Improvements in Dynamo Electric Machines, and Methods of Compounding the same.
Year: 1896

page_text: Date of Application, 7th July, 1896-Accepted, 8th Aug., 1896
COMPLETE SPECIFICATION.
Improvements in Dynamo Electric Machines, and Methods of
Compounding the same.
We, THE BRITISH THOMSON-HOUSTON COMPANY, LIMITED, of 38 Parlia-
ment Street, Westminster, in the County of London, Electrical Engineers, do
hereby declare the nature of this invention (which has been communicated to us
from abroad by Charles P. Steinmetz, Electrical Engineer, of Schenectady, in the
State of New York, United States of America) 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 dynamo electric machines, particularly to those
of the polyphase type of alternating apparatus, and also to novel ways of
compounding such apparatus. It is in part applicable also to other dynamo electric
machines, particularly to those of the single-phase type, but finds its greatest
usefulness in polyphase apparatus.
as it
The main objection to the use of the polyphase systems now well known in the
art, lies in the fact that the load must be distributed with substantial equality
upon the different branches of the system, in order to avoid "unbalancing,"
is called; that is, having different voltages in the different phases or branches.
In the ordinary construction of machines, however, since all the phases issue from
the same magnetic field, and thus have the same induced electro-motive force, at
unequal loads there would be different drops, and hence different terminal voltages
in the different phases. To overcome this difficulty, it is desirable to compound
the different phases independently, or otherwise independently regulate them to
compensate for the different terminal electro-motive forces. This it is possible to
accomplish by coupling two single-phase machines rigidly in quadrature for
poly phase apparatus, and in this case the phases may be compounded independently,
and the voltages regulated in any desired manner, and this whether the load be
distributed equally or not. It has been found that the most convenient way, in
which this may be accomplished is in an inductor dynamo of novel construction
forming a part of the present invention. In it are provided two separate
armatures, each armature baving its own field, and these armatures are, as in
other machines of this class, stationary; the magnetization being furnished by a
field coil also stationary; an inductor with suitable salient poles or projections
being provided, which sets up by its revolution the alternations in magnetic
fluxes necessary for the generation of current. The two sets of armature coils
are arranged for a two-phase machine in quadrature; and the two field coils
(which are independent, or substantially independent, as will be more fully
described hereafter), are provided with separate excitation and independent
regulation by which the phases may have their terminal electro-motive forces
adjusted in any desired way to compensate for inequalities of load.
Between
the two fields is provided a magnetic shunt, the particular utility and functions of
which will presently be more fully pointed out.
The machine thus described differs from the ordinary inductor dynamo in which
two sets of armature coils are provided with a revolving inductor and a single
field coil, inasmuch as in this well known arrangement the two phases, being
induced in the same field, have similar terminal electro-motive forces, and hence
differences of load will unbalance them and reduce the efficiency of the system.

page_text: As the armature coils are traversed by the same flux, it will not be possible to
regulate for the independent control of the phases.
Another form of dynamo which has been proposed is composed of two
independent inductor machines embodied in a single structure and provided with
a return circuit for the lines of force, which passes between the two field-magnet
coils, the two magnetic circuits being energized in opposite senses so that this
return circuit carries all of the lines of force in the two circuits, passing in the
same direction. This form of machine is however extremely heavy for its
out-put, and while the different phases, if the two armatures be coupled to
produce different phases, could be compounded independently, there is a reaction
of one phase upon the other which is objectionable, inasmuch as an increase
of load in one side, and a consequent stronger magnetization, backs down the
lines of force in the other magnetic circuit, and reduces the terminal voltage.
The machine constituting the present invention, however, differs from both of
these forms in that, instead of magnetizing the two circuita in opposite senses, the
yoke of the field magnet and armature cores and the inductor form a single
magnetic cirenit; between the field magnet coils, which are so wound as to
energize this circuit in the same sense, there is provided a magnetic shunt which
may be of small size; and this shunt forms a path for the lines of force in one
circuit which are in excess of those in the other; thus by the present 'invention,
where the phases are separately compounded, upon increase of load and current in
one side of the machine, there is but little reaction upon the other side, and such
magnetic action as does exist tends, as will hereafter be pointed out, to assist the
weaker side of the machine, rather than to cut down its electro-motive force.
While the present invention has been described as being embodied in an inductor
dynamo, it is manifest that in one aspect of it it might be embraced in machines
which have ordinary wound armatures revolving before field poles of ordinary
type, where such machines embrace separate fields substantially independent of
one another having separate means of excitation and independent regulating
arrangements whereby their compounding or variation under change of load is
accomplished. It is believed however that the particular type of machine which
has been illustrated and described herein has advantages over other constructions.
The accompanying drawings show the invention,
Figs. 1 and 2 being respectively a section and side elevation of an inductor
dynamo embodying the invention.
Fig. 3 is a detail of the arrangement of the armature coils in diagrammatic
perspective.
Fig. shows a diagram of the various circuits.
Fig. 5 is a detail showing the magnetic circuits of the machine of the invention.
Referring now to Figs. 1, 2 and 3, the arrangement of the preferred. form of
machine is illustrated. A is the base, B, B are the pillars for the bearings, C is
the shaft, and D is the pulley of the machine. A ring-shaped field magnet His
also provided, energized by the field magnet coils E, E. Upon opposite sides of
the ring or cylinder are the armature coils F, F mounted upon laminated
projections G. The two armatures are arranged in quadrature, the arrangement
being best shown in Fig. 3, wherein the coils are for sake of clearness illustrated
with a single line. The revolving inductor K is provided with laminated
projections L, L', which serve, as in such machines is common, to vary the
magnetic flux passing through the coils F, F¹ of the two armatures. At I between
the coils E, E is the magnetic shunt to which reference is made. It is to be
understood that the two coils are wound in the same direction so that the fluxes in
the magnetic circuit (indicated by the arrows) will be in the same direction.
Referring now to Fig. 4, we illustrate the circuits of the machine, together with
the means for compounding the two circuits, and for regulating not only the output,
but the change of voltage under change of load, or ratio of compounding. E, E' are
as before the field magnet coils giving the two field fluxes for the armatures.
F, F¹ are the armature coils, those of one armature being in quadrature to those

page_text: upon the other. The field magnet coils E, E' are respectively supplied with
current from the exciters e, e', which are machines of the ordinary type, provided
with regulating resistances r, in the circuits of their shunt coils S', $3. The-
machines are also furnished with compounding coils S, S₁ and rectifying
commutators O, O' supplied from the transformers N, N', having their secondaries
connected to the rectifiers by collecting rings; these commutators are shown as-
having but two segments, but this is diagrammatic only, as they would of course-
be provided with a sufficient number to commute the current properly, the usual.
arrangement being one segment for each arınature coil; this however is well.
understood by those skilled in the art. Resistances R, R' are respectively coupled
across the series coils for the purpose of changing the ratio of compounding. The-
transformers N, N₁ are of the series type, their primaries being respectively
connected in the circuit of the mains a b and c d. Lamps 1, are connected in.
each of the two circuits, while motors' M, M' representing diagrammatically
induction and synchronous motors of the two-phase type, are connected by means
of the transformers N2, N3 to all of the mains, being thus supplied with current of
two phases either through independent or interlinked windings upon the motors.
At V, V₁ volt-meters are indicated by the readings of which the regulating-
resistances would be adjusted.
In the machine as illustrated in Figs. 1 and 5, the two armatures are excited by
the magnetizing coils in such a way that both the inductor core and the armature-
yoke are magnetized in a single circuit; the gap or magnetic shunt I is therefore-
of small size, inasmuch as it does not carry the entire magnetic flux, but only that.
due to the difference between the two sides of the machine. Obviously at equal
voltage and equal load on the two sides of the machine no lines of force would.
pass across the gap, since it lies between two magnetic equipotential points. If
however, the load on one side be increased and the field excitation be correspondingly
increased so that the magnetic flux in one armature increases beyond that in the
other, the difference between the two passes through the gap, and does not affect
materially the second armature. The independent compounding or regulation of
the two sides of the machine is thus effectively provided for, as the two sides are
independent, while whatever tendency to reaction exists between them is in a
direction to assist the side having the lower voltage, instead of decreasing its-
terminal electro-motive force. This reaction is however quite small, as it is only
that due to a small portion of the difference between the two sides; the larger
portion of this difference passing through the shunt.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed as communicated to us from
abroad, we declare that what we claim is:
1. In combination, two separate armatures connected in quadrature and.
energized by different fields, independent circuits extending from each armature,.
and independent compounding and regulating means in each of the circuits.
2. A dynamo comprising armatures disposed in inductive relation to separate
fields energized in the same sense so as to constitute a single magnetic circuit, a
magnetic shunt between the fields through which passes the excess of lines of force
in one field over those in the other, and a revolving inductor; in' combination with
line circuit extending from each armature, and independent means for regulating
ach circuit.
3. A dynamo electric machine comprising armatures disposed in inductive
relation to separate fields energized in the same direction so as to constitute a
single magnetic circuit for both armatures, and a magnetic shunt between the
fields.
4. An inductor dynamo comprising armatures having separate field coils.
energizing in the same sense a single magnetic circuit for the armature, a magnetic
shunt between the fields, and a revolving inductor.
5. An inductor dynamo of the two-phase type, comprising two separate armatures

page_text: having their coils arranged in quadrature, field coils energizing in the same sense a
single magnetic circuit for both armatures, a magnetic shunt between the fields, and
a revolving inductor.
6. In a polyphase alternator, a magnetic shunt permitting independent control of
the fields.
Dated this 7th day of July 1896
J. C. CHAPMAN,
70, Chancery Lane, London, W.C., Chartered Patent Agent,
Agent for Applicants.