Improvements in Apparatus for Starting and Reversing the Motion of Electromotors.
Year: 1894

page_text: [Communicated from abroad by Messrs. SIEMENS & HALSKE, of Berlin, in the
German Empire, Electrical Engineers.]
Improvements in Apparatus for Starting and Reversing the Motion
of Electromotors.
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::
For starting and reversing the motion of electromotors there is required, as is
well known, in addition to the starting or reversing switch, a special starting
resistance for the purpose of preventing the strength of the current 'in the armature
from exceeding a certain maximum, and which is 'consequently only cut out by
degrees, in proportion as the counter electromotive force of the armature increases
with the increase of speed.
The cutting out of the starting resistance can therefore only be effected gradually
and must in many cases be independent of the apparatus worked by the operative.
For this purpose the starting apparatus, in particular for such electromotors as are
controlled by unskilled operatives, such as is the case with lift motors, all have the
arrangement that the sliding contact of the starting resistance is not forced to
move together with the starting or reversing switch, but is released thereby on
starting. The motion of this sliding contact can be effected by various means; it
is generally done by means of a spring or weight. The necessary retardation is
then effected for instance by causing the piston of a dash pot or cataract to act on
the contact brush in opposition to the weight or spring.
If now it be ascertained for example that the motor when starting under its
greatest load, will attain its normal speed within 10 seconds, then by correctly
adjusting the dash pot it can be arranged that the sliding contact brush of the
starting resistance shall pass over all the contacts of the resistance in the space of
10 seconds, and the sections can be so adjusted that a resistance is always produced
proportionate to the speed at a given moment.
This arrangement will always act reliably if the motor really attains its nòrmal
speed within the stated time; but it may happen that, in consequence of over-
loading or of an external resistance, the motor is not able to start, so that the said
10 seconds pass by without motion ensuing, and consequently the entire resistance
will be cut out before the armature has attained the proper speed, resulting
possibly in the burning of the insulation by the overheating of the wires.
The present invention has for its object to prevent this possibility, and consists
of an arrangement which we will describe with reference to the accompanying
drawing which shews by way of example its application to an electromotor working
a lift.
A is the starting resistance, B 'the contact brush for the same, and 'U the
reversing mechanism, which is actuated from the 'lift cage by means of the rope.
The mechanical connection between U and B is, as shewn, so arranged that at the
interrupting position of U a pin S on the steering wheel is situated in its lowest
position, in which it presses down the rear extension of the brush B, thus holding
the brush in its highest position, in which consequently the entire starting

page_text: resistance is included in the armature circuit. On the other hand, on turning U to
the right or left, the brush B is released so that it is then drawn downwards by the
weight G, sliding over the several contacts of A. and thereby gradually cutting
out the resistance.
For retarding such motion the brush is connected to the piston of a dash
pot P.
The drawing shews the moment in which the reversing device U has already
been turned through a certain angle by a rapid movement of the rope, while the
brush B has not yet commenced its downward motion.
The armature current now passes through the winding of an electro magnet E,
in front of which is a catch K that is drawn away from the electromagnet by a
spring f. This spring is sufficiently strong to overcome the attraction exercised by
the electro magnet upon the catch when a current of allowable strength is passing
through the armature of the motor, so that the catch K is then held thereby out
of engagement with the toothed segment K on the brush arm B.
As long as this is the case therefore, the brush is free to descend slowly. If on
the other hand the motor armature, running at a slow speed, were prevented by any
circumstance from running faster, the continued descent of the brush and consequent
cutting out of the resistance would soon cause the current to become too strong.
As soon as this takes place, the proportionately increased power of the electro-
magnet will cause it to attract the catch K, which, in then engaging with the
toothed segment will prevent the farther descent of the brush, and consequently
also the exclusion of resistance.
This condition will continue as long as the speed of the motor is prevented from
increasing. When the obstacle to such increase is overcome and the speed of the
motor is accelerated, the current of the armature will decrease, whereupon the
spring will again draw the catch K out of gear and the brush B will continue to
descend and cut out resistance.
Instead of effecting the descent of the brush by a weight, a spring or the
attraction of a magnet or solenoid may be used.
Also, instead of a dash pot or cataract any other braking device, such as a train
of wheels with controlling vaues, &c., may be used, and the catch and the toothed
quadrant might also be replaced by any equivalent stopping device.
Dated this 3rd day of November 1894.
ABEL & IMRAY,
Agents for Applicants.
Improvements in Apparatus for Starting and Reversing the Motion
of Electromotors.
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 :-
For starting and reversing the motion of electromotors there is required, as is
well known, in addition to the starting or reversing switch, a special starting
resistance for the purpose of preventing the strength of the current in the armature
from exceeding a certain maximum, and which is consequently only cut out by
degrees, in proportion as the counter electromotive force of the armature increases
with the increase of speed.
The cutting out of the starting resistance can therefore only be effected gradually
and must in many cases be independent of the apparatus worked by the operative.

page_text: For this purpose the starting apparatus, in particular for such electromotors as are
controlled by unskilled operatives, such as is the case with lift motors, all have the
arrangement that the sliding contact of the starting resistance is not forced to-
move together with the starting or reversing switch, but is released thereby on
starting. The motion of this sliding contact can be effected by various means, it
is generally done by means of a spring or weight. The necessary retardation is
then effected for instance by causing the piston of a dash pot or cataract to act on.
the contact brush in opposition to the weight or spring.
If now it be ascertained for example that the motor when starting under its
greatest load, will attain its normal speed within 10 seconds, then by correctly
adjusting the dash pot it can be arranged that the sliding contact brush of the
starting resistance shall pass over all the contacts of the resistance in the period of
10 seconds, and the sections can be so adjusted that a resistance is always produced.
corresponding to the speed at a given moment.
This arrangement will always act reliably if the motor really attains its normal
speed within the stated time; but it may happen that, in consequence of over-
loading or of an external resistance, the motor is not able to start, so that the said
10 seconds pass by without motion ensuing, and consequently the entire resistance
will be cut out before the armature has attained the proper speed, resulting possibly
in the. burning of the insulation by the overheating of the wires.
The present invention has for its object to prevent this possibility and consists of
an arrangement which we will describe with reference to the diagram accompanying
the Provisional Specification which shews by way of example its application to an
electromotor working a lift.
A is the starting resistance, B the contact brush for the same, and U the
reversing mechanism, which is actuated from the lift cage by means of the rope.
The mechanical connection between U and B is as shewn, so arranged that at the
interrupting position of U a pin S on the reversing wheel is situated in its lowest
position, in which it presses down the rear extension of the brush B, thus holding
the brush in its highest position, in which consequently the entire starting resistance
is included in the armature circuit. On the other hand, on turning U to the right
or left, the brush B is released so that it is then drawn downwards by the weight G,
sliding over the several contacts of A and thereby gradually cutting out the
resistance.
For retarding this motion, the brush is connected to the piston of a dash pot P.
The drawing shews the moment in which the reversing device U has already
been turned through a certain angle by a rapid movement of the rope, while the
brush B has not yet commenced its downward motion.
The armature current now passes through the winding of an electromagnet E,
in front of which is a catch K that is drawn away from the electromagnet by a
spring. This spring is sufficiently strong to overcome the attraction exercised by
the electromagnet upon the catch when a current of allowable strength is passing
through the armature of the motor, so that the catch K is then held thereby out of
engagement with the toothed segment K on the brush arm B.
As long as this is the case therefore, the brush is free to descend slowly. If on
the other hand the motor armature, running at a slow speed, were prevented by
any circumstances from running faster, the continued descent of the brush and
consequent cutting out of the resistance would soon cause the current to become
too strong. As soon as this takes place, the proportionately increased power of
the electromagnet will cause it to attract the catch K, which, in then engaging
with the toothed segment will prevent the further descent of the brush, and
consequently also the exclusion of resistance.
This condition will continue as long as the speed of the motor is prevented from
increasing. When the obstacle to such increase is overcome and the speed of the
motor is accelerated, the current of the armature will decrease, whereupon the
spring will again draw the catch K out of gear and the brush B will continue to
descend and cut out resistance.

page_text: Instead of effecting the descent of the brush by a weight,.
attraction of a magnet or solenoid may be used.
a spring or the
Also, instead of a dash, pot or cataract any other braking device, such as a train
of wheels with controlling vanes &c. may be used, and for the catch and the toothed
segment might be substituted any equivalent stopping device.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare 'that what we
claim is :-
In starting and reversing apparatus. for electromotors. in which the sliding
contact for the starting resistance. is..moved independently of the starting or
reversing switch, the use of a catch operated by an electromagnet energized by
the current strength, so as to arrest farther withdrawal of resistance whenever the
current strength exceeds the. predetermined limit.
Dated this 27th day of July 1895.
ABEL & IMRAY,
Agents for the Applicants.