Improvements in Dynamo-electric Machines.
Year: 1890

page_text: COMPLETE SPECIFICATION.
Improvements in Dynamo-electric Machines.
I RANKIN KENNEDY Electrician 10 India Streut Kilmarnock N.B. 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 improvements in the magnetic circuit of dynamo electric
machines more particularly for alternating currents and has for its object the
prevention of the generation of waste currents in, and of leakage from the magnetic
circuit of such machinery.
The magnetic circuit in these machines according to this invention is formed of
two laminated armature cores one multipolar electromagnet and an outer cylindrical
iron casing or shell.
The multipolar field magnet has only one coil for exciting all the poles when the
machine is separately excited but when excited by two pulsating unidirection currents
it has two exciting coils one for each current.
The field magnet is a straight bar magnet its ends radiating out into as many
poles, at one end N and at the other end S, poles, as are required.
One of the laminated iron cores of the armatures encircles the N poles only, the
other laminated armature core encircles the S poles only, and the one core fits into
one end of the outer cylindrical iron casing, and the other core fits into the other end
of said casing and both are fixed securely therein. The multipolar magnet is keyed
to the shaft and revolves inside of the armatures.
In some cases it may be of advantage to fix the exciting coils also inside of the
outer casing in the middle section thereof between the armatures. In that case the
only piece revolved in operating the machine would be the field magnet core.
This invention is equally applicable to both alternating generators and alternating
motors. The armature coils are in number twice the number of poles on the field
magnet, and the generated currents from each armature may be taken off together or
separately, and at any difference of phase between them.
The advantages of such a construction of the magnetic circuit of a dynamo electric
machine as herein described are-First. There being no reversal of magnetic flow in
the magnetic circuit there is little or no loss due to hysterisis. Second. All the
N poles being at one end and all the S poles at the other and enclosed by the
armature cores and outer iron casing there is no magnetic leakage. Third. The mag-
netic flow in the field magnet and outer casing being steady and uniform there is
no loss in them due to the generation of eddy currents or waste currents.
In order that others skilled in the art to which my invention relates may clearly
understand the said invention I have appended a sheet of drawings showing and
explaining particularly the nature of my said invention and the manner and method
of carrying the same into effect and practice.
Fig. 1 is an end view of a dynamo electric machine according to this invention.
Fig. 2 is a cross section vertically through the centre line of the shaft.
Fig. 3 is an external view showing outer iron casing C, bearings and shaft.
Fig. 4 is a side elevation of the field magnet, all the N poles on one end all the S poles
on the other with space X for winding the exciting coil or coils.
Fig. 5 is the same with coils shown in place XX.
Fig. 6 is an end view of the S pole end of the field magnet with exciting coil
seen through spaces P between poles.
Fig. 7 is a view of one of the laminated armature cores showing armature-coils
laid on in place at A.
Referring to Figure 1 N N N are the N poles on one end of the field magnet
U is the outer iron casing A. the laminated iron armature core showing four armature

page_text: coils in place. At F F F is shown the path of the magnetic flow from the field
magnet poles through the armature into the outer casing. The armature cores are
made deep enough to allow the magnetic flow to spread out into a uniforin density
before entering the outer iron casing. For this purpose the radial depth should bo
at least equal to half the breadth of the polar faces.
Referring to Fig. 2 the magnetic circuit is herein shown complete in section & as
made according to this invention. C is the outer iron casing: A A A A are sections
of the luminated iron armature cores; N N-S S is the section of the field magnet
core: the exciting coil or coils being wound into space X' on magnet or fixed into
space in casing, the arrows show the path of the magnetic How through this
section in the improved magnetic circuit.
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
1st. In a dynamo electric machine for generating electricity or motive power the
combination of an electromagnet having all its N poles on one end and all its S poles
on its other end with two armatures having laminated iron cores and coils on their
inner periphery and with an outer iron casing completing the magnetic circuit
substantially as herein described.
2nd. In dynamo electric generators or motors having an electromagnetic or other
field magnet constructed with all its N poles at one end and all its S poles at the
other end of a short cylinder, combined with two armatures contained in the ends of
an outer iron casing completing the magnetic circuit and enclosing the field mingnet
substantially as herein described.
3rd. In a dynamo electric generator or motor as herein described, two armatures
having coils on their inner periphery one armature enclosing field magnet N poles
only and the other armature enclosing field magnet S poles only, two armature cores
of laminated iron deep enough to allow the magnetic flow from adjacent poles to
spread into uniform density before entering the cylindrical outer iron casing
substantially as herein described and illustrated in accompanying drawings.
Dated this 9th day of September 1890.