Improvements relating to the Generation of Multiphase Currents and Multiphase Electro-motive Forces from Single-phase Currents and Single-phase Electro-motive Forces, and to the Utilization of the same.
Year: 1897

page_text: Date of Application, 21st Oct., 1897-Accepted, 29th Jan., 1898
Improvements relating to the Generation of Multiphase Currents
and Multiphase Electro-motive Forces from Single-phase Currents
and Single-phase Electro-motive Forces, and to the Utilization
of the same.
I, FRIEDRICH TISCHENDORFER, Electrical Engineer, of 111, Wiesenstrasse, Nürnberg,
in the Kingdom of Bavaria, 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 numerous methods hitherto known for working motors with rotating or with
oscillating fields by means of single-phase currents or by polyphase currents (split
phases) derived therefrom electrically have been unsatisfactory.
The starting torque is small, as compared with that of multiphase motors, because
the ratio between the weak rotating field and the size of the motor is unfavourable.
By the new method hereafter described, it is intended, not only to shift the phase
of the E.M.F., as has been done till now, but simultaneously that of the current,
which means a displacement of the phase of the energy; in other words, the power
factor of the secondary phase (generally indicated by cos ) is to be brought as near
as possible to the value of 1. In this way, it is intended to create a powerful rotating
field with a minimum expenditure of energy and material, or to obtain as many as
possible of the advantages of the multiphase motor. In order to explain this
inethod theoretically and to show, how it is to be applied, I will refer to Figs. 1 to 21
of the accompanying drawings.
An induction coil D₁ (choking coil) inserted into an alternating current circuit
causes the phase of the E.M.F. in the shunt (shown in Fig. 2) to be shifted
almost 90° relatively to the E.M.F. of the main current H H. In the diagram
Fig. 1, the lines E and J represent the E.M.F. and the current of the main circuit,
while e and i represent the E.M.F. and current of the shunt. In the diagram
Fig. 2, I and II indicate the two coils of the motor M, that are magnetically placed
at 90° to each other.
If, however, two coils 1 and 2 are wound on a common core, as represented by
Fig. 4, a displacement of the phases of the two currents will occur, the amount of
which may vary from 0 degrees to 180 degrees, according to the ratio between the
number of turns of the two coils. The displacement of the currents that
corresponds to the arrangement shown in Fig. 4, is represented by Fig. 3. (The
behaviour of the E.M.F. will be explained later on with the aid of Figs. 9, 10 and 11.)
E and J respectively are the E.M.F. and the direction of the current in the motor
coil I and in the induction coil 1, while e and i represent the same with reference to
the motorcoil II and the induction coil 2.
The combination of these two arrangements constitutes a part of the present
invention.
If the two arrangements are combined to a new one, as shown in Fig. 6, the result
will be, that the phases of the E.M.F. and of the current are shifted or modified
simultaneously. By adjusting the number of turns and the self-induction of both

page_text: induction coils (D, and D¸ in Fig. 6), it is possible, to shift the phases of the E.M.F.
and of the current uniformly, as indicated by the lines e i of Fig. 5, and at the same
time into the most advantageous position for the two motorcoils, viz. to where they
deviate 90° from the main E.M.F. and current. In Fig. 5, E and J again represent
the E.M.F. and the current respectively in circuit I of the motor.
It is not required,
that e and should be equiphase. They may, as was the case in the main current,
be placed at an angle. It will, however, be advisable, to make the angle as small as
possible, as the maximum of energy is turned into motor circuit II, if the angle
between the phases e and i is 0.
Fig. 6 shows, how the inductor D, which causes the shifting of the E.M.F. and
the inductor D, which causes the shifting of phase of the current, are connected to
separate motor coils. These two coils, which are connected in parallel, form the
motor circuit II. The two induction coils may be united, when leaving the inductors
and may then he connected with the equally united motor coil II (Fig. 7). This
method of connection may be further continued and applied to the two inductors,
and the same result will be obtained. But the coils 1 and 2 which are mounted on
the same inductor, are to be connected to the motor coils I and II, as shown in
Fig. 8.
The larger the angle, through which the phase has been shifted, the more E.M.F.
will the inductor consume, and if the angle of displacement can be made small, the
transformation will be more economical. This is indicated in Fig. 9, where the
impressed E.M.F.E is divided into e, (which represents the useful E.M.F. with displaced
phase), and el which represents the loss of E.M.F. due to self-induction. As already
shown in Fig. 1, the currents I and i under these conditions continue equiphase, and
the angle that measures their lagging behind the E.M.F. E increases at the same
ratio, as the self-induction of the motor-coil I.
A good ironclad transformer, however, creates a displacement of the E.M.F. e of
the secondary coil against that of the primary coil of almost 180 degrees. The
poorer the transformer, viz. the higher its self-induction and the higher its magnetic
resistance, the larger is the angle which supplements that formed by E and e₂ to
180 degrees, and the larger also is the angle formed between J and E. Whether the
secondary current will be equiphase or lag behind the E.M.F. e, will depend on its
being free from self induction or subject to it.
If the angle of the phase and the E.M.F. e₁ (Fig. 9) and e₂ (Fig. 10) are properly
adjusted, a resultant E, is obtained (Fig. 11) which lags 90 degrees behind the
E.M.F. E. Similarly, the resultant J, of the components i, i assumes an angular
position, that coincides with that of E, or that deviates only little from it.
If one of the coils (1) of an inductor is inserted into the main circuit H H,' while
the other (2) is connected to the main circuit by only one terminal, the shifting
of phases and of the current and E.M.F. just explained would take place in
circuit 2.
The way in which such an inductor may be constructed, is shown in Fig. 13. It
must not be ironclad, moreover the straying of lines may be induced by iron
dises F on either side of the coils. Fig. 14 shows, how such an inductor is connected
to the motor-coil II.
The lagging resultants of the E.M.F. and of the current may be adjusted to form
any other angle of phase with the E.M.F. E, from 0 up to 180 degrees. For example,
a displacement of 120 degrees is assumed in Fig. 15, and it is obtained there in the
same way as in Figs. 9, 10 and 11.
For convenience sake, only E₁, е₁ and e̟ were considered in Fig. 15, while the
corresponding currents, which can be compounded in a similar way, are omitted.
This composition of the electromotive forces E and E, (Fig. 16) gives a resultant e
which when applied in the opposite direction produces an E.M.F. E differing in
phase 120 degrees from the E.M.Fs. E and E₁.
Again, as shown in Figs. 17, 18 and 19, an inductor with a phase set at 120 degrees
may be connected to an induction motor, whose coils are wound on the three-phase

page_text: principle; the third motor coil will receive the current resulting from the other two
under 240 degrees and will have to be connected in the opposite direction.
If a motor wound on the monocyclic system by which its supplementary coil II is
connected with one of the terminals of the middle of the main coil, is worked with a
single-phase alternating current, the connection of the conductor would have to be
made in a similar manner, as in Figs. 20 and 21, and this mode of winding the coils
would produce the same effect, as in the previous cases.
The method thus specified may be used for either working alternating induction
current motors continuously, or for starting the same.
As these methods permit to choose the angles of phase ad libitum and to adjust
them exactly, this invention may be applied also to measuring instruments, arc lamps,
and other electrical apparatus.
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. The generation of multiphase currents and multiphase E.M.F's. from a single
phase current and a single phase E.M.F. by means of one or more inductors with
several coils on the same core, substantially as described, whereby the phases of both
intensity and pressure of the current are simultaneously displaced.
2. The generation of multiphase currents and multiphase E.M.Fs. from a single
phase current and a single phase E.M.F. by means of one or more inductors with
several coils on the same core, substantially as described, whereby the phases of both
intensity and pressure of the current are shifted through equal angles.
3. In apparatus for generating multiphase currents and electromotive forces by
the methods specified above, the use of two inductors (Figs. 6 and 7), one of which
causes the shifting of the phase of the current, while the other causes the shifting of
the phase of the E.M.F.
4. In apparatus for generating multiphase currents and electromotive forces by
the methods specified above, the use of a single inductor with two coils, so arranged
that each of them is in series with the corresponding motor coil (Fig. 8) or so, that
one connects the mains directly, while the other is connected to the corresponding
coil of the motor, (Fig. 14).
5. The application of the methods specified above to three phase motors in such a
manner, that an inductor is used which produces E.M.F. and current, the phases of
which are displaced by 120 degrees and that the three coils of the motor are
consecutively transversed by the main current, the inductor current, and the resulting
current.
6. The application of the methods specified above for working monocycle motors
with single phase current in such a manner, that the primary coil of the inductor,
like that of the motor, is connected to the main phase (primary circuit) in parallel
or in series, and that the secondary coil of the inductor is connected at one end
either to the middle of its own primary coil or to one of the mains, while the other
end is connected to the supplementary motor winding II, whose other end again is
connected to the middle of the motor winding I (Figs. 20 and 21).
Dated this 21st day of October 1897
FAIRFAX & WETTER,
Agents, 37 and 39, Essex Street, Strand, London.