings.
6. In electric train or railway traction the formation of one or both cores of a
divided transformer with enlarged ends or pole-pieces, substantially as described,
and illustrated in the accompanying drawings.
7. In electric tram or railway traction, carrying the primary coils of a divided
transformer along the portions of the core turned up to face the ends of the
secondary core, substantially as described, and illustrated in the accompanying
drawings.
8. In electric tram or railway traction forming the cover of a conduit containing
the primary portion of a divided transformer of a laminated construction of iron and
wood or other material, substantially as described, and illustrated in the accom-
panying drawings.
9. The construction of an alternating-current tram- or railway-car motor without
a commutator, similarly to a "unipolar continuous current generator, substantially
as described, and illustrated in the accompanying drawings.
10. In electric tram or railway traction, the employment as the motor machinery
of a unipolar apparatus or machine in combination with a divided transformer and
adapted to be worked by an alternating current; for the purposes specified.

page_text: 11. In a dynamo electric machine constructed on the "unipolar" principle, the
division of the armature into separately insulated sectors for the current to pass
through in series, substantially as described, and illustrated in the accompanying
drawings.
12. The combination of a closed subway, with laminated cover, and a divided
transformer for tram- or railway-car traction, substantially as described, and
illustrated in the accompanying drawings.
13. The combination of a closed subway, without iron in, the cover, and a divided
transformer, for the purpose specified.
14. In electric tram or railway traction, the combination of bare insulated con-
ductor (or conductors), closed subway, and divided transformer, forming a complete
means of transferring energy from the current generator or supplier to the
locomotive motor, substantially as described, and illustrated in the accompanying
drawings.
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W. S. BOULT.