Resistance Switch Apparatus for Starting Electromotors.
Year: 1895

page_text: Date: of Application, 18th Dec., 1895
Complete Specification Left, 16th Sept., 1896-Accepted; 14th Nov., 1896
of Germany, Electrical Engineers.]
Resistance Switch Apparatus for Starting Electromotors.
We, SIEMENS BROS. & Co. LIMITED, of 12 Queen. Anne's Gate, Westminster,
in the County of London, Electrical Engineers, do hereby declare the nature of
this invention to be as follows:-
This invention relates to switch apparatus for including and excluding resistances
in the winding circuits of polyphase and single phase electromotors for regulating
the torque on starting.
C1
Such resistances have heretofore been constructed, for example, for three-phase
currents as shewn diagrammatically at Fig. 1 of the accompanying drawing
in which A, A, &c. B₁ B, &c. C, C, are three sets of resistances connected
respectively to the circuits I II III of the motor winding, all the resistances being
included if the connections are made at a, b, c, while if the connections are made
at a b₁ c₁ the thrée resistances A, B, C, are cut out, and so on, until by making
the connections at a b c all the resistances are cut out: Fig. 2 shews a
construction employed for carrying out this method of operating, the three armed
switch being made by turning to make contact either with the plates a. bo co for
including all the resistances or with a₁ b₁ c₁ &c. for cutting out any desired number
thereof, as above. In order with this construction to effect as gradual and uniform
a variation in the torque as possible, the resistances must be divided into a
considerable number of steps.
The present invention lias for its object to reduce the number of resistance steps
as much as possible, while providing for a very gradual variation of torque and
also to enable the same construction of resistance-device to be used both for
continuous current machines and for multiple phase current machines. For this
purpose, instead of, as heretofore, effecting the inclusion or exclusion of precisely
similar resistances in each of the winding circuits, a resistance is first short
circuited in one of the circuits then in the second, then in the third and so on,-if
there be more than three; that is to say, referring to Figs. 1 and 2, instead
of moving the contacts from a, b, c, at once to a₁ b₁ c₁, first the contacts a, b, co,
then a b₁ co and so on are made, so that, instead of having only 4 different stages
of contacts as before, 12 stages will now be possible for gradually altering the
torque..
The variations of resistance in the several circuits will now no longer be
symmetrical as before, but it has been proved by experiment that this asymmetrical
arrangement has not only no detrimental influence upon the working of the motor,
but that, on the contrary, the fluctuations of the currents will be considerably less
than with the existing arrangements.
A second advantage of the improved arrangement is, that the necessary contacts
only form a.single group, so that all the contacts can be passed over by a single
contact switch.
It is not therefore necessary to provide a special construction for polyphase
current starters, the construction for continuous currents being equally available
for this purpose with the above described arrangement. A construction of the
Baid resistance switch apparatus is shewn by way of example at Fig. 3. The

page_text: contact plates are arranged in a circle, at the centre of which is pivotted a contact
arm H having an arc-shaped sliding contact piece G which always makes contacts
with three of the plates. Thus when G makes contact with a bo co all the
resistances A₁ &c. B₁ &c. C₁ &c. are included in the three circuits I II III, and
the motor will start with a small amount of torque. When G is moved so as to
come in contact with a₁ and out of contact with a,, then the resistance A₁ will be
cut out; by a farther motion, the resistances B₁ C₁ A, B, C, &c. will be consecu-
tively cut out, thereby gradually increasing the torque to a corresponding extent.
The improved mode of operating is of particular importance in enabling the
starting and reversing resistance apparatus with carbon contacts described in
the Specification to Siemens and Halskes German Designs Patent No. 43220 for
continuous current motors, to be applied to polyphase current motors, because by
the use of the carbon contacts, the wear thereof is very much reduced, and
the number of resistance stages required for starting the motor can be reduced.
The said apparatus of Design No. 43220 consists of a casing containing a series
of resistances, on the front side of which casing are arranged two rows of contacts
connected to the said resistances, which rows are arranged at a certain angle on
each side of a central vertical line. The contacts consist of a carbon block carried
by a metal holder pressed forward by a spring. Between the two rows is a
pivotted switch lever on each side of which, facing the carbon contacts is fixed a
carbon bar. When the lever is in the vertical middle. position all the resistances
are included in the circuit to be controlled; when the lever is turned on its pivot
towards the one set of contacts, its carbon bar first makes contact with the two
lowest spring contacts of the row thereby cutting out one of the resistances. On
still farther inclining the lever it presses backward the said spring contacts, and
comes in contact with the next one of the row, and so on, till all the spring
contacts are in contact with the carbon bar of the lever, thereby cutting out all
the resistances. The one row of contacts serves for directing the current in one
direction and the other one for reversing it. Fig. 4 shews the arrangement of this
apparatus for the purposes of the present invention.
The contacts a, b, c, &c. consisting of carbon blocks in spring supports are
arranged in a straight line and a contact lever H having a carbon or preferably a
copper contact under surface, in being turned on its pivot causes the plates ao bo co
to be first put in contact therewith, all the resistances being then in circuit. On
turning H farther so as to make contact with a' the resistance A₁ will be cut out,
a farther movement of H on to b₁ will cut out resistance B₁ and so on, until the
contact with o will cut out all the resistances.
Resistance apparatus of the above described kind can be connected either to the
inducing circuit of the motor, or to the closed induced circuit.
As asynchronous single phase current motors work with the same induction-
armatures as polyphase current motors, the said resistance starting apparatus is
also applicable to them.
Dated this 18th day of December 1905.
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
Resistance Switch Apparatus for Starting Electromotors.
We, SIEMENS BROS. & Co. LIMITED, of 12 Queen Anne's Gate, Westminster
in the County of London, 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:-
This invention relates to switch apparatus for regulating the torque on starting

page_text: polyphase and single phase electromotors by including and excluding resistances in
their winding circuits.
In the polyphase motors in which only the magnetic field receives current from
the supply circuit, while currents induced by the magnetic field flow through the
closed armature windings, the regulation of the torque is ordinarily effected by
starting resistances which are introduced either in the inducing or induced circuit
of the motor. These starting resistances consist, as shewn diagrammatically at
Fig. 1 of the drawings filed with our Provisional Specification, of as many equal
resistance groups as there are circuits.
If the starting resistances are included in the induced part, the ends of the
several groups a° 6° c° are connected together; the commencements I II III, are
connected to the motor windings which are here arranged for a three-phase
current. If it be desired to increase the torque of the motor, the resistances are
cut out by degrees by short circuiting proceeding from left to right, until the
motor runs without resistances, and thus works with the maximum torque.
In the starting resistances heretofore employed, it has been the custom to insure
the symmetry of the several branch circuits, by simultaneously cutting out the
same number of resistances from each circuit.
Thus in Fig. 1 the cutting out would proceed according to the successive dotted
lines a, b, c, a, b, c, &c. Fig. 2 shews a known construction for this mode of
operating with a starting device having four resistance stages.
The 3 x 5 circuit closing contacts are arranged in a circle, round the centre of
which are arranged three contact switches placed at an angle of 120° to each
other, and having a conducting connection with each other. By turning these
switches to the left they are first brought on to the contacts a, b, c. for
starting the motor. On their being turned farther, they will make contact
with a bi c, thereby cutting out of the circuit I the resistance A¹, out of II the
resistance B', and out of III the resistance C¹; by short circuiting. By a farther
motion of the switches, three other resistances are cut out in like manner, until,
on connecting with the contacts a b c the motor will run without resistances.
In order, with this starting device to obtain a very gradual alteration of the
torque, the resistance coils must be divided into a considerable number of stages;
a starting device for rotary phase currents, will, for example, require a considerably
greater number of resistance stages and consequently of contact plates, than a
continuous current starter of the same capacity.
The present invention relates to means for obviating this disadvantage, whereby
the number of resistance stages requisite for starting polyphase motors are
considerably reduced, and it also has for its object to render the usual arrange-
ment of continous current starters, directly applicable for polyphase current
starters.
For these purposes instead of, as heretofore, causing the contact switch, that
cuts out the resistance stages to advance simultaneously over an equal number of
stages on each branch circuit, we cause the corresponding resistance stages of the
several branch circuits, to be cut out consecutively, so that, for example, in the
arrangement shewn at Fig. 1, the sliding contact switch instead of passing at once
from the position a° ° co into the position a b₁ c', would be made to assume
consecutively the following positions ;-a° 6° c°, a¹ bº cº, a¹ b¹ cº, a¹ b₁ c¹, a² b' c', and
so on. By this means instead of having in the three groups of four resistance
stages, only four different degrees of variation of the resistances, there will be
twelve such variations, and consequently, all twelve of these resistance stages can
be utilised for the gradual variation of the torque of the motor.
Of course this method of operating involves an unsymmetrical variation of the
resistances in each of the circuits corresponding to the different current phases, but
experiments have shewn that this asymmetry has no influence upon the working of
the motor and that, on the contrary, the current fluctuations are much less with
this new method of starting than with the method heretofore employed of
simultaneously cutting out equal resistance stages from each circuit.
:

page_text: A second advantage of the new-method.of starting arises from the fact, that the
necessary circuit closing devices only constitute a single group, so that they all
have to be brought consecutively in contact with the same sliding contact switch.
Consequently no special constructions are necessary for polyphase current starters,
as was the case formerly, the ordinary continuous current starters being.capable of
application if the resistance stages are arranged in the above described manner.
Fig. 3 shews the construction of a rotary phase current starter according to the
present invention. The sliding contact switch can be the same as that of a
continuous current starter with metal circuit closing plates. The circuit closing
plates are arranged in a circle, at the centre of which is pivotted an arm H having
an arc shaped sliding contact piece G, which always makes contact with three
contiguous plates, the corresponding resistance stages of the three circuits being
connected to contiguous plates.
If G is made to connect the three circuit closing plates a° 6° cº, the circuit of the
motor is closed. As the entire starting resistance is included, the motor will start
with a small amount of torque. By slightly turning the same arm H, G will be
brought upon plate a' and will leave a°.
The resistance A' will thus be cut out of branch circuit I of the motor; by
farther partial rotation of the arm H in the same direction, the resistance
stages B, C, A, B, C, &c. will be consecutively cut out, and the torque of the
motor will be correspondingly increased.
The improved mode of operating is of particular importance in enabling the
starting and reversing resistance apparatus with carbon contacts described in the
Specification to Siemens and Halske's Germau Designs Patent No. 43220 for
continuous current motors to be applied to polyphase current motors, because by
the use of the carbon contacts, the wear thereof is very much reduced, and the
number of resistance stages required for starting the motor can be reduced.
The said apparatus of Designs No. 43220 consists of a casing containing a series
of resistances, on the front side of which casing are arranged two rows of contacts
connected to the said resistances, which rows are arranged at a certain angle
on each side of a central vertical line. The contacts consist of a carbon block
carried by a metal holder pressed forward by a spring. Between the two rows is a
pivotted switch lever on each side of which, facing the carbon contacts is fixed a
carbon bar. When the lever is in the vertical middle position all the resistances
are included in the circuit to be controlled; when the lever is turned on its pivot,
towards the one set of contacts, its carbon bar first makes contact with the two
lowest spring contacts of the row thereby cutting out one of the resistances. On
still farther inclining the lever is pressed backward by the said spring contacts and
comes in contact with the next one of the row, and so on, till all the spring
contacts are in contact with the carbon bar of the lever, thereby cutting out all the
resistances.
The one row of contacts serves for directing the current in one direction and the
other one for reversing it. Fig. 4 shews the arrangement of this apparatus for the
purpose of this present invention.
The circuit closing parts, which consist of carbon plates carried in spring
sockets are arranged in a straight line and a contact lever H having a carbon or
copper bar on its under surface, in being, turned on its pivot, is put consecutively in
contact with the said plates.
Experiments have shewn that it is preferable to make either only the circuit
closing plates, or only the contact bar of carbon the other parts being made
of copper.
The ends of the resistance coils are connected respectively to the three
plates ab co which, on the turning of the switch lever H, are first connected
together for starting the motor. The ends of the several resistance stages are
connected to the several circuit closing plates in the manner shewn on the drawing.
The commencement I II III of the resistance coils are connected to the motor
winding.

page_text: On turning the switch lever to the right from the above described position..
it first makes contact with A'; it then makes contact with 6 cutting out.
resistance B and so on, until on the switch making contact with the whole
of the resistances are cut out.
Starting resistances of the above described kind can be connected either with the
inducing circuit, which receives the polyphase current from the supply network, or
with the induced circuit of the motor closed in itself.
As asynchronous single phase current motors work with exactly the same
induction armatures as the polyphase current motors, the above described
arrangement of the starting device can also be used with single phase current
motors.
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 :-
1. Resistance switch apparatus for starting single phase and polyphase current
motora wherein a series of resistances are so arranged in combination with circuit
closing plates and a contact switch that by the motion of the latter the said
resistances are singly and consecutively cut out of circuit so as to obtain a
considerable number of variations of resistance by means of a comparatively small
number of resistances, substantially as and for the purposes set forth.
2. In a resistance switch apparatus such as is referred to in the first claim, s0.
combining the resistance stages with circuit closing plates arranged in a circle that
the contiguous plates correspond to resistance stages in different branch circuits of
the motor winding, so that by means of a single contact switch a series of
contiguous plates belonging to resistances in the different circuits are put in
conducting connection with each other, while at each movement of the switch.
a farther plate and resistance are added to the connected group, substantially as
described.
3. In resistance switch switch apparatus such as is referred to in the first claim,.
arranging the circuit closing plates, in a straight line in combination with a contact
switch by the motion of which each plate is successively put in conducting
connection with the preceding ones, the contiguous plates being connected to
resistances in different branch circuits, substantially as described.
Dated this 5th day of September 1896.
ABEL & IMRAY,
Agents for the Applicants..