Improved Circuit Connections for Continuous-current Shunt Machines.
Year: 1898

page_text: Date of Application, 25th May, 1898
Complete Specification Left, 10th Jan., 1899-Accepted, 11th Mar., 1899
PROVISIONAL SPECIFICATION.
Improved Circuit Connections for Continuous-current Shunt
Machines.
I, ADOLF SENGEL, Professor at the Electrotechnical Institute at Darmstadt,
Germany, do hereby declare the nature of this invention to be as follows:-
--
As is well known, the construction of the magnet winding in continuous current
shunt machines for higher potentials, involves great difficulties because with an
increasing potential the cross-section of the shunt wire employed diminishes with
the increasing number of windings, so that on one hand there is an increase in the
cost of material and manufacture whilst on the other hand there is an increased
risk of striking through the magnet winding in case of careless throwing of the
shunt circuit current out of circuit. The two first mentioned drawbacks are
especially perceivable in small machines. Resistances might certainly be employed
to diminish the potential at the terminals of the shunt circuit, to any desired
extent. but this would entail a permanent loss of energy in the resistance and the
saving in the manufacture of the magnet winding would be more or less balanced
by the increased cost of the resistance.
The arrangement hereinafter described allows of exciting the magnets in a shunt
machine without any loss and with only half the potential at the brushes.
Figure illustrates an arrangement of connections of this kind.
A indicates the armature of a continuous-current machine, C indicates the
current delivery device or commutator, with the two collecting brushes B and B'.
There is further mounted on the shaft an insulated rubbing ring S which is con-
ductively connected with any point of the armature winding (for example by means
of the current collector or commutator segment s) and upon which there rubs a
third brush B. When the machine is set in operation and is normally excited,
there is produced between the brushes B and B as is well known, a constant
potential, that is to say a potential which has at every moment the same direction
and the same value. Now the potential which exists between the brush B rubb-
ing on the contact ring S and one of the brushes B or B', although having the
same direction, is yet continually varying in amount according to the position of
the segments (that is connected with the rubbing ring S) in relation to the brush B
or B
On considering, for example, the course of the potential between B" and B, it
will be seen that the potential between the two brushes is equal to zero when the
segments comes under the brush B. The potential reaches its maximum when
the segments, after half a revolution, comes in contact with the brush B and it
is in this case equal to the potential at the terminals of the machine B-B¹. In
the other positions the potential B B has a value which is situated between the
maximum and zero. Consequently the potential is a pulsatory one.
This pulsatory
potential may be conceived to be produced by the combination of a pure con-
tinuous current, and of an alternating current potential, which are of such amounts
that both the continuous current potential, as also the amplitude of the alternat-

page_text: ing current potential, become equal to half the potential at the terminals. If an
inductionless resistance be included between B and B a current which will also
continually vary between zero and maximum will be produced in this resistance
and this current can also be split up into a pure continuous current and an alter-
nating current. Both currents are of an amount such as if a continuous current
potential of half the potential of the machine and an alternating current potential
having an amplitude also equal in value to half the potential of the machine, were
to act simultaneously at the terminals of the resistance. If now the resistance
which is inserted between 1 and B also receives self-induction, the latter will not
affect the continuous current in any way but will seek to weaken the alternating
current and in a higher degree the greater the co-efficient of the self-induction
and the higher the periodic number or frequency of the alternating current, so
that with self-induction and periodic number of any reasonably high value the
current which is produced can be practically considered to be a continuous current
having a potential equal to half the potential at the brushes. Now the shunt wind-
ings of dynamo machines have an extremely high self-induction. If therefore the
ends of the shunt winding be placed as shewn in Figure 1, between the brushes B
and B with the inclusion of a regulating resistance R, then even with a low
periodic number the current strength produced in the shunt current circuit will reach
exactly the same value as if this circuit were fed with half the brush
potential B-B¹.
In the same manner this arrangement of connections may be employed in shunt
circuit motors.
Figure 2 shews an arrangement of this kind in combination with a starting
resistance W. The other reference letters are the same as those employed in
Figure 1. The connections of the armature are made in the usual manner. One
end of the shunt circuit winding is connected through the contact bar & with one
pole of the lead, whilst the other end is connected to the brush_B".
The use of this arrangement of connections in motors has further the advantage
that so long as the armature is at rest, the full working potential will act at the
terminals of the shunt circuit and therefore the exciting current will be twice as
great as in normal working and the attractice force will be considerably higher
than when the ordinary arrangement of connections is used. With increasing
speed of the armature the potential at the terminals of the shunt circuit will
diminish and will reach its normal amount which is equal to half the potential
in the lead when the whole of the resistance in the armature current circuit has
been cut out.
The rubbing ring S may be dispensed with when the armature winding is con-
nected at one point with the iron body and in this manner with the shaft and with
the magnet frame, and the one end of the shunt circuit winding is connected to
the frame instead of to the brush B. This does not make any alteration with
reference to the mode of operation of the entire arrangement.
Dated this 25th day of Now 1898
Improved Circuit Connections for Continuous-current Shunt
Machines.
I, ADOLF SENGEL, Professor at the Electrotechnical Institute at Darmstadt,
Germany, do hereby declare the nature of this invention and in what manner the

page_text: same is to be performed to be particularly described and ascertained in and by
the following statement:
As is well known the construction of the magnet winding in continuous current
shunt machines for higher potentials, involves great difficulties because with an
increasing potential the cross-section of the shunt wire employed diminishes with
the increasing number of windings so that on one hand there is an increase in the
cost of material and manufacture whilst on the other hand there is an increased
risk of striking through the magnet winding in case of careless throwing of the
shunt circuit current out of circuit. The two first mentioned drawbacks are
especially perceivable in small machines. Resistances might certainly be employed
to diminish the potential at the terminals of the shunt circuit, to any desired
extent, but this would entail a permanent loss of energy in the resistance and the
saving in the manufacture of the magnet winding would be more or less balanced
by the increased cost of the resistance.
The arrangement hereinafter described allows of exciting the magnets in a shunt
machine without any loss and with only half the potential at the brushes.
Referring to the drawing filed with my Provisional Specification, Figure 1
illustrates an arrangement of connections of this kind.
A indicates the armature of a continuous-current machine, C indicates the
current delivery device or commutator, with the two collecting brushes B and B¹.
There is further mounted on the shaft an insulated contact ring S which is con-
ductively connected with any point of the armature winding (for example by means
of the current collector or commutator segment s) and upon which there rubs a
third brush B". When the machine is set in operation and is normally excited,
there is produced between the brushes B and B', as is well known, a constant
potential, that is to say a potential which has at every moment the same direction
and the same value. Now the potential which exists between the brush B rubb-
ing on the contact ring S and one of the brushes B or B', although having the
same direction is yet continually varying in amount according to the position of
the segments (that is connected with the contact ring S) in relation to the brush B
or B
On considering for example the course of the potential between B1 and B, it
will be seen that the potential between the two brushes is equal to zero when the
segments comes under the brush B. The potential reaches its maximum when
the segments, after half a revolution, comes in contact with the brush B and it
is in this case equal to the potential at the terminals of the machine B-B¹. In
the other positions the potential B B has a value which is situated between the
maximum and zero. Consequently the potential is a pulsatory one. This pulsatory
potential may be conceived to be produced by the combination of a pure con-
tinuous current and of an alternating current potential, which are of such amounts
that both the continuous current potential as also the amplitude of the alternat-
ing current potential, become equal to half the potential at the terminals.
If an
inductionless resistance be included between B and B a current which will also
continually vary between zero and a maximum will be produced in this resistance
and this current can also be split up into a pure continuous current and an alter-
nating current. Both currents are of an amount such as if a continuous current
potential of half the potential of the machine and an alternating current potential
having an amplitude also equal in value to half the potential of the machine were
to act simultaneously at the terminals of the resistance. If now the resistance
which is inserted between B and B is subject to self-induction the latter will not
affect the continuous current in any way but will tend to weaken the alternating
current and in a higher degree the greater the co-efficient of self-induction
and the higher the periodic number or frequency of the alternating current, so
that with self-induction and periodic number of any reasonably high value the
current which is produced can be practically considered to be a continuous current
having a potential equal to half the potential at the brushes. Now the shunt wind-

page_text: ings of dynamo machines have an extremely high self-induction. If therefore the
ends of the shunt winding be placed as shewn in Figure 1 between the brushes B
and B with the inclusion of a regulating resistance R, then even with a low
periodic number the current strength produced in the shunt current circuit will reach
exactly the same value as if this circuit were fed with half the brush
potential B-B¹.
In the same manner this arrangement of connections may be employed in shunt
circuit motors.
Figure 2 shews an arrangement of this kind in combination with a starting
resistance W. The other reference letters are the same as those employed in
Figure 1. The connections of the armature are made in the usual manner. One
end of the shunt circuit winding is connected through the contact bar k with one
pole of the lead, whilst the other end is connected to the brush B".
The use of this arrangement of connections in motors has further the advantage
that so long as the armature is at rest, the full working potential will act at the
terminals of the shunt circuit and therefore the exciting current will be twice as
great as in normal working and the attractive force will be considerably higher
than when the ordinary arrangement of connections is used. With increasing
speed of. the armature the potential at the terminals of the shunt circuit will
diminish and will reach its normal amount which is equal to half the potential
in the lead, when the whole of the resistance in the armature current circuit has
been cut out.
The contact ring S may be dispensed with when the armature winding is con-
nected at one point with the iron body and in this manner with the shaft and with
the magnet frame, and the one end of the shunt circuit winding is connected to
the frame instead of to the brush B. This does not make any alteration with
reference to the mode of operation of the entire arrangement.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what I
claim is:-
1. In a shunt dynamo or shunt motor the connection of one end of the shunt
with a point of the main line and the other end of the shunt with an intermediate
point of the armature winding substantially as described.
2. In a shunt dynamo or shunt motor the connection of one end of the shunt
with a delivery brush of the main line and the other end of the shunt with a
rubbing ring placed in the winding of the armature at an intermediate point
thereof substantially as described.
Tad this 10th day of Tunuary 1800
A. M. & WM. CLARK,
Chartered Patent Agents, 53, Chancery Lane, London.