In the case of electro-motors these conditions are changed. In the first
place, we assume that the current put through the coils of the magnets
is continuous; and secondly, we can count upon the momentum of the
armature, as well as the momentum of the driven object, to assist us
over slight irregularities. With electric launches we are bound
to employ a battery current, and battery currents are perfectly
continuous--there are no sudden changes; it is consequently a question
as to how small a mass of iron we may employ in our dynamo as a motor
without sacrificing efficiency. The intensity of the magnetic field
must be got by saturating the iron, and the energy being fixed, this
saturation determines the limit of the weight of the iron. Soft wrought
iron, divided into the largest possible number of pieces, will serve
our purpose best. The question of strength of materials plays also an
important part. We cannot reduce the quantity and division to such a
point that the rigidity and equilibrium of the whole structure is in any
way endangered.
Pages:
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48