Improvements in Distributing Electric-energy.
Year: 1891

page_text: COMPLETE SPECIFICATION.
Improvements in Distributing Electric-energy.
I, EMIL ALFRED WAHLSTRÖM, of 30 Bad Strasse, Cannstatt, in the German
Empire, 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 :-
This invention relates to improvements in the distribution of electric energy by
applying alternating currents."
Great difficulties have been experienced in the application of alternating currents
to convert electricity into motive power, as is of particular importance for central
stations, unless a turn-current system is employed either by inter-chaining the
currents like is done by the "Allgemeine Elektricitätsgesellschaft, of Berlin," or by
producing differences in the phases of the different parts of the current created by
self-induction in one portion, as is the case in the motors of N. Tesler of
New York.
Each of these arrangements has its drawbacks. In the first the regulating is
extremely difficult without transforming the current and such transformation always
creates losses of power, moreover distributing the current for lighting purposes,
according to this system, embodies the same difficulties as arise in the four-wire
system, whereby especial care must be taken that the three groups of lighting or
other apparatus are of about the same size. However this may not agree with
circumstances and then expensive and aggravating means must be employed.
the other arrangement the variation of the phases between the different parts of an
alternating current caused by the self-induction of one single portion also naturally
creates a loss of energy and besides demands a very complicated construction of
the motor.
In
Now there are no such defects in my present invention, which will completely over-
come the afore-mentioned difficulties. The idea is to send two different alternating
currents coming from the generator E and E' in displaced phases into a common
conductor 3 (Fig. 1), which conveys both currents, and to employ the current
passing this central conductor in combination with the two alternating currents to
produce a rotary magnetic field.
The difference in the phases of the two equally powerful alternating currents is
in this case about one third of a period, that is so say, about 120°. Searching for
the amount of energy of the combined current passing the central-conductor, which
is produced by the two alternating currents generated at E and E¹, that pass the
conducting-wire 3 both at the same time, one must bear in mind, that at any time,
the resulting energy will be equal to the algebraic sum of the intensities of the two
single currents, taking the current in one direction to be positive and the one in the
other direction negative. The Figure 2 illustrates the progresses of the currents
by curves, taking the horizontal line as axis of the abscissae in which the lengths
are proportional to the rate of time. The curve I represents the progress of the
alternating current in the conductor 1 and 3, and curve II that in the conductor 2
and 3. Both are sine-curves. Now adding algebraically the ordinates of the two
curves together a curve III results, which represents the progress of the current in
the conductor 3. This also is a sine curve. Bearing in mind that the two single
currents passing the wire 3 are equal to each other as to their energy, and their
difference of the phases being 120°, it is evident that the resulting current and the
difference of the phases in comparison to each of the former ones will be of a
period that is to say 60°.
I therefore have three alternating currents equal in energy, of which each is
displaced in its course against the other at about of a period or 60°. To produce

page_text: a rotary magnetic field by these three alternating currents, a ring may be furnished
with coils, two and two standing opposite each other, and being wound like in Fig. 1.
The coils belonging together are indicated respectively by I and IV', II¹
and V', III and VI, and two and two, conveying the same current, produce
magnetic poles of the same name in the ends pointing out in the same direction.
But
The progress of the alternating current in the coils I and IV, which both are
put in the circuit of the wire 1 will be represented by the curve I in Fig. 2. The
progress of the current in the coils II and V being in the circuit of the wire 2
will be represented by the curve II, and finally, that of the compound alternating
current in the coils III and VI, completing the circuit of the wire 3 and the other
coils, is represented by the curve III. It may be said, that the magnetic effect
will alternate equally to the current as far as the direction in the axis of the coil
is concerned, and as far as the energy is concerned the magnetic effect will be
approximately proportional to that of the current, therefore the magnetic moment
produced by such a coil and alternating with the current, may be represented by
the same curve, which illustrates the progress of the alternating current.
nevertheless there yet is a difference in the direction of magnetisation of two
diametrical opposite coils as regards to an annular continuous line of the ring. The
direction of this line inside of one coil will be the same as the direction of circula-
tion, yet in the other coil it will be reverse to the same, both, it may be said, would
belong to an opposite magnetic state of the complete ring and therefore may be.
distinguished by calling them positive and negative and may be graphically repre-
sented as algebraic opposite ordinates. But then, the produced magnetisation is
not to be represented by the same curves illustrating the current in two opposite
coils, but by otherwise equal, sine-curves, being displaced as much as half a period
or 180°. In this way the curves I and IV, III and VI, II and V in Fig. 3 elucidate
the progress of magnetisation by the coils as arranged in Fig. 1 and initialed with
similar numbers.
It therefore now is evident, that at the time t, the coils I¹, III' and V¹ magnetize
positive and the coils II', IV and VI magnetize negative. Magnetic poles
therefor arise in the ring between the coils V and VI (south) and between II'
and III (north). This magnetic state of the ring at the time t is illustrated by
Fig. 1. At the time t¹ the coils I and III' magnetize positive and IV and V₁₁
magnetize negative, V' and II' alternate the direction of the magnetization produced
by the same and the poles also lie near V₁ and II'.
In
At the time I II and III' magnetize positive, and IV1, V₁ and VI negative,
and the poles will be between l' and V and between II and IV' and so on.
fields with more poles one need only increase the number of coils and arrange them
similar to Fig. 1.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is :-
In distributing electric energy: The employment of three currents in this manner,
that two alternating currents are displaced in their phases and have a common
central conductor, so as to create a third alternating current passing this central
conductor by the combined effect of the two first named alternating currents, for
the purpose of producing rotating magnetic fields as set forth.
Dated this 8th day of May 1891.
EMIL ALFRED WAHLSTRÖM.
By Rayner & Cassell,
37, Chancery Lane, London, W.C., Agents for the Applicant.