Improvements in Direct Current Dynamo Electric Generators.
Year: 1896

page_text: Date of Application, 15th Dec., 1896
Complete Specification Left. 15th Sept.. 1897-Accepted. 13th Nov. 1897
[Communicated from abroad by BENJAMIN G. SAMME of Pittsburg, County of
Allegheny and State of Pennsylvania, United States of America, Engineer.]
Improvements in Direct Current Dynamo Electric Generators.
I, REGINALD BELFIELD, of 32, Victoria Street, in the County of London,
Electrician, do hereby declare the nature of this invention to be as follows:-
My invention relates to multipolar direct current generators having parallel wound
armatures, aud it has for its object to provide a method and means whereby the
magnetic circuits of such machines may be automatically balanced.
In multipolar direct current generators the field magnet poles should be all of the
same strength in order that they may exert the same magnetic effect upon the
armature. It sometimes happens, however, that one pole is weaker or stronger than
the others, and when this condition is present the avoidance of serious disturbances
in the operation of the machine necessitates the 'employment of some means for
correcting the inequalities in the magnetic circuits. As the different sections of the
armature winding are connected in parallel through the brushes and their connecting
leads if the magnetic circuits are not properly balanced current will flow from the
sections of higher electromotive force through the brushes and their connecting
leads to the sections having lower electromotive force. The reaction upon the field
due to such currents will serve to distort it and thus cause an increased difference
between the electromotive forces in the different sections of the armature winding.
The disturbance of the arinature circuits which tends to unbalance the machine may
be due to any one of a variety of causes, such, for example, as the unequal wear of
bearings and consequent displacement of the armature with reference to the poles
of the field magnet, defective castings, unequal field inagnet coils, a wrong lead
of the commutator brushes, an unequal rate of increase or decrease of the polar
strengths with changes in electromotive force due to changes in load and consequent
changes in the series ampere turns on the field magnets.
In a parallel wound arinature as ordinarily constructed the different armature
circuits are to a certain extent independent of each other, and variations in the
strength of one of the field magnet poles will vary the magnet circuits of which
it forms a part. Variations in the electromotive forces of the corresponding
armature circuits necessarily result, and such variations may give rise to local
currents which will injuriously affect the operation of the generator. This
unbalancing of the armature circuits is due to the fact that the section or
sections having the higher electromotive force will send currents through. the
brushes and brush holder leads to and through the circuits of lower electromotive
force, or the circuits having higher electromotive force may furnish the greater part
of the current to the external circuit, while the currents having lower electromotive
force may do almost nothing. If the conditions are such that the current is merely
unequally divided between the armature circuits, then those carrying the greater
currents will cause a greater distortion of their respective field magnetizations, and
a consequent reduction in strength provided the armature teeth or the pole tips or

page_text: faces are partially saturated, but if the current feeds back through the circuit or
circuits having the lower electromotive force, there will also be distortion and
consequent weakening of the corresponding pole or poles. If several circuits
having a higher electromotive force are feeding into one having a lower electromotive
force, the latter is subject to greater distortion and weakening than the former,
since it carries a greater current, therefore the unbalancing effect increases until the
local currents in the armature reach an excessive amount.
The structure of a parallel wound, multipolar armature is such that it may be
represented by a series of direct current bi-polar arinatures running at equal speeds-
and connected in parallel. If such a series of bi-polar armatures are running at
exactly the same speed in fields of exactly the same strength they will feed equally
into mains common thereto. If one of the fields is weaker or stronger than the others,
however, there will be an unequal division of current between the armatures and
some may even feed back through the others. By adjusting the field strengths of one
or more of the machines, or by otherwise adjusting the magnetic circuits a restoration
of the necessary balance between them might be effected. If a series of alternating
current generators are arranged in the same manner to run at exactly the same speed
and connected in similar phase relations the armatures may be connected to the same
mains and run with fairly well balanced circuits, even with considerable differences in
the strengths of their respective fields, this condition being due to the fact that the
currents in the different armatures are flowing at different phase relations and are
leading or lagging with reference to their respective electromotive forces and are thus
magnetizing or demagnetizing their field magnets in such a way as to effect the
necessary balance between them. If commutators be attached to such a series of
machines or direct current windings with commutators be added to these armatures,
they will be found capable of delivering direct current to their mains with very little
unbalancing, even with unequal field strengths. The alternating current leads need
not be connected to an external work circuit, but may merely serve for the passage
between the armatures of the several machines of leading and lagging currents.
This balancing effect due to the flow of leading and lagging currents between
generators arranged to run at the same speed, I propose to secure in a parallel wound
multipolar armature by electrically connecting a suitable number of points of normally
equal potential by means of leads through which leading and lagging currents may
be conducted to weaken or strengthen the several magnetic circuits as may be
necessary, and thus secure the necessary balance in the machine.
A plurality of compound wound generators provided with my balancing means and
run in synchronism, may have their armatures connected by alternating current leads
as indicated above. Since they are in synchronism there will be no electromotive
force generated by any of the machines which will serve to transmit true energy
through the alternating current leads to the other machine or machines. Any
tendency to unbalance the system will necessarily be due to the differences in the
field magnetizations of the different generators, and this tendency will be corrected
by the transfer of leading and lagging currents through the alternating current leads
in the manner already pointed out. It follows, therefore, that the necessary balance
will be maintained by the transfer of apparent energy only between the armatures of
the several generators. By this means each machine will be compelled to carry its
share of the load, and the equalizer ordinarily employed in such relations may be
dispensed with.
If only two alternating current leads were employed in such an arrangement instead
of three, the balancing effect would take place, but it would be intermittent or
pulsating in effect. With three leads arranged 120° apart the effect is more nearly
constant and with four leads at 90° the balancing effect is as nearly uniformn as is
necessary in practice. It follows, therefore, that a multipolar, parallel wound armature
should have at least three alternating current leads, and in many cases four would be
preferable. As this method of balancing involves the utilization of armature reaction
the best results will be attained in connection with the slotted iron-clad type of
armature with a small air gap or clearance between the arinature and field magnet,

page_text: poles, and with an armature which is relatively powerful with respect to the field
magnet. Another advantage incident to the invention is that it diminishes the
iron losses to some extent. Such losses being dependent upon the maximum
induction exerted by the strongest pole, they will be diminished by making the poles
of equal strength.
Improvements in Direct Current Dynamo Electric Generators.
I, REGINALD BELFIELD, of 32, Victoria Street, in the County of London, England,
Electrician, do hereby declare the nature of this invention and in what manner the
sane is to be performed to be particularly described and ascertained in and by
the following statement :-
My invention relates to multipolar direct current generators having parallel
wound armatures, and it has for its object to provide a method and means whereby
the magnetic circuits of such machines may be antomatically balanced.
In multipolar direct current generators, the field magnet poles should be all of
the same strength in order that they may exert the same magnetic effect upon the
armature. It sometimes happens, however, that one pole is weaker or stronger than
the others, and when this condition is present, the avoidance of serious disturbances
in the operation of the machine necessitates the employment of some means for
correcting the inequalities in the magnetic circuits. As the different sections
of the armature winding are connected in parallel through the brushes and their
connecting leads, if the magnetic circuits are not properly balanced, current will
flow from the sections of higher electromotive force through the brushes and their
connecting leads to the sections having lower electromotive force. The reaction
upon the field due to such currents will serve to distort it and thus cause an
increased difference between the electromotive forces in the different sections of
the armature winding. The disturbance of the armature circuits which tends to
unbalance the machine may be due to any one of a variety of causes, such, for
example, as the unequal wear of bearings and consequent displacement of the
armature with reference to the poles of the field magnet, defective castings,
unequalfield magnet coils, a wrong lead of the commutator brushes, an unequal
rate of increase or decrease of the polar strengths with changes in electromotive
force due to changes in load and consequent changes in the series ampere turns
on the field magnets.
In a parallel wound armature, as ordinarily constructed, the different armature
circuits are, to a certain extent, independent of each other, and variations in the
strength of one of the field inagnet poles will vary the magnetic circuits of which
it forms a part. Variations in the electromotive forces of the corresponding
armature circuits necessarily result, and such variations may give rise to local
currents which will injuriously affect the operation of the generator. This
unbalancing of the armature circuits is due to the fact that the section or sections
having the higher electromotive force will send currents through the brushes
and brush holder leads to and through the circuits of lower electromotive force,
or the circuits having higher electromotive force may furnish the greater part of
the current to the external circuit, while the circuits having lower electromotive
force may do almost nothing. If the conditions are such that the current is.

page_text: merely unequally divided between the armature circuits, then those carrying the
greater currents will cause a greater distortion of their respective field magnetiza-
tions, and a consequent reduction in strength, provided the armature teeth or the
pole tips or faces are partially saturated; but if the current feeds back through the
circuits or circuit laving the lower electromotive force, there will also be distortion
and consequent weaking of the corresponding pole or poles. If several circuits
having a higher electromotive force are feeding into one having a lower electromotive
force, the latter is subject to greater distortion and weakening than the former since
it carries a greater current, therefore the unbalancing effect increases until the local
currents in the armature reach an excessive amount.
The structure of a parallel wound multipolar armature is such that it may be
represented by a series of direct current bi-polar armatures running at equal speeds
and connected in parallel. If such a series of bi-polar armatures are running at
exactly the same speed in fields of exactly the saine strength they will feed equally
into mains common thereto. If one of the fields is weaker or stronger than the
others, however, there will be an unequal division of current between the armatures
and some may even feed back through the others. By adjusting the field strengths
of one or more of the machines, or by otherwise adjusting the magnetic circuits a
restoration of the necessary balance between them might be effected. If a series
of alternating current generators are arranged in the same manner to run at exactly
the same speed and connected in similar phase relations, the armatures may be
connected to the same mains and run with fairly well balanced circuits, even with
considerable differences in the strengths of their respective fields, this condition.
being due to the fact that the currents in the different armatures are flowing at
different phase relations and are leading or Ingging with reference to their respective
electromotive forces and are thus magnetizing or demagnetizing their field magnets
in such a way as to effect the necessary balance between them. If commutators be
attached to such a series of machines, or direct current windings with commutators
be added to these armatures they will be found capable of delivering direct current
to their mains with very little unbalancing even with unequal field strengths. The
alternating current leads need not be connected to an external work circuit, but may
merely serve for the passage between the armatures of the several machines of
lending and lagging currents.
This balancing effect due to the flow of leading and lagging currents between
generators arranged to run at the same speed, I propose to secure in a parallel wound
multipolar armature by electrically connecting a suitable number of points of normally
equal potential by means of leads through which leading and lagging currents may
be conducted to weaken or strengthen the several magnetic circuits as may be
necessary, and thus secure the necessary balance in the machine.
A plurality of compound wound generators provided with iny balancing means and
run in synchronism may have their armatures connected by alternating current leads
as indicated above. By this means each machine will be compelled to carry its share
of the load, and the equalizer ordinarily employed in such relations may be
dispensed with.
In the accompanying drawing Figure 1 is a diagrammatical development of the
winding of a parallel wound armature of an eight-pole generator provided with my
balancing means. Figure 2 is a diagram of three direct current compound wound
generators connected in parallel with an external circuit, and having their
armatures connected by alternating current leads. Figure 3 is a diagram of an
eight-pole machine shewing the balancing conductors, and Figure 4 is a similar
diagram showing the commutator and brush connections.
Reference being now had to Figures 1, 3, and 4, of the drawing, N, S, N, S¹,
N2, S3, and N, S, are the field magnet poles and À the armature winding of an
eight pole direct current generator. Band B are the brushes, and C the commutator
cylinder. The alternate brushes are electrically connected together and to the
external circuit, as is usual in such machines. In Figure 4 the brushes are shown as
bearing upon the inner surface of the commutator cylinder merely for convenience

page_text: of illustration. The armature winding A is connected by means of conductors a, a¹ a²,
and a, to rings b, b, b, and b, which may be located at any convenient place with
reference to the coils, the points of normally equal potential being connected with
the same ring. As shewn in the drawing these points which are electrically connected
together by means of the leads and rings are 90° apart. This arrangement I have
found to be one which will balance the circuits of a machine satisfactorily, and in
inany cases three points at 120° apart would give fairly satisfactory results.
As has already been stated if one of the field magnet poles, as, for example, the
pole N should be weaker, or have a lesa magnetizing effect upon the armature than
any of the other poles, the electromotive forces generated in the sections of the.
arinature adjacent to the stronger poles would, by reason of the parallel winding,
drive back through the section adjacent to the pole N, and tend, by the reaction, to
still further weaken this pole. This weakening effect. would also be communicated
in a less degree to the poles S and S, on the two sides of the pole N. By reason
of the connections involved in my present invention, however, the leading and
lagging alternating currents will serve by their magnetizing and demagnetizing
effect to maintain or restore the desired balance among the several magnetic
circuits.
Figure 2 illustrates three direct current machines having their armatures
connected for the transmission from one to the other of alternating currents.
c, c¹, and c², are the direct current armatures the windings of which are not shewn.
It is to be understood however that the winding of each armature is provided with
balancing connections like those shewn in Figures 1 and 3, except that the connections
are made at three points 120° apart, instead of at four points 90° apart. These
armatures are all connected in parallel with mains e, e', through commutators,,,
and leads, g, g, g. h, h, and , are the shunt, and i, s, and 2, the series field
magnet coils for the respective machines. Each of the armatures is provided with a
set of three collector rings, k, l,, the corresponding rings of the three sets being
connected by leads 4, 6, and 12.
As the conductors (not shewn) which correspond to the conductors a, a¹, a², and a³,
of Figures 1 and 3 are connected to the rings k, k¹, and k², and the rings of the
several machines are connected by the leads 1, 1, and 2, the armatures will not only
supply direct current to the mains e, el in parallel, but will be maintained substan-
tially in balance irrespective of variations in their field strengths provided they run
at substantially the same speed, Each machine will therefore carry its own share of
the load and the results attained will be the same as those heretofore secured by
means of equalizing wires.
When a plurality of direct current generators are connected in parallel to distributing
mains and provided with balancing connections as indicated in Figure 2 of the
drawings, it is understood that the armatures are to be run at substantially the same.
speed. Such being the case there will be no electromotive force generated by any of
the machines which will serve to transmit true energy through the alternating
current leads to the other machine or machines. Any tendency to unbalance the
system will necessarily be due to differences in the field magnetizations of the
different generators, and this tendency will be corrected by the transfer of leading and
lagging currents through the alternating current leads in the manner already pointed
out. It follows therefore, that the necessary balance will be maintained by the
transfer of apparent energy only between the armatures of the several generators.
If only two alternating current leads were employed in such an arrangement.
instead of three, the balancing effect would take place, but it would be intermittent
or pulsating in effect. With three leads arranged 120° apart, the effect is more
nearly constant, and with four leads at 90° as indicated in Figures 1 and 3 of the
drawings the balancing effect is as nearly uniform as is necessary in practice. It
follows, therefore, that a multipolar parallel wound armature should have at least
three alternating current leads, and in many cases four would be preferable. As this
method of balancing involves the utilization of armature reaction the best results
will be attained in connection with the slotted iron-clad type of armature with a

page_text: small air gap or clearance between the armature and field magnet poles, and with an
armature which is relatively powerful with respect to the field magnet. Another
advantage incident to the invention is that it diminishes the iron losses to some
extent. Such losses being dependent upon maximum induction exerted by the
strongest pole, they will be diminished by making the poles of equal strength.
Having now particularly described and ascertained the nature of my invention and
in what manner the same is to be performed as communicated to me by my foreign
correspondent I declare that what I claim is :--
1. The method of balancing the magnetic circuits of a multipolar direct current
dynamo having a parallel wound armature which consists in transmitting leading and
lagging currents between a plurality of sections of the armature winding of normally
equal potential.
2. The method of balancing a number of direct current dynamos joined in parallel
to the distributing mains which consists in transmitting leading and lagging currents
between the armatures of the several machines, the currents passing along wires
connecting points of normally equal potential in all the armatures.
3. For a mulipolar direct current dynamo, a parallel wound armature provided with
connections between a plurality of points of normally equal potential, through which
connections leading and lagging currents may be transmitted for the purpose
specified.
4. A number of direct current dynamos joined in parallel to the distributing mains
and having their armatures connected together at points of normally equal potential,
for the purpose specified.