Improvements in or relating to Developing Displaced Magnetic Phases and Producing Rotary Magnetic Fields.
Year: 1895

page_text: Date of Application, 26th Sept., 1895-Accepted, 16th Nov., 1895
COMPLETE SPECIFICATION.
Improvements in or relating to Developing Displaced Magnetic
Phases and Producing Rotary Magnetic Fields.
A communication by CHARLES SCHENCK BRADLEY, of Avon, in the County of
Livingston and State of New York, United States of America, Electrical
Engineer.
1, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 6 Lord Street, Liverpool and 6 Bank Street,
Manchester, both in the County of Lancaster, 118 New Street, Birmingham
in the County of Warwick and 31 High Holborn in the County of Middlesex,
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 :-
The invention is especially designed to develop rotary magnetic fields from a single
phase alternating current with a view to transmission of power efficiently over a
single pair of conducting wires or mains. Rotary magnetic fields are now commonly
developed by the employment of two or more alternating currents having proper
phase differences; motors may be efficiently operated by such systems, and such
motors are not only self-starting but increase in torque with increase of load. Such
systems, however, for efficient operation require three or more line wires, for the
reason that no means have been at hand for efficiently developing a rotary magnetic
field by a single alternating current.
In carrying out this invention two harmonic magnetomotive. forces, differing by
a quarter period in phase are employed. These are obtained by the use of two
coils, one simple and the other compound, which may be wound either on the motor
or adjacent thereto and which are fed in series by the same alternating current.
If the coils are on the motor they are wound directly upon the magnetic core
which is the better arrangement; if adjacent thereto, they form the primaries of
two transformers, the secondaries being used in the motor windings. The compound
coil is wound in a peculiar manner. Two wires are preferably wound together on
an iron core, the last end of one being joined to the first end of the other so that
should a current be sent through them from end to end, both would co-operate to
magnetize the core in one direction, but if a current is sent in via the connecting
wire, the current splitting into two equal parts and passing out by the ends or
vice versa a differential effect is produced and no magnetism results. In this
invention, in series with one wire of the compound coil is placed a condenser or
other phase-advancing device, and when the inductance of the other wire within
the compound coil is not sufficient inductance is placed external thereto; this,
however, is not generally necessary as we have a condition of resonance
approaching it, so that by adjusting the condenser to the proper capacity we obtain
the desired result. Thus when the two branches of the divided circuit are properly
proportioned as to capacity and inductance, there is developed in the compound
coil a magnetomotive force resulting from the current or currents flowing therein
differing from the magnetomotive force of the simple coil by a quarter-period
displacement. It is evident that if the two coil systems be properly spaced upon a
core, a rotary magnetic field may be developed and utilized with an armature
provided with a closed coil to form an efficient single phase alternating current
motor
or

page_text: This invention therefore comprises a mode of displacing phases of magnetomotive
forces by using a compound coil of the character referred to, either with or without
the assistance of a simple coil; the invention also comprises the proper relation of
such coils on an iron core to develop a rotary magnetic field, and other features
which will be more particularly hereinafter set forth.
Referring to the accompanying drawings, which form part of this description,
Figure 1 is a diagram showing a compound coil in connection with a capacity and
inductance arranged so as to make the inagnetomotive force of the compound coil
differ in phase ninety degrees from that in the simple coil in the supply circuit;
Figure 2 is a diagram of a transformer in which a rotary magnetic field is
developed from a simple alternating current by means of two magnetomotive forces
differing in phase by a quarter period obtained in two coils, one simple and the
other compound;
Figure 3 is a diagram of a motor operative from a simple alternating circuit; and
Figures 4 and 5 are modified forms of motor.
In Figure 1, G represents a source of alternating current, (a capacity, and I an
inductance employed in parallel relation to the circuit, the two leading through a
compound coil D surrounding an iron core and then passing back to the generator.
It will be seen that the two branches are in differential relation in the compound
coil. In this organization, current arriving at the compound coil will be divided
into two components, one of which, that through the capacity, will lead the supply
current ninety degrees in phase, and the other, through the inductance, will lag
behind the supply current by ninety degrees in phase, provided suitable adjustment
of the capacity and inductance be made; the combined effect of these two
components in the compound coil will be that its magnetomotive force will differ
by a quarter-period in phase from any coil in the supply circuit in series with this
combination; for since one component leads ninety degrees and one component lags
ninety degrees, they will be one hundred and eighty degrees apart or in series
relation with respect to each other and the two windings of the compound coil, and
the phase of magnetomotive force of the coil as stated above will be ninety degrees
behind the magnetomotive force of the simple coil. If through change of load a
decrease of lag should occur in the inductance brauch a similar decrease of lead
will occur in the capacity branch; now if the lag should decrease to eighty degrees,
the lead would also decrease to about eighty degrees, but with respect to the
compound coil this lead of eighty degrees acts the same as one hundred degrees lag,
due to the manner in which the connections are made; hence the resultant magneto-
motive force will still lag ninety degrees as before, for the resultant of two
components, one of eighty and the other of one hundred degrees lag is ninety
degrees lag; furthermore the mutual induction of the two windings of the compound
coil will tend to prevent any departure from the one hundred and eighty degrees
phase relation between the currents in the two branches. This compound coil may
be used either as the primary of a transformer or as one set of coils of a rotary
field motor.
In the lower part of Figure 1, A' D' represent secondary circuits taken from
cores A and D respectively, and since the magnetomotive forces in the cores are
ninety degrees apart, the secondary currents will differ by a quarter period
in phase.
In Figure 2 is exemplified a transformer in which a rotary field is developed by
an application of the principles just set forth. M M' represent two supply wires
fed by a source of simple alternating current. One of these wires leads to
coils A A' on the transformer core. The circuit after leaving the winding A A¹
divides one branch passing through the condenser C, and the other branch through
a reaction coil I, the first branch leading through branches B B of the compoun
coil on the transformer, the second branch leading through a coil C C in the same
inductive relation to the transformer core as the coils B B' and differentially
connected with respect to the latter. The terminals of these two branches connect
with the main line. The compound coil is placed ninety degrees distant on the

page_text: core from the coils A A¹. The current, as we have seen, flowing over the local
circuit, CIHF KL and compound coil forming the coil system B B, C C will
develop a magnetomotive force ninety degrees from the magnetomotive force in
the coil system A A¹, and thus a rotary field will be produced in the core of the
transformer in a manner well understood. Upon the core may be wound secondary
circuits S, S¹, S*, S³, from which induced alternating currents of the required
tension and phase displacement may be derived. These may be employed for any
desired work. Evidently if an iron armature provided with a closed circuit be
mounted within the core, a motor will be produced. Such an organization is shown
in Figure 3, where the laminated armature O is provided with copper bars P set in
peripheral grooves and electrically connected at the ends by conducting rings Q
in a manner well understood. Instead of employing an auxiliary inductance, such
as the reaction coil I, the motor or transformer winding may itself be employed as
the inductance, and produce a resultant wave of the desired displacement. Such
an organization is exemplified in the rotary field motor shown in Figure 4, where
the current leads from the main line or from a transformer, as indicated in dotted
lines, through the motor circuit A A', and thence by direct connection into the
motor circuit C C. In such an organization the inductance will be furnished by
the motor and its winding. The two parts of the compound coil being wound side
by side in intimate inductive relation to the core, have a strong mutual induction ;
auy tendency to a stronger current flow in one than in the other of the differential
coils will cause a mutual reaction which steadies the phase displacement of the
magnetomotive force in the core; moreover since there is a magnetomotive force
displacement in the core of the inductance I which is intermediate between the
magnetomotive force of the simple and compound coils respectively, in some
organizations the inductance or an equivalent thereof is placed on the core in an
intermediate position between the simple and compound coils, as shown in Figure 5.
The coil system A A' might be placed in parallel with the compound circuit, as
indicated in dotted lines in Figure 1. With this organization, however, in order to
produce a quarter period displacement between the magnetomotive force in the
coil A and the coil D, the capacity and inductance should be so combined as to
produce a magnetomotive force phase displacement in coil D of more than ninety
degrees to compensate for the lag in coil A.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed as communicated to me
by my foreign correspondent 1 declare that what I claim is:
1. Means for producing a definite displacement of magnetomotive force phase
displacement in a magnetic core, comprising a compound coil of the character
described, in combination with a phase advancing device, such as a condenser.
2. The organization referred to in Claim 1 in combination with auxiliary
inductance in one branch of the compound coil.
3. Means for producing a definite displacement of the kind referred to, comprising
a simple and compound coil in series relation.
4. Simple and compound coils of the character described, combined with a
condenser and inductance and suitably wound on an iron core to produce a rotary
magnetic field.
Dated thie 25th day of September A.D. 1895.
WM. P. THOMPSON & Co.,
Agents.