Improvements in Alternating Current Dynamos.
Year: 1895

page_text: Improvements in Alternating Current Dynamos.
I, WILLIAM BEEDIE ESSON, of Montpelier House, Blackheath, in the County
of Kent, Electrical Engineer, do hereby declare the nature of this invention to be
as follows:-
My invention relates to improvements in alternating current dynamos by means
of which certain advantages are obtained.
In constructing an armature according to a part of my present invention I build
it up in annular form in the following manner :
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I take wrought iron plates cut to a form somewhat resembling a truncated
wedge and arrange these side by side and insulated from one another so as to
constitute (when bound together in any convenient known manner) what I shall
term core sections" that is to say sections which when put together as I shall
hereinafter describe form an annular armature core. The sections are placed
together in such manner that the tapering sides of one section are placed in contact
with or in close proximity to the tapering sides of the neighbouring sections.
Each of the said sections is separate and distinct so as to be easily detached or
otherwise separately handled when desired and the whole are secured to a framing in
any convenient manner.
I provide the said sections with armature coils in the following manner :
I imbed the coils in tunnels formed in the said sections the said tunnels being
made up of coincident orifices of the separate iron core plates. The said orifices
have cuts extending from them to an edge of the core plate so that the latter may
be bent aside at the said cuts then slipped over the previously formed coil and
then have the bent part or parts straightened into position again. The advantage
of an armature core with a smooth clearing surface is thus secured. By this
means the building up of the armature is greatly facilitated as compared with that
method of construction in which the armature winding has to be threaded through
tunnels and a greater efficiency is obtained as compared with the case wherein the
coils are wound over armature sections.
The number of armature sections and coils which I contemplate employing is
equal to half the number of the field magnet poles. By this means great magnetic
continuity of the core is obtained and an iron path as little interrupted as possible
secured for the lines of force passing between the poles.
I have hereinbefore spoken of the number of armature coils being equal to the
number of armature sections. This is the case in monophase and triphase
alternators constructed according to my invention but in the case of diphase
alternators there would be two coils to each section suitably displaced relatively to
one another..
For the purpose of diminishing loss due to eddy currents in the field magnets
I sometimes find it convenient to provide the core plates with orifices preferably
arranged annularly and preferably symmetrically with and similar in size and
shape to those hereinbefore mentioned as containing the conductors.
Another method of diminishing loss in the field magnets due to eddy currents
which I sometimes find it convenient to adopt is to furnish the wrought iron or

page_text: soft steel field magnet pole pieces with cast iron shoes or tips which by reason
of their increased electrical resistance offer opposition to the said eddy currents.
Dated this 25th day of March 1895.
ppcaint
J. G. LORRAIN, M. Inst. E.E., M. Inst. M. E.,
Norfolk House, Norfolk Street, Strand, London, W.C.,.
Chartered Patent Agent.
Improvements in Alternating Current Dynamos.
I, WILLIAM BEEDIE ESSON, of 31 Woburn Place, London, W.C., in the
County of Middlesex, formerly of Montpelier House, Blackheath, in the County
of Kent, 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 :-
My invention relates to improvements in alternating current dynamos by means
of which certain advantages are obtained.
In constructing an armature according to a part of my present invention I build
it up in annular form in the following manner :
I take wrought iron plates cut to a form somewhat resembling a truncated wedge
and arrange these side by side and insulated from one another so as to constitute
(when bound together in any convenient known manner) what I shall term "core
sections" that is to say sections which when put together as I shall hereinafter
describe form an annular armature core. The sections are placed together in
such manner that the tapering sides of one section are placed in contact with or
in close proximity to the tapering sides of the neighbouring sections. Each of
the said sections is separate and distinct so as to be easily detached or otherwise
separately handled when desired and the whole are secured to a framing in any
convenient manner.
I provide the said sections with armature coils in the following manner:
I imbed the coils in tunnels formed in the said sections the said tunnels being
made up of coincident orifices of the separate iron core plates. The said orifices
have cuts extending from them to an edge of the core plate so that the latter may
be bent aside at the said cuts then slipped over the previously formed coil and
then have the bent part or parts straightened into position again. The advantage
of an arinature core with a smooth clearing surface is thus secured. By this means
the building up of the armature is greatly facilitated as compared with that method
of construction in which the armature winding has to be threaded through tunnels
and a greater efficiency is obtained as compared with the case wherein the coils are
wound over armature sections.
The number of armature sections and coils which I contemplate employing is
equal to half the number of the field magnet poles. By this means great magnetic
continuity of the core is obtained and an iron path as little interrupted as
possible is secured for the lines of force passing between the poles.
I have hereinbefore spoken of the number of armature coils being equal to the
number of armature sections. This is the case in monophase and triphase
alternators constructed according to my invention but in the case of diphase
alternators there would be two coils to each section suitably displaced relatively to
one another.
For the purpose of diminishing loss due to eddy currents in the field magnets
I sometimes find it convenient to provide the core plates with orifices preferably
arranged annularly and preferably symmetrically with and similar in size and shape
to those hereinbefore mentioned as containing the conductors.

page_text: Another method of diminishing loss in the field magnets due to eddy currents
which I sometimes find it convenient to adopt is to furnish the wrought iron or
soft steel field magnet pole pieces with cast iron shoes or tips which by reason
of their increased electrical resistance offer opposition to the said eddy currents.
Having now briefly described the nature of my invention, I shall proceed
to show how it may be carried into effect, and for that purpose I shall refer
to the accompanying sheet of drawings illustrating a preferred form of my
iuvention.
Fig. 1 is a general view of the machine as constructed for single phase
alternating currents, showing the core sections E, E disposed circumferentially and
attached to the outer supporting framing or shell A, A. The armature coil
appertaining to each core section is shown at F, F. The outer shell is made for
convenience in two halves with a horizontal joint, the bottom half being provided
with projecting flanges or feet B, B for securing the shell to a suitable bed plate or
foundation. D, D shows the revolving field magnet which is securely keyed to
the shaft C.
Fig. 2 is a perspective view showing one of the core sections E with its coil F
in position as intended for a single phase or triple phase alternator.
Fig. 3 shows part in elevation and part in section of an armature and field
magnet while
Fig. 4 shows a cross section through armature, magnet and outer shell.
Fig. 5 is a plan of one of the core sections E with its coil F in position.
Figs. 6, 7 and 8 show the manner in which the armature coils are arranged in
the core sections of a two-phase alternator i.e. a machine giving two alternating
currents displaced as regards phase relatively to each other.
The armature coils I make by winding insulated copper wire, tape or ribbon on
a separate former or dummy. After I remove the coils from this former or dummy
I thoroughly insulate them on the exterior by coverings of prepared rubber tape
or micanite cloth or other suitable material. To prevent damage while the coils
are being embedded in the core sections I sometimes cover them additionally
with micanite sheet, fibre, ebonite or other insulating material suitable for the
purpose.
When building up a core section I embed the armature coil in it at the same
time and in the following manner. The sections I build up of a number of thin
charcoal iron plates of the shape shown at E, E (Fig. 3) with orifices p, p cut or
punched in same of which two or more are utilised for holding the armature coils;
and cuts or slits s¹, s² are made from said orifices to the edge of the plates as shown.
I lay these plates one above the other each being separated from its neighbouring
plates by thin paper, varnish or other insulating material. Each individual plate
is slipped over the armature coil the parts of the plate at s¹, s¹, s², ³, Fig. 3. being
bent aside at the cuts shown to allow this to be done and flattened again when the
plate is in position. In this way the plates are laid one upon the other until they
form the completed section as shown in Fig. 2, the coil lying in the tunnels formed
by the coincident orifices of the plates. In Figs. 3 and 4 the coils are shown in
section lying in the tunnels so formed. The whole section is held together by
insulated bolts, K, L (Figs. 3 and 4) passing through substantial end plates G, H
(Figs. 3 and 4) of gun metal, delta metal, brass, Gerinan silver, or other suitable
material.
The section is supported in the outer shell at both front and back. At the
front, the end plate G, Fig. 3. is provided with two lugs through which pass screws
or studs J, Fig. 4, to secure the section to the front flange of the supporting shell.
The support of the section to the other flange of the shell at the back is secured
by an elongation of two of the insulated bolts K, which holds the plates of the
section together. The elongated parts are screwed as shown clearly in Fig. 8 and
over these are threaded coned nuts M, which when screwed up fit corresponding
coned or tapering holes in the back flange of the shell. These coned nuts are
locked by an outer nut N¹ as shown. To remove any core section it is only

page_text: necessary to slack the nuts N¹ unscrew the coned nuts at the back and the screws J
at the front.
The field magnets may be of any of the types usually employed for alternating
current machines. In Figs. 3 and 4 is shown part of the magnet of an alternator
in which an engine flywheel R, forms the central portion, with steel segments U, U,
bolted to same forming the poles. The north and south poles are marked N and S
respectively and the system is energized by a single magnetizing coil F, wound
on the flywheel rim. To reduce the loss in the field magnets due to eddy
currents I sometimes furnish the poles of the magnets, if of steel or wrought iron,
with cast iron shoes or tips. By reason of the cast iron having a higher electrical
resistance than the steel or wrought iron the magnitude of the eddy currents is
greatly reduced.
The number of core sections and armature coils which I prefer to employ is,
in single phase alternating current machines, equal to half the number of magnet
poles as shown in Figs. 1, 3 and 4. In this way the number of joints in the iron
core of the armature is reduced and the variation in the flow of lines of force
through the magnetic circuits of the machine correspondingly diminished. The
contiguous core sections are intended to touch each other when all are in position
in the containing shell so that there is practically no space between them.
Notwithstanding this the sections can be removed easily as when the coned nut
is slacked back the section can be tilted outwards from the centre towards the
periphery of the shell.
For the purpose of still further reducing the variation of the flow of lines
through the machine due to varying positions of the field poles relatively to the
core sections, I sometimes find it advantageous to provide the core plates with
orifices additional to those actually required for the coils as shown at p, p, Fig. 3,
these being arranged annularly, symmetrically with, and similar in size and section
to the orifices utilized for the coils. In the arrangement shown in Fig. 3 I
utilize one of the additional tunnels so formed for the central insulated bolt L.
vary the number of the orifices and the size of them, also their distance from
the inner edge of the core section and the width of the cuts or slits s¹, s²,
according to the condition under which the machine is intended to run. Some-
times the plates are cut without taking any metal out at s¹, s2, sometimes an eighth
of an inch or more or less is taken out.
For triple phase alternating current dynamos I prefer also to embed one
armature coil in each core section. In these machines the number of sections is
such as to admit of coupling the coils in sets to give the three currents displaced
in the proper degree relatively to each other as regards phase.
For two phase alternating current dynamos I prefer to embed two coils in each
core section suitably displaced relatively to each other. Figs. 6, 7 and 8 show
how in a two phase machine the armature coils are embedded in the core sections.
Fig. 6 shows the finished core section with its two coils F and F in place also
the adjacent core section with the coils shown in section. The orifices s', s¹ are
utilized for one coil and 2, 82 for the other the coils being bent up and down at
the ends as shown to get them into position, and embedded in the core sections
while the latter are being built up in the manner hereinbefore described. Fig. 7
is a plan of the core section and Fig. 8 a side elevation, the coils being in all the
figures correspondingly lettered.
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 an armature the employment of truncated wedge shaped core sections
built up of plates cut and perforated substantially as and for the purpose set
forth.
2. In the armature of a diphase alternator the employment of two coils in a
single core section substantially as set forth.

page_text: 3. In the armature of an alternator the employment of orifices additional
to those in which the coils are embedded arranged substantially as and for the
purpose set forth.
1
1005
For the Applicant,
J. G. LORRAIN, M.I.E.E., M.I. Mech. E.,
Chartered Patent Agent.