Honolulu star-bulletin. [volume] (Honolulu [Oahu, Hawaii]) 1912-2010, 1917-02-17
GOWN EAY r1oToa Ao

iarmature and decrease the efficiency
sof the machine. The armature core
serves the double purpose OF conduct
Ing the, MAGNETIC lines from pole to
1 pole and at the same time supporting
the armature winding.
! Second: The afr gap. which IS the
clearance between the armature core
and the end Of the poles.
ahird: The pole shoes, or pole
pieces. which are the ends of the poles
adjacent to the air gap They are in
some cases given a special shape in
order to improve the distribution and
arrangement of the magnetic lines
/, forming the magnetic field. In some
cases the pole shoes are made separ.
ate from the field core and bolted to
the cores.
| Fourth: The field cores, which are
the parts of the magnetic circuit about
which the field windings are placed.
Fifth: The yoke, which is the out
side portion OF the magnetic circuit
Econneeting the field cores. The yoke
forms part Of the magnetic circuit
and at the same time serves as me-
lchanical support for the field cores
land pole shoes. holding the pole shoes
in their proper position with respect
i to the armature.
Series Generator
I A series generator is one in which
/. the armature and field windings are
! connected in series. and any current
supplied by the armature passes
through the field winding. The con-
neetions of series generator are
shown in Fig. 6. The operation of
such a machine. in brief, is as fol-
lows: Assuming that there Is some
residual magnetism In the fields due
i to their having previously been mag
netized. there will be low electrical
pressure induced in the armature
winding when the armature is reyolved
| in This weak magnetic field. This
induced electrical pressure Will not
produce a current unless the terminals
Of the machine be connected directly
together or by means of an external
circuit. The current due to this low
induced electrical pressure will flow
through the field winding and increase
the strength of the magnetic field,
which in turn will increase the In
duced electrical pressure. which will
increase the current, etc. This opera
j ton would continue indefinitely and
1.-THE induced pressure and current
would both become dangerously high
unless some means were provided for
controlling them.
As the current In the field winding
increases the number of magnetic lines
/ in the field increases, but after a GER
tain field strength has been reached
the magnetic lines cease TO increase,
due to given increase in current, as
rapidly as they did at first, and fin
ally there is very little Increase in
these lines. due to an increase In the
field current. and the iron forming
the MAGNETIC circuit Is said to be sat
urated. The series field winding is
composed Of relatively small num-
Der Of turns OF wire of ample size to
safely carry the maximum current the
machine is designed to deliver.
shunt Generator
A shunt generator is one In which
the field winding is connected directly
to the terminals OF the armature. as
shown In Fig. Z. The current in the
field winding at any time Is equal to
the pressure between the brushes di-
vided by the resistance Of the wind
ing and Is Independent of the current
the generator may be supplying to a
circuit connected to its terminals, UNI
less the current supplied changes the