Apparatus for Controlling the Electric Current on Putting Electromotors in Circuit.
Year: 1892

page_text: Date of Application, 13th Aug., 1892
Complete Specification Left, 24th Apr., 1893-Accepted, 10th June, 1893
PROVISIONAL SPECIFICATION.
Apparatus for Controlling the Electric Current on Putting
Electromotors in Circuit.
[Communicated from abroad by Messrs. SIEMENS & HALSKE, of Berlin, in the
German Empire, Electrical Engineers.]
We, SIEMENS BROTHERS & CO. LIMITED, of 12 Queen Anne's Gate, Westminster,
in the County of Middlesex, Electrical Engineers, do hereby declare the nature
of this invention to be as follows:-
In order to prevent too strong a current from passing through an electromotor
on putting this in circuit, it is usual to introduce resistances in the circuit which are
gradually cut out until the electromotor has attained a normal speed, when no
further artificial resistance is required.
The present invention relates to an appliance whereby all kinds of electromotors
can be put in circuit without the use of such resistances.
For this purpose there is interposed in the conductor leading from the starting
switch of the motor to the one terminal of the latter a wire coil or solenoid, through
which the current froin the generator is made to pass on coupling up the motor by
the switch. This coil is however not directly connected to the conductor leading
to the motor, but is connected by a flexible connection to a vertical iron socket
extending up into the coil and carrying a carbon rod which, under the normal
working of the motor or when the starting switch is open is in contact with a
second carbon rod that forms part of the conductor leading to the motor, the two
carbons being thus made to form part of the motor's circuit. On closing the
circuit by means of the switch, the current will momentarily pass of its full strength
through the carbon rods to the motor and as there is as yet no back E.M.F. being
produced thereby, the current will pass of its full strength through the windings
and back to the generator; the circuit will however be immediately afterwards
broken or the current will be greatly weakened by the action of the solenoid
through which the current passes, in attracting the socket carrying the upper
carbon, and thus moving the latter out of contact with the lower carbon either to
such an extent as to entirely break the circuit, or only to the extent required to
form an arc, and thus to introduce a considerable resistance. In the meantime the
momentary current that passed through the motor will have started this in motion.
As soon as the circuit is broken or the current weakened as described, the attrac-
tion of the solenoid will cease or be diminished to such an extent as to allow the
upper carbon to drop on to the lower carbon again. The current will now pass to
the motor again, imparting a further impulse thereto, and becoming proportionately
weakened owing to the counter E.M.F. produced thereby, and this alternate
breaking and closing of the circuit by the carbons or lengthening and shortening
of the are will continue until the motor, by a succession of impulses, will have
attained its normal speed, when the current will have become weakened to such an
extent that the solenoid will no longer exercise sufficient attraction on the socket
of the upper carbon to raise this from off the lower one, and consequently the
circuit will now remain closed, so long as the normal working continues.
Dated this 13th day of August 1892.
ABEL & IMRAY,
Agents for the Applicants.

page_text: COMPLETE
SPECIFICATION.
Apparatus for Controlling the Electric Current on Putting
Electromotors in Circuit.
We, SIEMENS BROTHERS & CO. LIMITED, of 12 Queen Anne's Gate, Westminster,
in the County of Middlesex, Electrical 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:―
In order to prevent too strong a current from passing through an electromotor
on putting this in circuit, it is usual to introduce resistances in the circuit which
are gradually cut out until the electromotor has attained a normal speed, when no
further artificial resistance is required.
The present invention relates to an appliance whereby all kinds of electromotors
can be put in circuit without the use of such resistances.
For this purpose, there is interposed in the conductor leading from the starting
switch of the motor to the one terminal of the latter a wire coil or solenoid through
which the current from the generator is made to pass on coupling up the motor by
the switch. This coil is however not directly connected to the conductor leading
to the motor, but is connected by a flexible connection to a vertical iron socket
extending up into the coil and carrying a carbon rod which, under the normal
working of the motor, or when the starting switch is open, is in contact with a
second carbon rod that forms part of the conductor leading to the motor, the two
carbons being thus made to form part of the motor's circuit. On closing the circuit
by means of the switch, the current will momentarily pass with its full strength
through the carbon rods to the motor and, as there is as yet no back E.M.F. being
produced thereby, the current will pass at its full strength through the windings
and back to the generator; the circuit will however be immediately afterwards
broken or the current will be greatly weakened by the action of the solenoid
through which the current passes, in attracting the socket carrying the upper
carbon, and thus moving the latter out of contact with the lower carbon either to
such an extent as to entirely break the circuit, or only to the extent required to
form an arc, and thus to introduce a considerable resistance. In the meantime the
momentary current that passed through the motor will have started this in motion.
As soon as the circuit is broken or the current weakened as described, the
attraction of the solenoid will cease or be diminished to such an extent as to allow
the upper carbon to drop on to the lower carbon again. The current will now pass
to the motor again, imparting a further impulse thereto, and becoming pro-
portionately weakened owing to the counter E.M.F. produced thereby, and this
alternate breaking and closing of the circuit by the carbons or lengthening and
shortening of the arc will continue until the motor, by a succession of impulses, will
have attained its normal speed, when the current will have become weakened to
such an extent that the solenoid will no longer exercise sufficient attraction on the
socket of the upper carbon to raise this from off the lower one, and consequently'
the circuit will now remain closed, so long as the normal working continues.
The accompanying drawing shews a diagram illustrative of the above described
invention.
A is the primary machine, B the electro motor, C the switch for closing the
circuit of the electro motor, and D) the apparatus which forms the subject of the
present invention; it consists of a coil S and two carbons k' of which k¹ has its
upper end fitted in a soft iron tube t which is connected to and is freely suspended
in the coil, the carbon k' being fixed. The current for actuating the electro motor
passes from the generator through the coil S, thence through the carbon k¹ and
from this to the carbon whence it passes to the motor B.
When the circuit is closed by the switch C for starting the motor, then, as this
does not yet produce any back electro motive force, the current will pass at its full

page_text: force through its windings and back to the generator. The coil S will consequently
draw upward the iron socket t and carbon k', thereby breaking the circuit or
considerably weakening the current, the motor having however in the meantime
received an impulse from the current. The carbon then again drops on to k³,
closing the circuit, and the above described action is repeated, until the motor B
has attained its normal speed, when the carbons will remain in contact as before
described.
It will be evident that the coil and carbons might also be arranged horizontally
and the carbon ¹ be acted upon by a spring for making contact with k³.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
Apparatus, for controlling the current supplied to an electro motor, wherein two
carbon electrodes, maintained in contact by gravity or equivalent means, are
combined with a wire coil or solenoid and an iron core, all being included in the
circuit of the electro motor and current generator in such manner that when the
current of full strength passes through the coil and electrodes before the electro
motor has been started, the coil will be made to move the electrodes momentarily
out of contact, thus either weakening the current passing to the motor or
momentarily breaking the circuit entirely for a time, such making and breaking of
contact being repeated until the motor has attained its normal speed, substantially
as described.
Dated this 24th day of April 1893
ABEL & IMRAY,
Agents for the Applicants.