Improvements in Dynamo Electric Machines and Motors.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Dynamo Electric Machines and Motors.
SIDNEY GEORGE BROWN, Van Buren, Poole Road, Bournemouth, in the County
of Hants, Electrical Engineer, do hereby declare the nature of this invention
to be as follows:-
This invention relates to improvements in dynamo-electric machines and motors
and especially to that class having its armature conductors placed in holes or
slots in the perhipery of the armature dises, and working with narrow air space
or clearance, the object being to economise material and at the same time to
obtain an easily commutatiable machine.
In applying my invention to a multipolar I make each alternate pole,
and which I shall here call the commutating pole, sufficiently strong to
effect the commutation of the whole of the armature section, while on
the other poles I effect as great a saving of material as possible by
the use of a narrow air gap or clearance.
If the machine is supplied with a series wound ring or drum armature, then
a less number of poles, say only one, need be strengthened for commutating
purposes, allowing of a still greater saving in field magnet iron and copper.
In the case of a bipolar, there need be only one commutating pole, while a
saving in weight and material can be gained by the employment of a narrow air
gap or clearance, on the other.
The commutating poles may have the polar area restricted by cutting deep
notches in the pole face, or else the air space or clearance can be increased, so
us to gain the desired regidity of magnetic field.
To eliminate back turns I may increase the polar spans of all or any of the
commutating poles, so that as one armature conductor is entering the field
for the purposes of commutation another conductor in series with it may be
leaving the field.
For the object of compounding or otherwise I may place any of the poles out
of their position of symitery.
Doted this Twenty-eight day of June 1898.
Improvements in Dynamo Electric Machines and Motors.
SIDNEY GEORGE BROWN, Van Buren, Poole Road, Bournemouth, in the County
f Hants, Electrical Engineer, do hereby declare the nature of this invention
DQ17

page_text: and in what manner the same is to be performed, to be particularly described aud
ascertained in and by the following statement;-
This invention relates to improvements in dynamo-electric machines and motors
and especially to that class having its armature conductors placed in holes or
slots in the perhipery of the armature discs, and working with narrow air space
or clearance, the object being to economise material and at the same time to
obtain an easily commutatable machine.
In applying my invention to a multipolar I make each alternate pole,
and which I shall here call the commutating pole, sufficiently strong to
effect the commutation of the whole of the armature section, while on
the other poles I effect as great a saving of material as possible by
the use of a narrow air gap or clearance.
If the machine is supplied with a series wound ring or drum armature then
a less number of poles, say only one, need be strengthened for commutating
purposes, allowing of a still greater saving in field magnet iron and copper.
In the case of a bipolar there need be only one commutating pole, while a
saving in weight and material can be gained by the employment of a narrow air
gap or clearance, on the other.
The commutating poles may have the polar area restricted by cutting deep
notches in the pole face, or else the air space or clearance can be increased, so
as to gain the desired regidity of magnetic field.
To eliminate back turns I may increase the polar spans of all or any of the
commutating poles, so that as one armature conductor is entering the field
for the purposes of commutation another conductor in serie with it may be
leaving the field.
For the object of compounding or otherwise I may place any of the poles out
of their position of symitery.
Referring to the drawing Fig. 1, which represents a multipolar dynamo or
motor constructed according to my invention.
In this case the armature A is represented as fitted with a series winding,
the conductors being placed in slots or tunnels in the iron of the core.
One section b, c, d, e, f, g, only of the whole series winding is shown, the
two commutator bars of which are passing under the brush and are in a position
for commutation.
The multipolar has six poles B, C, D, E, F, G.
On the poles C, D, E, F, G, a great saving of copper and iron has been effected
by reducing the air space, between the polar faces and the armature iron to its
least workable distance.
By these means the number of exciting ampere-turns to drive any given magnetic
flux across such air space has been materially reduced, while the length of iron
necessary for carrying the field copper has been likewise diminished.
As the armature sections say at reasonable loads have to be commutated and
as they cannot rely on the poles C, D, E, F, G, for this purpose, one pole Bas
is shown has been wound with a much greater number of ampere exciting turns,
This will increase the regidity of the field but as the magnetic flux from
such commutating pole must be kept preferably the same, as from the others
a greater length of air space should be placed between the pole face and the
armature iron, or else deep notches may be cut in the iron so as to restrict the
area of the pole face. By these means the armature section b, c, d, e, f, g, as
it passes under and is shortcircuited by the brush will be commutated, for the
conductor will be passing into a magnetic field from the pole B of right
direction and will be capable of reversing the current throughout the whole
section.
If the air gap between the pole pieces of C, D, E, F, G, and the armature iron
was made very small, and the current circulating in the armature conductors was
very strong, an actual reversal of magnetism under the forward horns of these poles

page_text: may take place, it is therefore important that the commutation should take place
while the conductors are passing as near as possible the neutral axis.
To do this I may widen the polar span as is shown in Fig. 2 so that when the
conductor is on the point of entering the field of the commutating magnet a
conductore in series with it may be leaving the field.
By these means considerable stability may be given the commutation, very
little motion of the brushes, if any, being required, while at the same time the
conductors c, d, e, f, g, will be kept as far away as possible from the pole tips
of the magnets C, D, E, F, G.
Instead of spreading the polar horns H and K over a greater angle I might
only have increased H, the other horn being kept to its normal dimensions.
By this a fair amount of compounding action from the armature currents
may be arrived at. This construction for the purpose of compounding
wise amounts to the same thing as placing some of the poles out of their position
of symitery.
or other-
If the armature A in Fig. 1 was fitted with a parallel winding it would be
necessary to have more than one commutating pole.
In this case the poles B, D, F, would be strengthened while the poles C, E, G,
would be designed for economy by having the air gaps reduced to the least per-
missable dimensions. If so constructed it would be from a manufacturing point
of view convenient to place equal weights of copper on each of the poles, but
the ampere turns from same would be utalized more in driving the magnetic
flux across the air gaps of the poles B, D, F, than across the air gaps of C, E, G.
In the case of a bipolar, say of that class having a double magnetic circuit,
the polar span of one of the polar faces may be increased, but as the armature
conductors would have to depend upon the field from same for commutation the
regidity of the field may be increased, not only by increasing the air gap if
necessary, but by restricting the polar area, say by cutting a broad division
between the two halves of the magnetic pole piece and at right angles or there-
abouts to the direction of the magnetic lines in the magnet.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the said is to be performed, I declare that what
1 claim is-
1. The herein described form of field magnet substantially as and for the
purposes specified
2. A form of field magnet for bipolar or multipolar dynamos or motors in
which one or more of the pole pieces are constructed with narrower air spaces,
or clearances.
3. A form of field megnet, for bipolar or multipolar dynamos or motors, in
which one or more of the pole pieces have their faces restricted, by slots or gaps
cut in the iron.
4. The construction of a field magnet for multipolar dynamos or motors in which
one or more of the polar spans are greater than the others.
5. The construction of a bipolar dynamo or motor in which one of the polar
spins is greater than the other.
6. A field magnet for a multipolar dynamo er motor, where one or more of the
poles are placed out of their position of symitery.
7. A multipolar dynamo or motor, having an armature fitted with a series
winding, the conductors of which are sunk in the perhipery of the iron core,
and having one or more of the poles of the field magnet, (less than the full number)
sufficiently strong to effect the whale of the commutation.
8. A multipolar dynamo or motor having an armature, the conductors of
which are sunk in the perhipery of the iron core, and having each alternate pole
sufficiently strong to effect the whole of the commutation.
9. The construction of a bipolar dynamo or motor having a divided magnetic
circuit, one pole of which has a face, spanning a greater angle than the other,

page_text: the iron adjoining such pole face being divided at or near the centre of the
span by a broad air space.
10. A dynamo-electric generator or motor furnished with a field magnet sub-
stantially as described, with reference to the forms illustrated in the accompanying
drawing for the purpose specified.
D 41,399...1 dve of Lah 1900