Improvements in Electromotors and Dynamos, and in Apparatus for Use therewith.
Year: 1896

page_text: This Print is in accordance with the Original Specification as it stands after
Amendment (under Section 18 of the Patents, &c., Act, 1883), as allowed by
the decision of the Chief Examiner of the 28th day of November 1896.
Date of Application, 6th May, 1896-Accepted, 20th June, 1896
COMPLETE SPECIFICATION (AMENDED).
Improvements in Electromotors and Dynamos, and in Apparatus for
Use therewith.
1, EMIL LANHOFFER, of Colmarervorstadtstrasse 164, Mülhausen, in the
Province of Alsace and Empire of Germany, 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 :-
The object of the present application consists of an electric motor characterised
by having the number of revolutions continuously, that is, not abruptly, changeable
within desired limits.
The motor is designed to be driven with uniform constant difference of potentials,
and is therefore capable of being connected to any lighting circuit. It will work
with the highest possible efficiency at very varying speeds.
This problem is solved in the following manner :-
Proceeding from the fact that the number of revolutions of a motor is proportional
to the working potential difference of its armature, it follows that by using an
auxiliary dynamo having a potential, variable at will which cau be added to or
subtracted from the main potential the armature of the motor can be worked
with very various terminal electromotive forces according to the amount and
direction of the potential difference supplied by the auxiliary machine.
This auxiliary machine is driven by the motor direct and for this purpose both
the armatures are mounted upon the same shaft. This method of mounting
possesses the advantages as compared with a separate driving of the auxiliary
machine, that firstly, the latter when the motor speed increases, also runs with an
increased number of revolutions, whereby the dimensions of the machine can be
kept small and secondly a relatively small difference in the excitation of the
magnets of the auxiliary machine causes in consequence of the simultaneous
alteration in speed a relatively large difference in the electromotive force
developed.
In a power distribution according to this system each separate motor should be
provided with such an auxiliary apparatus, forming one machine with it. The
motor is driven by the principal and auxiliary dynamos which are to be regarded
as arranged in series.
The accompanying drawings illustrate the invention in several figures as
follows:-
Figure 1 shows a diagram of the arrangement of a motor in which the auxiliary
dynamo is placed upon the shaft of the motor but in which two armatures separate
from each other are present.
Figure 2 illustrates in diagram the auxiliary resistance requisite for this motor.

page_text: Figure 3 shows a diagram of the motor as already displayed in Figure 1 except
that the two armatures are united together.
Figure 4 shows the method of winding for the armatures shown in Figure 3.
Figures 5 and 6 show methods of arranging a motor of this kind in diagram with
reference to the arrangement of the magnetic field.
In order to make the nature of the motor intelligible it is necessary to explain
the theory whereby the construction will be explained at the same time.
The
In the diagram (Fig. 1) M indicates the armature of the motor, ZD indicates
that of the auxiliary dynamo which as shown.in the figure is located upon the same
shaft as armature M. The letters k' and indicate the contact brushes of the
motor armature, 61 and 62 those of the armature of the auxiliary dynamo.
current coming from the principal generator, the constant potential of which may
be denoted by E, flows through the armature ZD of the auxiliary dynamo whose
electromotive force è is added to or subtracted from the potential E according to its
direction. The difference of potential existing between the brushes k¹ and k² of
the motor armature consequently is equal to E±e.
The field strength of the motor remains constant because its magnets m are
supplied direct from the principal conductor with a current at constant potential.
Disregarding secondary actions such as armature reactions etc. the consideration of
which is not here important the number of revolutions n of the motor can be
regarded as proportional to the difference of potential existing between its brushes,
that is
that is to say the number of revolutions of the motor at a given potential difference E
only depends upon the field strength f of the auxiliary machine.
If f=0 then the number of revolutions of the motor n = E and for the extreme
cases in which the field strength of the auxiliary machine is equal to that of the
motor consequently f= 1, the speed of the revolution will according to the direction
off either equal 0.5 E or be equal to infinity. The conclusion to be drawn from
these results may be expressed as follows:-
If the magnetic field of the auxiliary dynamo be so excited that the electro-
motive power e supplied by it has a direction opposed to that of the principal
current the number of revolutions of the motor may be varied by alteration of the
field strength of the auxiliary machine from F to 0 in the limits from 0-5 E to E.
The machines then work as two motors arranged in series. If, on the other hand,
the field strength f be so directed that the electromotive force e of the auxiliary

page_text: for a given turning moment to be developed by the motor the current strength
flowing to the same under constant potential E from the principal conductor
increases proportionally with the speed.
Finally Figures 5 and 6 show two further arrangements in which the auxiliary
electromotive force e is generated in single armature or bobbin sections. The
alterable auxiliary poles fare here interposed between the constant motor poles m.
Figure 5 shows the application to a six pole machine in which four motor poles
and two wider auxiliary poles are made use of. The armature winding here is that
of a usual bi-polar Gramme winding.
Figure 6 shows an application to a four pole machine, the armature winding is
preferably so arranged that each armature reel M' is divided into two equal halves
each of which is placed half under a motor pole and half under the contiguous
auxiliary pole.
The advantages of these arrangements are that the speed of the motor is
alterable within any desired limits and continuously, because by sufficient increase
of the number of contacts of the reversing resistance any desired number of
revolutions of the motor can be obtained. The motor can moreover be connected
to any desired lighting machine or current circuit. If such a motor be run as a

page_text: dynamo the retarding potential may be reduced from its maximum value to 0 and
the machine will then run without sparking on full current.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
-claim is :-
1. In electro-motors or dynamos the arrangement of an auxiliary dynamo driven
by the main machine whose electromotive force e alterable in quantity and direction
is connected with the constant potential difference E of the main current in such a
manner that in the electro-motor at the brushes a variable potential difference is
generated whereby the motor can run at any desired number of revolutions
continuously (not suddenly) altering whilst in the dynamo two electromotive
forces e and E are generated which according to the direction of the alterable pole
system or magnetic field can be added algebraically one to another so that a
dynamo driven with a constant number of revolutions can supply any desired
difference of potential between 0 and the maximum tension and can be loaded up
.to the full current.
2. In electro-motors or dynamos as set forth in Claim 1 the generation of an
electromotive force e alterable at will both in direction and strength in the
conducting elements of the motor or dynamo armature which algebraically
considered adds itself to the tension E momentarily prevailing at the brushes for
the purpose set forth in Claim 1.
3. In electro-motors or dynamos as set forth in Claim 1 the arrangement of a
magnetic field or pole system alterable in strength or direction in combination with
.an unalterable constant magnetic field or pole system.
4. In electro-motors or dynamos such as set forth in Claim 1 the arrangement of
an auxiliary resistance so arranged that the exciting winding of the machine may
be short-circuited through the resistance at the reversal so that sparking at opening
is avoided.
Dated this 6th day of Mov 1906
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.