Year: 1897

page_text: I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, do hereby declare the nature of this invention to be as follows:-
This invention relates to alternating current motors and more particularly to that
kind or class of motors in which alternating currents differing in phase are supplied
to one member of the motor known as the primary member the other member of the
motor known as the secondary member being in general provided with a closed
circuit winding. Such motors are commonly known as non-synchronous induction
motors.
The chief object of the invention is to provide means whereby a resistance shall
be normally included in the winding on the secondary member of the motor, said
resistance being able to be readily cut out when desired for example when normal speed
has been attained. A further object of the invention is to construct a primary
member which shall have a substantially uniform pole strength and which will
consequently exert a uniform maximum inductive effect on the secondary member.
In carrying out the invention the secondary member consists of an iron core
having a winding distributed on its polar surface, said winding being formed of
bars connected together at either or both ends so as to form a closed circuit in a
manner known to the trade. The ends of a suitable number of alternate bars are
also connected by a suitable resistance. Under these circumstances the secondary
winding will have resistance. Means are provided for readily shortcircuiting the
resistance joining the ends of the bars and at the same time connecting all the bars
together at one or both ends. In a modification the ends of all the bars forming
the secondary winding are normally joined through resistances which can be readily
shortcircuited at one operation when desired. A very simple means for short-
circuiting the ends of the bars as hereinbefore mentioned consists of a ring adapted
to rotate concentrically with the motor shaft a suitable distance back and forth, the
said ring is provided with projections or brushes which in one position of the ring
touch all the bars and in the other position do not touch said bars. I do not, how-
ever, confine myself to this specific device for the purposes of my invention.
The improved primary member is provided with electrically independent windings
equal in number to the number of phases in the currents. Each winding comprises
as many groups of coils as there are poles to the machine. In order to obtain
uniform pole strength each group of coils extends over a space on the polar surface
wider than the pitch, that is to say, the extreme distance along the polar face from
the first coil of a group to the last coil of a group is greater than the pitch. The.

page_text: groups of coils of the different windings. are symmetrically arranged with regard to
each other. For example, in a motor having four poles for use with two phase
currents there will be two distinct windings on the primary member each having
four groups of coils and I arrange that the coils of one group shall partly overlap
the coils in the adjacent groups of the same winding, preferably about half the coils
of one group overlap half the coils of the next group. Under these conditions the
portion of the polar surface enclosed and not covered by the coils of one group
are covered by the coils of the other group. The coils are preferably wound in
grooves in the polar surface and so arranged that the same number of wires are
placed in every groove.
The of 1007
Improvements in Alternating Current Motors.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
Electrician, 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 alternating current motors and more particularly to that
kind or class of motors in which alternating currents differing in phase are supplied
to one member of the motor known as the primary member the other member of the
motor known as the secondary member being in general provided with a closed
circuit winding. Such motors are commonly known as non-synchronous induction
motors.
The chief object of the invention is to provide means whereby a resistance shall
be normally included in the winding on the secondary member of the motor, said
resistance being able to be readily cut out when desired for example when normal speed
has been attained. A further object of the invention is to construct a primary
member which shall have a substantially uniform pole strength and which will
consequently exert a uniform maximum inductive effect on the secondary member.
In order that the invention may be clearly understood I have shewn in the
accompanying drawings how the same may be carried out in practice.
Figure 1 is a rear end elevation of a motor constructed according to this invention
the end plate of the primary member being removed to shew the winding of said
member.
Figure 2 is a diagrammatic development of the winding of the secondary member.
Figure 3 is a diagrammatic development of the primary winding for one phase
of the current and
Figure 4 is a similar diagram for the other phase of the current.
Figure 5 is a view similar to Figure 1 shewing a modification of the secondary
winding.
Figure 6 is a portion of the transverse section of the secondary member.
Figures 7 and 8 are detail views hereinafter explained.
Referring now to Figures 1 and 2 of the drawings 101 is the frame of the machine
the portion 102 of which is the ring-shaped core of the armature or secondary
member provided with eighty-two slots around its inner periphery in which are
located the alternately arranged long conductor bars 103 and short conductor
bars 104. The short conductor bars. 104 are respectively connected with the long

page_text: bars 103 by means of the connecting conductors 105, so as to form a continuous
closed circuit winding. These connecting conductors are soldered to the ends of
the bars 103 and 104, and are alike in construction and arrangement at both enda
of the machine, except that those at the end of the machine shewn in Figure 1 span
twenty bars, while those at the opposite end, span.twenty-two bars. With this
arrangement of armature conductors a four-pole field magnet is necessary, as will be
readily understood. It will also be understood that the armature conductor bars
may be so connected as to form a winding adapted for a field magnet having a
different number of poles by making the connectors of such length as to span,
the
requisite number of bars, and that the number of slots and corresponding bars may
be varied as may found necessary or desirable in practice.
Suitably fastened to the ends of several of the long bars 103 so as to make good
electrical connection therewith, are several resistance pieces 106 twenty of such
resistance pieces being shewn in the drawing. They may be constructed of any.
conducting material of high resistance, but preferably of iron, as this is inexpensive
and entirely satisfactory in its operation. The number and size of these resistanco
pieces will of course depend upon the character of the particular machine to which
they are applied. With a four pole machine like that shown in the drawing, it is
obvious that twenty resistance pieces connected together and to twenty-one con-
secutive long bars at one end of the armature, as shewn, will provide the necessary
starting resistance for the entire armature circuit.
It will be readily understood that practically the same result may be effected by
employing ten resistance pieces and connecting them to the corresponding ends of
twenty-one consecutive bars. As it is much more convenient to attach the resistance
pieces only to the ends of the long bars, I prefer the arrangement shewn, in which a
space double the pitch is covered. It is obvious that the resistances might be con-
tinued all the way around the armature, if desired, but the number shewn is
ordinarily all that is necessary or desirable.
Soldered to each connecting conductor 105 at the point nearest the outer peri-
phery of the core is a contact block 107. Mounted in the frame of the machine so
as to be capable of having a limited movement around the axis of the machine is
a ring 108 of good conducting material to which are bolted contact brushes 109,
these brushes being in the same vertical plane as the contact blocks or pieces 107.
A handle 110 is pivoted in a slot in the upper portion of the frame of the machine,
and its lower end is connected to the ring 108 so that as the handle is moved back
and forth the contact brushes 109 will be either brought into engagement with the
contact block 107 or moved out of engagement therewith. It will he apparent
from the foregoing description that when the brushes are out of contact with the
blocks 107 as shewn in Figure 1, the starting resistance will be in circuit with the
armature winding, this relation of the parts being maintained until the motor
reaches normal speed. When full or normal speed is attained, the ring 108 is
rotated a sufficient distance to bring the brushes 109 into engagement with the
blocks 107 thus short-circuiting the starting resistance and connecting all the
bars 103, 104, together. It will be understood that approximately the same result
may be effected by means of a less number of blocks or contact pieces 107 and
brushes 109, twenty of each of these devices, if properly located with reference to
the resistance pieces 106 being operative for the purpose intended, hence I do not
desire to be understood as limiting my invention to a construction in which a brush
and contact block is employed for every connector 105.
The primary member or field magnet 110 is provided with a winding 111 which
will be particularly described with reference to Figures 3 and 4. In the particular
field magnet shewn, the core is provided with ninety-six slots, but a different number
suitable to the number of poles and the number of coils to each
pole may be employed as may be found desirable. For example, one
half or
one fourth the number shewn, would be suitable for a four
pole machine. Each coil preferably comprises several turns, three being
indicated in Figure 1, and each slot contains one side of each of two coils, one above

page_text: the other. For convenience of illustration, the portions of the two coils in the same
slot are indicated in Figures 3 and 4 as located side by side. The coils shewn in
Figure 3 constitute the winding for one phase and those in Figure 4 the winding
for the other phase, these two windings being identical except as regards location.
The coils are separately wound upon suitable forms and are all exactly alike. Each
group contains twelve coils and each coil spans twenty slots; for example, in group A
the coils are in slots 1 to 12 and 20 to 31, all connected in series as shewn to form a
continuous winding. The coils of group B are in slots 25 to 36 and 44 to 55, and are
also connected in series. The coils of group C are in slots 49 to 60 and 68 to 79,
and those of group D in slots 73 to 84 and 92 to 7. The ends of the four groups of
coils are brought out and connected as follows: the end of coil A from slot 31 is
connected with the end of coil D from slot 7, the end of coil B from slot 55 with the
end of coil C from slot 79; the end of coil C from slot 49 with the end of coil D
from slot 73. The ends of coils A and B from slots 1 and 25 are left free to be
connected to the corresponding collector rings for this phase. Instead of connecting
the groups in series, as shewn, they may be in parallel, if desired.
The direction of current flow at any given instant will be apparent from the arrow
points on the drawing. It will also be observed that when this winding is in
position, each polo comprises seven slots each of which contains conductors belonging
to two adjacent groups of coils, and five slots on each side each of which contains
only one conductor, and that between each two consecutive poles seven slots are left
empty.
The winding for the other phase shewn in Figure 4 comprises groups A¹, B¹, C¹
and D, group A' occupying slots 13 to 24 and 32 to 43, group B slots 37 to 48
and 56 to 67, group C slots 61 to 72 and 80 to 91, and group D slots S5 to 96 and 8
to 19, the coils of each group being connected in series the same as those belonging
to the first phase. The several groups are connected as follows: the end of group A
from slot 43 is connected to the end of group 1' from slot 19; the end of group B₁
from slot 67 to the end of group C from slot 91; the end of group D₁ from slot 85
with the end of group C₁ from slot 61, and the ends of groups A and B from
slots 13 and 37 are carried out for connection with the corresponding collector rings
for this phase. It will be seen that in each winding each coil embraces a space
represented by twenty slots which is four less than the pitch.
If the groups constituting the winding for the first phase are connected in
parallel, it is obvious that those shewn in Figure 4 must be so connected.
The direction of current at any given instant which determines the number and
location of the poles will be apparent from the arrow points in the drawing. It
will also be observed that the double and single arrangement of conductors and
empty slots is the same as that which has already been described with reference to
the other phase winding, except that the empty slots in this figure are the filled
slots in Figure 3 and vice versa.
It will be understood from the foregoing illustration and description that a
practically uniform maximum inductive action is secured and that the magnetiza-
tion produced by each winding and also that produced by the combined action of
both windings will be that of a wave substantially sinusoidal in form provided the
electromotive force wave is of that form. The number of filled and the number of empty
slots which will be present with only one of the windings will, of course, vary with
the number of slots in the core and the number of poles, but in general each will
preferably cover a space approximately equal to one third of the pitch.
The winding above described is not only of great value by reason of the magnetic
results secured, but is also important and of great value by reason of its ready
applicability to the core, its symmetrical arrangement and the reduction in the
amount of copper employed and consequently in the resistance.
It is to be further understood that the invention is not limited to either the
specific number or the arrangement of coils or groups of coils shewn and described.
In Figures 5 and 6 of the drawing, is shewn an armature winding suitable for use

page_text: in connection with a field magnet having any number of poles. In these figures the
frame 101, slotted ring armature core 102 the ring 108, its brushes 109, and actuat-
ing handle 110 are substantially the same in construction as the corresponding
parts shewn in Figure 1. In this form of the invention, however, instead of
employing alternately arranged long and short armature conducting bars and con-
necting conductors 105, as in Figure 1, bars 112 are provided all of the same length
and a conducting ring 113 is fastened to their ends at each end of the machine,
one or both of these rings being made of high resistance material. In small or
moderate sized machines one of these rings 113 may be made of good conducting
material, but in the machines of larger size it may be desirable to make them both
of high resistance material in order to secure the necessary amount of starting
resistance in the armature circuit. In this form of machine, the brushes 109 carried
by the rings 108 are 50 located as to engage with the outer edges of the armature
conductor bars 112 adjacent to the rings 113. In case only, one high
resistance ring is employed, obviously only one ring 108 and one set
of brushes 109 are necessary. Any suitable means may be employed for sup-.
porting the ring or rings 108 in such manner as to permit of shifting the same
to bring the brushes into or out of contact with the conductor bars, such means
being shewn in the present instance as screws or pins 113 which engage with an
annular groove 114 in the frame of the machine. In Figure 5 the field magnet 110
is shewn merely in outline, the winding being concealed by the end plate. It will
preferably have the general construction shewn in Figures 1, 3 and 4, the number
of poles being, however immaterial.
In machines in which the number of conductor bars employed in the armature is
so large that adjacent bars are located very near together, some special arrangement
is necessary whereby, the brushes may be thrown completely off the bars, when it is
desired to introduce the starting resistance. I have shewn an arrangement by means
of which this may be effected in Figures 7 and 8 which show portions of the bars,
ring and brushes in perspective. Each brush in Figure 7 is shown in contact with
its corresponding conducting bar, and in Figure 8 each brush being shewn as out of
contact. In the construction here shewn, each bar 115 is provided either at one or
at both ends, according to whether one or two switch rings are employed, with a
notch or recess in its upper edge, half of said conductors having notches 116 at the
extreme end next the ring 113 and the alternate bars having notches 117 located
at a distance from the ring 113 at least equal to the width of the brushes, the brushes
being also alternated in position so that each set will be in the same vertical plane
as the corresponding notches or recesses. With this arrangement of notches and
brushes it is apparent that when the ring 108 is shifted to include the resistance in
circuit, the brushes will move from the outer edges of the conductor bars into the
corresponding recesses in the adjacent bars.
While I have illustrated and described certain specific details of construction, I
desire it to be understood that these details may be varied within considerable limits
without departing from the spirit and scope of my invention.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is;-
1. An electric motor comprising an armature having a distributed winding, a
starting resistance normally in circuit therewith, and a short-circuiting device for
said resistance movable into engagement with said winding.
2. A polyphase induction motor the primary member of which is provided with
electrically independent windings for the several phases respectively comprising as
many groups of coils as the said member has poles, the spaces included between the
sides of each coil being less than the pitch.
3. An induction motor constructed substantially as described with reference to
Figures 1 and 2 or to Figures 5 and 6 of the accompanying drawings.
4. The device for connecting and disconnecting the ends of the armature bars

page_text: constructed as described with reference to Figures 7 and 8 of the accompanying
drawings.
5. For an induction motor a primary member constructed as described with refer-
ence to Figures 3 and 4 of the drawings.
Dated th 10th dow of Tonu 1800
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham,
Patent Agents for the Applicant.