IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES
Year: 1885

page_text: COMPLETE SPECIFICATION
I GEORGE FORBES of 34 Great George Street in the Parish of St Margareta
Westminster in the County of Middlesex, Engineer do hereby declare the nature
of my invention for IMPROVEMENTS IN DYNAMO ELECTRIC MACHINES and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement
-
My invention has for its object improvements in dynamo electric machines of the
well known types invented by Gramme, Siemens, Schuckert, Elphinstone and
Vincent &c, in which a revolving part consists of a ring or drum &c with coils of
wire wound thereon, and a fixed part consists of electromagnets with poles or polar
extensions close up to the revolving coils.
My improvement consists in a new method of arranging the parts whereby a
great saving in copper wire and in iron is effected and less energy is required to
magnetize the machine.
To effect this I fix a coil or coils of wire round the revolving part (which part
may be identical with or equivalent to the revolving part of any of the well known
types as mentioned above) These coils when traversed by an electric current serve
to magnetize the revolving part and they enclose it completely except where the
poles of the field magnets are found in the usual types I enclose the whole of
Thus
the revolving coils and of the fixed coils as close as is convenient with iron.
a section of the magnetizing coils is surrounded entirely by parts which are to be
magnetized by them
In ordinary dynamo electric machines of the above mentioned types the
magnetizing coils are in contact with iron only on one side and thus half of their
magnetizing power is wasted upon the air. In such machines also the revolving
part is magnetized principally by magnetic induction which 18 less effective than the
direct magnetization by the coils in my invention By my invention the coils are
surrounded on all sides by the material which requires to be magnetized and by
this means smaller quantities of wire and of energy suffice to magnetize the
machine. Moreover, by my invention, all the material which requires to be
magnetized being brought as close as convenient to the magnetizing coils, a smaller
weight of iron is used
I have now described the mode of carrying out my invention in its most perfect
form from an electrical point of view In practice I may vary the form without
departing from the spirit of the invention. I may, for example, find it convenient

page_text: to remove part of the fixed iron. Or again if I wish to be able to draw out the
revolving part from the rest of the machine in the direction of its axis I may bend
the magnetizing coils at their ends so as to give room for this purpose.
DESCRIPTION OF THE DRAWINGS
In the drawings the same letters apply to the same parts. Figure 1 is a
longitudinal section of a machine constructed according to my invention with a
ring armature Figure 2 is a transverse section of the same Figure 3 18 a plan of
the same. Figure 4 is a transverse section of a machine constructed according to
my invention with a cylinder armature
A is the armature. α is the core a₂ 18 the wire. ag 18 the hub
B B are the magnetizing coils enclosed in cases b, and b, which are arranged so
that the machine can be readily taken to pieces and put together
The enclosing iron is made in pieces C C₁ for the same purpose
The magnetic
poles of the enclosing iron are at c. c facing the poles of the armature. The
parts of the enclosing iron are held together by bolts c
D is the commutator connected in the usual order with the coils of the armature
by the strips d₁
E is the base with standards e, carrying bearings &
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 18
1 The construction of dynamo electric machines with magnetizing coils enclosing
the armature
2. In dynamo electric machines, the combination, with iron in the armature and
with fixed poles, of magnetizing coils surrounding the armature in those parts of
its periphery not occupied by the magnetic poles of the fixed iron.
3 The construction of dynamo electric machines in which the fixed iron
magnetic circuit is reduced to the minimum which leaves just enough space
between the fixed iron and the armature to conveniently contain coils sufficient
for magnetizing the armature, substantially as described and set forth in the
drawings.
4 The construction of dynamo electric machines substantially as described and
represented in the drawings marked figures 1 2 & 3
5 The construction of dynamo electric machines substantially as described and
represented in the drawing marked figure 4.
Dated this first day of April 1885.