Improvements in and relating to Electro-motors.
Year: 1893

page_text: Date of Application, 20th May, 1893
Complete Specification Left, 10th Feb., 1894-Accepted, 31st Mar.,
1894
PROVISIONAL SPECIFICATION.
Improvements in and relating to Electro-motors.
WILLIAM GREENHALGH, Electrical Engineer, 29 Carlton Street Leeds do
hereby declare the nature of this invention to be as follows:
"
My invention relates to the class of electro-motors designed to be operated
by alternating currents, the object being to provide a motor which will readily
start from a state of rest & maintain a uniform speed under varying loads.
In general, improvements adapting the motor to be inexpensively & conveniently
constructed & easily operated. The field-magnet is laminated, & although
I prefer to make it of circular form with 2 poles, this particular shape
& number of poles is not an essential part of my invention & may be varied
according to requirements. The armature is of that form known as the "Gramme
or "Pacinotti "type & is provided with a commutator similar to that in continuous
current motors. Instead of mounting the armature on the shaft in the usual
manner with metal supports I prefer to use an insulating substance, such as plaster
of Paris. Attached to the shaft is a governing device, which under the normal
speed of rotation of the armature, "short circuits" the armature coils through the
usual brushes. It is essential to the proper working of the motor with alternating
currents, that the armature & field magnet should be properly proportioned to each
other & that the brushes should be in a certain position relative to the field magnet
poles, different from that necessary on continuous current motors. I. employ several
methods of electrically connecting the different parts. I may connect the field
magnet coils & the armature in "series," the governing device "short circuiting
the armature, excepting at such times that the speed of rotation rises above the
normal. In another method the field magnet coils alone are connected to the
source of supply, an induced current produced by the field magnetism circulating
round the armature & the "short circuiting" or governing device, or if the load on
the motor is unvarying the armature may be permanently "short circuited." In
another method I connect a "shunt" coil of suitable resistance across the governing
device, so that the induced current in the armature is only weakened when the
governing device comes into action.
Dated this 19th day of May 1893.
"
WM. GREENHALGH.
COMPLETE SPECIFICATION.
Improvements in and relating to Electro-motors.
I, WILLIAM GREENHALGH Electrical Engineer 29 Carlton Street Leeds,
Yorkshire 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 :-
My invention relates to the class of electro-motors designed to be operated by
either alternating currents or continuous currents as used for electric lighting &
power purposes. In general improvements adapting the motor to be inexpensively
& conveniently constructed & easily operated. The field magnet is laminated &
although I prefer to make it of circular formn with two poles, this particular shape
& number of poles is not an essential part of my invention. The armature may be
of the type known as the "Grainme or Pacinotti," & is provided with a
66

page_text: commutator similar to those in general use. In mounting the armature on the
shaft I use an insulating substance, such as plaster of Paris, instead of the usual
metal support. It is essential to the proper working of the motor that the armature
& field-maguet should be suitably proportioned to each other & when used with
alternating currents the brushes should be in a position relative to the field-magnet
poles different from that necessary on continuous current motors. Attached to the
shaft is a governing device, which by automatically altering the electrical
connections controls the speed of rotation.
When used with alternating currents I may employ either of the following
methods of electrically connecting the different parts. I may connect the field-
magnet coils & armature in "series," the governing device "short circuiting" the
armature, excepting at such times that the speed of rotation rises above the
normal. In another method, the field-magnet coils are alone connected to the source
of supply, an induced current-produced from the field magnetism-circulating
round the armature & governing device; or if the load on the motor is unvarying
the armature may be permanently short-circuited. In another method I connect a
* shunt" coil of suitable resistance, or a reactive coil, across the governing device,
so that the induced current in the armature is only weakened when the governing
device comes into action.
Referring to the accompanying drawings,
Figs. 1 & 2 illustrate the general design of the motor, of which they are
respectively the side & end elevations. The field-magnet A is constructed of
laminated iron in the manner now well known in the art of construction of electrical
machines. B, B, are the coils of insulated wire used for exciting the field-magnets.
The armature C is also constructed of laminated iron & wound with coils of
insulated wire which are connected to the commutator D in the usual manner.
The armature & shaft are supported by suitable brackets E, E, & the brushes are
shown at F, F.
The governing device G is shown in detail in Fig. 3, where H is the shaft of the
motor, the support for the moveable arm K of the governor; La resisting
spring & G an insulated cover which supports the contact stud N. When the
moveable arm flies out, from centrifugal force at the required speed, electrical
contact is broken between K & N.
Fig. 4, shows more particularly the relative shapes which I prefer for the iron of
the field-magnet & armature.
Fig. 5, illustrates the method I adopt of mounting the armature on its shaft.
C is the laminated iron core, on which are wound the coils of wire P. On the
shaft H is fixed the metal sleeve R, on the end of which is the tightening nut T.
The space between the coils of wire & the metal sleeve, which may form part of
the commutator, is filled in with plaster of Paris or other suitable insulating
material. This not only forms a simple & firm support, but effectively protects the
wire coils & connections from damage, as they may be completely buried in the
insulating material.
Figs. 6, 7 & 8 indicate three different methods which may be adopted in making
the electrical connections. In Fig. 6, the field magnet coils are connected in
series" with the armature, through the brushes F, F, & commutator D. The
brushes are also "short-circuited" through the governor except when the speed
rises above the normal, at which time contact is broken between K & N.
In Fig. 7, the field magnet coils alone are connected to the source of supply.
An induced current circulates round the armature & through the governor
causing the armature to rotate & at a predetermined speed the contact between K
& N is broken in the manner already described. I may also dispense with the
governor & permanently short circuit the brushes. Fig. 8, shows a further
modification of Fig. 7, in which a resistance coil, or reactive coil, of any convenient
design is connected as a "shunt" across the contact points K & N of the governor,
which is useful in preventing excessive sparking at the contact points & steadies
the action of the motor.

page_text: Having now particularly described & ascertained the nature of my said inven-
tion, & in what manner the same is to be performed, I declare that what I
claim is :-
1. In an electro-motor to be actuated either by continuous currents of high or
low pressure, or by alternating currents, the combination of a laminated iron field
magnet & laminated iron armature of the shape substantially as described.
2. In an electro-motor to he actuated either by continuous currents of high or
low pressure, or by alternating currents, the use of an insulating material, such as
plaster of Paris, as a means of supporting the armature in position, substantially as
described.
3. In an electro-motor to be actuated either by continuous currents of high or
low pressure, or by alternating currents, the combination therewith of a governing
device for regulating the speed of the motor, substantially as described.
Dated this 9th day of February 1894.
WILLIAM GREENHALGH.