An Improved Starting Switch with Automatic Cut-out for Electric Motors.
Year: 1897

page_text: Date of Application, 1st June, 1897-Accepted, 10th July, 1897
An Improved Starting Switch with Automatic Cut-out for Electric
Motors.
I, HENRY HENDERSON CUTLER, of 78 West Jackson Street, Chicago, in the County
of Cook and State of Illinois, United States of America, Electrical Engineer, 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 switches, rheostats or resistance boxes for electric
motors, of the kind or class in which an automatic electro-magnetic circuit-breaker or
cut-out is employed.
The object of my said invention is to provide an improved apparatus whereby the
motor-circuit can be closed and all the starting resistance cut out, and then, upon the
flow of an abnormal current through the electric motor, the starting resistance will be
gradually put into circuit and the circuit opened or broken automatically, thus
protecting the motor and preventing damage thereto; my said invention also affords
the means for automatically cutting the motor out of circuit when the flow of
current ceases, so as to prevent damage to the motor when the current is again
turned on.
According to my said invention I provide a retaining electro-magnet which acts
directly upon the movable element or contact-arm of the rheostat when the same is
in position to exclude the starting resistance from the motor-circuit, and maintains
the said arm in such position during the normal flow of the current; and I provide a
releasing electro-magnet which, upon the flow of an abnorinal current through the
motor, will act to short circuit the said retaining electro-magnet and thus de-energize
the same so that the contact-arm will be released. The said arm will then be moved
through the agency of a spring or otherwise to put in the starting resistance step by
step, and finally to open the motor-circuit. It is obvious that the same action will
take place in the event of a cessation of the flow of current to the motor.
In the accompanying drawing:-
Figure 1 is a plan of one form of my improved apparatus, some of the parts being
removed and the contact-arm being shown in position to exclude the starting-
resistance from the motor-circuit.
Figure 2 is a similar view, showing also the circuit connections and illustrating the
application of the controller to a shunt-motor, the contact-arm being shown in
the position it occupies when moved forward as far as the second contact of the
series.
The contact-arm a is movable over the series of terminals or contacts 61, 61, between
which are connected the coils c, c of the starting resistance. A dead terminal b
is provided, and, when the contact-arm rests upon the same, the motor-circuit
is open.

page_text: A stop e limits the movement of the contact arm a towards the left. A curved
contact-plated is provided, with which the under face of the contact-arm a, or a
spring mounted thereon; engages to complete the circuit between the said contact-
plate and one or other of the contacts b'.
fis the retaining electro-magnet which is so arranged that it will retain the
contact-arm in its extreme position towards the right, as shown in Figure 1, with all
the resistance cut out of the motor-circuit. To enable the retaining electro-magnet f
to thus act upon the contact-arm a, the said arm is made wholly or partially of
magnetic material so that it will be attracted and held by the said magnet. g is the
releasing electro-magnet the armature g₁ of which bears a contact g³, which, when the 1
said armature is attracted, will electrically connect the contacts gº, g' and short-
circuit the coil of the electro-magnet f as will hereinafter appear.
The current passes from the generator or source through the conductor 1 to the
binding post m, thence through the releasing magnet g to the contact-plate d, thence
through the contact-arm a to the terminal b¹ with which the arm a is in contact,
thence to the binding post m³ and through the conductor 1, the armature ol of the
motor and the conductor 15 back to the generator l. From the conductor la branch
extends through the coils 02, 02 of the motor, thence by the conductor 18 and binding
post m through the retaining electro-magnet f and by the conductor to the
terminal b' at the extreme left. The field coils o² and the retaining magnet f are
thus connected in parallel with the armature o' of the motor. From the ends of
the retaining magnet f conductors 18, 19 extend to the contact terminals gº, g²
respectively.
The armature-lever g1 is pivoted at g² and rests upon a nut h screwed upon a rod h¹
and locked in position by a lock-nut h². Upon the armature-lever g' is fixed an
index k moving over a graduated scale kl upon the magnet. By means of the nut h
the air-gap between the armature and the pole-piece of the releasing magnet may be
adjusted so as to cause the said magnet to respond to any predetermined maximum
current strength.
During the normal running of the motor, the contact-arm a is maintained in
position at the extreme right by the retaining magnet ƒ acting directly upon it. The
normal flow of current through the motor-armature and consequently through the
releasing magnet g is insufficient to cause the attraction of the armature-lever 91, but,
when the current exceeds the predetermined maximum, the armature-lever gl is
attracted, thus moving the contact g³ into engagement with the contact terminals g®, g
and electrically connecting the same, so as to short-circuit the retaining magnet ƒ and
de-energize the same. The contact-arm a is then moved by means of a spring p or
otherwise over the rheostat-terminals b' so as to put in the resistances c step by step
and finally upon reaching the terminal b to open the motor-circuit.
While I have illustrated my invention as applied to a shunt-motor, it is equally
" as used in the
applicable to other types of motors. The term "electro-magnet'
description and claims comprehends both electro-magnets in the restricted meaning
of that terin, and solenoids.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
First. An apparatus for the purpose above specified, wherein the movable element
or contact-arm is made wholly or partially of inagnetic material and the retaining
electro-magnet is arranged to act directly upon the same to retain it in position to
exclude the starting resistances from the motor-circuit.
Second. The combination, with the movable element or contact-arm of a starting
switch or rheostat, of a retaining electro-magnet arranged to act directly thereon to
retain the same in position to exclude the starting resistances from the motor-circuit,
a short-circuit about the said electro-magnet, a releasing electro-magnet for closing
the said short-circuit to release the said contact-arın, and means for moving back the

page_text: said arm when released to alter the condition of the circuit, substantially as, and for
the purposes, above specified.
Third. The combination, with the movable element or contact-arm of a starting
switch or rheostat, of an electro-magnet for retaining the same in position, a releasing
electro-magnet adapted to respond to an abnormal current to de-energize the said
retaining magnet, means for moving back the said arın, when released, to change the
condition of the circuit, and means for adjusting the armature of the said releasing
electro-magnet to respond to any predetermined current strength, for the purposes
above specified.
Fourth. The improved apparatus constructed substantially as described with
reference to the accompanying drawing and operating as, and for the purposes, above
specified.
DATCH THE Ist day of May 1897.
D. YOUNG & Co.,
11 and 12 Southampton Buildings, London, W.C.,
Agents for the Applicant.