Improvements in Regulating Transformers.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in Regulating Transformers.
ALFRED STILL, Civil Engineer, of Bow Green Farm, Bowdon, Cheshire, and
EDWARD WOODROWE COWAN, Civil Engineer of Hart Hill Woodville Road Dunham
Massey, Cheshire do hereby declare the nature of this invention to be as follows:-
Our invention relates to Regulating Transformers & particularly to that type for
which Letters Patent No. 7142 A.D. 1895 were granted to us.
Our invention provides means whereby the drop in the secondary volts of the said
Regulating Transformer which occurs between no load & full load due to self
induction is materially reduced and a further part of our invention provides means
whereby the Magnetising Current of the Primary Coil is reduced in certain positions
of the inoveable core relatively to that of the fixed core.
We effect the improvements first referred to by winding a portion, approximately
half, of the secondary winding on the moveable core together with the primary
winding & by fixing on either the moveable Core, or the fixed Core, or both, short
circuited or shading coils in such positions as to prevent Magnetic leakage. The
effect of winding approximately half the secondary coils on the moveable core is to
reduce the number of secondary coils which are placed on the fixed Core in which
position they tend to set up Magnetic leakage & consequent secondary drop of
pressure.
The action of the apparatus is then as follows:-
In the position of maximum effect the shuttle is in a vertical position as in the
design for which Letters Patent No. 7142 /95 were granted to us & the magnetic flux
set up by the primary windings cuts both the secondary turns on the shuttle & those
on the ring in a positive sense. In the position of no effect the shuttle is revolved
through an angle of 180 deg. & the magnetic flux then cuts the secondary coils on the
shuttle in a positive sense & those on the ring in a negative sense; these effects being
practically equal & opposite, the resultant E.M.F. in the complete secondary circuit
is nil.
In intermediate positions of the shuttle relatively to the ring the resultant E.M.F.
in the secondary circuit is intermediate. If it is desired that the regulating
transformer should, when connected up as a Feeder Regulator or "Booster," subtract
as well as add E.M.F. it is necessary to alter the ratio of the number of turns on the
shuttle relatively to those on the ring, so that the position of no effect is reached
before the shuttle has travelled through 180 deg. Between that position & 180 deg.
volts will be subtracted from the circuit in series with the secondary of the
Transformer, the maximum amount of subtracting depending on the number of
secondary turns on the ring in excess of those on the shuttle.
The effect of the short circuiting or shading coils is to screen the magnetic flux set
up by the secondary coils on the fixed Core & thereby reduce their self induction
which results in loss of pressure.

page_text: We effect the second part of our invention, namely, the reduction of Magnetising
Current in certain positions of the shuttle relatively to the ring, by reducing the
number of slots in the fixed core & thereby increasing the area of the air-gap between
the fixed Core and the moveable core. The reduction of the number of slots is
permissible because, as explained in the first part of our invention, the number of
secondary turns on the fixed Core is reduced by approximately half, & a further
reduction in the number of slots means a reduction in the space occupied by insula-
tion. Again the reduced number of slots are placed in such positions on the fixed
Core that the area of the air gap is, in all positions of the moveable Core relatively to
the fixed Core, as large & as equal as possible. The short circuited or shading coils
on the shuttle counteract the self induction which would otherwise result from
winding the secondary coils on the ring in recesses bridged by the poles of the primary
core.
ALFRED STILL Civil Engineer of Bow Green Farm Bowdon Cheshire and EDWARD
WOODROWE COWAN of Hart Hill Woodville Road Dunham Massey Cheshire, 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:-
Our invention relates to Regulating Transformers, and particularly to that type for
which letters Patent No. 7142 A.D. 1895 were granted to us.
Our invention provides means whereby the drop in the secondary volts of the said
Regulating Transformer, which occurs between no load and full load due to self
induction, is materially reduced, and a further part of our invention provides means
whereby the Magnetising Current of the Primary Coil is reduced in certain positions
of the moveable core relatively to that of the fixed Core.
We effect the improvements first referred to by winding a portion, approximately
half, of the secondary winding on the moveable core, together with the primary
winding, and by fixing on either the moveable Core, or the fixed Core, or both, short
circuited or shading coils in such positions as to prevent Magnetic Leakage. The
effect of winding approximately half the secondary coils on the moveable core is to
reduce the number of secondary coils which are placed on the fixed Core in which
position they tend to set up Magnetic Leakage and consequent secondary drop of
pressure. The action of the apparatus is then as follows:-In the position of
inaxiínum effect the shuttle is in a vertical position as in the design for which
Letters Patent No. 7142 /95 were granted to us, and the magnetic flux set up by the
primary winding cuts both the secondary turns on the shuttle and those on the ring
in a positive sense. In the position of no effect, the shuttle is revolved through an
angle of 180 deg. and the magnetic flux then cuts the secondary coils on the shuttle
in a positive sense and those on the ring in a negative sense, these effects being
practically equal and opposite, the resultant E.M.F. in the complete secondary circuit
is nil.
In intermediate positions of the shuttle relatively to the ring the resultant E.M.F. in
the secondary circuit is intermediate. If it is desired that the Regulating
Transformer should, when connected up as a Feeder Regulator or "Booster," subtract
as well as add E.M.F. it is necessary to alter the ratio of the numbers of secondary

page_text: turns on the shuttle relatively to those on the ring, so that the position of no effect
is reached before the shuttle has travelled through 180 deg.: Between that position
and 180 deg., volts will be subtracted from the circuit in series with the secondary
of the Transformer, the maximum amount of subtracting depending on the number
of secondary turns on the ring in excess of those on the shuttle.
The effect of the short circuiting or shading coils is to screen the magnetic flux set
up by the secondary coils on the fixed Core and thereby reduce their self induction,
which results in drop of pressure.
We effect the second part of our invention, namely, the reduction of Magnetising
Current in certain positions of the shuttle relatively to ring, by reducing the number
of slots in the fixed core and thereby increasing the area of air gap between the fixed
Core & the moveable Core. The reduction of the number of slots is permissible
because, as explained in the first part of our invention, the number of secondary
turns on the fixed Core is reduced by approximately half, and further, the reduction
of the number of slots means a reduction in the space occupied by insulation. Again,
the reduced number of slots are placed in such positions on the fixed core that the
area of the air gap is, in all positions of the moveable Core relatively to the fixed Core,
as large and as equal as possible. The short-circuited or shading coils on the shuttle
reduce the secondary drop which would otherwise result from winding the secondary
Coils on the ring in recesses which are in some angular positions of the shuttle
bridged by the pole pieces of the moveable core.
In Figure I of the accompanying drawing, the arrangement of the windings and
short-circuited or shading Coils is diagramatically shown.
In this figure S is the secondary and p is the primary winding. We do not confine
ourselves to the form of secondary winding shown on this diagram, but sometimes
prefer to wind that portion of the Secondary Circuit which is wound on the ring
shaped core in the form known generally as "drum" winding.
In Figures I & II the Regulating Transformer is shown with its secondary in series
with another circuit, whereby volts can be added to or subtracted from that circuit.
Fig. I shows the moveable core with its winding in the position of minimum effect,
the secondary turns on the shuttle acting against the secondary turns on the ring.
Fig. II shows the moveable core with its winding in the position of maximum effect,
the secondary turns on the shuttle acting with the secondary turns on the ring. The
short circuited or shading coils on the moveable core are marked S C on the drawing.
They are wound with their axes at right angles to the axis of the primary winding.
Each short circuited coil may consist of either a single turn or a number of turns all
joined in series; the resistance being kept as small as possible. The recesses for the
secondary winding on the ring are arranged as shown on the drawing, they are
marked rand are placed in such positions that, taking into consideration their
width and the width of the pole pieces of the moveable core, there shall be the
smallest possible resistance of air gap hetween the moveable and stationary cores in
any position between minimum and maximum effect; thus ensuring that the
maximum magnetising current shall be as small as possible.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we hereby declare that what
we claim is:
1. The construction of a Regulating Transformer of the type which depends for its
action upon the relative movement of different parts of its iron circuit, with a portion
of its secondary winding on the moveable part of the iron cirenit, and a portion upon
the fixed part of the iron circuit, so arranged that in one position of the moveable part
of the iron cirenit relatively to the fixed part, these two portions of the secondary
winding shall act against each other, and in another position they shall act with
each other.
2. The addition of short circuited or shading coils of low resistance upon the
noveable part of the iron circuit of the Regulating Transformer hereinbefore
described.

page_text: 3. The arrangement of the recesses in the fixed part of the iron circuit of the
Transformer hereinbefore described, approximately in the positions shown in
Figures I and II of the accompanying drawing.
Dated this Seventh day of September 1897.