Improvements in the Generation and Distribution of Electricity by Means of Alternating Currents, and Appliances connected therewith.
Year: 1897

page_text: Date of Application, 9th Sept., 1897
Complete Specification Left. 3rd May, 1898-Accepted, 11th June, 1898
Improvements in the Generation and Distribution of Electricity
by Means of Alternating Currents, and Appliances connected
therewith.
I, LLEWELYN BIRCHALL ATKINSON, of Western Mail Buildings, St. Mary's Street,
Cardiff, in the County of Glamorgan, Civil Engineer, do hereby declare the nature of
this invention to be as follows:-
This invention relates to improvements in the means of generating and distributing
electricity and obtaining power therefrom by means of alternating currents and has
reference to the use of synchronous or induction generators..
It is known that under certain conditions an induction motor may be used as a
generator to develop electric power when driven by a prime mover, the first and
essential condition being that there shall be in connection with the circuit a source
of alternating E. M. T. of defined period, the second essential condition being that
the speed of revolution shall be greater than the synchronous speed, the
synchronous speed being that at which any point on the armature passes one pair of
poles in the time of one complete alternation.
My invention consists in the use of such asynchronous or induction generators in
connection with alternators of the ordinary or synchronous type, in such manner that
the current supplied to the circuit is provided by the asynchronous generator and
further consists in the use of such asynchronous generators in connection with
alternators of the ordinary type with synchronous or asynchronous motors for the
purpose of regulating or modifying the relative phase of the electromotive forces and
currents in the circuits.
My invention further consists in appliances for carry these into effect.
In my improved method of working induction generators for supplying current to
lighting or other circuits. I couple the terminals of the generator to the mains, and
to the same mains I connect the terminals of a synchronous alternator which may be
either excited from a continuous current dynamo or may have permanent magnets.
The method of working according to my present invention may be explained thus.
The alternator is run at the speed necessary to give the required number of periods, the
field being excited until the terminal E.M.T. at no load is the required E.M.C.
The induction generator now has its speed raised above the synchronous speed until
the alternation gives little or no current the current in the mains being wholly given
by the induction generator. As this method involves rather close regulation of the
speeds of the alternator or induction generator I prefer the following.
The induction generator is run at a fixed speed or as near thereto as possible. The
alternator having been started up to the proper speed is allowed to run free as a
motor, and the terminal pressure is regulated by varying the field exciting current of
the alternator. In this case if the induction generator speed increases a little, the
alternation speed also increases and the tendency to an increase in current from the
induction generator is compensated for by the rise in frequency of the alternator
current. Several such generators may be in parallel connected to circuits with one
exciting alternator as described.

page_text: So far, my invention relates only to the use of induction generators for the supply
of current to lighting or power purposes without reference to modifications of the
phase of the current relative to the electromotive forces.
In the case of alternators supplying a load partly or wholly consisting of induction
motors or other inductive load, the current is not in phase with but lags behind the
phase of the line E.M.T. The result is that the armature reaction becomes large
and causes trouble in the regulation of the line pressure. In my invention I obviate
this by coupling to the circuit also an induction generator which supplies a current
the phase of which leads on the phase of the line E.M.T. and which may be regulated
such manner that the leading component of the current supplies the idle current
required, so that the alternator only supplies current in phase with its E.M.T. This
part of my invention is also applicable in the following manner. Instead of provid-
ing a generator working at the supplying point or points of the circuit, I provide an
induction generator or generators at the receiving point of the circuit, such induction
generator being driven by an induction motor specially used for the purpose, or being
coupled direct or by gearing to the motors, working on the supplying circuit. By
this means the idle component of the lagging current is supplied at the receiving
point and does not traverse the lines or mains, thereby allowing considerable economy
in the latter.
Where the purpose of the induction generator is to supply the idle or lagging
current only, its function being equivalent to that of an exciter, and where therefore
it is desirable to have the current as nearly period as possible in advance of the
E.M.T. special constructions of induction generator may be adapted, the object
being the reverse of that which, holds in the case of induction motors, that is the
idle current is to be made as large as possible at no load, and this is effected by
increasing the magnetic resistance of the motor, not however by increasing the air
gap between the fixed and moving parts, but by adding an air gap or otherwise in
some part of the magnetic circuit not lying between the primary and secondary
coils.
In the case of such idle current induction generators, supplying current to a
motor, the generator may be driven by gearing or belts so as to give it the proper
speed which may be adjusted as the load on the motor varies or the generator may be
direct coupled to the motor in which case the number of its poles must be greater
than the number on the motor so that its synchronous speed occurs at a lower speed
than that of the motor, or the motor and generator may be combined in one machine,
and in all these cases the generator part may be used to assist the motor at starting
or at overload or whenever below its synchronous speed.
In order to regulate the current and phase of current and E.M.F. of such induction
generators I insert resistance or capacity in the inducing or in the induced armature
or circuit in manner well understood, but a further part of my invention consists in
the use of self induction in the circuit of the induced winding, or in parallel with
the mains for the purpose of bringing the E.M.F. and current of the induction
generator into phase with one another and with the phase of the E.M.F. of the
exciting or coupled alternator, or generally of varying its phase as desired.
The induction generators used may be either polyphase or monophase according as
the circuits and motors are polyphase or monophase, but in either case the synchronous
alternator may be of one phase only and coupled to one phase only of a polyphase
system, or may be coupled to an exciting phase only on a monophase machine in
which case the alternator is not necessarily in direct connection with the actual
supply mains.

page_text: Improvements in the Generation and Distribution of Electricity
by Means of Alternating Currents, and Appliances connected
therewith.
I, LLEWELYN BIRCHALL ATKINSON, of Western Mail Buildings, Cardiff, in the
County of Glamorgan, Civil 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 means of generating and distributing
electricity and obtaining power therefrom by means of alternating currents and has
reference to the use of synchronous or induction generators.
It is known that under certain conditions an induction motor may be used as a
generator to develope electric power when driven by a prime mover, the first and
essential condition being that there shall be in connection with the circuit a source
of alternating E.M.F. of defined period; the second essential condition being that
the speed of revolution shall be greater than the synchronous speed, the synchronous
speed being that at which any point on the armature passes one pair of poles of each
phase in the time of one complete alternation. My invention consists in the use of
such synchronous or induction generators in connection with alternators of the
ordinary or synchronous type in such manner that the current supplied to the
circuit is provided by the asynchronous generator, and further consists in the use of
such asynchronous generators in connection with alternators of the ordinary type and
with synchronous or asynchronous motors or other inductive load for the purpose of
regulating or modifying the relative phase of the electromotive forces aud currents
in the circuit.
In my improved method of working induction generators for supplying current
to lighting or other circuits, I couple the terminals of the generator to the mains,
and to the same mains I connect the terminals of a synchronous alternator which
may be either excited from a continuous current dynamo or may have permanent
magnets. The method of working according to iny present invention may be
explained thus. The alternator is run at the speed necessary to give the required
number of periods, the field being excited until the terminal E.M.F. at no load is
the required E.M.F.
The induction generator now has its speed raised above the synchronous speed
until the alternator gives little or no current, the current in the mains being
wholly given by the induction generator. As this method involves rather close
regulation of the speeds of the alternator and induction generator I prefer the
following:
The induction generator is run at a fixed speed or as near thereto as possible
the alternator having been started up to the proper speed is allowed to run free
as a motor, and the terminal pressure. is regulated by varying the field exciting
current of the alternator. In this case if the induction generator speed increases
a little, the alternator speed also increases and the tendency to an increase in current
from the induction generator is compensated for by the rise in frequency of the
alternator current. Several such generators may be in parallel connected to circuits
with one exciting alternator as described.
Fig. 1 shows diagrammatically the arrangement of the circuits of the induction
generator and the alternator according to my present invention and shows a two
phase system, though one or more phases may be used, in manner understood.
a is two phased alternator with exciting coils d excited in this case by the shunt
wound continuous current generator 6 and having resistances allowing the excitation

page_text: to be varied. The alternator a is driven by an electric motor or steam engine or
other prime mover at such a speed as to give the required frequency and approximately
the required line pressure at its terminals this being regulated by the excitation.
The induction generator i is revolving at the synchronous speed in which case the
line circuits being open there is a current passing between the alternator and
the induction generator which is the magnetizing or exciting current. If now the
lines jj and k k are connected through consuming devices the current required is
provided by raising the speed of the induction generator i above synchronism, so that
the line current is furnished by it, the exciting current being supplied by the
álternator. By methods of regulation presently to be described the induction
generator may be made to give a current in phase with the line E.M.F. and the only
function of the alternator is to impress a wave of E.M.F. on the system and it may
be indefinitely small.
The alternator I being once started to speed, may be allowed to run as a motor as
before described, not being itself a source of supply to the mains the source of power
being the prime mover driving the induction generator and in this case the frequency
may vary a little as the speed of the induction generator is varied.
So far my invention relates only to the use of induction generators for the supply
of current to lighting or power purposes without reference to modification of the
phase of the current relative to the electromotive forces.
In the case of alternators supplying a load partly or wholly consisting of induction
motors or other inductive load, the current is not in phase with but lags behind the
phase of the line E.M.F. The result is that the armature reaction of the alternator
becomes large and causes trouble in the regulation of the line pressure whilst the
efficiently of transmission is diminished. In my invention I obviate this by
coupling to the circuit also an induction generator the current in which leads on the
phase of the line E.M.F. and which may be regulated in such manner that the
leading component of the current equals the idle current required, so that
the alternator only supplies current in phase with its E.M.F. or leading thereon.
Fig. 2 shows the arrangements of the generating plant according to this part of
my invention. The alternator a and in induction generator i are coupled to the
mains and the induction generator i is arranged so that the current leads on the
phase of the line E.M.F. that is, lags behind the phase of the internal E.M.F. of
the induction generator, and this lagging or idle current furnishes the idle current
required by the consuming devices so that the alternator a only supplies current in
phase with its E.M.F. or leading on its E.M.F.
This case differs from that illustrated in Fig. 1 in the following manner. In Fig. 1
the source of electric supply is primarily the induction generator the alternator acting
principally as exciter, in Fig. 2 the source of electric supply is primarily the
alternator, the induction generator serving primarily to supply the idle current so as
not to disturb the regulation of the alternator.
This part of my invention is also applicable in the following manner :
Instead of providing a generator working at the supplying point or points, of
the circuit, I provide an induction generator or generators at the receiving point
of the circuit, such induction generator being driven by an induction motor or
other source of motive power specially used for the purpose, or being coupled
direct or by gearing to the motors working on the supplying circuit. By this means
the idle component of the lagging current is supplied at the receiving point and
does not traverse the lines or mains, thereby allowing considerable economy in the
latter. Where the purpose of the induction generator is to supply the idle or
lagging current only, its function being equivalent to that of an exciter it is desirable
to have the current as nearly 4th period as possible in advance of the E.M.F. of
the lines.
a
Figure 3 illustrates the arrangement in the case of this part of my invention.
is the alternator or source of alternating supply at the generating station or point of
supply jjkk are the lines, m is a two phase induction motor running below the
synchronous speed g is a two phase induction generator running above the synchronous

page_text: speed and arranged as presently described to supply the idle current required by the
motor m or other consuming devices, but not supplying the working or power
current which comes over the lines j j k k from the generating station.
The induction generator g is driven either direct or by belting or gearing by the
motor m, or by a motor specially set apart for the purpose.
Special constructions of induction generator may be adopted, the object being the
reverse of that which holds good in the case of induction motors, that is the idle
current leading on the phase of the line E.M.F. is to be made as large as possible
at no working load.
In the case of such idle current induction generators, supplying current to a motor,
the generator may be driven by gearing or belts so as to give it the proper speed
(that is above synchronism) which may be adjusted as the load on the motor varies,
or the generator may be direct coupled to the motor in which case the number
of its poles must be greater than the number on the motor so that its synchronous
speed occurs at a lower speed than that of the notor, or the motor and generator
may be combined in one machine, and in all these cases by suitable regulating
appliances the generator part may be used to assist the motor at starting or at
overload or whenever below its synchronous speed.
In order to regulate the current and the phase of the current and E.M.F. of such
induction generators I may insert resistance or capacity in the inducing or in the
induced or armature circuit in manner well understood, that is in the case of
the inducing circuit the resistance may be in series with the inducing coils and if
capacity is to be inserted it may be either in series or in parallel with the inducing
coils, and in the case of the induced circuit, whether, resistance or capacity is to be
used it is connected in series with the coils of the induced circuit which for this
purpose must be grouped or connected in coils and not merely be of the short
circuited or squirrel cage type.
But as the use of condensers to give capacity is for many reasons difficult, and as'
the use of resistances gives rise to loss of efficiency I prefer to adopt a further part
of my present invention which consists in the use in the circuit of the induced.
winding or in parallel with the mains of self induction for the purpose of varying the
relative phases of the current and E.M.F. of the induction generator relative to one
another and relative to E.M.F. of the coupled alternator as may be desired..
Figure 4 shews an induction generator i having self induction coils & connected to
the induced circuits, coupled to mains j j k k supplied by a two phase alternator, and
between one phase of which are various consuming devices, viz.:-an induction
motor m, lamps 1, and devices having capacity c and depending on which of these
devices are in circuit so an idle current is required either leading or lagging on the
phase of the line E.M.F.
Where the induction generator is driven as described above the synchronous speed,
but not so much as to deliver power to the circuit, if there is no self induction in the
secondary or induced circuit the idle current will lead on the phase of the E.M.F. of
the generator, that is, will lag behind the phase of the E.M.F. of the mains, when a
moderate amount of self induction exists in the induced circuit the current will be in
phase with the E.M.F. of the generator, that is the generator will deliver power to
the circuit or if the speed is only slightly above the synchronous speed practically no
current will pass in or out of the generator, the current in the induced circuit then
serving as the magnetizing current, whilst if the amount of self induction be still
further increased an idle current is set up in the reverse direction to that first
described lagging behind the E.M.F. of the generator, or leading on the E.M.F.
of the mains. Thus by varying the value of the self induction in the induced
circuit, a compensating current of any desired phase can be obtained, as may be
required for the various purposes before described and illustrated in Figures 1, 2, 3
and 4.
Figure 5 shews approximately by a vector diagram for one phase the relative. phases
in each of these cases of the three quantities, viz. -E.M.F. of the line E, E.M.F. of
the induction generator e and current c delivered to the line by the induction

page_text: generator. In Figure 5ª the induction generator has no self-induction in the induced
circuit, and the current leads on the E.M.F. of the generator. In Figure 5B there is
moderate self induction and the current is in phase with the E.M.F. of the generator.
In Figure 5° there is considerable self-induction in the induced circuit and the
current lags behind the E.M.F. of the generator. The internal E.M.F. of the
generator e is here taken as the element of the constant phase for comparison.
Figure 6 shews the same qualities referred however to the line E.M.F. as
the element of constant phase.
If however the self induction in the induced circuit of the generator is fixed
instead of variable then it should be fixed at the largest value, and to regulate
the amount and phase of the compensating current a self induction coil or apparatus
may be placed in parallel with the mains as tt, in Figure 4 so that the leading current
from the mains into the over compensated induction generator may be balanced by a
lagging current from the mains into the self induction apparatus.
The self induction in the circuits of the induced windings is preferably external
to the windings on the armature or secondary member of the induction generator,
and for the following reason. In either an induction motor or generator when
running at the synchronous speed the effect of the reactive E.M.F., due to self
induction is balanced by the effect of the motion of the conductors in the leakage
magnetic field to which the reaction is due. In the case of a motor running below
synchronous the reactive E.M.F. is greater than the rotational E.M.F., in the case of
an induction generator the rotational E.M.F. is greater than the reactive, in other
words, the effect is as of a negative self induction in the secondary circuit, whereas,
as has been shewn a positive value is required, which is given by the external self
induction.
The induction generators used may be either polyphase or monophase according as
the circuits and motors are polyphase or monophase, but in either case the syn-
chronous alternator may be of one phase only and coupled to one phase only of a poly-
phase system or may be coupled to an exciting phase only on a monophase machine
in which case the alternator is not necessarily in direct connection with the actual
mains. Thus for example in Figure 1, the alternator might be connected to the
mains K K only and the consuming devices to the mains jj only, in which case the
alternator cannot deliver current to the mains, and acts purely as an exciter. It will
be further understood that the connections between the various devices may be made
through transformers, instead of direct as shewn in the diagrams.
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 :-
1st. In combination an induction generator and a synchronous alternator connected
in parallel to a circuit or circuits the former only supplying power to the external
circuit the latter supplying the exciting current or impressed E.M.F. to the in-
duction generator, substantially as and for the purposes described.
2nd. In combination an induction generator and a synchronous motor running free
connected in parallel to a circuit or circuits, the former only supplying power to the
external circuit, the latter supplying the exciting current to the induction generator,
substantially as and for the purpose described.
3rd. In combination an alternator, and an induction generator arranged to give a
current lagging behind the phase of its own E.M.F., connected in parallel to a circuit
or circuits having an inductive load, so that the current given by the alternator is in
phase with or leads on its E.M.F., substantially as and for the purpose described.
4th. In combination a source of supply of alternating currents, an induction motor
or other consuming device having self induction and an induction generator adapted
to run above synchronism and arranged so that the current leads on the phase of the
E.M.F. of the source of supply, so that the idle current is not supplied from the
source of supply, substantially as and for the purpose described.
5th. An induction generator arranged to be run above its synchronous speed and

page_text: having in combination, inducing circuits, and induced circuits having a considerable
or variable amount of self induction for the purpose of varying or modifying the
relative phase of the current with respect to the E.M.F. of the generator, and of the
line, substantially as described.
6th. In combination a source of supply of alternating current, consuming or
translating devices, an induction generator arranged so that the current leads on the
phase of the E.M.F. of the supply, and a reactive coil in parallel, for the purpose of
regulating the total compensating current, substantially as described.
7th. The combination with an induction motor of a direct coupled induction
generator, the latter having a greater number of poles per phase than the former, so
that at the same speed the motor is below and the generator above synchronism for
the purpose of providing current of variable phase relation, substantially as
described.
8th. The arrangement of alternators, induction generators, induction motors,
circuits, consuming and regulating devices, as described and illustrated in Figures 1,
2,3 4.
Dated this 3rd day of May 1898.
FELL & JAMES,
1, Queen Victoria Street, London, E.C., Agents for the Applicant.