Improvements in Alternating Electric Current Motors.
Year: 1899

page_text: Date of Application, 8th Aug., 1899-Accepted, 27th Jan., 1900
COMPLETE SPECIFICATION,
Improvements in Alternating Electric Current Motors.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 83, Cannon Street,
in the City of London, Electrical Engineers, do hereby declare the nature of
this invention (which has been communicated to us from abroad by Charles P.
Steinmetz, residing at Schenectady, County of Schenectady, State of New York,
United States of America, Electrical Engineer,) and in what manner the same
is to be performed to be particularly described and ascertained in and by the
following statement:-
The present invention relates to certain improvements in the construction and
use of alternating current dynamo-electric machines, and also to the connection
of translating devices in tandem, and will be readily understood by reference
to the following description taken in connection with the accompanying draw-
ings, while its scope will be indicated in the appended claims.
Referring to the drawings, Figs. 1 and 2 illustrate in two sections at right
angles to one another, an alternating current motor designed to operate in
accordance with the present invention, and in which the armature is surrounded
longitudinally by the field coils, Fig. 2 is taken on the section, line, Fig. 1.
Figs. 3 and 4 illustrate in two similar sectional views another form of alter-
nating current motor. Fig. 4 is taken on the section line y-y of Fig. 3.
Fig. 5 is an end view of an alternating current motor, in which the arma-
ture is surrounded by a field magnet having multiple field poles provided with
a suitable arrangement of field coils.
Fig. 6 is a diagramatic view of the winding of the field coils of an alternat-
ing motor of the type herein described.
Fig. 7 is a diagramatic illustration of the invention as applied to a series of
motors connected in tandem.
Fig. 8 is an illustrative diagram which will be referred to later on in describ-
ing certain of the electrical actions involved in the invention.
The form of motors illustrated in Figs. 1 and 2 will be described first.
The armature A is in this machine the rotating element, and it may be widely
varied in character. As here shown, it comprises a cylindrical mass of lami-
nated magnetic metal mounted upon a suitable shaft a which may be provided
with a pulley or other means for transmitting its rotative power. The iron
forming the field magnets of this machine consists of two laminated masses B, B¹
separated from each other in a line parallel with the axes of the armature by
spaces, as indicated at b, b. These masses of magnetic metal are supported in
position by a suitable frame of non-magnetic material best seen in Fig. 2,
having end pieces c, c, connected by cross bolts c¹ and brackets affording bear-
ings for the armature shaft. Each of these masses of iron affords appropriate
concave cheek faces of poles d and d. the check faces d d¹ are separated
by a rectangular recess for the reception of the sides of substantially rectangular
field coils, and the same is true of the faces but the faces and
and and d are not only separated by similar recesses but also by the air
spaces ¹. Assuming now that these masses of metal have been magnetized

page_text: it will be seen that there are four co-operating magnetic circuits, to wit; the
first from d to d to the rear of the intervening recess and including an appro-
printe portion of the magnetic metal of the armature A. In this circuit there
is a minimum of magnetic resistance, the latter only resulting from the restricted
annular air spaces necessarily present between the cheek faces and the armature.
Second, in the magnetic circuit from to de, special magnetic resistance is
afforded by the air space b; third, from 2 to there is a minimum, resistance
as in the first circuit, and in the last or fourth circuit from to d there is the
same special resistance as in the second circuit, because of the air space ¹.
There is therefore in this machine a series of magnetic circuits, each one of
which is between two magnetic circuits which have either a greater or a lesser
magnetic resistance than it.
i
The magnetization of the field metal depends upon the currents supplied to
the coils, which as already stated, longitudinally surround the armature A, and
have their sides within the recesses between the cheek faces. These coils are
clearly indicated in Figs. 1 and 2, and they are divided into two groups at right
angles to each other. Although each group includes four coils considered as
separate structures, these are in substance, but two coils in each group, the
separation of each coil into two parts being merely for securing their symme-
trical distribution across the ends of the armature, and with relation to the
armature shaft. Two of these coils in each group are in circuit with a source
of alternating single-phase currents, which, for example, entering at C, pass
into one section of coils D and and then directly to the other section D', thence
around to a smaller coil 12 to the second section of this coil D³, and thence out
at C. The other two coils of each group are secondary coils in a closed circuit
having a resistance therein, as at R the connections being from R, through E
to the coil F, thence to coil F¹, thence around to coil 12, thence to coil F3 and
by E to resistance R.
2
The electrical organization of the field coils is diagrammatically illustrated
in Fig. 6, wherein the subdivision of the coils is not shown, but they are
illustrated as divided into two groups of two coils each and arranged at right
angles to one another. The alternating currents enter at C, traverse the large
primary coil D, and thence through the small primary coil D2 at right angles
to D, and thence out at C. The large secondary coil F is placed along side of
the small primary coil D2 and the small secondary coil F2 along side the large
primary coil D.
The two secondary coils are in a closed circuit with the resistance R, as
already described.
The current in coils D and F2 tend to magnetize the armature in an axis at
right-angles from that of the coils F and D2. Supplying alternating electric
currents to the primary coils D and D2 produces secondary currents in the
coils F and F2. The primary and secondary currents, as is well known are
dephased with respect to each other and the strength of the secondary currents
is regulated or determined by the resistance in the secondary circuit. For illus-
tration it will be assumed that the secondary currents in coils F, F2 will lag
behind the primary or main current in coils D, D2 by 150 degrees or, in other
words, five twelfths of a 360 degree period. The magnetism in the two mag-
netic circuits will not follow or conform either to the primary or secondary
currents, but it will follow or correspond with the resultant magneto-motive
forces of both currents, and therefore the maximum of magnetic phases will
occur between the maximum electric phases of the two currents. In other
words the resultant magnetism will reach its maximum, succeeding the maximum
action of the primary current, and preceding the maximum of the secondary
current.
By giving the primary coil of one magnetic circuit more ampere turns, and
hence more magnetizing power than the secondary coil acting on the same
magnetic circuit, and in the second circuit reversing the arrangement so that
the secondary coil has greater magnetizing power than the primary coil, the

page_text: magnetism in the first named circuit will more nearly coincide in phase with
the primary current, and in the second circuit the magnetism will more nearly
coincide in phase with the secondary current. Now on the assumption that the
secondary current lags 150 degrees or five-twelfths of a period behind the pri-
mary current, the number of ampere turns in the different primary and secondary
coils can be readily arranged so that the magnetic maximum in one circuit will
occur one fourth of a period after or before the maximum of magnetism in the.
other circuits. The two electro-motive forces induced in the secondary coils F
and will also differ correspondingly from each other in phase, that is, one-
fourth of a period, and the said combined electro-motive forces will yield a
secondary current which lags behind the primary current five-twelfths of.
a period, as before stated.
To further, illustrate, the large primary coil D in one magnetic circuit may
have 156 turns and the adjacent secondary coil 12 may have 90 turns, and
with the currents in both circuits of equal strength, (as may be ensured by a
resistance in the closed circuit), the maximum of the resultant magnetism will.
occur one-twelfth of a period or 30 degrees after the primary current, and four-
twelfths of a period of 120 degrees before the secondary current. Now, in the
other magnetic circuit the primary coil 12 having 30 turns, and the secondary
coil F 52 turns, the resultant magnetism in this circuit will occur four-twelfths
of a period of 120 degrees behind the primary current, and one-twelfth of a
period of 30 degrees before the secondary current, and therefore it will occur,
one-fourth of a period after the maximum of magnetism in the first circuit.
That is to say the magnetisms in the two circuits will differ by 90 degrees in
phase. With these two circuits at right-angles to each other and the primary
coil fed with alternating single-phase currents, the magnetic poles produced
will be shifted correspondingly and make one revolution or rotation of the line
of magnetization during each period of the alternating currents. By provid
ing in the first magnetic circuit three times as much magnetic resistance
as in the second magnetic circuit, the magnetism afforded by the two circuits
will be of equal strength, and the two electro-motive forces induced in the
secondary coils F and F being proportioned to each other as are the number
of their turns, 90 to 52 the secondary current lags behind the electromotive
forces in F by one-twelfth of a period of 30 degrees, and this last electromotive
force being 90 degrees behind the magnetism of D. The resulting magnetism
of DF lags behind the primary current 30 degrees and the secondary current
lags behind the primary current 150 degrees.
Reference is made to the diagram shown in Fig. 8 in order to further illus-
trate and explain the operation of the invention and to make more clear the
illustration discussed in the immediately preceding portions of this description.
Assuming that the current in the secondary circuit lags 150 degrees behind the
primary current, then the line OD in the diagram may represent the primary
current and the line OE the secondary current. The value of the secondary
current can be made equal to that of the primary by a suitable adjustment of
the resistance R in the secondary circuit. If the primary coil has 150 turns
in the first magnetic circuit, its magnetizing force can be thus represented in
ampere turns by the line OD. The secondary coil in the first magnetic circuit,
is assumed to have 90 turns, and thus its magnetizing force can be represented
in the diagram by the line 0 F2, OD and F being proportioned respectively
to 156 and 90. OD and OF2 combine by the parallelogram of forces to a
resultant magnetizing force OA, which under the conditions assumed will lag
30 degrees behind OD and is 120 degrees in advance of F. The magnetism
of the first magnetic circuit is produced by the resultant magnetizing force OA!
and thus can be represented by the line M in phase with OA (if we neglect
hysteresis and other secondary reactions).
In the second magnetic circuit the primary coil of 30 turns can be repre-
sented in magnetizing power by O2 and the secondary coil of 52 turns by OF,

page_text: OD and OF being again proportioned respectively to 30 and 52. 012 and OF
combine to a resultant magnetizing force of the second magnetizing circuit 0 A²,
which, with the numerical value assumed is one-third as much as the resultant
magnetizing force A¹ of the first magnetic circuit, and thus produces in the
second magnetic circuit a magnetism M², equal to that in the first named
circuit, since the magnetic resistance of the second magnetic circuit is one-third
of that of the first magnetic circuit.
The magnetism (M² of the second magnetic circuit is in phase with the
resultant magnetizing force 0 A2 of the second magnetic circuit, and thus with
the numerical values assumed, 120 degrees behind D2 and 30 degrees in advance
of OF. It is therefore apparent that OM2 is 90 degrees behind OM, or, in
other words that two equal magnetic fluxes, which may be represented by M¹
and OM², displaced from each other by 90 degrees difference of phase, will be
produced in two magnetic circuits under the conditions assumed.
By the combined magnetizing influence of the single-phase alternating cur-
rents fed to the motor, and the secondary currents induced as herein described,
and as represented in Figs. 1 and 2, an effective and highly satisfactory con-
version of electrical energy into mechanical motion is accomplished. In this
machine the number of ampere turns in the several coils are so proportioned,
and the variations of magnetic resistance are such, that the magnetism produced
by the coils in one circuit lags one-fourth of a period of 90 degrees behind the
magnetism produced by the coils in the other circuit, and both magnetisms
being of equal strength and perpendicular to each other, cause a rotation of the
two oppositely induced poles of the armature at regular and uniform speed.
As before stated, the armature may be widely varied so long as it can be
rotated by rotating magnetic poles in the field; it may be of sclid iron, or lami-
nated against eddy currents, or laminated lengthwise, so that eddy currents
flowing therein will be of such direction. relatively to the magnetizing force of
the field poles and of such difference in phase, as to cause electro-dynamic repul-
sion between the field, and the armature. So also may be the "H" or shuttle
core used, and this is specially when a motor is to be operated synchronously.
An armature with wire coils in closed circuits may also be used, or a laminated
iron core, coated with copper, or tin, for affording a special path for induced
currents.
So also may the exterior magnetic metal be widely varied in its form arrange-
ment and distribution, as for instance, as shown in Figs. 3 and 4, wherein the
rotative element A is the field magnet, and it is within a stationary iron ring B³
which may be termed the armature. The core of the magnet is composed of
laminated iron, so disposed as to afford four arms convex at their outer ends.
Two of these, diametrically opposite, as at e and e¹ have their convex faces
closely adjacent to the coincident inner surface of the iron ring B2, and the
other two faces e² and e³ are separated from said ring by wider spaces, thus
affording variable magnetic resistance. Surrounding each of the arms and &
there are large or primary coils D1 and around the arms e and e¹ there are
smaller primary coils D and all of which are connected in circuit with the
terminals C and C by which the alternating current is supplied by way of the
brush contacts f.
Surrounding the arms e and e¹ there are also large secondary coils F and F
and around the arms e² and there are other secondary coils F and F, these
all being in one closed circuit, and including the resistance R, the latter being
in connection by way of the brush contacts at f'.
In this machine as in the one first described one magnetic circuit is mag-
netized by the large primaries DD³ in conjunction with the small secondaries FG
and F and the other magnetic circuit by the large secondaries FF and the
small primaries D6 and D7 and their resultant operation is such that the magnet
is caused to rotate with greater efficiency; and with a speed corresponding with
the speed of the alternations of the electric current supplied thereto. If, on

page_text: the other hand, the magnet should be the stationary, and the ring B2 provided
with axial supports, then the line of magnetization would be rotated as before.
and the ring would become the rotative element.
In each of the two organizations thus far described the shifting phase is one
quarter of a period, or 90 degrees but the shifting of phase in other proportions
may be readily provided for, as for instance, as illustrated in Fig. 5. In this
organization the armature A2 may be as before described, but as shown, it has
an iron core, and a set of coils in closed circuit. The field metal B is an annular
mass of iron, with inwardly projecting cores, paired with each other on diame-
trical lines as at gg, hhand. These cores have concave faces which are
variably separated from the surface of the armature, the pair gg having the.
least spaces, the pair a little more, and the pair i still more, and the
pair the greatest space, thus securing variable magnetic resistance in the
magnetic circuits. The resistances of these different magnetic circuits are, as
before in Figs. 1 and 2, proportioned relatively to the magneto-motive forces
so that displaced magnetism of equal strength are maintained.
Each of these cores carries a primary and secondary coil, and as in the other
machines, said coils are variably proportioned. The cores ggl have the largest
primary coils, and the smallest secondary coils m, the cores h¹ have the next
smaller primary coils and the next larger secondary coils m¹; the cores i i¹
have still smaller primary coils 1, and their secondary coils m² are larger than
on the cores hh; the cores kk have the smallest primary coils 3, and the largest
secondary coils m³. The primaries are connected in series, and are fed by way.
of the terminals at C, and the secondaries are all in one closed circuit, contain-
ing the resistance R.
These four pairs of magnet poles, when excited by single-phase alternating
currents, afford shifting magnetic phases 45 degrees displaced in phase. The
magnetism of the circuits at hh reaches its maximum 45 degrees behind the
magnetisms at gg; and that at reaches its maximum 45 degrees behind h h¹
while at it reaches its maximum 45 degrees behind it, and therefore the
line of magnetic polarity is successfully shifted at uniform speed from yg¹ over.
to h, to and then to kk during each period of the alternating current.
In this machine, the magnetism in each magnetic circuit is induced and con-
trolled, varied or adjusted as in the previous machines, by the two electric,
currents, whose magnetizing powers are variably proportioned relatively to each
other, and the lag of the secondary current can be varied by variations of the
resistance in the closed circuit.
The electro-motive force developed in the closed magnetizing motor circuit
may furnish current to a second motor, or series of motors coupled in tandem,
as shown in Fig. 7, the required resistance being in the closed circuit of the
last motor of the series. In Fig. showing this tandem coupling of motors,
the first motor of the set is connected to a source of current. The secondary
circuit of this motor, instead of being closed through a resistance as in Fig. 6,
is connected to and supplies currents to a second motor K, and to the second
motor is connected in a similar manner a third motor L. The secondary circuit
of the last motor contains the resistance R.
In these machines shuttle armatures are indicated and these are specially
desirable for securing synchronous operation. In the motor I, the primary
coils D D¹ are arranged as already described, and so are the secondary coils FF,
the terminals of the latter connecting with the coils which serve as primaries
in the motor K, and so on through motor L, and other motors may also be
added in like manner.
Having now particularly described, and ascertained the nature of our said
invention (as communicated to us from abroad) and in what manner the same
5 is to be performed, we declare that what we claim is:-
:-
1 In an alternating current motor, the combination substantially as herein

page_text: before described, of a rotative element, and two groups of field exciting coils
at right-angles to each other, enclosing the rotative element and affording
separate magnetic circuits, each of said groups containing a primary coil and a
secondary coil, the primary coils being of unequal magnetizing power, connected
in series and adapted to be supplied with single phase alternating currents, and
the secondary coils, also of unequal magnetizing power, and in a closed circuit.
2 In an alternating current motor, the combination substantially as herein
before described, of a rotative armature, masses of magnetic metal surrounding
said armature, affording an appropriate set of check faces each included in two
magnetic circuits, and having between appropriate cheek faces open spaces for
affording greater magnetic resistance in certain of the circuits than in the next
adjacent magnetic circuit, and two groups of exciting coils at right angles to
each other, each group. containing a primary coil and a secondary coil, the
primary coils in both groups being connected in series, and the secondary coils
being connected in closed circuit.
3 The combination of two or more dynamo electric machines in which rota-
tion of the movable member is produced by the inductive action of primary
alternating currents, and secondary currents induced therefrom in a secondary
circuit, and means for coupling said machines in circuit tandem-wise with the
secondary circuit of one machine connected to the primary circuit of another
machine.
4-The combination of two or more electric translating devices which com-
prise a primary conductor connected to a source of alternating electric currents,
and a secondary conductor in which flow secondary currents induced by the
primary currents, and two or more magnetic circuits, each magnetic circuit
being in inductive relation to both the primary and secondary circuits, and con-
nections coupling such translating devices in tandem, the secondary of one of
such devices being connected to the primary of the next, as set forth.
5-The combination of a source of alternating current, an alternating current
motor having inducing and induced windings and receiving energy from "said
source, and a second alternating current motor fed with the current derived
from an induced winding on the first motor.
6 The method of producing mechanical power by alternating currents, which
consists in inducing in a series of magnetic circuits magnetic waves by the mag-
netizing action of the alternating currents, modifying the phase of each of the
magnetic waves by corrective magneto-motive forces so as to produce the phase
displacement desired, inducing by said waves current in a relatively rotatable
induced member, and reacting by the said current upon the magnetic waves to
cause rotation.
In an alternating current motor, the combination of a plurality of coils
carrying alternating currents and acting on different magnetic circuits, and
means for superposing upon each magnetic circuit a deplased magneto-motive
force of such character that the resultant magnetic fluxes form an approximately
correct rotary field.
SIn an electric motor, a plurality of magnetic circuits each having a plurality
of exciting coils, and means for supplying the exciting coils of each of said
circuits. with dephased currents, the coils being so proportioned that the fluxes
in the magnetic circuits bear to each other a phase relation different from the
phase relation of the exciting currents.
9-In an alternating current motor the combination of two coils set at an
angle to each other and carrying alternating currents, thereby giving rise to
alternating magneto-motive forces and means for generating additional magneto-
motive forces of such magnitude and phase as to cause the resultant magnetic
fluxes to differ in phase approximately ninety degrees.
10 In an alternating current electric motor, an inducing member provided
with a plurality of magnetic circuits having energizing coils carrying dephased
currents, the magnetic circuit being of different magnetic resistance.

page_text: 11-The method of producing a rotary magnetic field, which consists in setting
up two magneto-motive forces having a definite phase difference, one of which
is the resultant of two magneto-motive forces differing from each other by a
certain angle, and the other of which is the resultant of two other magneto-
motive forces differing from each other by the same angle but having a different
ratio to each other.
12 The method of producing torque between the two relatively rotatable
members of an alternating current dynamo electric machine which consists in
causing a plurality of phase-displaced electric currents to flow in circuits in
fixed relation to one member of the machine, producing two definitely phase-
displaced magneto-motive forces each by the joint action of a plurality of said
currents and submitting the other member of the machine to the influence of
said magneto-motive forces.
13 The method of producing torque between the two relatively rotatable
members of an alternating current dynamo-electric machine which consists in
causing a plurality of phase differing alternating currents to flow in circuits in
fixed relation to one member of the machine deriving from said currents a
plurality of phase-differing magneto-motive forces each of which is out of phase
with any one of said currents and submitting the other member of the machine
to the influence of said magneto-motive forces.
14 The method of producing a rotary magnetic field, which consists in setting
up in two different circuits two electric currents one of which is derived directly
from a source of energy, the other indirectly, and producing by the joint action
of said currents a plurality of single-phase magneto-motive forces out of phase
with each other, and each of which is out of phase with the current in any one
of said circuits.
15 The method of producing a rotary magnetic field which consists in setting
up in two different circuits two electric currents one of which is derived induc-
tively from the other, and producing by the joint action of said currents a
plurality of single-phase magneto-motive forces out of phase with each other,
and each of which is out of phase with the current in either of said circuits.
73
1000
THE BRITISH THOMSON-HOUSTON CO. LTD.
W. MARTINDALE,
A. R. MoxкS,
ALFRED CLEMENTS-
}
Directors.
Assistant Secretary.