A Regulating Transformer for Rotary Phase Current or Polyphase Current Installations.
Year: 1898

page_text: Date of Application, 25th Nov., 1898-Accepted, 18th Feb., 1899
COMPLETE SPECIFICATION.
A Regulating Transformer for Rotary Phase Current or Polyphase
Current Installations.
We, SIEMENS BROTHERS & Co., LIMITED, of 12, Queen Anne's Gate, Westminster,
S.W., Electrical Engineers, do hereby declare the nature of this invention (which
has been communicated to us from abroad by Siemens and Halske Aktien-Gesellschaft,
Markgrafen Strasse No. 94, Berlin, S.W., Electrical Engineers), and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement :-
If the windings of one part of a bipolar alternate current dynamo be connected
to an alternating current network there are produced by induction in the windings
of the other part electromotive forces which have substantially the same phases
as the inducing electromotive forces; their amplitude however depends upon the
angle which the resulting magnetic field forms with the plane of the secondary
winding. If this angle be altered, the amplitude of the secondary electromotive
forces and consequently their magnitude will also alter.
The alternate current dynamo therefore behaves as a transformer, the ratio of
transformation of which can be altered by the turning of the one part, to a greater
or less extent. Such a transformer can be employed for purposes of regulation,
either by itself, for producing a variable electromotive force, or, as auxiliary trans-
former, for increasing or decreasing at will the voltage of the network.
This arrangement is only applicable for single phase alternating currents; for
polyphase currents it can only be used after splitting up the polyphase current into
separate single phase currents.
The present invention relates to an improved arrangement of apparatus of the
above described kind by means of which the network pressure of rotary phase or
polyphase current installations can be increased or decreased by the employment of
an additional pressure.
This improved arrangement differs from the arrangement for single phase
alternating currents, in that the amplitude of the additional pressure is in this
case maintained practically constant, while the phase is rendered variable, the
reverse being the case for single phase alternating currents.
With the new arrangement there is obtained from the primary pressure by
induction a secondary pressure, the phase of which is altered by turning the
moveable part of the apparatus and this altered pressure is then added to or sub-
tracted from the primary pressure for the purpose of regulation.
Referring to the accompanying diagrammatic drawings, the outer ring in
Figure 1 is assumed to be fixed, and the inner concentric ring is so arranged
that it can be turned through a certain angle relatively to the outer ring. Both
rings are provided with bi-polar windings, the inner ring having the three
windings A, B,; A₂ B₂; A, B₁; while the outer ring has the three windings a₁ b; a, b ;
a, b,. If the inner windings be connected to a rotary phase current network, having
the pressures E, E, E, respectively shifted 120°, there will be produced a rotary field
in the inner ring, and by induction a second rotary field will be produced in the outer
n

page_text: ring, which will have the same angular velocity and the same strength as the rotary
field in the inner ring if the leakage is neglected.
There will consequently be produced in the coils a₁ b₁; α₂ by; a b₁; electro-
motive forces ₁₁ е, the magnitude of which will only depend upon the ratio
between the number of turns of the windings of the inner ring and those of the
outer ring; and that will have a phase-difference of 120° relatively to each other.
If now the inner ring be turned through a certain angle, the phase of the electro-
motive forces induced in the several windings of the outer ring will be shifted
through the same angle, namely to the extent of 360° for a complete rotation of the
inner ring.
For the above described arrangement may be employed induction motors for
rotary phase and polyphase currents, of suitable construction such for example as
are described in the Electrotechnische Zeitschrift of 1895 page 551.
For this purpose the rotating part of the motor will be rendered stationary, but
capable of being turned at will within certain limits by suitable means such as worm
and worm wheel gear.
The above mentioned property, that the amplitude of the electromotive force of
the induced part remains constant, renders the described arrangement unsuitable for
producing a variable pressure, without the combination therewith of other devices.
In the United States Patent No. 522,820 means have been described for enabling
the induced electromotive forces to be varied, consisting in the use of a commutator
and revolving brushes, which convey the primary polyphase current through the
commutator to the outer ring, whereby the speed of the rotating magnetic field is
increased or decreased. By this arrangement of course both the magnitude and the
periodicity of the electromotive force in the induced part are altered. It is therefore
evident that this arrangement is inapplicable in all cases where the periodicity is to
remain constant, and only the electromotive force is to be varied.
The arrangement which fulfils this last condition is based on the following.
=
E₁
=
-
Let A Figure 2 be the electromotive force of one of the three windings of the
inner ring, such as E₁, and A D the electromotive force produced by induction in
one of the coils of the outer ring; then OD will represent the resultant of E, and e₁.
With the turning of e, the value of the resultant will be altered; when ₁ is in the
same direction as E, and forms an extension thereof, the resultant will be=0 H=E₁
+e. If on the other hand e, lies in line with E₁, but in the contrary direction, the
resultant will be = OK.
e₁, while when e, is at right angles to E, that is,
when D is in the positions J or L the resultant will be equal to VE₁²+e₁₂²
The resultants of E, and e,; E, and €3 will vary in a corresponding manner.
Each of these resultants will therefore lie between the limits E, +e, and E
(1.2, 3) and as the pressure e, can be made equal to any desired fractions
of E by a suitable determination of the number of windings, the resultants will lie
between optional limits.
11
2
2
In the diagram Figure 2 it is assumed that E, is constant and e₁ variable; the
resultant of E, and e, is in that case also variable. If on the other hand E' is
variable, then for every value of E₁, ₁ can be so determined by the rotation of the
inner ring, that the resultant of E, and e, remains constant.
We propose to call apparatus by means of which the pressures resulting from the
pressures E and are obtained by the turning through a certain angle,
rotatable regulating transformers."
11
While in Figure 2 the resulting pressure from the pressures E, and e („= 1,
2,3) is indicated geometrically, Figure 3 shews a diagram of practical construction
for the purpose.
The commencements a₁ a, a, of the coils of the outer ring are connected to the
rotary phase current network with the leads L, L, L, while the ends b₁ by b₁ thereof
are respectively connected to the leads N₁ N, N.. The windings of the inner ring
can be connected in star or mesh form; in Figure 3 they are shewn connected to
the leads L L L by mesh connection.
The windings of the inner ring which have the pressures E. E. E are in this case

page_text: the exciting windings, and produce a rotary field that induces in the coils of the
fixed ring the electromotive forces e e
2
These pressures produce, together with the pressures E, E, E, in the leads L, L, L,
the resultant pressures in the leads N, N, N.
By suitably turning the inner ring the pressures in N, N, N, can be varied between
determined limits or they can be maintained constant.
In the diagram at Figure 4 the inner rotatable part is the inducing part, to which
the pressure is supplied from the leads L, L, L, through three sliding contact rings
at 8 8 8
The ends of the three coils of the fixed part are led to the terminal posts a₁ b₁
b, by. The connections with the networks correspend with those of Figure 3.
If in a rotatable regulating transformer current is generated in the secondary part
by magnetisation of the primary part, a turning moment is produced and the rotatable
part has the tendency to revolve.
To prevent this it is necessary to apply a brake to the rotary part. For this
purpose there may be provided on the axis of the rotatable part a worm wheel gearing
with a worm.
By this means also the rotatable part can be very accurately adjusted by suitably
revolving the worm, so that the resulting pressure can be continuously regulated with
great precision.
The worm and worm wheel can be actuated by land or by means of any suitable
known automatic regulating device arranged to turn the worm in the one direction or
the other according as the pressure is too high or too low.
In the arrangements above described various modifications can be made; the
inducing pressure, instead of being supplied to the inner ring, can be supplied to
the outer ring, while the inner ring has the induced pressures.
In Figures 3 and 4 the rotatable regulating transformer is excited by means of
currents from the leads ILL; the leads NNN, can also be used for the purpose;
in the former case the excitation is variable, in the latter case it is constant.
It has been assumed in the above that the rotatable regulating transformer is
employed for producing a constant working pressure with a variable network pressure;
it will be readily seen that the converse can be effected, namely a variable working
pressure be produced from a constant net work pressure.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, we declare that what we
claim is
Transformer apparatus for varying and regulating the pressure of a polyphase or
rotary phase current system, consisting of a fixed and a moveable part, which parts
are both wound in a similar manner to a synchronous polyphase or rotary phase
current motors, a winding or group of windings of the induced part being connected
respectively to one of the leads of the polyphase current system, while the inducing
winding is connected as shunt to the leads of the polyphase current sytem either in
front of or behind the connection of the induced windings of the transformer,
substantially as described.
Dated this 25th day of November 1808