Improvements in Dynamos for Generating Electricity.
Year: 1891

page_text: Date of Application, 13th Aug., 1891
Complete Specification Left, 13th May, 1892--Accepted, 18th June, 1892
PROVISIONAL SPECIFICATION.
Improvements in Dynamos for Generating Electricity.
WILSON HARTNELL Consulting Engineer Benson's Buildings, Park Row,
Leeds, Yorkshire, do hereby declare the nature of this invention to be as
follows:-
My improved dynamo has a disc-armature.
The field-magnets are annular, about the same diameter as the armature placed
on opposite sides of it, and each furnished with a succession of pole-pieces. Into
the side of each annular magnet is recessed the exciting coil which magnetizes the
magnets so that if the outer edge is north the inner edge is south (or vice-versa).
The pairs of pole pieces on opposite sides of the disc-armature are so coupled
to their respective magnets that the magnetic circuit through any two adjacent
pairs resembles the figure 8 when the magnets are viewed in section through the
spindle.
Thus if a pole-piece be connected to the outer edge of the annular magnet on the
right side of the armature, the left polar face will be connected to the inner edge of
the annular magnet on the left side of the armature.
The next pair of pole-pieces will be coupled to the inner edge on the right side
and the outer edge on the left side, and so on for all the other adjacent pairs of
pole-pieces. In this way, the magnetic induction flows alternately opposite ways,
say, from the outer edge on the right side to the inner edge on the left side and
returns in the next pair of pole-pieces from the outer edge of the magnet on the
left side to the inner edge on the right side.
The armature may be constructed without any iron near its conductors and
therefore the pole-pieces on opposite sides may be very near together.
Either the field-inagnets may be fixed and the armature revolve, or the armature
may be fixed and the field magnets revolve.
The armature may be wound for a simple alternating current; or for several
independent alternating currents by placing several independent windings similar
to those requisite for a simple alternating current.
The armature may also be wound for a continuous current by using a much
greater number of independent windings and a commutator.
My improvement consists in the field-magnets being much simpler than where a
number of independent exciting coils are needed. Magnetic circuits are very short,
the magnetic lines are nearly equally distributed over the polar faces and either
the armature or the magnets may be revolved as most convenient.
Dated this Eleventh day of August 1891.
WILSON HARTNELL.
COMPLETE SPECIFICATION.
Improvements in Dynamos for Generating Electricity.
1. WILSON HARTNELL, of Benson's Building, Park Row, Leeds, Yorkshire,
Consulting 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 :-
My improved dynamo has a disc armature. The field-magnets are annular,
about the same diameter as the armature, placed on opposite sides of it, and each
furnished with a succession of pole-pieces.

page_text: In order to explain my meaning I have annexed two sheets of drawings.
Fig. 1 is a section taken longitudinally through the driving spindle (taking the
field-magnets as being driven, and the central armature not shown except as to
position in the lower part of the figure);
Fig. 2 is a corresponding end view showing one set of poles, and
Fig. 3 is a diagrammatic plan-view.
By the aid of these three figures the general principle on which I arrange and
found my invention will be understood as I proceed.
Figs. 4, 5, 6, 7, 8 and 10 are diagrammatic end views of various armature
windings which lend themselves to the development of my invention but to which
individually I lay no claim. The relative positions of the polar faces behind are
shown by the dotted circles.
Fig. 9 is an edge view corresponding to Fig. 8: and
Fig. 11 a similar view corresponding to Fig. 12, which latter shows, in section,
the position taken up by an armature between the poles.
Into the side of each annular magnet A. is recessed the exciting coil B which
magnetises the magnets, so that if the outer edge is north the inner edge is south,
or vice versa.
The pairs of pole-picces, on opposite sides of the disc armature, are-in general-
so coupled to their respective magnets that the magnetic circuit through any two
adjacent pairs resembles the figure 8, when the magnets are viewed in section through
the spindle, as shown by the arrows at the head of Fig. 1. Thus if a pole-piece C₁
be connected to the outer edge of the annular magnet A' on the right (top) side of
the armature, the left polar face C will be connected to the inner edge of the
annular magnet A on the left side of the armature.
The next pair of pole-pieces, see Fig. 3, will be coupled to the inner edge on the
right side and the outer edge on the left side, and so on for all the other adjacent
pairs of pole-pieces. In this way the magnetic induction flows alternately opposite
ways say from the outer edge on the right side, to the inner edge on the left side,
and returns in the next pair of pole-pieces from the outer edge of the magnet on
the left side to the inner edge on the right. To meet this, the current, through the
coils B and B', is passed in, in opposite directions. When the field-magnets are
revolved the necessary contact rings must of course be arranged for the passage of
the current, but I am not here entering into or showing minor details which will be
clearly understood by those with ordinary electrical knowledge.
Although from this it will be correctly understood that in general-I arrange
pole pieces of an opposite sign to face one another, as shown by the letters and s
(north and south), nevertheless similar poles may be brought together as explained
later.
The field-magnets here described are adapted for any existing forms of armature
which require any such multiple magnetic poles.
The armature may be constructed without any iron in the core, and therefore the
pole-pieces on opposite sides may be very near together, thus :-it may consist of
radial conductors a, a, Fig. 4, arranged between the line of polar faces of the
magnets and connected alternately outside and inside the circle of poles, as shown
diagrammatically by the lines & b, but disconnected at c, c, where they join the
outside circuit.
When either the magnets or the conductors are revolved, so that these latter
pass between the magnetic poles, electric currents arise, as exemplified by the
arrows. These currents being reversed, when the conductors pass the next adjacent
poles; an alternating current is passed through the system.
Instead of there being only one radial conductor to each pole, there may be any
convenient number of conductors, after the manner shown at Fig. 5, and these may
be connected in series, or in parallel, as required.
The radial conductors may also be connected to form right and left handed coils,
as shown diagrammatically by Fig. 6. The number of turns in each of the coils
may be made to suit the special requirements.

page_text: When it is desired to use iron in the armature, it may be done as shown in
Fig. 7, where d, d, are iron cores of convenient length with right and left hand
coils of wires round them. In this case the alternating current arises chiefly from
the reversals of the polarity of the iron cores..
The armature may consist also of a laminated disc with coils e at suitable
intervals embracing it. But in this case the opposite pairs of poles must be similar
or "consequent," which may be conveniently brought about by sending the exciting
currents through both coils in the same direction; the magnetic circuit being thus
completed to the adjacent pairs of poles through the armature disc.
To produce two independent alternating currents it is merely necessary to
provide a second independent series of conductors placed midway between the
others, as indicated diagrammatically by the relationship of the dotted line to the
full line in Fig. 10. These currents are "two phase," and are sometimes used
for electric motors driven by alternating currents.
دي
In like manner, by three intermediate independent windings,
currents are produced, and so on for "multi-phase" currents.
"three phase"
Fig. 11 shows, in a diagrammatic plan, low a "three phase" set of armature
windings, h, i, j, can be arranged, in advance of one another; and Fig. 12 shows in
corresponding cross section, how such coils, whose connections would necessarily
overlap one another, may be brought into line between the lines of magnetic
poles Cand C. Here, the positions of annular mountings for securing the armature
coils are shown, D' outside, and D2 inside, the dynamo.
When field-magnets arranged on my system are used for continuous currents, it
is merely necessary to place a large number of sets of conductors, each slightly
in advance of the other, and the whole equally distributed, between the pole-pieces,
coupled in series, or part in series and part in parallel. These circuits must of
course be connected to a commutator as usual in other continuous-current dynamos.
If, with continuous currents, there be no iron in the armature, the mode of
winding may be that shown in Figs. 4, 5, and 6: but if there be iron present, the
mode of winding may be on the plans shown in Figs. 7 and 8, which latter is the
usual form of disc armature for continuous currents.
As before referred to, either the field-magnets-the pole-pieces of which may be
of any convenient shape, and laminated if required-may be fixed and the armature
revolved, or the armature may be fixed and the field-magnets revolved: as
momentum, however, in the revolving parts is advantageous I prefer to fix the
armature and revolve the field-magnets. I have not shown supports, etc. for the
dynamo shaft in Fig. 1, as the whole machine-the further details of which are of
no special moment may be arranged as most convenient; one side of the machine
(or both if the armature be fixed) must, however, be arranged to draw away along
the shaft to give access to the interior. The armature D, Fig. 1, beside being
fixed at its periphery D' to any outer foundation plate (such as at E) may have an
inner annular staying frame, as at D³. This latter, when an armature is revolved,
is fixed on the central shaft.
My arrangement of field-magnets is of course equally adaptable when the machine
is used as a dynamo-motor.
The sets of polar faces, instead of being side by side, may be arranged one above
the other, the outer set being made to overhang as it were; in this case a section
of the armature would stand in a line parallel with the driving shaft, and its shape
would be annular.
My system of arranging and exciting the magnets with two coils only renders
the manufacture of dynamos a simpler matter, more especially as a choice of
armature to suit special circumstances may be left to the last, variations being had-
by altering the direction of the currents in the coils (i.e. by running them in the
same or opposite direction) and choosing an armature to suit. The magnetic
circuits are also very short.
The two and other phase currents may be simultaneously used for supplying
independent circuits, thus obtaining a maximum amount of work from one machine.

page_text: 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. The arrangement and use in a dynamo of two annular exciting coils used for
magnetising two circles of pole-pieces placed opposite one another, with an armature
between the said pole-pieces, substantially after the manner described herein and
set out on the drawings whether used with an armature suited for single, two, three,
or multiple phase alternating currents, or for continuous currents.
2. The system of building up dynamos with two circles of polar faces, and
exciting the magnets by two coils, by which the poles may be made either
consequent," or opposite, (according to the direction of the currents in the
exciting coils), thus leaving to the last a choice of armature according to the
ultimate use to which the machine may be put, substantially after the manner
described herein.
Dated this 12th day of Max 1892
WM.
SNOWDON,
9, Old Bank Chambers, Leeds, Yorks, Agent for the Applicant.