The following equation expresses this relationship:
F BlI
(N)
where tesla, metres, amperes and newtons.c. Figure 10. Figure
10. Calculate the force the conductor when 15A flows the coil.13(c) force will
be exerted the conductor push out the magnetic field. The
armature winding rotates between the poles and connected the com-
mutator. Let
us try understand this action. 10.
Figure 10.
Example
A coil which made conductor some 15m length, lies right angles magnetic
field strength 5T. Contact with the external circuit made through carbon brushes
rubbing the commutator segments. motors
Practical motors are constructed shown Fig.Alternating current theory and electrical machines
207
Direct current motors
All electric motors work the principle that when current carrying con-
ductor placed magnetic field will experience force. Figure 10.15 shows
FIGURE 10. motors
contain field winding wound pole pieces attached steel yoke.14.
F BlI
(N)
F 1125
T N
Practical d. All d.c. current carrying conductor placed
into the field permanent magnet shown Fig. electric
motor uses this magnetic force turn the shaft the electric motor. Direct current motors are classified
by the way which the field and armature windings are connected, which
may series parallel.
SERIES MOTOR
The field and armature windings are connected series and consequently
share the same current.
(a)
S
N
(b)
(c)
Force F
S
N
.13(c) shows the effect the combined magnetic fields which are dis-
torted and, because lines magnetic flux never cross, but behave like
stretched elastic bands, always trying find the shorter distance between
a north and south pole, the force exerted the conductor, pushing it
out the permanent magnetic field.13(a) shows the magnetic field due the current carrying con-
ductor only. The series motor has the characteristics high
starting torque but speed which varies with load.13
Force conductor magnetic field.13(b) shows the magnetic field due the perma-
nent magnet which placed the conductor carrying current.
To understand the force, let consider each magnetic field acting alone.
This the basic motor principle, and the force dependent upon the
strength the magnetic field the magnitude the current flowing in
the conductor and the length conductor within the magnetic field l. 10
