Improvements in Dynamos.
Year: 1898

page_text: Improvements in Dynamos.
I, HENRY JOHN WALKER, of Victoria Works, Gateshead-on-Tyne, in the
County of Durham, Electrical Engineer, do hereby declare the nature of this
invention to be as follows:-
-
It is well known that the output of a continuous current dynamo is limited by
the heating of the armature conductors and by sparking at the collecting brushes,
and that it is advantageous to be able to work a dynamo at any load up to its
rated capacity without having to alter the position of the brushes.
Now this invention has reference to an improved construction of continuous
current dynamos, whereby tendency to sparking at the collecting brushes, and
distortion of the magnet field by armature reaction can be lessened and fixity of
position of the brushes obtained, so that an increased electrical output can be
obtained from a machine of given weight.
According thereto the field magnet poles are made narrow and near together
and instead of being arranged parallel to the axis of the armature, as usual,
they are arranged diagonally thereto so as to extend in a spiral or screw-like
direction partly around the same so that each armature coil at the moment of
commutation will be partly under and be subject to the differential action of
two adjacent and dissimilar field magnet poles.
My invention can be applied in dynamos having two, four or other even
number of poles.
In one construction of four pole machine according to this invention, there are
four field magnets of U or U shape arranged with their polar extremities
extending spirally partly around the armature core and each provided with a
winding on one of its two limbs, the N and S poles of one magnet being next the
N and S poles respectively of the adjacent magnets, and the several magnets
heing placed at right angles, or approximately so, to one another around the
armature. The breadth of each polar face in this case may, for example, have
an angular width of about 25°; the air gap between the N and S poles of the
several magnets and between similar poles of adjacent magnets may be made
equal and of an angular width of about 20° and the amount of twist or screw
of the polar faces in the length of the armature may be about 30°. Each field
magnet is self-contained and it may be, only long enough to allow of the field
winding being placed on one of the limbs thereof, no magnetic circuit being
required between adjacent magnets. For a dynamo having a different number
of poles the angular breadths of the parts mentioned would be varied.
By the improved construction hereinbefore described, it is possible with a
given strength of magnetic field, length of air gap, and turns of conductor
on the armature, to obtain a much greater output with an unaltered position
of the brushes and an absence of sparking, than is possible with the
ordinary method of construction. Also the field magnet circuit can be made
of short length so that a saving can be effected. An air gap is introduced
into the path of the armature field by the spaces between the similar poles,

page_text: thus reducing such armature field and lessening distortion of the field-magnet.
Furthermore, the space wherein commutation must take place is narrow, and
the armature coil under commutation is in a strong field, so that the reversal
of large currents as well as small ones, can be made on the same line, thus
enabling the brushes to be fixed for varying loads.
As a result of the reduced armature reaction and better commutation, larger
currents can be carried by the armature of a dynamo according to my invention
for a given strength of magnet field and length of air gap than has heretofore
been usual with other constructions of dynamo.
I, HENRY JOHN WALKER, of Victoria Works, Gateshead-on-Tyne, in the
County of Durham, 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:-
It is well known that the output of a continuous current dynamo is limited by
the heating of the armature conductors and by sparking at the collecting brushes,
and that it is advantageous to be able to work a dynamo at any load up to its
rated capacity without having to alter the position of the brushes.
Now this invention has reference to an improved construction of continuous
current dynamo, whereby tendency to sparking at the collecting brushes, and
distortion of the magnet field by armature reaction can be lessened and fixity of
position of the brushes obtained, so that an increased electrical output can be
obtained from a machine of given weight.
According thereto the field magnet poles are made narrow and near together
and instead of being arranged parallel to the axis of the armature, as usual,
they are inclined thereto so as to extend in a spiral or screw-like direction partly
around the same so that each armature coil at the moment of commutation will
be partly under and be subject to the differential action of two adjacent and dis-
similar field magnet poles.
My invention can be applied to dynamos having two, four or other even number
of poles.
Fig. 1 of the accompanying drawings shows partly in cross section and partly
in end elevation, a four pole dynamo machine constructed according to this
invention. Fig. 2 is a sectional plan on the line of Fig. 1; Fig. 3 is a
developed view showing diagrammatically, the relative arrangement of the
several poles.
In this construction of four pole machine there are four field magnets A, B, C, D,
of more or less U shape arranged with their respective polar extremities
N S, N¹ S¹, N° S². N³ S3 extending spirally partly around the armature E and
each provided with a winding F on one of its two limbs, the N and S poles
of one magnet being next the N and S poles respectively of the adjacent magnets,
and the several magnets being placed at right angles, or approximately so, to
one another around the armature.
The exciting coils F are arranged on opposite pairs of limbs or cores of

page_text: similar sign viz. the limbs or cores having the polar extremities N N¹ and N2 N3
in the example shown, the adjacent limbs or cores of each pair being arranged
near together to economize the amount of wire in each winding F but their polar
extremities being spaced apart.
In the example shown the two limbs or cores of the south poles S S¹ of the
field magnets A and B are cast in one piece with a connecting yoke to which
the limbs or cores of the two adjacent north poles N, N', also cast in one piece
with an air gap or space G¹ between them, are secured by bolts or set screws H.
The limbs or cores of the adjacent south poles are for convenience arranged
parallel to the axis of the armature, only their polar extremities being inclined
to the armature axis as shown. The field magnets C and D are similarly con-
structed, the two main castings being connected together by bolts I and forming
an enclosed type of dynamo.
This mode of construction admits of the field magnets being made in a cheap
and convenient manner but the four field magnets may, if desired, be made
separately, and each of the limbs or cores of north polarity be provided with a
separate winding, provided the polar extremities of the limbs or
arranged as described.
cores be
The breadth of each polar face in a four pole machine, may, for example, have
an angular width of about 25° the air gaps G between the N and S poles of
the several magnets and the air gaps G1 between similar poles of adjacent magnets
may be made equal and of an angular width of about 20°; and the amount of
twist or screw of the polar faces in the length of the armature may be about 30°,
measuring along the centre line of the armature. Each field magnet is self-
contained and it may be only long enough to allow of the field winding being
placed on one of the limbs thereof, no magnetic circuit being required between
adjacent magnets. For a dynamo having a different number of poles the angular
breadths of the parts mentioned would be varied. y y indicates approximately
the planes of commutation.
By the improved construction hereinbefore described, it is possible with a
given strength of magnetic field, radial width of air gap, and turns of conductor
on the armature, to obtain a much greater output with an unaltered position
of the brushes and an absence of sparking, than is possible with the ordinary
method of construction. Also the field magnet circuit can be made of short
length so that a saving in material can be effected. An air gap is introduced
into the path of the armature field by the spaces G₁ between the similar poles,
thus reducing such armature field and lessening distortion of the field-magnet
field. Furthermore, the space wherein commutation must take place is
narrow, and the armature coil under commutation is in a strong field, so that
the reversal of large currents, as well as small ones, can be made on the same
line, thus enabling the brushes to be fixed for varying loads.
As a result of the reduced armature reaction and better commutation, larger
currents can be carried by the armature of a dynamo according to my invention
for a given strength of magnet field and radial width of air gap than has hereto-
fore been usual with other constructions of dynamo.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is
1. A dynamo electric machine wherein the field magnet poles are made narrow
and near together and are inclined to the axis of the armature so as to extend in
a spiral or screw-like direction partly around the same the arrangement being
such that each armature coil at the moment of commutation will be partly under
and he subject to the differential action of two adjacent and dissimilar field
magnet poles, substantially as described for the purpose specified.
2. A continuous current dynamo constructed with pairs of narrow field magnet
poles that are inclined to the axis of the armature and are separated from each
•

page_text: other and from adjacent pairs of poles by air gaps, the N and Spoles of each
pair being next the N and S poles respectively of adjacent pairs, substantially
as described for the purpose specified.
3. A dynamo-electric machine constructed substantially as described and shown.
JATCIT
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.
For the Applicant,
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C.,
Chartered Patent Agent.