Improvements in or relating to Converting Electrical Energy into Mechanical Motion.
Year: 1898

page_text: Date of Application, 21st Nov., 1898-Accepted, 28th Jan., 1899.
Improvements in or relating to Converting Electrical Energy into
Mechanical Motion.
A communication by CHARLES SCHENCK BRADLEY, of Avon, in the County of
Livingston, and State of New York, United States of America, Electrical
Engineer.
I, 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 322, 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:-
This invention relates to transmission of power by alternating currents, the
object being to transmit energy by means of single phase alternating currents and
economically utilize it for the operation of electric motors. The invention is
especially applicable to railroad service where the motor is connected with the
supply conductors by means of a traveling contact or contacts. At the point where
the electrical energy is to be converted into mechanical motion an alternating
current motor is provided, one element of which is charged with single phase
currents from the supply conductors, and in the other element a rotary magnetic
field is created, the magnetizing current of which is supplied through a phasing
transformer which converts the single phase line currents into polyphase currents.
A polyphase induction motor-generator is interposed between the phasing trans-
former and the rotary field winding of the principal motor, the motor-generator
having a rotary magnetic field set up in one element by the phasing transformer
and having its secondary circuit connected to charge the rotary magnetic field of
the principal motor. The flow of current in the circuit supplied by the armature
of the motor-generator including the polyphase winding of the motor is increased
by rendering it consonous or approximately resonant by the introduction of con-
densers. The generator is provided with a retarding device for varying its load
and the rate of alternation of the magnetizing circuit of the motor.
In the accompanying drawings is shown diagrammatically a system embodying
these improvements :-
A is the generator of single phase alternating currents, and 1, 2 a pair of supply
wires connected therewith. B, 1 represent a pair of trolleys constituting a
movable connection with the supply wires and leading to a travelling vehicle con-
taining the apparatus illustrated in the diagram. It will be understood that
instead of the trolley connection, a fixed connection may be made for operating
a stationary motor, and that if desired transformers may be interposed to
reduce the tension of the current on the trolley wires, thus admitting if desired
of a grounded circuit and a single trolley connection with the vehicle. The
trolleys lead to a phasing transformer by conductors 3, 4; this phasing trans-

page_text: .
former is a device by which a single phase current is transformed into polyphase
currents. The device is diagrammatically shown in the drawing. 5, 5" represent,
respectively, the simple and compound coils in which a difference in phase of
90 degrees or thereabout is produced by connecting the terminal of the simple
coil with the middle point of the compound coil, and leading one terminal of the
latter directly and the other terminal through a suitable condenser to the trolley.
By suitably combining the coils in inductive relation to the simple and compound
coils and inverting the phases by reversing the "coil connections, when necessary,
any desired phase displacement may be produced in the secondary circuits of the
transformer; for example, the coils 6, 6, inductively related, respectively to the
simple and compound coils, may be combined in suitable proportions to shift the
phase of resulting current 120 degrees from coil 7 in inductive relation only
to the simple coil; for twice as many turns of a coil displaced 90 degrees would
bring the resultant phase closer to that phase. Similarly, coils 8 and 8. may be
combined, one being reversed and thereby shifting its phase 180 degrees. Let us
suppose that coil 6 is provided with three turns and coil ( with six turns; the
phase of resultant current in the circuit including the two will
be closer to that of the compound coil
the phase of current
5";
in coil 10 of the rotary field winding of the generator 6 will there-
fore be two thirds of 90 degrees or 60 degrees from coil 9, but the phases of
magnetomotive force will be 120 degrees apart by reason of the reverse con-
nections of the two coil systems with relation to the coils 9 and 11 of the rotary
field winding. Similarly, coil 11 may be made 120 degrees in advance of coil 9.
Thus triphase currents 120 degrees apart are set up and a rotary magnetic field
will be established in C. The secondary element of C may be a closed coil winding
tapped at three symmetrical points, as shown, and connected with a rotary field
winding in the motor 1). In the several connecting wires are interposed devices
(shown as condensers) for varying the capacity inductance product of the circuit
which includes the two windings to produce electrical consonance, and thus varying
the flow of current. The other element of the motor I) is provided with two ring
contacts connecting with brushes E, E in parallel relation with the phasing
transformer to the leading-in wires 3, 4. The condensers F, F1, F2 are provided
with regulating switches to vary their adjustment. The induction generator C
is shown in sectional side elevation at C₁; "as seen here one end of the armature
shaft is provided with a conducting disk G entering the field of a direct charged
electromagnet H in the charging circuit of which is included a switch and variable
resistance to provide a variable load for the motor-generator C. Thus it will be
seen that the whole duty of the phasing transformer and motor-generator is to
develop triphase magnetizing currents to create a rotary field in motor 1). The
controlling switches for varying the adjustment of the condensers may be operated
simultaneously with the resistance which graduates the load of the motor-generator,
since a change of the resistance alters the load of said generator and changes its
speed, thus producing a different rate of alternation in the magnetizing current
supplied to the field magnet of D by the motor-generator and therefore requires
a different condenser capacity to produce electrical consonance.
In starting up the motor, the switch controlling the condensers is adjusted to a
position as indicated in the drawing, in which the smallest capacity is included in
the circuits which supply the rotary winding of the motor D. The switch which
graduates the retardation of the motor-generator C is adjusted for a position of
minimum resistance, thus the motor generator C will have a low speed and there
will be a maximum difference between the speed of its rotary field, established
by the phasing transformer and its revolving element; therefore currents of high
frequency will be supplied to the rotary field of the motor D, such frequency being
a small percentage lower than that of the supply current. In the revolving
element of the motor D) is established alternating poles of the same frequency as
the supply current; thus the rotary field poles being, slightly retarded in position
with relation to those of the revolving element of motor 1) will produce a torque

page_text: on said element, and as the revolving element rises in-speed its torque would
decrease if the speed of the rotary field remained the same; but if the speed of
said rotary field be reduced, such torque may be preserved. This result may be
effected by adjusting the condensers so as to increase the capacity and simul-
taneously decreasing the load of the motor-generator C by cutting in resistance
at the switch then the motor-generator assumes a higher speed, approximating
more closely to the speed of its rotary field which is synchronous with the supply
current, thereby furnishing to the consonous circuits a lower rate of alternation and
this graduation may be carried on to any extent desired within the speed limits
of the motor D which, of course, never can exceed the rate of alternation of the
supply circuit. While my correspondent has shown herein a lagging device for
controlling the speed of the motor-generator, such device is not in all cases.
absolutely necessary, as the condenser adjustment will, by its reaction and con-
sonous relations, control the speed of the motor-generator and thereby the speed
of the main motor D).
66
"
The motor generator may be quite small in size relatively to the motor, D, since
the consonous condition of the magnetizing circuits eliminate the opposing effect
of inductance and permit a comparatively small current to produce a large
magnetizing effect. The condition of the circuits hereindescribed as consonous
is such as arises when the capacity and inductance are such that the product of
the capacity in microfarads by the inductance in henries will equal the value
25,300 divided by the square of the rate of alternation of the circuit. It is analogous
to electrical resonance.
Having now particularly described and ascertained the nature of this invention
and in what manner the same is to be performed as communicated to me by my
foreign correspondent I declare that what I claim is:-
1. The method of converting electrical energy into mechanical motion consisting
in converting a single phase alternating current into polyphase currents, varying
the rate of said currents, charging a rotary magnetic field therewith, and charging
a co-operating independently movable motor element within said field with the
single phase currents.
2. The method of converting electrical energy into mechanical motion consist-
ing in converting a single phase alternating current into polyphase currents,
charging a rotary magnetic field therewith, neutralizing the inductance by a
suitable capacity, and charging the co-operating motor element within said field
with the single phase current.
3. An alternating current motor having on one element a single phase winding,
a rotary field winding on its co-operating element, a phasing transformer for
supplying the latter with polyphase currents from a single phase circuit, and
condensers in the polyphase circuits.
1
4. The method of varying the speed of an alternating current motor, consist-
ing in supplying one of its elements with a single phase alternating current,
supplying polyphase currents to create a rotary magnetic field in the co-operating
element, and varying the capacity inductance product of the polyphase circuits
and its rate of alternation.
5. An alternating current motor having a winding on one element for con-
nection with a single phase supply circuit, a polyphase winding on its co-operating
element, and an independent motor-generator supplying the latter with polyphase
currents.
6. An alternating current motor having on one element a winding for connection
with a single phase supply circuit, a polyphase winding on its co-operating element,
and a variable speed-generator for supplying the latter with polyphase currents
of variable rates.
7. The combination of an alternating current motor having on one of its
elements a rotary field winding, a phasing transformer for converting single phase
into polyphase currents, a motor-generator driven thereby, the armature of said

page_text: generator connecting with the rotary field winding at a plurality of points to set
up polyphase currents therein, a single phase winding on its co-operating element
supplied by a source of single phase currents, and means for varying the slip of
the generator armature.
Dated th 10th day of Novomhor AT) 1898