Improvements in Alternating Current Dynamos.
Year: 1891

page_text: Date of Application, 11th Nov., 1891
Complete Specification Left, 11th Aug., 1892-Accepted. 24th Sept.. 1892
PROVISIONAL SPECIFICATION.
Improvements in Alternating Current Dynamos.
WILSON HARTNELL Consulting Engineer 8, Blenheim Terrace Leeds, do hereby
declare the nature of this invention to be as follows:
:―
My improved dynamo in one of its simple forms, consists of an exciting coil with
a generator coil on each side, of the same diameter and fixed to the frame. The
generator coils are partially embrased, at equal intervals by a series of electro-
magnets shaped like the letter E forming a channel wide enough to cover two coils
and the space between them, the bottom of the magnets being flush with the inside
of the coils. The magnets are placed around the coils and arranged alternately to
cover the centre and right-hand coil, and centre and left-hand coil. The armatures
revolve inside the coils, they are straight and extend to the outsides of the magnets.
There are as many armatures as there are pairs of magnets. The electro-magnets
may be bolted at their outside edge to a ring forming the frame, or they may be
extended across and secured at their ends to side frames. Both electro-magnets
and armatures are laminated.
The action is as follows-
When the armatures are under the magnets, closed magnetic circuits are formed
over two coils. These magnetic circuits are excited by the electric current flowing
through them in the generating coil. As the armature revolves, these circuits are
alternately formed and broken over the centre and right coil, and centre and left
coil, but over the central exciting coil, the magnetic induction is nearly constant.
Thus, alternating currents are produced in the generating coils in opposite phase,
but the central exciting coil is not much disturbed.
This dynamo may be constructed with the three coils concentric, the armatures
forming radial arms on one side, and the magnets being bolted to a frame on the
other.
By a variation in the construction, the three coils are placed close together and
surrounded by an almost continuous laminated magnet of the same section as before
with any convenient number of armatures.
But the generating coils are now not circular but wound zig-zag so as to be
alternately inside and outside the magnetic ring as many times as there are
armatures.
By using three generating coils wound zig-zag in succession inside and outside
the magnetic ring, three-phase currents are produced, suitable for driving self-
starting motors. These coils may be placed inside or outside the generating coil,
with radial armatures. The dynamo will work with one generating coil if the.
magnetic circuit be arranged to allow an approximately uniform flow around the
exciting coil.
The generating coils may consist of several coils giving different potentials if
desired.
The magnets as described may be arranged inside and revolve with the coils,
the armatures being fixed. But in this case rubbing contacts are necessary on
the axis.
The advantage of this invention is that the construction is simple, the generating
coils are free from the difficulties of insulation and are easily wound to give a very
high voltage, and still more easily wound to give a very large current.
Dated this Ninth day of November 1891.

page_text: COMPLETE SPECIFICATION.
Improvements in Alternating Current Dynamos.
I, WILSON HARTNELL, Consulting Engineer, of 8. Blenheim Terrace, Leeds,
Yorkshire, 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, in one of its simplest forms, consists of an exciting coil
with a generating coil. on each side, of the same diameter, and fixed to the frame.
The generating coils are partially embraced at equal intervals by a series of electro-
magnets, shaped (approximately) like the letter E, forming a channel wide enough
to cover two coils and the space between them, the bottoms of the magnets being
flush with the inside of the coils.
In order to explain my invention fully I have annexed four sheets of drawings,
to the figures on which I refer as I proceed. The same letters refer to the same
parts, or their equivalents, in all the figures. The drawings which are intended to
show mainly the essential features of my invention are not necessarily otherwise
complete.
Fig. 1 is an end view, partly in section, of a dynamo arranged after my plan,
whilst Fig. 2 is a relative longitudinal sectional elevation. The magnets in the
upper half of Fig. 2, and also in Figs. 5, 9, 13, and 16, are sectioned on the
line X, Y, and those, below, on the line Y, Z, so as to show the right and left hand
coils embraced. Here, A is the exciting coil, B' and B2 the two generating coils,
and C¹ and C2 the two classes of magnets.
The magnets are placed round the coils and arranged alternately to cover the
centre and right-hand coil, and the centre and left-hand coil, as shown in Fig. 3
which is a plan of the inner faces of the magnets and coils laid out on the flat.
The armature, which revolves inside the coils, has bars D, which are straight,
and extend to the outside of the magnets as shown. There are as many bars I as
there are pairs of magnets, carried by any suitable arms or rings E.
The electro-magnets may be bolted at their outside edge to a ring forming the
frame, after the manner shown in Figs. 1 and 2, where F is the ring, and f¹ and f'
are brackets supporting the magnets. Fig. 4 is a plan showing the arrangement of
the magnets and the outer ends of their brackets laid out on the flat, after the
manner of Fig. 3. The mode of fixing may be varied to suit circumstances, as the
fixing of the various parts is subservient to their positions. The magnets, or their
supports, may be extended across and secured at their ends to side frames, as shown
in Fig. 9, where F1 and F2 are the frames and C the magnets. In Fig. 2 the
armature is mounted on the shaft G, supported on standards F³, and driven by the
drum G¹, or otherwise.
The action is as follows :—
:-
When the armature-bars are under the magnets, closed magnetic circuits are
formed over two coils. The magnetic circuits are excited by the electric current
flowing through them in the exciting-coil. As the armature revolves these circuits
are alternately formed and broken, (1) over the centre and right-hand coil, and
(2) over the centre and left-hand coil; but over the central exciting coil the
magnetic induction is nearly constant. Thus alternating currents are produced in
the generating coils in, what may be termed, opposite phase, but the central exciting
coil is not much disturbed.
This dynamo may be constructed with the three coils concentric, the armature
bars forming radial arms on one side, and the magnets being bolted to a frame on
the other, as shown in Fig. 5, a sectional elevation, and in Fig. 6, a front elevation
with half of the armature disc removed. This arrangement, with its lettered

page_text: parts, will be easily understood by comparing it with Figs. 1 and 2. Fixing
blocks f³ may be used for securing the magnets to the frame F. The bars, D,
are supposed, Fig. 5, to be fixed in grooves previous to the axle G being fitted
in situ.
By a variation in the construction the three coils are placed close together, and
surrounded by an almost continuous laminated magnet of the same section as before
(approximately), with any convenient number of armature bars. See Figs. 8 and 9,
which are similar views to 1 and 2, and refer to the previous letterings. But the
generating coils are not now circular (annular), but zigzag, so as to be alternately
inside and outside the magnetic ring, as many times as there are armature bars, as
shown in Fig. 8. In Fig. 9 the magnets are shown extended across and secured to
the frames and F2, whilst the central portion F³ is left loose to allow its removal
when the armature is withdrawn. This arrangement leaves the periphery of the
magnets free for the inter-twining coils B1 and B2. In the upper half of the
figure B' is encircled and B2 left out, and in the lower half B2 is encircled and B¹
(on the outer side of the magnet) left out.
By using three generating-coils, arranged zigzag, inside and outside the magnetic
ring, three phase currents are produced, suitable for driving self-starting motors.
In Fig. 10, which is a portion of a longitudinal section, arranged after the manner
of Fig. 9, the coil B₁ is encircled, B2 and B³ (outside the magnet C) being left
out. Each coil, however, is encircled in turn, as shown in the plan Fig. 11, which
is a view of the working face laid out on the flat (like Fig. 3). In this figure,
which corresponds to Fig. 10, A is the exciting coil, and B', B2 and B³ are the
generating coils, which, in turn, lie twice on the far side of the magnet, C, to once
on the working face.
These three-phase coils may be placed inside or outside the exciting coil, with
radial armatures. This arrangement will be easily followed by a reference to
Fig. 7, which is a portion of a sectional elevation corresponding to Fig. 5. Here
B is the coil encircled, but each coil is influenced in turn, the whole being arranged
after the manner shown in Fig. 11, i.e. twice outside and once in.
A modified arrangement of this Fig. 10 system is shown in Figs. 12 and 13,
portions of sections of end and longitudinal elevations, where, instead of using
zigzag generating coils, annular ones are fixed, and three differently shaped magnets
are used. Each magnet so far embraces its own generating coil and the common
exciting coil that it only requires a passing armature bar to complete the circuit.
The shape of the magnet C2 is shown in Fig. 13: C' is shown by itself in
Fig. 134; and that of C3 in Fig. 13. The relative arrangement of these magnets
is shown in plan in Fig. 14, where all is laid out on the flat, with the working
faces below.
The generating coils may consist of several coils giving different potentials, if
desired; for instance, one might have a different size of wire, or a different number
of turns, or partly one size wire and partly another in the same coil.
The magnets as described may be arranged to revolve with the coils, the
armatures being fixed as shown in Fig. 15, an end elevation, and in Fig. 16, a
longitudinal section. Here the upper half of the frame and its armature bars may
be lifted off for access to the interior. But in this case rubbing contacts are
necessary on the axis.
Either the magnets or the armature bars may have the requisite gaps arranged
therein, for embracing or non-embracing the respective coils to some extent this
is shown by the arrangement of Fig. 16 where the armature bars D¹ and D² are
differently shaped.
Both the magnets and the armature bars are laminated.
The advantage of the invention is that the construction is simple, the generating
coils are free from difficulties of insulation, they are easily wound to give a very
high voltage, and still more casily wound to give a very large current.
Magnetic circuits are denoted by the arrows.

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 improvements in alternating current dynamos substantially as described
herein and shown on the drawings.
2. The arrangement of dynamo substantially as described and shown in Figs. 1,
2, 3 and 4.
3.
The arrangement of dynamo substantially as described and shown in Figs. 5
and 6.
4. The arrangement of dynamo substantially as described and shown in Figs. 8
and 9.
5. The arrangement of dynamo substantially as described and shown in Figs. 10.
and 11.
6. The arrangement of dynamo substantially as described and shown in
Figure 7.
7. The arrangement of dynamo substantially as described and shown in Figs. 12,
13, 13, 13, and 14.
8. The arrangement of dynamo substantially as described and shown in Figs. 15
and 16.
Dated this Tenth day of August 1892.
WM.
SNOWDON,
9, Old Bank Chambers, Leeds, Yorks, Agent for the Applicant.