Year: 1888

page_text: I, FREDERIK VILHELM SCHIÖDT of Copenhagen Denmark Engineer 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:
Heretofore the following three systems of winding for exciting the magnetic field
in dynamo machines have been used' viz.
1. In which wire coils of the magnet are passed from the main current of the
machine, series machines, so that the tension at terminal of machine alters with
strength of current.
2. In which the wire coils are traversed by a branch current which unites the
positive brush of the machine with the negative, shunt machines. The tension at
terminal will hence decrease when the current strength increases. If the tension is
to be constant a regulating resistance is used in the branch wire.
3. The compound system produced by combining the two aforesaid systems and
which makes the machines self regulating, so that the tension is kept constant while
the current strength may vary.
If several dynamo machines are to work on the same conductor system or if one
machine is to be substituted for another without disturbing. the working of the
installation, the shunt machines, system No. 2, become almost exclusively applicable,
because compound machines of different sizes cannot possibly work together, and
even with compound machines of the same size there is a risk of one machine even
when only for a short time coupled with another sending a current into the other
whereby the magnetism of the machine receiving the current obtains an opposite
direction and both machines are disturbed or rendered useless. There is not that
risk with shunt machines, inasmuch as the current in the magnet coils does not alter
its direction, even when the one machine sends the current through the other, and the
current strength of each of the coupled machines can be regulated.
From this reason in spite of the advantages as regards self-regulation compound
machines are hardly ever used on electrical central stations or for similar installations
with continuous working and hence one machine has to take the place of the other or
several are made to work together.
In electrical central stations and other considerable installations the conductors
often work with a great loss of tension in order to avoid inordinately large dimensions
of the same.
It is then impossible to construct compound machines according to
system 3 when a constant tension is to be kept in the lamps without at the same time
the compound machines losing their character as such when they are coupled.

page_text: These defects in the compound machines are avoided by the system of winding now
to be described and which is base upon the aforesaid loss of tension in the conductors.
The system consists in that besides the usual shunt-winding in the machine and
instead of the winding which is traversed by the main-current a second one is used
which connects two points either in the positive or negative conductor in such a
manner that this winding becomes a branch wire to the positive or negative side of
the conductor system. The wire will therefore be traversed by a current the strength
of which depends upon the loss of tension between the two points which it connects.
By this winding which might be called tension loss-winding and which wholly takes
the place of the main wire-winding in compound machines a coupling of such
machines is rendered possible and as the annexed drawing shows every danger of
the changing of the poles is avoided even if one machine accidentally should receive
the current from another. Let A and B for instance represent two dynamo machines
with commutators K and K 1 and which work together. And let E F and E1 F 1 be
the conductor which supply the lamps, motors &c., with electricity. In the drawing
I have shown an ordinary double-conductor system but the winding system may be
applied in all conductor systems such as ring, and three conductor systems.
Supposing that the main conductors are of considerable length a loss of tension will
take place between the points E and F and consequently also between the brush D
and the point H. which loss will be proportional to the current's strength in the main
conductor, and this will also happen between the brush C and the point G. The
tension loss-winding S of the machine A can pass from the brush C round the magnet
to the point G whilst the tension loss-winding S 1. of the machine B goes from the
brush D around the magnet to the point H.. The current directions will then under
ordinary circumstances be as indicated by the arrows. If now for instance the
electromotive force of the machine A by inadvertence becomes so much higher than
that of the machine B that the latter would receive current from the former then
the current direction will only alter in the conductors E D and E 1 D1 and in the
armature winding of the machine B, whilst it remains the same for all magnet
windings so that polarity of the magnets is not changed.
It is evident that a couple of other tension-loss windings may be applied which
unite the point F 1 of two other adjacent points in the same conductor with the
brushes C1 and D 1.
Having now particularly described and ascertained the nature of said inven-
tion and in what manner the same is to be performed I declare that what
I claim is.
In dynamo machines the application and use of one or more so called tension loss
windings S.for magnet winding each separately writing two points either on the
positive side C and G or on the negative side C1 and F1 in the conductor system
besides the usual shunt winding R.
Dated this 22nd day of November 1888.
FREDERIK VILHELM SCHIÖDT.
By Jensen & Son,
77, Chancery Lane, London, W.C.,
Patent Agents.