Improvements in the Automatic Regulation of Monophase or Polyphase Alternators.
Year: 1898

page_text: Date of Application, 28th Dec., 1898-Accepted, 25th Mar., 1899
Improvements in the Automatic Regulation of Monophase or
Polyphase Alternators.
I, ROBERT BOLTON RANSFORD, of 41, Waldegrave Road, Upper Norwood, in the
County of Surrey, Gentleman, do hereby declare the nature of this invention
(which has been communicated to me from abroad by the Société Sautter Harlé
& Cie, of 26, Avenue de Suffren, Paris, in the Republic of France, Manufacturers)
and in what manner the same 18 to be performed to be particularly described
and ascertained in and by the following statement.-
--
The automatic regulation of monophase or polyphase alternators has formed the
subject of numerous investigations, up to the present no satisfactory solution of
this difficult problem has been found.
In order to iegulate alternators. that is to say, to maintain the tension at their
terminals constant however much current is delivered, it is not sufficient, as with
continuous curent dynamos, to merely proportion the excitation of the alternator
to the current delivered to the line The total electro-motive force to be pro-
duced in the alternator is, as is known, the resultant of two electromotive forces:
one the tension at the teimunals, and the other the electromotive force of induced
caction or of self induction This latter alone is proportional to the curient
delivered, the tension at the terminals is independent of it
This being so the loss of voltage due to the ohmic resistance of the armature
of the alternator is supposed to be negligable compared with the tension at the
terminals The total electromotive force it is necessary to generate in the alter-
nator is thus found to be the resultant of two electromotive forces, which have
between themselves a difference of phase which is nothing else than the alternation
of phase due to the encuit or system fed by the alternator This difference in
phase may vary, as is known, according to the charge of the system and the
apparatus fed, such as transformers, asynchronous motois, synchronous motors,
incandescent lamps, or arc lamps and the like.
It is necessary therefore that the excitation necessary to be produced in the
alternator, that is to say, the exciting ampèie turns should increase in the same
atio as the total electiomotive force just mentioned which depends both on the
curent delivered by the alternator and on the alternation of phase of this current
and the tension at the terminals
If U be called the tension at the terminals, K I the electromotive force of self
induction in the alternator, the angle of difference in phase between the tension
at the terminals and the curent delivered, E the total electromotive foice to be
produced in the alternator, a simple well known graphic diagram will indicate
the relations of these several elements
Every practical system of regulation should therefore allow the excitor which
produces the continuous exciting cument to regulate its voltage at the terminals
proportionally to the value of the total electromotive force E
In order to obtain this result two things only have to be considered one the
current delivered, the other the tension at the terminals of the alternator It
1s by the aid of these two that a practical system of compounding has been
obtained which may be applied to all monophase or polyphase alternators.

page_text: DLSCRIPTION OF THE SYSTEM
Figure 1 represents the system of regulation applied to a tiphase cuent
alternator, Figue 2 represents the same system of iegulation applied to a mono-
phase current alternator.
This system comprises generally two alternating curent transformers, the com-
bined circuits of which are completed through the exciting dynamo, the action of
these two transformers is sufficient to regulate the voltage of this dynamo pro-
portionally to the total electiomotive force E to be produced in the alternator
In Figure 1 the armature A of the alternator which has an amature winding a
delivers a triphase current into the three line wies 1, 1, 1, 1-2, 2, 2, 2—3, 3, 3, 3
The excitor winding 13 of the alternator 18 shown diagrammatically inside the
aimature
The two triphase transformers are represented at C and D with then thier cores
Both transformers have a primary cucuit and a secondary cncuit
The primary
winding of the transformer C is formed with the thee line wues of the system
This primary cucuit is therefore traversed by the curient delivered by the alter-
nator
The primary circuit of the second transforme D 18 in shunt between the
terminals of the alternator, it is formed on the three cores with wires 4, 4, 4, 4–
5, 5, 5, 5-6, 6, 6, 6 whose three extremities are connected together at one common
neutral point by the wue 7, 7
The secondary circuits of the two transformers are connected one with the other
The secondary winding of the transformer C commences on the thice cores from
one common wie 8, 8 forming the neutial point, the first core canes the wind-
ing 9, 9, 9 which is continued to a winding upon the first core of the transformer I)
and one passing from this second transformer is continued to the connecting
ng 10 on the excitor The second secondary winding 11, 11, 11 of the trans-
former C is continued to a winding upon the second core of the transformer D
and is continued by the wie 11, 11 to the second connecting ring 12 on the
exciter Lastly the winding 13 on the thud core of the transformer C passes also
to the third core of the transformer D and by the wue 13 to the third
connecting ng 14 on the excitoi The numbers 10, 12 and 14 represent diagram-
matically thice contact rings carried by the aimature of the excitor. This excito
18 a simple continuous curient dynamo provided with a collector F and brushes f¹ f
delivering its continuous current into the exciting winding B of the alternator
The amature E of the excitor, wluch is provided with a winding e, is connected
on the one hand to the continuous current collector F and on the other hand to
the thire triphase 1ngs shown diagrammatically at 10, 12 and 14 The winding
of the inductors of this excitor is taken in seines on the collector, it is shown
diagrammatically at g q The continuous curicut delivered by the excitor starts
from the bush f¹, traverses the windings of the inductors gq in series and passes
by the wire 15, 15, 15 to the extremity 16 of the exciting winding B of the alter-
naton This current returns to the excitor by 18, 17, 17, 17 and the brush f
Figure 2 represents the same arrangement applied as has already been stated
to a monophase alternator
A represents the amature of the alternator with its winding a; 1, 1, 1-
2, 2, 2 the main line wires; C D the two monophase transformers
The primary circuit of the transformer I) is connected in derivation to the
terminals of the armature by the wires 3, 3, 3-4, 4, 4
The secondary encuit common to the two transformers is formed of the
wes 5, 6, 7, 7, 8. 8 and terminates at 8 in a connecting ung, placed upon the
armature of the excitor on the one hand, and on the other hand is connected
through 9, 9 to the second connecting ing of the monophase current.
The excitor comprises an armature E provided with a winding & connected
on the one hand to the two monophase 1ings 8 and 9, and on the other hand to
the continuous current collector F

page_text: The continuous current starts from the brush f', traverses the windings g g of
the inductors in series, and passes through 10, 10 to the extremity 1, I of the
excitor winding B and returns to the collector of the excitor through 13, 12, 12
and the brush .
WORKING Or THE SYSTEM
The figures alieady described themselves explain the working of the system.
One of the transformers D is placed in a shunt at the terminals of the alternator.
The primary winding of this transformer is therefore submitted to an electro-
motive force equal to the tension U at the terminals of the alternator. The
Becondary winding of this transformer generates therefore a secondary electro-
motive force which is proportional to the tension U at the terminals of the alter-
nator
The transformer C 18 on the contiary placed in series in the alternator circuit
When the alternator delivers no current the action of this transformer is sub-
stantially nil, when on the contrary the alternator delivers current the electro-
motive force produced in this transformer increases with the current The electio-
motive force of the secondary circuit of this transformer is therefore piopoitional
to the current
This secondary electiomotive force as is known differs in phase by 90° with
respect to the current it has produced The secondary electiomotive force of the
transformer D 18 in phase with the tension at the terminals of the alternator
It is therefore easily seen that by suitably proportioning the windings of these
two transformers, there is produced in the secondary encuit, which is common to
them, an electio motive force resulting, on the one hand from the tension at the
terminals, and on the other hand from the current delivered by the älternator,
the two components of this electiomotive force differing themselves in phase by
the angle of the system It results from this remark, that the electromotive forces
of the secondary cucuit, that is to say, the electiomotive forces created between
the three ng 10, 12 and 14 of the amature of the excitor will be exactly pro-
portional to the total electromotive force which is requned to be generated in the
alternator
The function of the excitor consists in producing between the brushes fl f
a continuous current, the voltage increasing proportionally to the total electro-
motive force to be produced in the alternator But as is known, the voltage of
a dynamo carrying three triphuse rings is always in a constant relation to the
voltage of the alternating current meeting these three rings. This remark shows
that this system will result in proportioning the continuous voltage of the excitor
to the voltage produced in the secondaries of the two transformers
The excito derives the energy that it requires from the alternator itself, either
by gid transmission, by gearing, or by its armature being mounted directly
on the shaft of the alternator, or driven by a belt. In these three cases the energy
it should deliver into its continuous current circuit, for the purpose of exciting
the alternator, is not derived from the alternating curient transformers
latter merely serve to govern the tension at the terminals of the excitor.
These
The alternating electro motive force produced at the rings of the excitor is
exactly balanced by the contrary electromotive force produced in the armature
itself. It results that when the permanent regime 18 established, no alternating
current will traverse the armature of the excitor. If the current delivered by the
armature commences to vary, the voltage produced in the secondary circuit of the
transformers varies equally, the alternating electromotive force at the contact
rings of the excitor varies in the same proportion, it is no longer balanced by the
counter electromotive force of this same armature and consequently an alternating
cument is generated and traverses the armature This current causes the con-
tinuous voltage at the brushes to vary in the same proportion. When the voltage

page_text: has been brought to the height it should have, the alternating current ceases of
itself and the inachine resumes its permanent regime.
It will be seen therefore that in this system, when the permanent regime is
established, no alternating current traverses the secondary transformer circuit or
the current which traverses it is extremely small, and only represents a very slight
fraction of the energy expended in exciting As the magnetic circuits of the
two transformers are absolutely separate no disturbing reaction of one transformer
on the other is possible. A reaction of this kind would be however proportional
to the common curent which traverses the secondary cucuit; this current being
very feeble, the disturbance which can result is equally so.
In certain cases the excitor need not be driven by the alternator itself, either
gidly on by belts. The energy necessary to drive the, excitor which it should
deliver to the exciting circuit, will then be derived from the alternating current
itself The windings of both transformers may then be calculated in such a
manner as to reduce to a minimum the disturbing effect due to the alternating
current traversing the secondary encut
When the excitor 18 driven synchronously with the alternator and when its
amature is keyed on the same shaft, it should have the same number of poles.
If it be diven by gearing, the speed should increase inversely to the number of
poles Lastly it may be driven by a synchronous motor or as above stated, by a
belt When driven by direct coupling, by gearing or by a synchronous motor,
the angle of the brushes of the alternator to those of the excitor should be nil,
that is to say, that the alternating electromotive force at the rings of the excitor
should be equal and directly opposed to the counter electromotive force
induced in the armature of the excitor This property is preseived whatever the
delivery of-the alternator may be, from nal to the full charge
The exciting coils of the excitor itself which have been described as being in
series, might equally well be in derivation; the excitation in series is however
preferable, the variation of the inducing flux being quicker than when the wind-
ing is in denvation the self induction of the circuit in series being less than that
of the circuit in derivation, in consequence of the less number of turns
To allow the excitor to rapidly follow the variations in voltage it is well to con-
struct the inductor circuit of sheet iron and not of massive cast iron
As above stated, the separation of the magnetic circuits of the two transformers
does not permit any duect mutual reaction The sole possible reaction which
might disturb the system would arise from the current of the secondary common
circuit This current as has just been explained will always tend to be at its
minimum when the permanent regime has been established. One may moreover
in order to still further reduce the disturbing effect, give to the secondary ampèie
turns of the transformei in series, a small value in comparison with the primary
ampère turns instead of equalising these two numbers of ampère turns as ordinarily
done. This latter precaution allows the secondary circuit common to the two
transformers to be employed for actuating the exciton instead of driving it by the
alternator, an arrangement which may be advantageous in certain cases.
In what has been described above account has not been taken of the ohmic resist-
ance of the amature of the alternator which should itself be corrected. In order
to take account of it, it 18 sufficient to increase a little the electromotive force
induced into the secondary of the transformer in series
When the alternator delivers a monophase current, and it is desired not to
dive the excitor directly but rotate it by means of the alternating current which
will furnish to it the necessary energy, it would be necessary to construct this
excitor as a monophase converter, provided with a tertiary circuit.
By means of this circuit the simple alternating current led by two rings to the
armature of the excitor will generate a rotating field just as if a polyphase current
were in question
In certain cases the transformer in shunt may be eliminated and replaced by
a circuit of low tension wound upon the armature itself of the alternator.

page_text: 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..
1. A system of regulating alternators to constant potential consisting in the
employment of an exciting dynamo driven synchronously with the alternator,
the said dynamo receiving by rings connected to suitable points of its armature,
a system of alternating currents of relatively feeble intensity, derived from a
secondary circuit common to two transformers, the primary circuits being for
the first transformer mounted in derivation upon the terminals of the alternator
and for the second transformer, traversed in series by the current going out from
this alternator the windings being proportioned in such a manner that the electro-
motive forces induced in the secondary windings of the two transformers are
between themselves in the ratio of the induced electromotive force of reaction of
the alternator to the tension produced at the terminals, the excitor itself being
driven by the alternating current of the secondary cucuit common to the two
transformers which then cause it to act as a converter
2. The regulation of monophase or polyphase alternators substantially as herein-
before described