Improvements in Alternating Current Motors.
Year: 1896

page_text: Improvements in Alternating Current Motors.
I, ALEXANDER HEYLAND of Darmstadt in the German Empire, do hereby declare
the nature of this Invention to be as follows:
All the different methods which have been devised for producing power for
the initial electro-motive force in one-phase alternating current
current motors
without resorting to the aid of current reversers or commutators are based upon
the principle of dividing the alternating current into two or more alternating
currents of different phase difference which are intended, by their joint operation
to generate a rotatory field, resembling those which are created by multiple phase-
motors.
The motors constructed on this principle comprise upon their exciting arma-
ture, two or more circuits connected with the alternating current supplied.
With a view to obtaining as extensive a phase difference as possible, all such
motors have the feature in common, that an increase of the phase difference is
in all cases effected by an increased self induction of the circuit under
consideration.
This operation is due to the fact that in a circuit which is independent and self
contained, phase difference must increase and decrease with the self induction.
But the exciting circuits are not independent circuits, in the motors in question.
These circuits, in accordance with the law of mutual induction, exercise an in-
ducing action upon the windings of the short-circuit armature, and the extent
of phase difference of the exciting currents is merely dependent upon the inducing
re-action of the short-circuit armature currents upon the exciting armature
circuits.
As regards the extent of the self induction of the exciting circuits, if these
effects of mutual induction be taken into account, its influence upon the phase
difference of the exciting currents is altogether insignificant and, for all practical
purposes, may be considered as non-existent.
Of all known arrangements therefore, at all events those attain the most
powerful effect in which the increase of the self induction is produced, not by an
increase of the number of the exciting windings or turns, but by the increase of the
shunt or in other words, by an increase of the magnetic leakage or by the inter-
position of a choking coil or the like.
Self induction in circuits, in addition to the feature above referred to, which,
alone, has hitherto been taken into consideration in all the various types of motors
that have been devised, viz: the property of retarding the phase of the alternating
current in relation to the electro-motive force, has still a further property, and
one that essentially differs from the peculiarity just mentioned, and this addi-
tional property which injuriously affects the operation of motors of the class

page_text: herein dealt with, may account for the unsatisfactory results hitherto attained
with all those different motors.
Every increase of self induction in the motor involves a reduction of the field
derived from the corresponding circuit. Where self induction is enhanced by an
increase in the number of windings, the field, in accordance with well known laws,
decreases in an inverse ratio to the square root of the self-induction; and where
such increase in the self-induction is owing to an increase in magnetic leakage,
or to the interposition of a choking coil the field becomes reduced to an extent
equivalent to the leaking lines of force, or (in the case of a choking coil) to tho
lines of force of such coil.
As has been shewn above, in motors of this.class, with short circuit windings
on the armature, it is by no means necessary, for the purpose of ensuring the
requisite phase difference to provide greater self-induction, than is that of the
circuit with a less phase difference. But the herein before mentioned second
property of self induction, owing to which the magnetic field in the motor obtained
from the corresponding circuit, rises or falls in an inverse ratio to the self
induction, has led me to the conclusions, upon, which the present invention
is based.
The leading idea of the invention may be expressed as follows:
The starting power of the motor is found by the product of current intensity
multiplied by field, taking the current intensity of the circuit with the lesser
phase difference and the component of the lagged field sections of the magnetic
field derived from the other circuit, with the greater phase difference.
The magnetic field of the first-mentioned circuit, being lagged, in accordance
with well known laws, to the extent of one fourth of a period, in relation to the
current, performs no work of any material amount.
Given, therefore, the proper phase difference, the course which it is advisable to
adopt in order to attain high starting moment is to increase as much as
the current and the number of windings in one circuit, and the field in the other
possible
circuit.
All the methods heretofore adopted have consisted in bringing about an in-
creased phase-difference in the second circuit by increasing self induction
yet every increase of self induction necessarily involves a reduction of the field
created by such circuit in the motor. It follows that, in order to secure a strong
magnetic field it is necessary to keep the self induction of the circuit with greater
phase difference low, in other words, such circuit should preferably consist of a
comparatively small number of windings.
In order to attain a greater phase-difference in such circuit, the mutual induction
on the windings of the short circuit armature, ought to be reduced; which is
preferably accomplished by diminishing the magnetic "concatenation" of the
said circuit with the windings of the short circuit armature.
It is here advisable to select a style of winding which has been found by
experience to give rise to the greatest magnetic leakage such as ring or spool
winding for example while for the other circuit "drum" winding, should
preferably be adopted.
It will, of course, be understood that other means may be employed in pro
ducing phase-difference, such as the insertion of an induction coil, or the like.
but in all cases the self induction of the entire circuit in question should be cou-
siderably less than that of the other circuit.
In the other circuit, for the smaller phase-difference it is well to reduce
magnetic leakage as far as practicable.
A substantially like result will be arrived at by starting from the following
premises based upon the same fundamental idea of the invention viz enhancing
the starting power by strengthening of the field of the circuit which shews the
greater phase-difference.
The strength of a field occuring in a circuit connected with an alternating
current is, according to welf known principles, approximately proportionate to

page_text: the electro-motive force and inversely proportionate to the number of windings.
In differently formed circuits is substituted, for the number of windings, the total
length of the so-called "active" wire connected in "series" i.e. of the wire
surrounded by the lines of force of the corresponding field in the motor.
To strengthen that field, therefore, the active length of wire of the circuit,
wherein the greater phase-difference occurs, should always be less than the
corresponding length of wire in the circuit exhibiting the smaller phase-difference.
Increased phase-difference may here be provided for, in the same way as in
the case instanced above. The last mentioned relation between the strength of
field, electro-motive force, and number of windings may, moreover, lead to the
attainment of the object in view by still another way. For inasmuch as the
strength of field increases proportionately to the electro-motive force, and in an
inverse ratio to the number of windings, the field might be rendered stronger,
also, by raising the electro-motive force in the circuit in which the phase-
difference is greater (say, by the introduction into the circuit, of a transformer or
condenser).
The last mentioned method may likewise be combined with the one above
referred to as will readily be understood.
Here, too, therefore, the principle which underlies the invention would be
embodied in an arrangement precisely the reverse of those hitherto knowa,
wherein the electro-motive force of one circuit is lowered while that of the other
circuit, frequently formed of thin highly resistant wire, is raised in order to
enable the resistance of such wire to be overcome.
One of the forms in which this invention may be carried out in practice is
represented in the accompanying diagram shewing by way of example a two-pole
arrangement.
The circuit a for small phase-difference here consists of a drum winding, mado
up of many turns which are distributed in grooves situated close to the inner
surface of the outer exciting armature I, and affording a favourable concaten-
ation or connection of the magnetic field, created by them, with the windings of
the short-circuit armature II. The circuits for the greater phase-difference here
consist of the spool winding formed of a less number of convolutions, all of
which are in this instance gathered together in one wide groove, so that the
magnetic concatenation with the winding of the short circuit armature is more
imperfect. The magnetic leakage of this circuit may be suitably increased by
closing up more or less the groove in the armature surface.
A convenient arrangement of the windings or coils is conceivable in many
different forms. The circuit b may be formed in a manner analogous to that in
which the circuit a is formed, and a self induction coil situated outside may be
inserted. This coil, however, should be so small, that the self induction of the
winding 6 plus that of the self induction coil should still be considerably less than
the self induction of the circuit a.
Finally the reduction of self induction may be ensured by raising the electro-
motive force of the coil b by the insertion of a transformer or condenser; and
conversely, the electro-motive force of the winding a may be reduced by means
of a transformer for the purpose of increasing self induction.
Various other modifications of the arrangement will also readily suggest
themselves.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.

page_text: Improvements in Alternating Current Motors.
I, ALEXANDER HEYLAND late of Darmstadt now of 57 Weserstrasse, Frankfort
on Main, both in the German Empire do hereby declare the nature of this Inven-
tion and in what manner the same is to be performed, to be particularly described
and ascertained in and by the following statement:-
All the different methods which have been devised for producing starting
power for the initial electromotive force in one phase alternating current motors
without resorting to the aid of current reversers or commutators are based upon
the principle of dividing the alternating current into two or more alternating
currents of different phase-difference which are intended by their joint operation
to generate a rotatory field, resembling those which are created by multiple phase-
motors.
The motors constructed on this principle comprise upon their exciting arma-
ture, two, or more, circuits connected with the alternating current supplied.
With a view to obtaining as extensive a phase difference as possible, all such
motors have the feature in common, that an increase of the phase difference is
in all cases effected by an increased self induction of the circuit under
consideration.
This operation is due to the fact that in a circuit which is independent and self
contained, phase difference must increase and decrease with the self induction.
But the exciting circuits are not independent circuits, in the motors in question.
These circuits, in accordance with the law of mutual induction, exercise an in-
ducing action upon the windings of the short circuit armature, and the extent
of phase difference of the exciting currents is merely dependent upon the inducing
re-action of the short circuit armature currents upon the exciting circuits.
As regards the extent of the self induction of the exciting circuits, if these
effects of mutual induction be taken into account, its influence upon the phase-
difference of the exciting currents is altogether insignificant and, for all practical
purposes, may be considered as non-existent.
Of all known arrangements, therefore, at all events those attain the most
powerful effect in which the increase of the self-induction is produced, not by an
increase of the number of the exciting windings or turns, but by the increase of the
magnetic shunt, or, in other words by an increase of the magnetic leakage or by
the interposition of a choking coil, or the like.
Self induction in circuits, in addition to the feature above referred to, which,
alone, has hitherto been taken into consideration in all the various types of motors
that have been devised, viz: the property of retarding the phase of the alternating
current in relation to the electromotive force, has still a further property, and
one that essentially differs from the peculiarity just mentioned, and this addi
tional property which injuriously affects the operation of motors of the class
herein dealt with, may account for the unsatisfactory results hitherto attained
with all those different types of motors.
Every increase of self induction in the motor involves a reduction of the ficid
derived from the corresponding circuit. Where self-induction is enhanced by an
increase in the number of windings, the field, in accordance with well-known laws,
decreases in an inverse ratio to the square root of the self-induction; and where
such increase in the self induction is owing to an increase in magnetic leakage,
or to the interposition of a choking coil, the field becomes reduced to an extent
equivalent to the leaking lines of force, of the choking coil.
As has been shewn above, in motors of this class, with short circuit windings

page_text: on the armature, it is by no means necessary for the purpose of ensuring the
requisite phase difference to provide greater self induction of the respective circuit
than is that of the circuit with a smaller phase difference.
But the herein before mentioned second property of self induction, owing to
which the magnetic field in the motor obtained from the corresponding circuit
rises or falls in an inverse ratio to the self induction has led me to the conclusions
upon which the present invention is based.
The leading idea of the invention may be expressed as follows:-
The starting power of the motor results from the product of intensity current
multiplied by field, that is to say, from the current intensity of the circuit with
small phase difference, and from the component of the lagged, field sections of the
magnetic field derived from the other circuit, with the greater phase difference.
The magnetic field of the first mentioned circuit being lagged in accordance
with well known laws to the extent of one fourth of a period in relation to the
current, performs no work of any material amount.
Given, therefore, the proper phase difference, the course which it is advisable to
adopt in order to attain high starting moment, is to increase as much as possible
the current and the number of windings in one circuit and the field in the other
circuit.
With regard to all known constructional arrangements the principal and funda-
mental idea is prevalent that a rotary field is to be generated in order to obtain
starting power. Each pulsation of the rotary field means loss, therefore all con-
structional arrangements are designed with a view to generating a rotary field
of constant intensity.
According, therefore, to these views, it would be a fundamental error if the field
of one or the other coil were made larger.
Contrary to this principle, my invention is based upon the fact that in order to
obtain starting power or momentum in alternating current motors, no rotary field but
solely an alternating field placed at right angles to the windings conveying the
working current proper (current of but a small phase difference) is required.
The starting power or momentum increases and decreases with the intensity
of such alternating field.
In all former devices this field of different phase could reach but a low degree
of intensity, owing to the high degree of self induction. The said field, according
to the then exclusively admitted rotary field theory could at most be equal to the
field of the working current, which latter was appropriately weakened by inserting
a resistance into the working current circuit.
On the contrary this invention leads to the principle of enlarging this field of
different phase as much as possible which in practice demonstrates that the said
field is at all events rendered' larger than the field of the working current.
This principle is new for the sole reason that it directly expresses an error
according to the existing rotary field theory, and because the starting power
becomes stronger in proportion as this alternating field of phase difference becomes
larger, that is to say, in proportion as the complete field of the motor which
results from the fields of both windings, assumes the character of a pure
alternating field.
All the methods heretofore adapted have consisted in bringing about an
increased phase difference in the second circuit by increasing the self induction,
yet every increase of self induction necessarily involves a reduction of the field
created by such circuit in the motor.
It follows that in order to secure a strong magnetic field it is necessary to keep
the self induction of the circuit with greater phase difference low, in other words
such circuit should preferably consist of a comparatively smaller number of
windings.
In order to attain a greater phase difference in such circuit the mutual induction
on the windings of the short circuit armature must be reduced, which is prefer-

page_text: concatenation of the said
ably accomplished by diminishing the magnetic
circuit with the windings of the short circuit armature.
The exciting coil and short circuit coil behave relatively to each other like the
primary and secondary coils of a transformer.
It is known however that in a transformer, the difference of phase in the
primary circuit decreases as soon as the secondary circuit is closed. The effect
from self induction of the primary coil; namely the causing of a phase difference,
is more or less suspended by the mutual induction of the secondary current upon
the primary coil.
This mutual induction is most perfect when all lines of force of the primary
coil traverse the secondary coil.
The phase difference however rapidly again increases if the magnetic "con-
catenation" between the primary and the secondary coils be imperfect, or in
other words if lines of force occur, which solely traverse the secondary circuit
that is to say, so called lines of leakage.
It is here advisable to select a style of winding which has been found by
experience to give rise to the greatest magnetic leakage such as ring or "spool
winding for example while for the other circuit "drum" winding should
preferably be adopted.
It will, of course, be understood that other means may be employed in pro-
ducing phase-difference, such as the insertion of an induction coil, or the like:
but in all cases the self induction of the entire circuit in question should be
considerably less than that of the other circuit.
In the other circuit, for the smaller phase-difference it is well to reduca
magnetic leakage as far as practicable.
A substantially like result will be arrived at by starting from the following
premises based upon the same fundamental idea of the invention viz. enhancing
the starting power by strengthening of the field of the circuit which shews the
greater phase-difference.
The strength of a field occurring in a circuit connected with an alternating
current is, according to well known principles, approximately proportionate to
the electro motive force and inversely proportionate to the number of windings
that is to say proportional to the electro motive force for each single winding. In
differently formed circuits is substituted for the number of windings, the total
length of the so called "active" wire connected in "series" i.e. of the wire
surrounded by the lines of force of the corresponding field in the motor.
To strengthen that field, therefore, the active length of wire of the circuit,
wherein the greater phase-difference occurs, should always be less than the
corresponding length of wire in the circuit exhibiting the smaller phase-difference.
Increased phase-difference may here be provided for in the same way as in
the case herein before instanced.
The last mentioned relation between the strength of field, electro motive force,
and number of windings, may, moreover, lead to the attainment of the object in
view in still another way. For inasmuch as the strength of field increases pro-
portionately to the electro motive force, and in an inverse ratio to the number of
windings, the field might be rendered stronger, also by raising the electro-motive
force in the circuit in which the phase difference is greater, (say by the intro-
duction into the circuit of a transformer or condenser).
The last mentioned method inay likewise be combined with the one above
referred to as will readily be understood.
Here, too, therefore, the principle which, underlies the invention would be
embodied in, and expressed by an arrangement precisely the reverse of those
hitherto known, wherein the electro-motive force of one circuit is lowered while
that of the other circuit, frequently formed of thin highly resistant wire, is raised
in order to enable the resistance of such wire to be overcome.
(ne of the forms in which my invention may be carried out in practice, is

page_text: represented in the diagram accompanying my Provisional Specification shewing
by way of example, a two-pole arrangement.
The circuit a for small phase difference here consists of a drum winding made
up of many turns which are distributed in grooves situated close to the inner
surface of the outer exciting armaturo Iand affording a favourable "concatena-
tion or connection of the magnetic field, created by, them, with the windings of
the short circuit armature II.
The circuit for the greater phase-difference here, consists of the spool winding b
formed of a less number of convolutions, all of which are in this instance gathered
together in one wide groove so that the magnetic "concatenation" with the
winding of the short circuit armature is more imperfect. The magnetic leakage
of this circuit may be suitably increased by closing up more or less the grooves
in the armature surface.
A convenient arrangement of the windings or coils is conceivable in many
different forms. The circuit b may be formed in a manner analogous to that in
which the circuit a is formed, and a self-induction coil situated outside may be
inserted. This coil, however, should be so small, that the self induction of the
winding plus that of the self induction coil should still be considerably less than
the self induction of the circuit a.
Finally the reduction of self induction may be ensured by raising the electro
motive force of the coil b by the insertion of a transformer or condenser; and
conversely, the electro-motive force of the winding a may be reduced by means
of a transformer for the purpose of increasing self-induction.
Various other modifications of the arrangement will also readily suggest
themselves.
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. An alternating current motor with circuits of unequal phase difference of
the current in relation to the electro motive force supplied; the main feature
of such machine being, that, for the purpose of attaining a high degree of starting
power, the magnetic field of the circuit in which occurs the greater phase
difference is made stronger than the magnetic field of the circuit wherein the
phase difference is less.
2. An alternating current motor constructed in accordance with the preceding
claiming clause wherein increased strength is imparted to the magnetic field of
the circuit, in which the phase difference is comparatively greater, by reducing
self induction in that circuit, while diminishing, at the same time, the mutual
induction between it and the windings or convolutions of the short-circuit arma-
ture; so that the self induction of the said circuit becomes less than that of the
circuit through which passes the less lagged current.
3. An alternating current motor such as is claimed in the first claiming clause,
wherein the magnetic field is strengthened in the circuit in which the phase
difference is comparatively greater by so reducing the total length of the active
wire of the said circuit, while diminishing at the same time, the mutual induction
between it and the windings of the short-circuit armature that such total length
becomes less than the total length of the active wire of the circuit through which
the less lagged current passes.
4. An alternating current motor as claimed in the first claiming clause wherein
the increase of the magnetic field in the circuit wherein the phase difference is
comparatively greater, is ensured by rendering the electro-motive force imparted
to such circuit higher than that of the circuit exhibiting less phase-difference.
5. A modification of the alternating current motor claimed by the
first claiming clause wherein for the purpose of obtaining an unfavour-
able magnetic "concatenation" with the windings of the short circuit
armature, the windings for conveying the current of comparatively great phase.

page_text: difference are so arranged in the intermediate spaces (left free by the main coil
proper which latter is in the known manner distributed over a large number of
grooves) that the turns constituting the said windings for conveying the current
of comparative great phase difference are severally situated in one groove or hole
or in but comparatively few grooves or holes.
Dated this 26th day of August 1897.
JOHNSONS & WILLCOX,
47 Lincoln's Inn Fields, London, W.C., Agents.