Improved Starting Mechanism for Electric Motors.
Year: 1899

page_text: [Communicated from abroad by THOMAS S. PERKINS, of Idlewood, in the County
of Allegheny and State of Pennsylvania, U.S.A., Electrical Engineer].
Improved Starting Mechanism for Electric Motors.
I, REGINALD BELFIELD, Electrician, of 32, Victoria Street, Westminster,
S.W., in the County of London, England, do hereby declare the nature of this
invention to be as follows:-
My invention relates to starting mechanism for electric motors, and has for
its object to construct an improved device for direct current motors the field-
magnets of which are either shunt or compound wound, the structure and
operation of the parts being such that the movement of a resistance varying arm
serves to operate a double-pole switch to either open or close the line circuit
according to the direction of said movement.
I furthermore provide means which act automatically when a current larger
than a predetermined maximum passes through the armature of the motor, to
short circuit the magnet which normally holds the resistance varying arm in
position when all the resistance is cut out.
By this means when an overload occurs the resistance varying arm being
released under the influence of a spring rapidly moves back introducing resist-
ance into the circuit and finally breaks the circuit through the double-pole
switch.
My invention is illustrated in the accompanying drawings, in which
Figure 1 is a plan of the device.
Figure 2 being a section on the line II-II of the same.
Figure 3 is a diagram shewing the circuits.
1 is the base of suitable insulating material to which are secured metallic
studs 2 and 3 arranged in the arc of a circle, the contact piece 2 being equal in
The resistance coils 4 con-
length to the united length of several of the studs.
6 is a
nected to the several studs are contained in a box 5 under the base 1.
switch arm pivotally mounted on the base, having a spring contact strip 7
adapted to engage with the fixed contacts 2 and 3 as the arm is revolved on its
pivot by means of the handle 8. 9 is a spring which normally maintains the
arm in contact with a stop 10. The hub 11 of the arm 6 is provided with two
teeth 12 and 13. the former of which is adapted to engage hetween two similar
teeth 14 on a hub 15 pivoted to the base adjacent to the pivot of the arm 6; these
two hubs are electrically connected by a strip or plate 16. Secured to the
hub 15 are two arms 17 and 18. the arm 17 carrying an insulated blade 19
adapted to engage with contacts 20 and 21. The arm 18 is adapted to engage
with the contact 22. and this is so located that such engagement occurs when
the contacts 20 and 21 are bridged by the arm 19. 23 is an electro-magnet con-
nected in series with the shunt field-magnet winding of the motor, and so located
on the base that when the switch arm 6 has reached the last of the studs 3 and

page_text: all the resistance 4 is cut out of circuit, it will be in a position to be held by
said electro-magnet; for this purpose said switch arm should be of magnetisable
material or be provided with a strip of magnetic metal to act as an armature for
the magnet. 24 is an electro-magnet connected in series with the armature of
the motor and provided with an 'armature 25, which, when attracted, makes con-
nection with a contact 26.
In order that the contact arm 25 may be set for any desired maximum current
value, provide a set screw 27 and a stop piece 28, against which the end of the
screw impinges as shewn.
The circuit connections will be readily understood from the diagram Figure 3,
in which 29 is a shunt field-magnet winding of the motor, and 30 is the armature,
31 and 32 being the supply mains.
The motor may, of course, be provided with a series magnet winding as well
as a shunt winding if desired.
The operation of the device is as follows:-
Assuming that the motor is at rest and the parts in the position shewn in
the drawings, if the switch arm 6 is moved by hand in the direction shewn by
the arrow, the tooth 12 engaging with the teeth 14 will rotate the hub 16 on
its pivot and cause the blade 19 to connect the contacts 20 and 21, and the
blade 18 to engage with the contact 22. This connection will be effected and
the circuit through the motor thereby made. before the strip 6 leaves the con-
tact 2. Further movement of the arm 6 in the direction indicated will cut out
the resistances 4 step by step until the last stud 3 is reached, when the magnet 23
will hold the switch arm in that position, and the tooth 13 will rest against
the adjacent teeth 14 on the hub 15 so as to prevent any accidental opening of the
circuit.
If during the operation of the motor the current flowing through the armature
exceeds the maximum for which the arm 25 of the magnet 24 is set, said arm
will be attracted and make connection with the contact 26, thereby short circuit-
ing the magnet 23. Said magnet 23 is de-energised, and the switch arm 6 being
released the spring 9 will act to return it to its original position, rotating the
hub 15 on its pivot and opening the circuit through the motor, thus preventing
any injury by reason of the excessive current.
If either the line or main circuit or the shunt circuit of the motor be opened,
the switch arm 6 will be released in the same manner, a path for the discharge
of the shunt field-magnet winding being provided through the armature 30
and the entire resistance coils 4.
.
Improved Starting Mechanism for Electric Motors.
I, REGINALD BELFIELD, Electrician, of Westinghouse Building, Norfolk Street,
Strand, W.C., formally residing at 32, Victoria Street, Westminster, S.W., in
the County of London, England, 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 starting mechanism for electric motors, and has for
its object to construct an improved device for direct current motors the field-
magnets of which are either shunt or compound wound, the structure and

page_text: operation of the parts being such that the movement of a resistance varying arm
serves to operate a double-pole switch to either open or close the line circuit
according to the direction of said movement.
I furthermore provide means which act automatically when a current larger
than a predetermined maximum passes through the armature of the motor, to
short circuit the magnet which normally holds the resistance varying arm in
position when all the resistance is cut out.
By this means when an overload occurs the resistance varying arm being
released under the influence of a spring rapidly moves back introducing resist-
ance into the circuit and finally breaks the circuit through the double-pole
switch.
My invention is illustrated in the drawings filed with my Provisional Specifica-
tion in which
Figure 1 is a plan of the device.
Figure 2 being a section on the line II-II of the same.
Figure 3 is a diagram shewing the circuits.
1 is the base of suitable insulating material to which are secured metallic
studs 2 and 3 arranged in the arc of a circle, the contact piece 2 being equal in
length to the united length of several of the studs. The resistance coils 4 con-
nected to the several studs are contained in a box 5 under the base 1. 6 is a
switch arm pivotally mounted on the base, having a spring contact strip 7
adapted to engage with the fixed contacts 2 and 3 as the arm is revolved on its
pivot by means of the handle 8. 9 is a spring which normally maintains the
arm in contact with a stop 10. The hub 11 of the arm 6 is provided with two
teeth 12 and 13, the former of which is adapted to engage between two similar
teeth 14 on a hub 15 pivoted to the base adjacent to the pivot of the arm 6; these
two hubs are electrically connected by a strip or plate 16. Secured to the
hub 15 are two arms 17 and 18, the arm 17 carrying an insulated blade 19
adapted to engage with contacts 20 and 21. The arm 18 is adapted to engage
with the contact 22, and this is so located that such engagement occurs when
the contacts 20 and 21 are bridged by the arm 19. 23 is an electro-magnet con-
nected in series with the shunt field-magnet winding of the motor, and so located
on the base that when the switch arm 6 has reached the last of the studs 3 and
all the resistance 4 is cut out of circuit, it will be in a position to be held by
said electro-magnet; for this purpose said switch arm should be of magnetisable
material or be provided with a strip of magnetic metal to act as an armature for
the magnet. 24 is an electro-magnet connected in series with the armature of
the motor and provided with an armature 25, which, when attracted, makes con-
nection with a contact 26.
In order that the contact arm 25 may be set for any desired maximum current
value, I provide a set screw 27 and a stop piece 28, against which the end of the
screw impinges as shewn.
The circuit connections will be readily understood from the diagram Figure 3,
in which 29 is a shunt field-magnet winding of the motor, and 30 is the armature,
31 and 32 being the supply mains.
The motor may, of course, be provided with a series magnet winding as well
as a shunt winding if desired.
The operation of the device is as follows:-
Assuming that the motor is at rest and the parts in the position shewn in
the drawings, if the switch arm 6 is moved by hand in the direction shewn by
the arrow, the tooth 12 engaging with the teeth 14 will rotate the hub 16 on
its pivot and cause the blade 19 to connect the contacts 20 and 21, and the
blade 18 to engage with the contact 22. This connection will be effected and
the circuit through the motor thereby made before the strip 6 leaves the con-
tact 2. Further movement of the arm 6 in the direction indicated will cut out
the resistances 4 step by step until the last stud 3 is reached, when the magnet 23
will hold the switch arm 6 in that position, and the tooth 13 will rest against

page_text: the adjacent teeth 14 on the hub 15 so as to prevent any accidental opening of the
circuit.
If during the operation of the motor the current flowing through the armature
exceeds the maximum for which the arm 25 of the magnet 24 is set, said arm
will be attracted and make connection with the contact 26, thereby short circuit-
ing the magnet 23. Said magnet 23 is de-energised, and the switch arm 6 being
eleased the spring 9 will act to return it to its original position, rotating the
hub 15 on its pivot and opening the circuit through the motor, thus preventing
any injury by reason of the excessive current.
If either the line or main circuit or the shunt circuit of the motor be opened,
the switch arm 6 will be released in the same manner, a path for the discharge
of the shunt field-magnet winding being provided through the armature 30
and the entire resistance coils 4.
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:
A starting device for electric motors, constructed and operating substantially
as described with reference to the accompanying drawing.
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1000
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.