In the cuts the general construction of an induction coil is shown. In
the sectional elevation, Fig. 100, A, is the iron core; B is the primary
of coarse wire; C is a separating tube, which may be of pasteboard; D is
the secondary of fine wire; E, E are the binding posts connected to the
secondary; H, H are the heads or standards; K, K are the terminals of
the primary; F is the vibrating contact spring; G, a standard carrying
the contact screw; J is the condenser with wires, L, M, leading to it.
Referring to the plan, Fig. 101, H represents the primary coil; B and A
are two of the separate sheets of the condenser, each sheet with
projecting ears; G, G are the heads of the coil; the dark lines are
connections to the condenser. One set of sheets connects with the
primary coil at C, and also with the vibrating spring shown in plan and
in the elevation at F. The other set of sheets connects with the post,
carrying the contact screw. The other terminal of the primary runs to a
binding post E. F, in the plan is a binding post in connection with the
standard and contact screw.
Coil, Induction, Inverted.
An induction coil arranged to have a lower electro-motive force in the
secondary than in the primary. This is effected by having more
convolutions in the primary wire than in the secondary. Such coils in
practice are used with the alternating current and then do not include a
circuit breaker or condenser. They are employed in alternating current
system and in electric welding. (See Welding, Electric--Converter.)
In the cut an inverted coil, as constructed for electric welding is
shown. In it the primary coil is marked P; the secondary, merely a bar
of metal, is marked E, with terminals S, S; the heavy coils, I, of iron
wire are the core; K is a screw for regulating the clamps; J, Z is a
second one for the same purpose, while between D and D' the heat is
produced for welding the bars, B, B', held in the clamps, C, C'. It will
be seen how great may be the difference in turns between the single
circle of heavy copper rod or bar which is the secondary of the coil,
and the long coil of wire forming the primary.
Fig. 102. INVERTED INDUCTION COIL FOR ELECTRIC WELDING.