Improvements in Alternating Current Induction motors.
Year: 1899

page_text: Date of Application (in United Kingdom), 22nd Dec., 1899
Complete Specification Left, 21st Sept., 1900-Accepted, 24th Nov., 1900
Improvements in Alternating Current Induction motors.
I, BENJAMIN GARVER LAMME, of 230, Stratford Avenue, Pittsburg, in the
County of Allegheny, State of Pennsylvania, U.S.A., Electrical Engineer, do
hereby declare the nature of this invention to be as follows:-
My invention relates to alternating current induction motors and has for its
object to provide a motor of this class which can be operated economically at
variable speeds.
In motors of this class, variations in the speed of which are effected by vary-
ing the electro-motive force applied to the primary members, it is desirable for
satisfactory operation that the secondary member should have a winding of
relatively high resistance and where such resistance consists of mechanical
structure permanently connected in circuit with the secondary member it must
be capable of taking care of comparatively high losses at low speeds since the
losses in the secondary for any given torque are proportional to the slip or the
drop in speed. If low speed running occurs at intervals during a given period
of operation it is desirable to store the heat due to the secondary losses during
such low speed running instead of dissipating it at such periods, and to dissi-
pate it during the times when the motor is running at higher speeds and conse-
quently when it is subject to a lesser degree of loss in its secondary winding.
My invention is directed to the construction of motors having these special
characteristics and comprises a special form of resistance to be included in cir-
cuit with the secondary member, which resistance is arranged to store heat
energy at low speeds and to dissipate the same at high speeds. This resistance
constitutes in effect a heat fly wheel which tends to promote a maximum degree
of economy in the operation of the motor.
In the accompanying drawings:-
Figure 1 is an end elevation of a motor constructed in accordance with my
invention, one of the end plates being removed.
Figure 2 is a detail end view on a larger scale of a portion of the secondary
member of the motor, and
Figure 3 is a detail sectional view of a portion of the secondary member.
The primary member of the motor comprises a frame 2 preferably of cast
iron or steel, a laminated core 3, and a winding 4 located in slots in the core
and suitable end plates, all these parts being of any suitable construction. The
secondary member is the rotating part and comprises a spider 6, a laminated

page_text: core 7, provided with longitudinal slots 8, in which are located conducting
bars 9, which preferably project beyond the ends of the core, and are suitably
insulated. The resistance rings 10, for providing the necessary amount of sec-
ondary resistance are placed preferably one at each end of the machine and are
made of comparatively large cross-section so as to afford much heat storage
capacity. Each ring is connected to the corresponding ends of the conducting
bars 9 by means of radial or substantially radial arms 11, some of which arms
may be provided with a shoulder-for engaging with a projection 13 on the spider
for the purpose of affording additional support and steadying the ring 10. The
arms 11 may be cast integral with or may be separately formed and bolted or
otherwise secured to the ring and are employed in order to provide the necessary
amount of resistance for starting and running at low speeds, since the ring alone,
if made of sufficient dimensions to store the heat due to losses during low speeds
in the manner desired, will not afford the necessary amount of resistance. The
arms 11 may be of such width as to constitute fan blades for promoting circu-
lation, in order to keep down the temperature of the machine and, if desired,
additional fan blades 12 may be provided as indicated in Figure 3.
While I have shewn a form of apparatus suitable for practising my invention,
I desire it to be understood that the form, dimensions and relation of parts may
be varied within considerable limits, if desired....
1
1000
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C.,
Patent Agents for the Applicant.
Improvements in Alternating Current Induction Motors.
I, BENJAMIN GARVER LAMME, of 230, Stratford Avenue, Pittsburg, in the
County of Allegheny, State of Pennsylvania, United States of America, Elec-
trical Engineer, do hereby declare the nature of this invention and in what man-
ner the same is to be performed to be particularly described and ascertained in
and by the following statement:―
My invention relates to alternating current induction motors and has for its
. object to provide a motor of this class which can be operated economically at
variable speeds.
In motors of this class, variations in the speed of which are effected by vary-
ing the electro-motive force applied to the primary members, it is desirable for
satisfactory operation that the secondary member should have a winding of
relatively high resistance and where such resistance consists of mechanical
structure permanently connected in circuit with the secondary member it must
be capable of taking care of comparatively high losses at low speeds since the
losses in the secondary for any given torque are proportional to the slip or the
drop in speed. If low speed running occurs at intervals during a given period
of operation it is desirable to store the heat due to the secondary losses during
such low speed running instead of dissipating it at such periods, and to dissi-
pate it during the times when the motor is running at higher speeds and conse-
quently when it is subject to a lesser degree of loss in its secondary winding.
My invention is directed to the construction of motors having these special
characteristics and comprises a special form of resistance to be included in cir-
cuit with the secondary member, which resistance is arranged to store heat
energy at low speeds and to dissipate the same at high speeds. This resistance

page_text: constitutes in effect a heat fly wheel which tends to promote a maximum degree
of economy in the operation of the motor.
In the drawings filed with my Provisional Specification.
Figure 1 is an end elevation of a motor constructed in accordance with my
invention, one of the end plates being removed.
Figure 2 is a detail end view on a larger scale of a portion of the secondary
member of the motor, and
Figure 3 is a detail sectional view of a portion of the secondary member.
The primary member 1 of the motor comprises a frame 2 preferably of cast
iron or steel, a laminated core 3, and a winding 4 located in slots in the core
and suitable end plates, all these parts being of any suitable construction. The
secondary member is the rotating part and comprises a spider 6, a laminated
core 7 provided with longitudinal slots 8, in which are located conducting
bars 9, which preferably project beyond the ends of the core, and are suitably
insulated. The resistance rings 10, for providing the necessary amount of sec-
ondary resistance are placed preferably one at each end of the machine and are
made of comparatively large cross-section so as to afford much heat storage
capacity. Each ring is connected to the corresponding ends of the conducting
bars 9 by means of radial or substantially radial arms 11, some of which arms
may be provided with a shoulder for engaging with a projection 13 on the spider
for the purpose of affording additional support and steadying the ring 10. The
arms 11 may be cast integral with or may be separately formed and bolted or
otherwise secured to the ring and are employed in order to provide the necessary
amount of resistance for starting and running at low speeds, since the ring alone,
if made of sufficient dimensions to store the heat due to losses during low speeds
in the manner desired, will not afford the necessary amount of resistance. The
arms 11 may be of such width as to constitute fan blades for promoting circu-
lation, in order to keep down the temperature of the machine and, if desired,
additional fan blades 12 may be provided as indicated in Figure 3.
While I have shewn a form of apparatus suitable for practising my invention,
I desire it to be understood that the form, dimensions and relation of parts may
be varied within considerable limits, if desired.
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 in which the resistance included in circuit with the
secondary member consists of a ring or rings of comparatively large cross-section
connected by resistance bars or arms to the corresponding ends of the conductor
bars of the secondary member, for the purpose specified.
2. An induction motor having a secondary member with a resistance included
in circuit constructed, arranged and operating as described and shewn in the
drawing.
1000
1000
Dated the 21st day of September
F. W. LE TALL,
Chartered Patent Agent,
The Westinghouse Patent Bureau,
Westinghouse Building, Norfolk Street,
Strand, London, W.C.