Improvements relating to the Regulation of Electromotive Force.
Year: 1898

page_text: Improvements relating to the Regulation of Electromotive Force.
I, NORMAN ROWE, of Wilkinsburg, County of Allegheny and State of Penn-
sylvania, United States of America, Electrical Engineer, do hereby declare the
nature of this invention to be as follows:-
My invention relates to the regulation of electro-motive force and in particular
to the regulation of the electro-motive force supplied by the secondary coil of
a stationary transformer, the primary coil of which is supplied with alternating
currents,
The object of my invention is to provide for increasing or decreasing the
work circuit electro-motive force gradually over any desired range without undue
expense and complication, as regard either the structure or operation of the
apparatus employed.
Among the methods heretofore proposed for varying the electro-motive force
in alternating current work circuits supplied directly by stationary transformers,
perhaps the most usual is that which involves varying the active length of either
the primary or the secondary transformer winding by means of suitable switch
devices.
-
In dealing with large transformers and high electro-motive forces, this method
involves the employment of either an excessively large and practically prohibi-
tive number of switch contact points and corresponding divisions of the
transformer winding, or excessively large and abrupt changes in the electro-
motive force between successive divisions of the transformer winding.
It has also been proposed to vary the work circuit electro-motive force by
means of a regulator having two inductively related windings which may be
relatively adjusted in position so as to magnetically vary the electro-motive
force: This method fails to satisfactorily meet all the requirements of a normally
high voltage circuit in which a wide range of variation is desired, chiefly on
account of the size and structure of the regulator which it is necessary to employ
for such purpose, and the consequent torque to be overcome in operating it.
According to my invention I combine the two methods above mentioned and

page_text: thereby obtain the advantages of both methods without their respective
disadvantages,
In carrying out my invention I divide one of the coils of the transformer into
sections which can be cut in or out in succession and at the same time I vary
the electro-motive force by means of a magnetic regulator which operates
separately for every action. In this way before a section is cut in or cut out the
electro-motive force is adjusted by means of the inductive regulator so as to
approximate to the new electro-motive force existing after the section has been
cut in or out.
In order that the nature of my invention may be clearly understood I will
describe by way of example one method of carrying out the same in practice.
In the accompanying drawing:
Figure 1 illustrates a switch adapted to cut in or out sections of the primary
coil of a transformer and thereby vary the electro-motive force given out by
the secondary coil.
Figure 2 is a diagram illustrating the action of the inductive regulator which
forms part of the switch shewn in Figure 1.
A and B are the alternating current supply mains, C the stationary transformer
of which is the primary coil and e' the secondary coil, G and F are the work
circuit mains. D is a switch base provided with an outer contact ring d and an
inner contact ring , and an outer set of contact segments 1, 3, 5 and 7, and a
similar set of inner contact segments 2, 4, 6 and 8, the segments of each set being
spaced apart and alternating, as regards radial position, with those of the other.
A switch arm D¹ is pivoted at one end upon a shaft D at the centre of the switch.
plate D and is provided with two brushes e³ and e³. The brush is so located
as to make contact with ring d at all times, and also with each of contact seg-
ments 1, 3, 6 and 7 during a portion of each revolution of switch arm D)!.
The brush is so located as to make contact with ring at all times and with
each of contact segments 2, 4, 6 and 8 during a portion of each revolution. of
arm D¹, the relation of the two sets of segments being such that each brush comes
into contact with a corresponding segment just before the other brush breaks
contact with its segment.
The primary c of the transformer C is provided with leads 1ª, 2ª, 3ª, 4ª, 5ª, 6ª,
17, and 8, at regular intervals, extending over a portion of its length, which
are respectively connected to the contact segments 1, 2, 3, 4, 5, 6, 7 and 8. An
end lead 9 constitutes the terminal of the line conductor A. E is an inductive
regulator the primary coil e of which is connected across the secondary circuit
that is to say in shunt to the secondary coil d of the transformer C. The
secondary coil e¹ is connected at one end to ring d and at the other end to ring d
and to the terminal of the line conductor B. One of the coils of the regulator E is
mechanically connected with the shaft D of the switch in such a manner that
the electromotive force induced in the coil e¹ by the current flowing in the coil e
of the regulator varies from a maximum on one side of zero to a maximum on
the other side of zero as the switch arm revolves over the space occupied by one
contact segment.
The operation of the above described apparatus is as follows:-
Assuming that the switch arm D¹ is in the position indicated by broken lines
in Figure 1. and that the inductive regulator is in such position as to afford a
maximum inductive effect in opposition to the main line electro-motive force,
as is indicated at m in Figure 2, if the arm D' and the movable member of the
regulator be now turned in the clockwise direction so as to gradually vary the
inductive effect of the primary coil e upon the secondary coil e¹ through zero,
represented by 2 in Figure 2, to a maximum positive value indicated at m¹ in
said figure, the main line electro-motive force will obviously be less than the
normal by an amount which gradually decreases from the point m to the point z,
and will then be gradually increased to an equal amount represented by the
linez, m³. Upon the whole therefore the electro-motive force applied to the

page_text: points 9 and 1" is gradually increased during the movement of the switch arm
and consequently the electro-motive force in the work circuit will be gradually
increased, until at the end of the movement of the switch arm, when the contact
is about to leave the segment 1 the electro motive force in the work circuit is approxi-
mately equal to that which would be developed in the work circuit when
section 1" 2 of the primary coil is cut out, and the normal electro-motive force
of the supply mains is applied to the remaining sections of the primary coil.
Just before the brush e leaves the segment 1 the brush e comes in contact with
segment 2, and in this position it will be seen that the section 1, 2, of the
primary and the coil e of the regulator are short-circuited, the electro-
motive force in the section 1, 2 opposing that of the coil e¹; hence when the brush e
leaves segment 1 there is no current to be interrupted in the coil or section. The
switch arm has now attained a position where the brush is in contact with seg-
ment 2, and the brush has left the segment 1, the coil el being cut out the
regulator E has no effect upon the electro-motive force of the supply mains but as
the switch arm is moved towards, the other end of segment 2 the coils of the
regulator are returning to the position they had when the switch arm D' was in
the dotted line position. The variation of the electro-motive force induced in
coil el is represented in the diagram Figure 2 by the dotted line m¹ 21 m³. When
the brush makes contact with the segment 3 and the brush e leaves segment 2,
the coil e' of the regulator comes into circuit again and acts to decrease the
electro-motive force of the supply mains by an amount indicated by the point m²
Figure 2. This reduced electro-motive force acting through the sections 3° to 9"
of the primary coil c of the transformer C induces in the secondary coil of said
transformer an electro-motive force equivalent to that produced by the normal
electro-motive force of the supply mains when connected to the sections 2 to 9°
of the primary coil c; consequently the electro-motive force of the work circuit
is not varied abruptly when the segment 2" to 3" is cut out.
During the movement of the brush along segment 3 the action of the regu-
lator E is indicated by the line m² 2 m³ Figure 2. When the switch arm Dr is
in the position shewn in full lines in Figure 1, the effect of the regulator upon
the electro-motive force of the supply mains is zero, corresponding to the point
Figure 2. In this position of the switch arm the normal electro-motive force of
the supply mains is applied to the sections 3" to 9" of the primary coil e. As
the switch arm is moved the electro-motive force applied to these sections is
increased and therefore the secondary electro-motive force increased until when
the section 3 to 4 is about to be cut out by the brush making contact with
segment 4 the electro-motive force in the work circuit is approximately equal
to that which would be given by the normal electro-motive force of the supply
mains being applied to the segments 4" to 9" of the primary coil.
It will be readily understood from the foregoing description that as the move-
ment of the switch armi D is continued the line electro-motive force is first
opposed by a gradually diminishing electro-motive force and then increased by
a gradually increasing electro-motive force when the brush es is in contact with
the segments 5 and 7, and that while the brush is in contact with the
segments 4, 6 and 8 the regulator E has no effect on the electro-motive force of
the supply mains. Briefly it may be stated that when the effect of the regulator E
is indicated by the point m³ the electro-motive force of the work circuit is that
obtained by applying the normal potential difference of the supply mains to
sections 4 to 9 of the primary coil o. When the effect of the regulator corre-
sponds to the point m Figure 2, the electro-motive force of the supply mains is
reduced, but it is applied to the sections 5 to 9 only of the primary coil G₁ the
section 4" to 5" being cut out. At point of diagram 2 the normal electro-
motive force of the supply mains is supplied to sections 5ª to 9* of coils c.
point m³ an increased electro-motive force is applied to sections 5 to 9 of the
coile and the electro-motive force of the work circuit is equivalent to that obtained
by applying the normal electro-motive force of the supply mains to the
At

page_text: sections 6 to 9* of the coil c. The case corresponding to point me of the diagram
Figure 2 is when the reduced E. M. F. of the supply mains is applied
to the sections 7" to 9" and at point 2" the normal electro-motive force is applied
to sections 7 to 9*; at point m an increased electro-motive force is applied to
the sections 7 to 9 which produces in the work circuit the same effect us if a
normal electro-motive force were applied to sections 8" to 9" which is the case
when the brush e comes into contact with segment 8. At points 27 and m³ the
coil e' is cut out and when the brush reaches the end of the segment 8 the
projection f on the arm ' comes in contact with the stop f and prevents further
Torward movement of the arm.
It will be seen that the work circuit electro-motive force is raised by means of
progressively added increments instead of by means of abrupt steps or jumps,
as would be the case if sections of the primary of the transformer were succes-
sively cut out of circuit without any intermediate variation of potential.
It will also be seen that the restriction of the inductive regulation to points of
comparatively small difference of potential, renders it feasible to employ a rela-
tively small regulator which may be easily and effectively operated.
It will be understood without further explanation that the secondary electro-
motive force may be decreased by moving the switcli arm D¹ in the opposite
direction to that already described.
If a greater range of electro-motive force regulation is desired than is afforded
by the construction indicated in the drawing, it may obviously be secured
by providing the requisite number of transformer leads and employing a switch
having the same number of stationary contact pieces, and providing suitable
means intermediate the inductive regulator and the switch whereby the switch
arm is intermittingly actuated when the movable member of the regulator reaches
the proper position for cutting a section of the transformer winding into or out
of circuit.
I desire it to be understood that variation of the active length of either the
primary or the secondary transformer winding is within the scope of my
inven-
tion, and that the construction and arrangement of parts both mechanical and
electrical, may be varied to suit the ideas of the constructor or operator without
departing from the spirit and scope of my invention.
improveMENTS REINting to the Regulation of Electromotive Force,
I, NORMAN ROWE, of Wilkinsburg, County of Allegheny and State of Penn-
sylvania, United States of America, Electrical 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:-
My invention relates to the regulation of olectro-motive force and in particular
to the regulation of the electro-motive force supplied by the secondary coil of
a stationary transformer, the primary coil of which is supplied with alternating
currents.
The object of my invention is to provide for increasing or decreasing the
work circuit electro-motive force gradually over any desired range without undue

page_text: expense and complication, as regard either the structure or operation of the
apparatus employed.
Among the methods heretofore proposed for varying the electro-motive force
in alternating current work circuits supplied directly by stationary transformers,
perhaps the most usual is that which involves varying the active length of either
the primary or the secondary transformer winding by means of suitable switch
devices.
In dealing with large transformers and high electro-motive forces, this method
involves the employment of either an excessively large and practically prohibi-
tive number of switch contact points and corresponding divisions of the
transformer winding, or excessively large and abrupt changes in the electro-
motive force between successive divisions of the transformer winding.
It has also been proposed to vary the work circuit electro-motive force by
means of a regulator having two inductively related windings which may be
relatively adjusted in position so as to magnetically vary the electro-motive
force. This method fails to satisfactorily meet all the requirements of a normally
high voltage circuit in which a wide range of variation is desired, chiefly on
account of the size and structure of the regulator which it is necessary to employ
for such purpose, and the consequent torque to be overcome in operating it.
According to my invention I combine the two methods above mentioned and
thereby obtain the advantages of both methods without their respective
disadvantages.
In carrying out my invention I divide one of the coils of the transformer into
sections which can be cut in or out in succession and at the same time I vary
the electro-motive force. by means of a magnetic regulator which operates
separately for every action. In this way before a section is cut in or cut out the
electro-motive force is adjusted by means of the inductive regulator co as to
approximate to the new electro-motive force existing after the section has been
cut in or out.
In order that the nature of my invention may be clearly understood I will
describe by way of example one method of carrying out the same in practice.
In the accompanying drawing:
Figure 1 illustrates a switch adapted to cut in or out sections of the primary
coil of a transformer and thereby vary the electro-motive force given out by
the secondary coil.
Figure 2 is a diagram illustrating the action of the inductive regulator which
forms part of the switch shewn in Figure 1.
A and B are the alternating current supply mains, C the stationary transformer
of which is the primary coil and the secondary coil, and I are the work
circuit mains. D is a switch base provided with an outer contact ring d and au
inner contact ring and an outer set of contact segments 1, 3, 5 and 7, and a
similar set of inner contact segments 2, 4, 6 and 8, the segments of each set being
spaced apart and alternating, as regards radial position, with those of the other.
A switch arm D' is pivoted at one end upon a shaft D at the centre of the switch
plate D and is provided with two brushes and e. The brush is so located
as to make contact with ring d at all times, and also with each of contact seg-
monts 1, 3, 5 and 7 during a portion of each revolution of switch arm ])'.
The brush e³ is so located as to make contact with ring at all times and with
each of contact segments 2, 4, 6 and 8 during a portion of each revolution of
arm D, the relation of the two sets of segments being such that each brush comes
into contact with a corresponding segment just before the other brush breaks
contact with its segment.
The primary of the transformer C is provided with leads 1, 2, 3ª, 4ª, 5ª, 6ª,
7, and 8, at regular intervals, extending over a portion of its length, which
are respectively connected to the contact segments 1, 2, 3, 4, 5, 6, 7, and 8. An
end lead 9 constitutes the terminal of the line conductor A. E is an inductive
regulator the primary. coil e of which is connected across the secondary circuit

page_text: that is to say in shunt to the secondary coil of the transformer C. The
secondary coil el is connected at one end to ring d and at the other end to ring d
and to the terminal of the line conductor B. One of the coils e¹ of the regu-
lator is mechanically connected through gear wheels k, with the shaft Da
of the switch. The coil e¹ is mounted on a vertical axle and it will be readily
seen that as the coil turns round on this axle, its magnetic relation to the coil e
will change in the manner hereinafter described. The gear wheel & being one-
quarter of the diameter of the gear wheel, the coil e will turn completely
round while the switch arm is moved from the beginning of the segment 1 to
the end of the segment 2, that is to say, through 90° of arc, and it will be seen
that during one half of the revolution of the coil el on its axle, the electro-motive
forco induced in it by the current flowing in the fixed coil e will vary from a
maximum on one side of zero to a maximum on the other side of zero.
The current may be led into and out of the coil through collecting rings as
shewn.
The arrangement shown for varying the electro-motive force of the regulator E
is merely illustrative, and I do not restrict myself to the device shewn.
-
The operation of the above described apparatus is as follows:
Assuming that the switch arm D' is in the position indicated by broken lines
in Figure 1, and that the inductive regulator is in such position as to afford a
maximum inductive effect in opposition to the main line electro-motive force,
as is indicated at m in Figure 2, if the arm D' and the movable member of the
regulator be now turned in the clockwise direction so as to gradually vary the
inductive effect of the primary coil e upon the secondary coil e through zero,
represented by z in Figure 2, to a maximum positive value indicated at m¹ in
said figure, the main line electro-motive force will obviously be less than the
normal by an amount which gradually decreases from the point m to the point z,
and will then be gradually increased to an equal amount represented by the
line, m. Upon the whole therefore the electro-motive force applied to the
points 9 and 1 is gradually increased during the movement of the switch arm
and consequently the electro-motive force in the work circuit will be gradually
increased, until at the end of the movement of the switch arm, when the contact e
is about to leave the segment 1 the electro motive force in the work circuit is approxi-
mately equal to that which would be developed in the work circuit when
section 12 of the primary coil is cut out, and the normal electro-motive force
of the supply mains is applied to the remaining sections of the primary coil.
Just before the brush e leaves the segment 1 the brush e³ comes in contact with
segment 2, and in this position it will be seen that the section 1, 2, of the
primary and the coil e of the regulator E are short-circuited, the electro-
motive force in the section 1ª, 2ª opposing that of the coil c'; hence when the brush e
leaves segment i there is no current to be interrupted in the coil or section. The
switch arm has now attained a position where the brush is in contact with seg-
ment 2, and the brush has left the segment 1, the coil e¹ being cut out the
regulator E has no effect upon the electromotive force of the supply mains but as the
switch arm is moved towards the other end of segment 2 the coils of the
regulator are returning to the position they had when the switch arm D¹ was in
the dotted line position. The variation of the electro-motive force induced in
coil e¹ is represented in the diagram Figure 2 by the dotted line m² 21 m³. When
the brush makes contact with the segment 3 and the brush leaves segment 2,
the coil e of the regulator comes into circuit again and acts to decrease the
electro-motive force of the supply mains by an amount indicated by the point m³
Figure 2. This reduced electro-motive force acting through the sections 3" to 9"
of the primary coil c of the transformer C induces in the secondary coil of said
transformer an electro-motive force equivalent to that produced by the normal
electro-motive force of the supply mains when connected to the sections 2" to 9°
of the primary coil e; consequently the electro-motive force of the work circuit
is not varied abruptly when the segment 2" to 3ª is cut out.

page_text: During the movement of the brush e along segment 3 the action of the regu-
lator E is indicated by the line m³ 22 m³ Figure 2. When the switch_arm D² is
in the position shewn in full lines in Figure 1, the effect of the regulator upon
the electro-motive force of the supply mains is zero, corresponding to the point 2
Figure 2. In this position of the switch arm the normal electro-motive force of
the supply mains is applied to the sections 3" to 9" of the primary coil c. As
the switch arm is moved the electro-motive force applied to these sections is
increased and therefore the secondary electro-motive force increased until when
the section 3 to 4" is about to be cut out by the brush making contact with
segment 4 the electro-motive force in the work circuit is approximately equal
to that which would be given by the normal electro-motive force of the supply
mains being applied to the segments 4" to 9" of the primary coil.
It will be readily understood from the foregoing description that as the move-
ment of the switch arm D¹ is continued the line electro-motive force is first
opposed by a gradually diminishing electro-motive force and then increased by
a gradually increasing electro-motive force when the brush e is in contact with
the segments 5 and 7, and that while the brush is in contact with the
segments 4, 6 and 8 the regulator E has no effect on the electro-motive force of
the supply mains. Briefly it may be stated that when the effect of the regulator E
is indicated by the point m³ the electro-motive force of the work circuit is that
obtained by applying the normal potential difference of the supply mains to
sections 4 to 9 of the primary coil c. When the effect of the regulator corre
sponds to the point m Figure 2, the electro-motive force of the supply mains is
reduced, but it is applied to the sections 5 to 9 only of the primary coil c, the
section 4 to 5" being cut out. At point of Diagram 2 the normal electro-
motive force of the supply mains is supplied to sections 5 and 9" of coils c.
point m³ an increased electro-motive force is applied to sections 5" to 9" of the
coile and the electro-motive force of the work circuit is equivalent to that obtained
by applying the normal electro-motive force of the supply mains to the
sections 6 to 9 of the coil c. The case corresponding to point m of the diagram
Figure 2 is when the reduced electro-motive force of the supply mains is applied
to the sections 7 to 9 and at point the normal electro-motive force is applied
to sections 7 to 9; at point m an increased electro-motive force is applied to
the sections 7 to 9 which produces in the work circuit the same effect as if a
normal electro-motive force were applied to sections 8 to 9 which is the case
when the brushe¹ comes into contact with segment 8. At points and m³ the
coil el is cut out and when the brush e reaches the end of the segment 8 the
projection on the arm D¹ comes in contact with the stop f and prevents furthor
forward movement of the arm.
At
It will be seen that the work circuit electro-motive force is raised by means of
progressively added increments instead of by means of abrupt steps or jumps,
as would be the case if sections of the primary of the transformer were succes-
Bively cut out of circuit without any intermediate variation of potential.
It will also be seen that the restriction of the inductive regulation to points of
comparatively small difference of potential, renders it feasible to employ a rela-
tively small regulator which may be easily and effectively operated.
It will be understood without further explanation that the secondary electro-
motive force may be decreased by moving the switch arm 1 in the opposite
direction to that already described.
If a greater range of electro-motive force regulation is desired than is afforded
by the construction indicated in the drawing, it may obviously be secured
by providing the requisite number of transformer leads and employing a switch
having the same number of stationary contact pieces, and providing suitable
means intermediate the inductive regulator and the switch whereby the switch
arm is intermittingly actuated when the movable member of the regulator reaches
the proper position for cutting a section of the transformer winding into or out
of circuit,

page_text: I desire it to be understood that variation of the active length of either the
Всоро of my
primary or the secondary transformer winding is within the
invén-
tion. Furthermore the connection of the inductive regulator may be other than
that described since it is obviously only necessary that one coil of said regulator
should be included in series with one of the transformer windings the other coi!
being supplied with current from any suitable source. The construction and
arrangement of parts both mechanical and electrical, may be varied to suit the
ideas of the constructor or operator without departing from the spirit and
scope of my invention.
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. For varying the electro-motive force supplied by a transformer, a switch
the movement of the arm of which varies the active length of one of the trans-
former windings and at the same time varies an inductive regulator, for the
purpose specified.
2. A switch constructed and operating substantially as described.
h day of May 1899.
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.