Improvements in the Method of and Apparatus for Starting and Controlling Electric Motors.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Method of and Apparatus for Starting and
Controlling Electric Motors.
THOMAS PREECE, of 16, Thornhill Place, Thornbury, near Bradford, Engineer,
and JoiN ALFRED EDMONDSON, of Globe Electrical Works, Kirkstall Road, Leeds,
Engineer, do hereby declare the nature of this invention to be as follows:-
The low resistance of an electric motor when at rest or after starting until it
has acquired considerable speed allows a comparatively large and in many cases a
dangerously powerful current to pass. It is thus not desirable to suddenly switch
on or apply the full force of the current at once and the object of this invention
is to enable a reduced current to be applied until the motor has acquired a fair
speed.
For this purpose we introduce a resistance frame or rheostat or similar device in
the circuit of a series wound or compound wound motor or in the armature
circuit of a shunt wound or compound wound motor whereby the resistance of
the circuit is increased.
And we employ to reduce the resistance of the circuit a windlass or its
equivalent attached by means of a cord or tape or its equivalent to a combination
of metal or carbon contacts so arranged to slide over a series of fixed metal or
carbon contacts placed in a horizontal or vertical plane.
To maintain the whole or part of the resistance in circuit we employ a
solenoid or electro-magnet or a magnetic clutch or brake so arranged that the
slide contacts can be left on any of the fixed series of contacts as may be desired
when the current is on. When the current is cut off the solenoid or electro-
magnet releases its hold the slide contacts automatically return to their original
off position, and cut the resistance and motor out of circuit.
Any convenient method of arranging the said magnetic brake or clutch may
be employed, the solenoid or electro-magnet can be arranged to apply a friction
brake on a wheel or apply a ratchet on a cog wheel attached to the windlass
spindle, but we prefer the following.
The several coils or their equivalent of the resistance device are connected
to the fixed series of metal or carbon contacts and insulated from each other.
The combination of metal and carbon contacts are fixed on a suitable slide box
or cage. Attached to the top of the box or cage is the cord or tape or its
equivalent which passes round the drum of the windlass and in connection with
this and the box are the necessary guide rods or plates. The slide box is so
arranged that it can be moved as desired and wound up or down the vertical
or horizontal plane and its position on such horizontal or vertical plane determines
the resistance in circuit either increasing or decreasing the resistance as required.
In combination with and attached to the slide box or cage are the solenoids or
electro-magnets connected in series with the shunt circuit of the motor, and so
arranged in combination with their armatures that when the current is on the

page_text: armatures grip the guide rods or plates and lock the slide box or cage in any
desired position.
In combination with the windlass spindle and handle we place a short circuit
switch connected across the brake or clutch coils and so arranged when the
spindle and handle is moved to move the slide contacts to their on or off position,
the switch cuts out of circuit the solenoid or electro magnet, thereby keeping
the brake or clutches out of action and thus allowing the slide contacts to move
freely. When the spindle and handle are at rest the short circuit switch is out
of action and the solenoid or electro magnet comes in action thereby locking the
slide box or cage in the desired position.
When all or part of the resistance is cut out a second solenoid or electro-magnet
may be provided in series with the main circuit; for the purpose of preventing
the dangerous flow of current which would result from the overloading of the
motor. This solenoid or electro-magnet to be so arranged as to short circuit by
means of a switch the clutch or brake coils immediately the current passes to the
extent for which the solenoid or electro-magnet is set to act the effect of this
being to release the brake or clutch coils and allow the slide contacts to return
to their "off" position thus stopping the motor.
In combination with the second coil and attached to its armature an adjustable
arm may be provided to set the cut off short circuit switch of the brake or clutch
coils within reasonable limit of the power of the motor.
Dated this 28th day of July 1898.
JOHN A. EDMONDSON.
THOMAS PREECE.
Improvements in the Method of and Apparatus for Starting and
Controlling Electric Motors.
We, THOMAS PREECE, förimerly of 16, Thornhill Place, Thornbury, Bradford,
Yorks, and JOHN ALFRED EDMONDSON, both of the Globe Electrical Works,
Kirkstall Road, Leeds, in the County of York, Electrical and Mechanical
Engineers, 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:-
-
The low resistance of an electric motor, when at rest or after starting, until it
has acquired considerable speed allows a comparatively large, and in many cases
a dangerously powerful current to pass. It is thus not desirable to suddenly
switch on or apply the full force of the current at once, and the object of this
invention is to enable a reduced current to be applied until the motor has acquired
a fair speed.
For this purpose we introduce a resistance frame or rheostat or similar device
in the circuit of a series wound or compound wound motor whereby the resistance
of the circuit is increased.
And we employ to reduce the resistance of the circuit a windlass or its
equivalent, attached by means of a cord or tape or its equivalent to a combination
of inetal or carbon contacts so arranged to slide over a series of fixed metal or
carbon contacts placed in a horizontal or vertical plane.
To maintain the whole or part of the resistance in circuit, we employ a solenoid
or electro-magnet, or a magnetic clutch or brake so arranged that the slide con-
tacts can be left on any of the fixed series of contacts, as may be desired, when
the current is on,

page_text: When the current is cut off the solenoid or electro-magnet releases its hold,
the slide contacts automatically return to their original off position, and cut the
resistance and motor out of circuit.
Any convenient method of arranging the said magnetic brake or
employed.
clutch be
may
The solenoid or electro-magnet can be arranged to apply a friction brake on a
wheel or apply a ratchet on a cogwheel attached to the windlass spindle, but we
prefer the following.
Fig. (1) Represents elevation of starter with front removed.
Fig. (2) Section through X-I.
Fig. (3) section through W-Z with carbon brushes removed.
The resistance coils numbering 1, to 24, are mounted between the slabs A and A¹
of nonconducting material, supported in position by the iron frame A The
coils 1 to 24 are connected in series and supported by means of the metal plates B
and B and preferably increase in conductivity from the first to the last, that is
to say, the wire forming the coil marked 24 is a considerably better conductor,
or is of a larger gauge than the wire forming, the coil marked 1 and there may
be a little difference in this respect between each coil.
Besides being connected in series the resistance coils are connected in pairs to one
of the metal contact guide plates C by the connecting screw C¹. The plates Care
mounted on the non-conducting material A The metal box D) containing the
two sets of electro-magnets E, E, E, 13, which are attached to the top of the
box E. The metal arms F, and F, carrying the carbon contacts F, F, F, F,
attached to the box D), by means of the screw F.
are
The magnetic clutch or brake arms G and G¹, are attached loosely to the box D,
by means of the screws G2, G3. The arms G, and G₁, serve the following
purposes: Being the armatures for the electro magnets E, E', E, E, it will be
seen when attracted they grip the contact guide plates C, and H', on both sides
thus holding the box 1), in any desired position. They are also the guide arms
to maintain the box D, in a true vertical or horizontal plane. They also serve
as additional slide contact arms in parallel with the arms F, and F¹, carrying the
carbon contacts F F F 15.
To start the motor the current enters at the positive terminal H to contact
guide plate H' to slide contacts F, F, G, G, to the divided contact plates C,
through the resistance coils marked 1 to 24 to connecting screw which is
connected to binding terminal 02, thus completing the main positive connection
to motor. The positive connection serving the shunt circuit of a shunt motor
is connected to terminal I to contact plate I' to contact plate I attached to box D
by means of non-conducting material through the electro magnets to the main
circuit slide contact arms F, F, G, G', thus completing the shunt circuit of the
motor.
To stop the motor the switch J, is connected as a short circuit switch across
It will thus be seen when the current is cut
the electro magnets E, E, E³, E.
out of the electro magnets they release their hold on the clutch or brake arms,
which in turn release their grip on the guide contact plates C, and H. The box
thus automatically returns to its off position and switching the motor out of
circuit.
The cord or tape K, is attached to the box D), and also attached to the wheel K
of the windlass K³.
L', and L are carbon blocks attached to guide contact plates C and H for the
purpose of both making and breaking contact when the motor is switched on
or off.
The electro magnet M is connected in the main circuit H, the armature M
with adjustable screw M³ and contact points M and M also serve as a short
circuit switch across the electro magnets E, E¹, E2, E³. It will thus be seen when
the current in the main circuit is above reasonable limit of the power of the motor
the electro magnet M becomes stronger and closes the contact points
and M³

page_text: and cuts out the electro magnets E, EL, E², E3, in the same manner as the switch J,
and thus switches the motor out of circuit.
The guide rods N, and N¹, are additional guides for the box D, to maintain the
slide contacts in a true vertical or horizontal plane when the motor is switched off
and the box D), is in the off position.
We would have it clearly understood that we make no claim with reference to
the general arrangement of the resistance frame.
Our invention relates to the employment of an electro magnet acting upon an
armature, the armature which also acts as a brake or clutch as well as the sliding
contact arm for switching the current on or off.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is:-
Claim (1) A motor starter consisting of a rheostat adapted to be cut out of circuit
by the electro magnets with the combined magnetic clutch or brake slide contact
arms or its equivalent, substantially as herein shewn and described.
(2) In a motor starter the device for cutting out the resistance consisting of
the combined magnetic clutch or brake slide contact arms operated by the electro
magnets, substantially as herein shewn and described.
(3) In a motor starter whereby the slide contact arm is operated upon by an
electro magnet to increase the contact pressure between the fixed and slide
contacts, substantially as herein shewn and described.
(4) The combination with the apparatus described in the first claim of the
electro magnets E, E, E, E³, combined magnetic clutch or brake slide contact
arms G, and G, substantially as herein shewn and described and for the purpose
of this invention.
Doted this 28th day of il 1900
THOMAS PREECE.
JOHN A. EDMONDSON.