IMPROVEMENTS IN DYNAMO-ELECTRIC AND MAGNETO- ELECTRIC MACHINES
Year: 1880

page_text: PROVISIONAL SPECIFICATION left by Alexander Melville Clark at the
Office of the Commissioners of Patents on the 30th September 1880.
A com-
munication from abroad by Alfred Niaudet and Emile Reynier, both of Paris,
France.
ALEXANDER MELVILLE CLARK, of 53,. Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN DYNAMO-ELECTRIC AND MAGNETO-
ELECTRIC MACHINES." [A communication from abroad by Alfred Niaudet and
Emile Reynier, both of Paris, France.]
This Invention relates to improvements in the Niaudet dynamo and magneto-
electric machines, whereby the effective capacity of the machine and its continuity
of action are increased.
The Niaudet machine in its original form is illustrated in Figures 1 and 2 of the
annexed Drawings. It consisted of a number of straight electro-magnets E on
a disc P mounted to rotate opposite the poles of a permanent magnet N, O, S, the
axis of rotation being perpendicular to the plane of the permanent magnet. The coils
are connected together, the egress end of each to the ingress of the next following,
so as to form a complete circuit. Radial bars of copper insulated from one another
pass between the coils, and are connected each to the point of junction of the wires
of the two adjacent coils. These bars converge towards the centre, where two
insulated contact springs R, R¹, rub against them at two opposite points situated
in the polar axis. To these springs are attached terminals for the connection of the
wires. The current divides in traversing the circuit of the coils by two derivations
of equal resistance in passing from one spring to the other. These springs R, R,
may have a roller, as shown in Figure 3, to obtain a rolling friction. By this Invention
the machine is modified as follows, without changing its principle of action-
(1.) The fixed magnet or magnets or electro magnets, instead of being per-
pendicular to the axis of rotation of the coils, as in the Clarke machine, is in line
with said axis, as in Figure, 4, and as in the Pixii machine, whereby the magnetic
reactions are greatly strengthened.
(2.) The ends of the core of the coils are connected by thin circles of iron, as
at C, C, Figure 5. In Figure G there is no such connection, and in this case the
coils 1 and 4, which are near the poles A, B, react energetically upon them, but the
others 2, 3, 5, 6, which are at a greater distance, react little; nevertheless, the wires
of these coils are in the circuit, and therefore augment the resistance withoue
greatly increasing the magnetic action. By means of the thin iron connecting rings

page_text: of this Invention, the coils distant from the fixed poles transmit their magnetism
and strengthen those which are near said poles; reciprocally the magnetic field of
the fixed magnet, which extends around each of its poles, reacts upon a considerable
portion of the iron ring; and, moreover, the impulsions resulting from the successive
passages of the coils are less abrupt, being blended and attenuated by the continuity
of action of the ring. The cross sectional area of this ring must be small, less than
that of the cores of the coils, otherwise it would form an armature, and cause a
diminution instead of an augmentation of the magnetic reactions. One of the two
rings may however consist of a thick back plate of iron D, Figure 7, but in this
case there would only be one fixed magnet (or electro magnet) opposite the free
ends of the coils connected by the thin iron ring.
(3.) The thin iron ring may be placed on the poles of the fixed magnet or magnets,
as in Figure 8, instead of on the cores of the coils, but the result is almost the same
in either case, the magnetism of the fixed poles being carried towards the distant coils,
so that each of the latter reacts during its entire revolution with a maximum effect
when opposite the poles of the fixed magnet. This thin ring applied to the fixed
poles must not be confounded with the enlargements or appendages of iron, such as
shown in Figure 9, which have already been applied to the poles, and which give
very different results from the thin metal ring of this Invention.
With this ring,
as shown in Figure 10, a rational distribution of the magnetism is obtained. The
magnetization which is nil on line n, n, gradually increases from this point to
points opposite poles A and B, where it is at its maximum. Suppose a coil E to
turn in front of this ring; in moving from 1 to 2 it is subject to a gradually
increasing magnetic influence, which decreases from 2 to 3, where it is nil; it then
gradually augments in the inverse direction from 3 to 4, being at its maximum at 4,
and thence gradually decreases until it arrives at 1 again.
With the enlargements a, b, c, d, a¹, b³, c¹, d', shown in Figure 9, the action is
different. As they are magnetised almost equally over their whole surface, there is
hardly any work done during the time that E passes before these surfaces, and
there is also but little done when E is moving out of their vicinity. It is then
only whilst the circumference of E is passing a, b, c, d, a¹, b', c¹, d', that any work
is done. Thus, for a complete revolution, and for each coil E, there are four periods
of reaction separated by four almost astatic periods. In like manner similar
appendages applied to the cores of the coils would prolong slightly the periods of
action of each of them, but would not give the advantageous results of the thin
metal ring, which connects together the cores of all the rotating coils, distributes
their action, and reinforces the magnetism of those nearest to the poles of the fixed
magnet by utilising the magnetism of those farthest from said poles.
(4.) The said thin metallic rings are applied to machines in which the rotating
coils are not parallel but radial to their axis of rotation, as shown in Figure 11, in
which C, C, is a thin iron cylinder or band encircling the poles of the cores.
(5.) The collector instead of being constructed of radial bars with intervening
spaces, as in Figure 1, is composed of metallic segments, as shown in Figure 12,
fixed on a disc of wood, ebonite, or other insulating material, and insulated from
one another, but close together, so that the contact springs pass from one to the
other almost without appreciable interruption.
The following Figures represent three examples of machines with the above
described improvements applied:-Figure 13 is a side elevation of a machine
having a single thin metallic ring; Figure 14 is a plan of the same; Figure 15 is
a cross section on line 1-2, Figures 13 and 14; Figure 16 is another cross section
of the same machine on line 3-4, Figure 13 and 14; Figure 17 is a longitudinal
elevation of a machine with two such thin metal rings; Figure. 18 is a plan of the
same; Figure 19 is a cross section of the same on line 5-6, Figures 17 and 18,
showing the contact springs; Figures 20 and 21, show the coils arranged radially.
In all these Figures the same letters of reference indicate the same or similar parts.
N, S, stationary magnets or electro-magnets; E, coils mounted to rotate on
axis A; C, thin iron band; R, R', contact springs; K, collector; ✗, base plate.

page_text: By means of a double commutator and a galvanometer, the value of the electro-
motive force developed in the wire of one of the coils E at different points of its
path may be ascertained, in order to regulate the thickness and width of the
metal ring accordingly, and, if necessary, to vary one or both of these dimensions
in the arc between two consecutive coils.
The fixed electro-magnets may be placed in the general circuit or in a derivation
of the principal current, as proposed by Wheatstone; in the latter case the circuit
of the electro-magnets should have a much higher resistance than in the first case.