Improvements: in Electro-motors and like Electro-magnetic Apparatus.
Year: 1894

page_text: Date of Application, 11th Oct., 1894
Complete Specification Left, 9th Aug., 1895-Accepted, 11th Oct., 1895.,
PROVISIONAL SPECIFICATION..
Improvements: in Electro-motors and like Electro-magnetic
Apparatus.
We, CHARLES, CONNORS, of 49 Brunswick Place, Brighton, in the County of
Sussex, Gentleman, and WALTER LANGDON-DAVIES, of 57 Comeragh Road,
West Kensington, in the County of Middlesex, Electrical Engineer, do hereby
declare the nature of this invention to be as follows:-
This invention relates to the production of an uniform field suitable for working
non-synchronous alternating current motors.
It is well known that if two coils A, B, Figure 1, of equal inductance be joined
in parallel and connected directly to the mains supplying an alternating E.M.F.
and if the resistance of one of them, say A, be greater than that of the other, or if
.a non-inductive resistance C be joined in series with one of them, the resulting
alternating current in B, will lag behind the current in A, that is to say, that the
current in coil A will start from zero and rise towards a + or maximum
before the current in B starts to rise in the same direction. Similarly the current
in A will reach its maximum before the current in B, and again arrive at zero first.
Although the currents.in the two coils perform the same series of cycles, the current
in coil A is always further advanced in its cycle than that in B.
.
If these coils have iron cores the magnetism produced in the cores varies with
the amount of current flowing in the coils, the magnetism in the core of A will
reach its maxiinuin before that in B and A will have fallen to nothing when B is
still magnetised, so that if a piece of iron were pivotted between the ends of these
cores, as indicated by D, it would be drawn alternately backwards and forwards,
and could be made to perform various mechanical functions. These two coils
producing magnetic fields could be combined in several ways to produce what. is
known as a rotating field.
"
From further inspection of Figure 1, it will be obvious that since the resistanco
of A is greater than the resistance of B,, the average current passing through A
will be less than the average current passing through B and consequently the
average strength of the magnetic flux in the core of A will be less than that in the
core of B, and the piece of iron D, or other mechanical device, will be acted upon
more strongly by B, than by A.
I
And if these two fields.be combined to make a rotary field, this field will vary,in
strength during each rotation.
Our invention removes this inequality and at the same time yields a furthor
advantage in that it reduces the amount of added resistance below that which would
otherwise be necessary.
We so proportion the coils that, notwithstanding, their difference of phase, and
resistance the magnetic flux produced by each coil is equal.
We will describe the method of winding two coils upon equal cores producing
magnetic fields of equal strengths, but having a difference of phase of 45°. The
number of turns required on coil B, the coil having the greatest lag to give the
required strength of field with the given D.M.F. are found, either by experiment
or by any well known method and this coil is wound with as little resistance, as
practicable. The angle of lag of this coil, Bis then ascertained, by the usual

page_text: methods, at the rate of alternation, at which, the coils are intended, to work, in
practice this will be usually nearly 90%, suppose it to be 89, then, it will be
necessary that coil A should lag,only 44° so that the difference between the two
coils shall be 45°. It will then be necessary, to wind coil A with such a number
of turns that the proportion of the number of turns on A are to the number of turns
on B as sine 44° is to sine 89%..
Having by, this means ascertained the turns required, by the two coils, we can
then calculate in a well-known manner the resistance necessary to produce the
required lag, and likewise the amount of current this coil A will be required to
carry in order that the product of the turns and the current of A and B may be
equal.
For practical purposes it is convenient to wind this coil A of suitable wire to
carry the current, and to make up. the resistance by the addition of non-inductive
resistance placed in series with it.
Since sine 44° is less tlian sine. 89° coil A, has fewer turns than coil B, and since
the coefficient of self-induction varies. as the square of the turns, coil; A will
have less self-induction and more current flowing through it.. for the same
impressed E.M.F, this excess of current will be reduced' by the increased
resistance required, but it will nevertheless be found greater than that in.B; the
final result being that the greater current in. A multiplied by the. fewer, turns,
equals the lesser current in B multiplied by the greater number of turns, and thit
therefore-the ampère turns, and the fields produced by the two coils are equal,
though lagging in-phase.
When, however, it is required to wind the coils on cores of different dimensions,
it will not be necessary to wind them of equal ampère turns, for suppose the core of
coil A to be smaller than the core of coil B; that we may have the same strength
of field produced by ench coil, it will be necessary to magnetise the smaller core
of A to a greater density than B, and, as is well known, the permeability of A,
will be less thinn that of B; supposing the same quality of iron to be used in each
case; it will therefore be necessary to have a larger proportion of ampère.turns on
coil A than would otherwise have been required, we therefore, by known methods,
calculate the number of ampère turns required to give the necessary magnetic flux
at the known permeability, and then by other well known methods we calculate
the number of turns required; on the supposition that this coil has no resistance
and therefore lags 90°. It has been found now that if this figure be multiplied: by
the sine of the angle the coil is required to lag, in this case. 44°, and the turns
wound' according to the number obtained; when the necessary resistance is inserted
the coil A will produce the same strength of magnetic field as B
Wo utilise this method in the construction of motors. in the following manner:
The field of one type of motor is represented by Figures 2 and 33, diagram-
matically.
The iron core is built up of sheet iron stampings insulated from one another.in
the usual manner, for the highest speed machines they are provided with, four pole
pieces, though we may in a two-phase machine use. also eight twelve, or higher
multiples of four, according to the working speed required; as.will be described
hereafter.
It will suffice to describe a four-pole machine.
The pole pieces are made broad at their interior ends, to reduce. the magnetic
reluctance of the air gap as much as possible.
Upon the iron ring and in the gaps between the pole pieces, the coils A Bare
wound.
It must be noted that the coils A and B are here. each divided into. four, coils,
the letters A and B; therefore, each represent a set of four coils, which are
individually lettered A, A, A, A and B, B, B, B.
All the A coils have an equal number of turns, and all the B coils have an equal
number of turns, but the turus on the A coils are not equal to the turns, on the
B'coils, and are calculated as shewn above.

page_text: 18 necessary that the two sets or cons and not have any erective manc
action upon one andther, they are therefore wound relatively to one another as det
forth 'below.
1
We commence by winding either one of the sets of coils, say set B. Referring
to Figure 2, we wind B₁, and B, connecting them in series. Oolls B, and B are
then wound in the opposite direction 'and connected 'in series with B, and B.
We may of course for practichl 'purposes wind all these coils in the same direction
and reverse the connections at E Figure 2, which will have the same effect.'
We then wind coil 'A on the top of B, commencing A on 'the 'top of B₂'a
Pand
winding round the ring in 'the sathe manner as for circuit B.
It will be seen that 'cuit B will produce a field across from pole G to,
Figure 2, and that the coils A will produce a field of equal density across I, J, but
since these coils have different 'lags these fields will not be 'set up at the 'game
instant, but will follow one another, the result 'heing that 'a' rotary fald is set up
capable of rotating a stiitable armature or 'roter place in the techtre of the ring.
The field makes one rotation for every alternation of the impresse E.M.F.
Figure 3 is a simplified diagram of the winding shewn in Figure 2, and from it,.
it can be hore clearly seen the way in which the injurious mitual in inctii of 'the
coils is avoided.
-1
3
Taking half the ring Figure 3, i.e. from pole through pole G to pole I
including the coils A, A., and B., B₂, it will be seen 'that the two coils 'A, 'and A
which are wound in the same direction, enclose two coils B, and B, which are
wound in opposite directions to one another. Therefore any current flowing
through the two portions of A; A, A,, 'wonld produce equal and opposite currents
in the two portions of B; B., and B, over which 'they are wound: Similarly any
current passing through the section B, B, will flow in equal and opposite directions
with respect to A₁, A, and its inductive effect will therefore be nil; this will be
seen to hold good for any section.
Figure 4 shews another way of placing these coils which is also effective.
When using four poles and two phases the field makes one rotation for cach
alternation of the current ns shewn 'above. When we build a machine 'to ran 'at a
slower speed we increase the number of poles to some higher inultiple of four, för
instance in an eight pole two phase machine the field will only make one complete
rotation in every two alternations.
We wind the coils on the pole pieces as in Figure 5, or if overwound, as shewn
in Figure 6.
The coils A and B, in 'the case of an eight pole overwound field, are divided into
eight parts, each pair being reversed as per Figure 6; the A coils are reversed at
the points O, F and M (marked with a cross) and the B coils at K, E and L, (also
marked with a cross).
Figure 7 shews another method of arranging the field.
The field is divided into two portions and wound separately, they are thien
placed side by side, having the poles set at 90° as shewa. The dotted pole-pioces
belong to one portion and those ehewn in full lines to the other portion.
In the case of small machines where it is not advisable to inake any change after
starting, we run the machine with a continuous rotary field, in other cases we
employ the rotating field only for starting the motor and after starting we alter
the connections in such manner that the field becomes single phase and the motor
rans synchronously.
To avoid excessive current in starting these machines, when we employ the
rotary field for starting we adopt the following arrangements shewn diagramniatically
in Figures 8, 9.
The coils A and B are wound as already described and so that B when in action
alone will give the required magnetic flux. If now we connect the two coils in
parallel for starting the motor the iron will be considerably over-saturated and a
large amount of current will flow owing to the drop in permeability of the core
due to saturation, without doing any useful work. Therefore when these coils"
1
.:
a

page_text: are connected in parallel for, starting, we connect in series with them a resistance
or preferably a choking coil P to reduce. the current sufficiently to produce only
a sufficient magnetic flux. When the motor is started; by means of a. suitable
witch, we switch out the coil A and the resistance P and place the coil B
directly across the mains, as shewn by Figure 9.
Figures 10, 11 shew another and better method, the coils A and B are wound
as usual but so that both are required to be in use to give the required flux.
After putting on the required number of turns for coil A we bring out a con-
nection, and then continue to wind, on turns until we have an equal number to
coil B, these extra turns are shewn at b, Figures 10, 11, so that A + b = B.
In series with the first portion of coil A, we connect the extra resistance C.
For starting the connections are as seen in Figure 10 and a rotating field is
obtained. The motor is then of the non-synchronous. type and will start freely.
When the proper speed is attained, we switch out the extra resistance C and
place coils A+ in parallel with B giving a single phase field of the same strength
as before.
Another way in which we produce a rotary maguetic field is illustrated in
Figures 12 and 13 where A and B are the field coils and coil A. forms part of the
secondary circuit of a transformer T. The primary coil of the transformer is
connected either in parallel or series with B. The coils are so proportioned that a
uniform field is obtained. The rotary field may be used either for starting only or
for. continuous running.
As the rotating part or armature of the motor we use an armature or roter, built
up of iron discs having coils wound' either on poles or in slots, as in Figure 14 or in
boles in the discs, and we connect all these coils together in parallel as shewn in
Figure 14 and short circuit them upon one another.
When one turn is sufficient for each coil we construct them of single copper wires
or rods placed through holes in the iron and all joined at each end by a stout
copper ring; this ring should have a cross section considerably in excess of that
of the individual copper rods.
The whole of these coils and connections should be well insulated from the iron
with asbestos paper or such other insulation as will not be injured by a moderate
rise in temperature and for the same reason we prefer to rivet the copper rods into
the connecting ring in place of soldering them.
We regulate the number of these copper rods or coils, or poles as the case may
be, in the following manner :-
We use three copper rods placed at equal distances round the armature i.e, at
1:0° from one another when such an armature is at rest in the centre of a rotating
magnetic field three phase currents are set up in the armature coils, themselves
producing a rotary field in the armature which follows the inducing rotating field
and there is no tendency to rotate the armature itself, this also applies to multiples
ol three, we therefore use some number of coppers, coils.or poles on the armature
which is not a multiple of three. The actual number used depends on the size of
the armature, but an odd number should be used. Therefore if a equals the
Dumber of poles on the field then X a is some multiple of these poles, we then wind
the armature with Xa1 coils, and take care to avoid multiples of three. For
example if there be four poles on the field, and we make X equal to 4 then Xa = 16
and X a- 115 which is a multiple of 3, we should therefore in this case use
Xa+1 which is equal to 17, and is not a multiple of 3, for the coils or coppers on
this armature.
When building a motor, of the type shown in Figure 7, we sometimes find' it
convenient to place the two sets of poles in the same plane, instead of setting them,
at 90°
as shewn. When this is the case we divide the rotor or armature into two
parte, Figure 15, and set one of these parts at an augle to the other, as shewn,, so
that the poles on the armature induced by one half of the field magnet do not lie
in a line with the direction of the subsequent field set up by the other half of the
field magnet.

page_text: We may set these two portions of the rotor at any convenient angle to one
another.
Sometimes in place of employing a revolving armature or rotor in the uniform
rotary field we place in the field an analogous stationary part. The secondary:
currents are set up in the arinaturo coil or coils and these we lead off by suitable
connections. By such means we can transform the primary current or currents,
into secondary currents of various phases.
Dated this 10th day of October 1894.
:
Improvements in Electro-motors and like Electro-magnetic
Apparatus.
We, CHARLES CONNORS, of 49 Brunswick Place, Brighton, in the County of
Sussex, Gentleman, and WALTER LANGDON-DAVIES, of 57 Comoragh Road,
West Kensington, in the County of Middlesex, 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 :-
This invention relates to the production of a rotating field suitable for working
non-synchronous alternating current motors.
f
I
It is well known that if two coils A, B, of equal inductance be joined in.
parallel and connected directly to mains supplying an alternating E.M.F., and if
the resistance of one of them, say A, be greater than that of the other, or if a non-
inductive resistance C be joined in series with one of them, the resulting alternating
current in B, will lag behind the current in A, that is to say, that the current in..
coil A will start from zero and rise towards a positive or negative.maximum
before the current in 13 starts to rise in the same direction. Similarly the current
in A will reach its maximum before the current in B, and again arrive at zero:
first, although the currents in the two coils perform the same series, of cycles the:
current in coil A is always further advanced in its cycle than that in coil B.
If these coils have iron cores the magnetism produced in the cores varies with.
the amount of current flowing in the coils, the magnetism in the core of A will;
reach its maximum before that in B and A will have fallen to nothing when B is'
still magnetised, so that if a piece of iron wore pivotted between the ends of these,
cores, as indicated by D, it would be drawn alternately backwards and forwards,
and could be made to perform various mechanical functions, or a magnetised needle
could be made to rotate. This arrangement is illustrated in Figure 1. These two
coils producing ningnetic fields could be combined in several ways to produce what:
is known as a rotating field!
It will be obvious that (other things being equal) since the resistance of. A is
greater than the resistance of B; the average current passing through. A will be
less than the average current passing through B, and consequently the average
Etrength of the magnetic flux in the core of A will be less than that in the core of B:
and the piece of iron D, or other mechanical device, will be acted upon more>
strongly by B than by A. And therefore if these two fields be combined to make:
arotary field, this field will vary in strength during each. rotation. For at one
instant the strength of the field depends wholly on A and at another on B.: One,
of the main objects of our invention is to remove this inequality and to producen
more uniform rotating field and this we do by proportioning the coils so, that
notwithstanding their difference of phase and resistance the magnetic flux produced:
by: each coil shall be equal.
!

page_text: We apply our invention to the construction of motors in the following
manner
I
The field magnet of one type infinator is represented diagrammatically by
Figures 2 and '3.
The iron core is built up of sheet iron stampings insulated from one another in
the usual inanner: Tor the highest speed machines they are provided with four pole
pieces, though we may in a two-phase machine use also eight, twelve, or higher
multiples of four, according to the working speed required, as will be described
hereafter.
It will suffice to describe a four pole machine.
The pole pieces are made broad at their interior ends to reduce the magnetic
reluctance of the air gap as much as possible.
Upon the iron ring and in the gaps between the pole pieces the coils A and B
are wound.
It must be noted that the windings A and B are here each divided into four
coils, the letters A and B therefore, cach 'represent a set of four coils 'which are
individually lettered A, A, A, A, and B, B, B.B¸.
All the A coils have an equal number of turns, and all the B coils have an equal
number of turns, but the turns 'on the A coils are not equal to the turns on the
B coils, and are proportioned so as 'to equalize the field in the manner herein
Bet forth.
When it is necessary that the two sets of coils should not have any effective
inductive action 'npon one another they are wound relatively to one another as set
forth below.
We commence by winding either one of the sets of coils, say set B. Referring
to Figure 2, we wind B, and B, connecting them in series. Coits B and B
are then wound in the opposite direction.and connected either in series or parallel
with Band B, in Figure 2 they are shown in series:
We may of course for practical purposes wind all these coils in the same
direction and reverse the connections at E Figure 2, which will have the same
.effect.
;
We then wind coils A on the top of B, commencing A, on the toptof B, and
winding round the ring in the same manner as for circuit B, either reversing the
direction of winding after winding A, and A, or else, if the winding be all in the
same direction, reversing the connections at F.
1
It will be seen that coils B will produce a field across from pole Gto H, Figure 2,
and that the coils A will produce a field of equal density across I, J, but since
these coils have different lags, these fields will not be set up at the same instant,
but will follow one another the result boing that a rotary field is set up capable
of rotating a suitable armature or roter placed in the centre of the ring. The
field makes one rotation for every alternation of the impressed E.M.F.
Figure 3 is a simplified diagram of the winding shown in Figure 2 and
shows more clearly the way in which the mutual induction of the coils is
avoided.
Taking half the ring Figure 3, i.e. from pole J through pole G to pole 1:
including the coils A, A, and B, B, it will be seen that the two coils Anand A,
which are wound in the same direction, enclose two coils B, and B3, which aro
wound in opposite directions to one another. Therefore any current flowing
through the two portions of A; A and A, would produce equal and opposite
currents in the two portions of B; B, and B, over which they are wound.
Similarly any current passing through the section B, B, will flow in equal and
opposite directions with respect to A, A, and its inductive effect will therefore
beil; this will be seen to hold good for any section..
Figure 4.shews another way of placing these coils which is also effective.
When using four poles and two phases the field makes one rotation for each:
alternation of the current as shewn above. When we build a machine to run at:
a slower speed we increase the number of poles to some higher multiple of four,

page_text: for instance in an eight pole two phase machine the field will only, make one completo
rotation in every two alternations..
We wind the coils on the pole pieces as in Figure 53(or if overwound;as shown
in Figure 6.
The coils A and B, in. the case of an, eight pole overwound field, are divided
into eight parts, each pair being reversed as per Figure 6, the A coils are
reversed, at the points O, F and M. (marked with a. cross), and the B: coils at K,
E and L. (also marked with a cross).
Figure 7 shews another method of arranging the field.
The field is divided into two portions and wound separately, they are then placeit
side by side, having the poles set at 90° as shewn.. The dotted pole pieces belong
to one portion and those shewn in full lines to the other portion.
In the case of small machines where it is not advisable to make any change aftor
starting we run the machine with a, continuous rotatory field, in other cases w
employ the rotatory field only for starting the motoriand after starting we alter the
connections in such manner that the fold becomes single phase and the motor runs.
synchronously.,
To avoid excessive current in starting these machines, when we employ the
rotatory field for starting we adopt the following arrangements shewn diagram--
matically in Figures 8 and 9.
The coils A and B are wound as already described and so that B when in action
alone will give the required magnetic flux. If now without precaution wo. were.to.
connect the two, coils in parallel for starting the motor the iron would be considerably
over-saturated and a large amount of current would flow owing to the drop in
permeability of the core due to saturation, and other injurious effects, would ba
produced. Therefore when these coils are connected in parallel for starting we
connect in series with them a resistance or preferably a choking coil P to reduce.
the current sufficiently to produce only a sufficient magnetic flux. When tho
motor bas started and is running at speed by means of a, suitable-switch, we switch
out the coil-A and the resistance. P, and place the coil B₁ directly across. the mains.
as shewn by, Figure 9.
Figures 10 and 11 shew another and better method; the coils A and B are
wound as usual but so that both are required to be in use to give the required flux..
After putting on the required number of turns for coil A we bring out a connection
and, then continue to wind on, turns until we have an equal number to coil B, these
extra turns are shewn at b, Figures 10, 11, so that A+ b = B. Also in series
with the first portion of coil A, we connect the extra resistance C.
For starting, the connections are as, seen, in Figure .10 and a rotatory field is.
obtained. The motor is then of the, non-synchronous, type and will start freely.,
When the proper speed, is attained, we switch out the extra resistance C and place
coils A+ in parallel with B giving; a single, phase field of the same strength
as before.
As the rotating part or armature of the motor we use an armature or roter, built.
up of iron,discs having coils wound either on poles or in sluts, nain Figure 14 or in
holes in the discs, and we connect all these coils together in parallel as shewntin
Figure 14,, and short,circuit them upon one another.
When one turn, is sufficient for each coil we construct them of single copper wires.
or rods placed through holes or in sluts in, the iron and all joined at each end by n
stout copper ring; this ring should have a cross section, considerably in excess of!
that of the individual copper rods...
The whole of these coils and connections should be well insulated from the iron,
with asbestos paper or such other insulation as will not be injured by a moderate.
rise in temperature and for the same reason we prefer to rivet the copper rods into
the connecting ring in place of soldering them.
When building a motor of the type shown in Figure 7, we sometimes find it-
convenient to place the two sets of poles in the same plane, instead of setting them
at 90° as shewn. When this is the case we divide the roter or armature into two

page_text: parts, Figure 15, and set one of these parts at an angle to the other, as shewn, so
that the poles on the armature induced by one half of the field magnet do not lie in
a line with. the direction of the subsequent field set up by the other half of the
field inagnet.
We may set these two portions of the roter at any convenient angle to one
another.
In this figure are the two parts of the armature each built up as usual of thin
iron discs. kk are copper rode passed, with suitable insulation, through holes in
the parts and bent at an angle in passing from one to the other; such as best to
suit the positions of the poles of the field magnet. are copper rings conpling
the rodsk k. m-is the axis of the motor.
We also use rotatory fields in the construction of transformers and by means of
these transformers we transform the primary current into two or more secondary
currents differing from one another in phase. We can also so construct such
transformers that the period of the secondary current is changed thus.
Figure 12 shews the construction of a transformer from the secondary 'circuit of
which two phase currents are obtained. The field magnet portion producing
a rotatory field is wound in the same manner as the field magnet for a motor shewn
in Figure 4 but since we do not require the central portion in which induced
currents are set up to rotate we form it all of a piece with the magnet core, and
build our transformer of stampings or discs as shewn in Figure 12. We wind our
secondary coils on the central portion, which is analogous to the 'armature or
rotating portion of the motor. The secondary coils are shewn at 0 to O' and
P to P Figure 12. When a rotatory field is set up in the central portion of our
field magnet currents of different phase or two phase currents are induced in the
circuits PP and 00. Since the field makes one revolution in every complete
alternation of the primary current the secondary currents are of the same period as
the primary currents. It will be seen that the secondary circuit practically consists
of a drum wound armature, fixed in the centre of a rotatory field.
Figure 13 shews the construction of a transformer in which secondary currents
are produced differing not only in phase but also in period, from the primary
current..
i
The field magnet or inducing portion of this transformer is wound in the same
way as the motor field magnet shewn in Figure 5 and there is also a central portion
of the magnetic circuit upon which to wind the secondary coil as in Figure 12 with
the exception that a single hole is left in the centre through which to wind
the secondary. In this case the secondary is shewn wound in the manner 'known'
as a "ring" winding and the secondary currents are drawn from four equidistant
points, shown at 001 and P P' in the centre.
Since the field makes one revolution for every two alternations of the primary
current the rate of alternation of the secondary current is half that of the
primary.
'
The secondary of this transformer may be drum wound as shewn in Figure 12
or the transformer shewn in Figure 12 may have its secondary ring wound.
If three-secondary currents differing in phase are required-connection is made
at three equidistant points in the secondary of a transformer built as shewn in
Figure 13, or in a transformer as in Figure 12 with the secondary ring wound.
In the like manner any number of secondary currents may be obtained, differing
from one another in phase.
We will now describe our method of ascertaining the proportions and dimensions
of two coils upon the same or similar cores producing magnetic fields of equal
strength.
From the results of our investigations we have discovered that when a set of
coils are wound upon the same, or similar cores, to have equal ampère turns at the
same impressed volts, then :-
(1.) The turns in the several coils are equal to the sine of the angle through
which the coil lags multiplied by a constant; thus, if Tthe number of turns on

page_text: :
a f
"i
:
In order to know with what size wire to wind this coil we calculate the current;
74....
=
1000
184-1 x sin 40°
8:415
which is equal to the ampère turns divided by a sin 0 -
ampères.
We wind the coil with suitable wire to carry this current and adjust the
resistance by placing in series with it a suitably proportioned non-inductive
resistance.
SECOND METHOD:""
"
In the case of motor, or some similar machine where neither of the coils are
known we proceed as follows
1
Having obtained by the usual methods the number of ampère turns required to
magnetise our field magnet, to the required density, we calculate the number of
B

page_text: ampere turns required by each of the ebils such that, their combined füx is
suitable: suppose the ampère turns required to produce each of the fields that are
to be combined to form the rotating field to be 256.
We wind on our field magnet a trial coil of a few turns of thick wire, say
20tr are used, and we connect in, series with these 20 turns, a resistance or
choking coil which can he used to vary the current flowing through the coil!
We then arrange as in Diagram Xant cause an alternating current to flow
through the coil at the frequency for which the field magnet is to be wound and by
means of the resistance R we'adjust this current to 12:8' ampères, the ampère turns
of the coil are then 12.8 x 20256, we then carefully measure the volts across
the coil on the volt meter eny V29 and we measure the resistance through the
coil, say '0662 ohms.
R

page_text: motive force operating in two windings so arranged that the turns in one winding
are fewer than in the other, whilst the resistance of the circuit with fewer turns is
greater than the resistance of the circuit with many turns.
2. A field magnet yielding a rotatory field produced by an alternating electro-
motive force operating in two windings having like ampère turns and dissimilar
current phases.
3. A field magnet yielding a rotatory field produced by an alternating electro-
motive force operating in two windings having like magnetizing effects and
dissimilar current phases.
4. A field magnet yielding a rotatory field and consisting of windings arranged
upon a core one over the other, the alternate sections of the core being wound
respectively with both the windings in the same direction and with the windings in
opposite directions so as to avoid the inductive effect of coil upon coil.
5. A field magnet yielding a rotating field and consisting of windings arranged
upon a core and producing a series of equal poles, in number and arrangement such
that two or more cycles of the alternating electro motive force are occupied in
producing one rotation of the magnetic field.
6. Field magnets for the production of rotatory fields substantially as described
and illustrated by the annexed drawings.
7. Apparatus for producing the magnetic field of an electro-motor and consisting
of a field magnet having windings lagging from one another in phase, a switch, and
an inductive or other resistance; the whole so arranged that the switch can either
connect the windings in parallel and the resistance in series to obtain a rotatory
field or for the non-rotating field can put all but one of the windings out of
circuit.
8. Apparatus for producing the magnetic field of an electro-motor and consisting
of a field inagnet with two windings lagging one from another in phase, a switch.
and an additional magnetising winding; the whole so arranged that the switch can
either couneet in parallel the two first mentioned windings to obtain a rotatory
field or for the non-rotatory field can switch in also the additional winding thus
altering the conditions so as to obliterate the difference of phase between the
windings.
9. A motor having a field magnet with poles lagging the one behind the other in
phase and an armature in two parts provided with coppers, coils or poles which are
coupled obliquely to adapt the armature to the positions of the poles of the field
magnet.
10. A transformer in which a rotatory magnetic field produces current in a
secondary winding or windings.
11. A transformer in which by a single alternating electro motive force a
rotatory magnetic field is produced which in turn is caused to induce in secondary
circuits, currents differing from one another in phase.
12. A transformer in which by a single primary alternating electro motive force,.
a rotatory magnetic field is produced, which in turn is caused to induce in secondary
circuits, alternating currents differing in frequency from the primary alternating
electro-motive force.
13. A transformer in which a single alternating electro motive force operating in.
two primary windings having like ampère turns or magnetising effects and
dissimilar current phases produces a rotatory magnetic field which in turn induces.
in secondary windings currents differing in phase.
Dated this 8th day of August 1895.
CHARLES CONNOR.
W. LANGDON-DAVIES..