Improvements in Speed Varying Devices and Electric Motors for Use therein.
Year: 1898

page_text: Date of Application, 21st June, 1898
Complete Specification Left, 20th Mar., 1899-Accepted, 21st June, 1899
[Communicated from abroad by ROBERT H. HASSLER, of Pittsburg, in the County
of Allegheny, and State of Pennsylvania, United States of America.]
Improvements in Speed Varying Devices and Electric Motors for Use
therein.
I, REGINALD BELFIELD, of 32, Victoria Street, in the City of Westminster,
England, Electrician, do hereby declare the nature of this invention to be as
follows:-
My invention relates to speed varying devices and has for its object to provide
an arrangement whereby the speed of a shaft or pulley which is rotated by means
of alternating current motors may be varied, the motors being operated at their
maximum efficiency.
My invention further comprises an improved electric motor of the kind above
mentioned, for use in the improved arrangement above mentioned.
According to the present invention I provide for rotating the shaft or pulley
at a speed which is the resulting speed obtained by combining the rotation of
two electric motors running at different speeds and then by reversing the direction
of rotation of one of the motors the shaft will rotate at a different speed, and if
necessary can be rotated in the opposite direction at two speeds, by reversing the
direction of rotation of both motors or of the other motor. Another arrangement
for varying the speed is to employ motors the number of poles of which can be
varied and the construction of such a motor forms a particular feature of my
invention.
In order that the invention may be clearly understood I will proceed to describe
the same with reference to the accompanying drawing in which,
Figure 1 is a diagram, and
Figure 2 is a horizontal, longitudinal section through two motors and shewing
the mechanical and electrical connections between them, the electrical circuits
and connections being shewn diagrammatically.
Figure 3 is a diagram of a modification of circuits for two motors and their
switches and connections.
Reference being now had to Figures 1 and 2 of the drawing, A is an electric
generator here shewn as a generator of two phase currents, although for certain
conditions a generator of a different number of phases may be employed, if desired.
The leads from the generator A are connected by means of the conductors B, C,
and D, E, with the coils on the primary member F1 of the motor F, and by the
conductors B. (", and D¹, E, with the coils on the primary member G of the
motor G. While I prefer to connect the circuits of the two primary members of
the motors F and G in parallel, as indicated, they may be connected in series. if
desired, and hence I do not desire to limit the invention to the particular con-
nection shewn. Motor F is provided with four inwardly projecting radial pole
pieces on which are wound the coils connected with the conductors B. C. and D. E.
there being thus produced a rotating magnetic field having two pols. This rotat-

page_text: ing magnetic field acts upon a closed circuit armature H.
The primary
member G is provided with sixteen inwardly projecting pole pieces on which are
wound two sets of alternately arranged coils, connected respectively with the con-
ductors B, C and D, E, by means of which a rotating magnetic field is produced
having eight poles which act upon a closed circuit armature I. I do not desire
to limit my invention to the specific number of poles shewn in the drawing, since the
number may be varied within considerable limits and the mechanism still be useful
and operative for the purpose intended, the particular form, number and arrangement
of parts being intended merely to illustrate one of a variety of modifications in which
the invention may be embodied in practice. In the circuit D, C, I have included a
reversing switch J, of any suitable type, for the purpose of reversing this circuit,
the object of this reversal being hereinafter stated.
As indicated in Figure 2, the secondary members H and I of the two motors
are rigidly mounted upon a shaft K, the latter being mounted at its ends in
bearings L and M. The primary member F1 of the motor F is stationary, and
the primary member G¹ of the motor G is so mounted as to be free to rotate inde-
pendently, it being shewn in the present instance as connected to sleeves or hollow
shafts N and N', through which extends the shaft K. These hollow shafts or
sleeves are respectively mounted in suitable stationary bearings 0 and 01, and the
shaft is provided with a suitable power transmitting device P, which may be
either a gear wheel or a pulley, according to the requirements of the particular
service in which the motor is to be employed.
In order to permit of the rotation of the member G¹ independently of the shaft K
and the parts carried thereby, I provide four contact or slip rings Q, upon which
bear two sets of suitable contact brushes Q¹ connected with the conductors 13', C,
and D, E, leading from the generator A, and the rings being connected with the
coils of the primary member G of the motor G. It will be seen that the shaft K
and the members H and I may be rotated at any desired speed, and the member G¹
and its bearing sleeves or hollow shafts rotated at a different speed either in the
same or in the opposite direction.
While I have illustrated and described the external members of the motors as
those to which the alternating currents are supplied, I desire it to be understood
that my invention is not limited to such an arrangement, as the inner rotating
members H and I may be made the primary elements and have the alternating
currents supplied thereto, the external members having the closed induced cir-
cuits, or one of the motors may have such arrangements of the parts and the other
be arranged as shewn in the drawing, if desired.
As
The operation of the apparatus thus far described is as follows, it being
assumed that the reversing switch J is in the position shewn in the drawings. As
the motor F has two, and the motor G eight poles, and they are excited by
currents having the same number of alternations, they will obviously run at
different speeds. Let us suppose, for example, that the primary current makes
3,000 alternations per minute. The number of rotations being equal to the
number of alternations divided by the number of poles, motor F will tend to run
at 1500 revolutions per minute, and motor G at 375 revolutions per minute.
the two members H and I are rigidly connected together by means of the shaft E,
they, with the shaft, will run at 1,500 revolutions, if there is no load, and as the
two magnetic fields revolve in the same directions, the speed of the primary
member G, and therefore that of the power transmitting device P, will be equal
to the difference between the speed of the shaft K and the speed at which the
member G tends to run by reason of the current supplied thereto, or 1125 revo-
lutions per minute, its direction of rotation being the same as that of the shaft K.
The two motors will then be at synchronism, as the speed of the secondary motor G
with respect to its primary will be 375 revolutions per minute.
The conditions above stated are theoretical and will vary somewhat in practice,
on account of the slip of the motors more particularly when they are working
under load. If now we reverse the circuit B', (", by means of the switch J, the

page_text: magnetic fields of the two motors will revolve in opposite directions and the resul-
tant speed of the member G¹ and its connected parts will therefore be the sum of
1500 and 375, or 1875 revolutions per minute, the two motors being again running
in synchronism, but the relative speed of the members I and G' will be the reverse
of that above described, as has already been stated.
It will thus be seen that with this combination and arrangement of two motors
and a reversing switch, we are enabled to run the power transmitting device l'
at two widely different speeds and at the same time maintain a comparatively high
degree of efficiency.
It will also be understood from the foregoing illustration and description that
various other speeds within practical limits may be secured, without impairing the
efficiency of the motors, by varying the number of magnetic poles of either or
both of the primary members; for example, if the number of poles of the motor F
be increased to six, so that its synchronous speed is reduced to 500 revolutions per
minute, the resulting speed of the shaft will be either 125 revolutions per
minute or 875 revolutions per minute, depending upon the relative direction of
the two rotating magnetic fields controlled by the switch J. Again,
if the number of poles on the motor G be increased to twenty-four, then
with six poles on motor F, the speed of shaft N¹ will be either 625 revolutions
per minuta or 375 revolutions per minute, depending upon the position of the
switch J. With twenty-four poles on motor G and two poles on motor F', the speed
of the shaft N will be either 1375 of 1625 revolutions per minute, depending upon
the position of the switch J.
These
It is not feasible to make the changes in the number of poles necessary for the
different speeds enumerated above in motors constructed as indicated in Figures I
aud 2, as the exciting coils are arranged upon projecting pole pieces.
changes in the number of poles may be effected, however, if the projecting pole
pieces and the winding be distributed in slots. I have shewn such an arrange-
ment diagrammatically in Figure 3, in which R and R' represent respectively the
circuits for the two phases of current in the primary member of the first motor,
and S and S respectively the circuits for the two phases of current in the primary
member of the second motor. The conductors of the two windings of each motor
will be arranged in the same slots, but in order to avoid confusion they have been
separated in the drawing. In this figure, H' represents the closed circuit secon-
dary member of the first motor, and the corresponding member of the second
motor. In this figure the generator A, the switch J for reversing the circuit S
of the second motor, and the conductors B, C, B, C, DE; and D, E, laading
from the generators to the motors are constructed and arranged substantially the
same as corresponding elements shown in Figures 1 and 2 of the drawings. In
this figure of the drawing I have indicated the location of those portions of the
conductor which lie in the slots by radial lines, the connections between these
radial portions being indicated by circumferential and transverse straight lines.
In the circuits R and R¹ the radial lines which represent the location of these
portions of the conductor which determine, by the direction of the current, flowing
through them, the magnetic poles I have indicated as a, b, c.
r, the arrangement being such that the poles produced by the conductors in
circuit R shall be displaced in phase 90° with reference to those produced by the
conductors in the circuit R', the poles of the circuit S being also displaced in
phase 90° with reference to those produced by the conductors in the circuit St.
The switches T and T and C and are employed for the purpose of changing
the number of poles in the two motors, as will be hereinafter more fully set forth.
Assuming the switches T and T to be in the position shewn in the drawing, at
any given instant the current flows in one direction through the conductors of
circuit R at a, b, c, d, e, f, g, t, u, v, w and x and in the opposite direction through
the conductors at h, i, j, k, l, m, n, o, p, q, r and s, thus producing two magnetic
poles. With the same arrangement of the switch T', the current in the circuit R',
which differs in phase a quarter period from that in the circuit R will flow

page_text: and in the opposite
through the conductors at b, c, d, e, f, g, h, i, j, k,l and m
direction through the conductors at n, o p q r, s, t, u, v, w, and a, thus producing
two magnetic poles which are displaced in phase 90° from those in the circuit R.
If now the switches T and T be reversed, so that the movable blades or contact
arms shall be in engagement with the lower stationary contacts, current will flow
at any given instant in the circuit R in one direction through the conductors at
x, a, b, c,h, i, j, k, p, q, r, s, and in the opposite direction through the conductors
at d e, f, g, l, m, n, o,- t, u, r, w, thus producing six magnetic poles. In the
same manner a current differing by a quarter period from that in the circuit R
will flow through the conductors of the circuit 1 at b, c, d, e, j, k, l, m, r, s, t, u,
in one direction, and in the opposite direction through the conductors at f, g, h, i,
-n, o, p, q, v, wr, a, thus producing six magnetic poles which are displaced in
phase 900 from those in the circuit R.
Referring now to circuits S and S1, with the switches U and U₁ in the position
shewn in the drawing the current at any given instant in the circuit S will be in
one direction through the conductors at 1, 2, 3, 4, 5, 6,-13, 14, 15, 16, 17, 18,
--25, 26, 27, 28, 29, 30,--37, 38, 39, 40, 41, 42, in one direction, and through
the conductors at 7, 8, 9, 10, 11, 12,-19, 20, 21 22, 23, 24, 31, 32, 33, 34,
35, 36, 43, 44, 45, 46, 47, 48, in the other direction, thus producing eight mag-
netic poles. In the same manner the current through the conductors in the
circuit S will produce eight poles which will be displaced 90° in phase from
those in the circuit S, such poles being located at 4.
9, . 10
15, 16.
21, 22
27, 28
33, 34.
39, 40
45, and 46
if now the switches U and U be reversed, the circuit S will produce twenty-four
magnetic poles by means of the current through the conductors at 1, 2 5, 6, 9,
10, etc., in one direction, and in the opposite direction through the conductors
at 3, 4, 7, 8, 11, 12 etc. In the circuit S', the current will flow in the same
direction through conductors at 2, 3, 6, 7, 10, 11, etc., and in the opposite
direction through the conductors at 4, 5, 8, 9, and 12, 13 etc., thus producing
twenty-four magnetic poles which are displaced in phase 90° with reference to the
poles produced by the current in the circuit S.
3.
It will obviously be necessary to throw the switches T and T at the same time
in order to have the same number of poles in both circuits of the same motor, and
for the same reason it will be necessary to throw the switches U and C at the
same time. In practice they may be connected in such manner that they must of
necessity be operated together.
The method of changing the number of poles herein before set forth may be
employed advantageously in connection with the usual forms of alternating
current motors, for some classes of work it may be found desirable in practice to
employ auxiliary windings for one number of poles and cut the same out of circuit
when a different number of poles is desired, or auxiliary windings may be employed
which can be thrown from one phase to the other when the number of poles is
changed. I therefore desire it to be understood that my invention is not limited
to the specific construction and arrangement of coils shewn, or to any specific
number of pole changing switches and circuits.
1
T
1000
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.

page_text: Improvements in Speed Varying Devices and Electric Motors for Use
therein.
I, REGINALD Belfield, of 32, Victoria Street, in the City of Westminster,
England, 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:-
11
My invention relates to electric-motors, and has for its object to provide an
improved winding for the primary members of induction-motors whereby the
number of poles formed by the current circulating round the primary coils may
be varied by the mere manipulation of a switch without making any alteration
in the mechanical structure of the motor.
The characteristic feature of my invention is that the various coils of the
primary winding of the motor are always connected in series although the direction
of the current flowing through certain of said coils is altered when the number
of poles is varied. By this means I avoid any complications arising from varying
the number of coils or number of coils in circuit and maintain constant the ohmic
resistance of the circuit.
My invention is illustrated, by way of example, in the accompanying drawings
which are diagrams showing my improved method of winding the primary member.
Figure 1 is a diagram illustrating a primary member provided with 24 slots in
which the coils are placed, and shews the coils connected up so that the primary
member has 4 poles. Figure 2 shews the same machine but having the currents
in some of the coils reversed in direction, by which the primary member is caused
to have 12 poles. Figure 3 is a diagram shewing the method of winding a two-
phase machine so that it may be caused to have either 2 or 6 poles, and Figure 4
is a view of a two-phase machine the winding of which is arranged so that the
primary member may have either 8 or 24 poles.
In
In these diagrams the locations of those portions of the conductors which lie
in the slots are indicated by radial lines, the connections between these radial
portions being indicated by circumferential and transverse straight lines.
Figures 3 and 4 the conductors of the two windings of the motor, one for each
phase of the current will be arranged in the same slots although, in order to
avoid confusion, they are shewn separate in the drawing. I indicates the secon-
dary member in each case.
The coils of the motor are arranged in two sections, one of which embraces
twice as many poles as the other, and the current in this portion of the winding
always flows in the same direction, that is to say, this winding is always con-
nected to the circuit in one manner. The other portion of the winding has its
polarity changed according to the number of poles which it is required to produce.
Referring to Figure 1 the two windings are indicated by the letters P and Q.
The winding passes through slots 1 and 2 in one direction, and 3 and 4 in the
opposite direction; it then misses slots 5 and 6, passes through slots 7 and 8 in
the same direction as 3 and 4, and through 9 and 10 in the opposite direction;
it then misses slots 11 and 12, passes through 13 and 14 in the same direction
as 9 and 10, and through 15 and 16 in the opposite direction; it misses slots 17
and 18, passes through slots 19 and 20 in the same direction as 15 and 16 and
through 21 and 22 in the opposite direction, and misses slots 23 and 24.
In
Slots 21 and 22 will have current flowing in them in the same direction as slots 1
and 2. This system of connections remains constant under all conditions.
circuit Q slots 5 and 6, and 17 and 18 have the winding connected so that current
passes through them in the same direction, while slots 11 and 12, and 23 and 24

page_text: are arranged so that the current passes through them also in the same direction,
but opposite to that flowing in slots 5 and 6.
If circuit Q be so connected in series with circuit l' that the currents in the slots
have the same direction as the currents in the adjacent slots supplied by P we
shall have currents flowing in slots 3, 4, 5, 6, 7 and 8 in one direction, and 9, 10, 11,
12, 13 and 14 in the opposite direction, that is to say, the currents in each 6
adjacent slots will be flowing in the same direction, making one pole. Hence the
primary member will have 4 poles, this state of the motor being shewn in
Figure 1; if now the current in circuit Q be reversed by turning the reversing
switch T the arrangement shown in Figure 2 will be obtained so that the currents
in the slots fed by circuits Q will be in the opposite direction to those in the adja-
cent slots. Each pole covers two slots only so that instead of having 4 poles the
motor will have 12 poles.
Referring now to Figure 3 the slots are designated by the letters a, b, c up to .r,
and the circuits for the two phases are indicated by R and R' respectively. The
arrangements of the conductors are such that the poles produced by the current
flowing in circuit R are displaced in phase 90° with reference to those produced by
the current flowing in the conductors of the circuit R¹. T and T are the revers-
ing switches for the two phases, A being a two-phase generator supplying current
to the motor. If the switches T and T be in the position indicated in the draw-
ing, at any given instant the current flows in one direction through the conductors of
circuit Rat a, b, c, d, e, f, g, t, u, v, w, and a and in the opposite direction through
the conductors at h, i, j, k, l, m, n, o, p, q, and s, thus producing two magnetic
poles. The current in the circuit R¹, which differs in phase a quarter period from
that in the circuit R will flow through the conductors at b, c, d, e, f, g, h, i, j, k, l, m,
and in the opposite direction through the conductors at n, o, p, q, r, St, U, V, W, it',
and, thus producing two magnetic poles which are displaced in phase 90° from
those in the circuit R.
If now the switches T and T¹ be reversed, current will flow at any
given instant in the circuit R in one direction through the conductors at
a, a, b, c, h, i, j, k, p, q, r, s, and in the opposite direction through the conductors
at d, e, f, g,--!, m, n, 0, ,,,, thus producing six magnetic poles. In the
same manner a current differing by a quarter period from that in the circuit R
will flow through the conductors of the circuit Rat b, c, d, e, j, k, l, m, r, s, t, u,
in one direction, and in the opposite direction through the conductors at f, g, h, i,
―n, 0, 1, 9,―r, w,,, thus producing six magnetic poles which are displaced in
phase 90° from those on the circuit R.
one
Referring now to Figure 4 the circuits for the two phases are indicated by S
and S. The primary member of the motor is provided with 48 slots and with the
reversing switches U and U. In the position shewn in the drawing,
the current at any given instant in the circuit S will be in
direction through the conductors at 1, 2, 3, 4, 5, 6,--13, 14, 15, 16, 17, 18,
--25, 26, 27, 28, 29, 30, 37, 38, 39, 40, 41, 42, in one direction, and through
the conductors at 7, 8, 9, 10, 11, 12,--19, 20, 21, 22, 23, 24, 31, 32, 33, 34,
35, 36, 43, 44, 45, 46, 47, 48, in the other direction thus producing 8 mag-
netic poles. In the same manner the current through the conductors in the
circuit will produce eight poles which will be displaced 90° in phase from
those in the circuit S, such poles being located at 4
16
45, and 46
21, 22
3.
27, 28.
33, 34
9, 10.
39, 40
15,
If now the switches and be reversed, the circuit S will produce twenty-four
magnetic poles by means of the current through the conductors at 1, 2, 5, 6, 9,
10, etc., in one direction, and in the opposite direction through the conductors
at 3, 4, 7, 8. 11, 12, etc. In the circuit S, the current will flow in the same
direction through conductors at 2, 3, 6, 7, 10, 11, etc., and in the opposite
direction through the conductors at 4, 5, 8, 9, and 12, 13, etc., thus producing

page_text: twenty-four magnetic poles which are displaced in phase 90° with reference to the
poles produced by the current in the circuit S.
It will obviously be necessary to throw the switches T and T at the same time
in order to have the same number of poles in both circuits of the same motor, and
for the same reason it will be necessary to throw the switches and U at the
same time. In practice they may be connected in such manner that they must of
necessity be operated together.
It is clear from the examples shewn that the invention is not restricted to the
cases where the motor has 24 or 48 slots in its primary member although these
numbers are very convenient for the winding. Nor is it restricted to motors
working on a one or two phase circuit, but is applicable to a motor working on
a circuit having a larger number of phases.
I have described in my Provisional Specification the application of such motors
as hereindescribed for the purpose of obtaining a variation in speed of a shaft or
pulley, I wish it understood however that I do not claim such arrangements but
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. An induction motor the number of poles in the primary member of which
can be changed by reversing the direction of the current in certain portions of the
primary winding with reference to the core in such a manner that the winding
is always connected in series.
2. An induction motor the primary winding of which is divided into two sections
connected in series, one of said sections embracing twice as many poles as the
other section, the direction of current in one of the sections being able to be
reversed relatively to the direction of current in the other section substantially
as and for the purpose specified.
3. Induction motors having a primary winding arranged substantially as
described with reference to the accompanying drawings.
Dated the 20th day of March 1899
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester, and Birmingham.