Like all magnets, electro-magnets have a north pole and south pole. North and south
poles attract each other. When two magnets are placed next to each other, the
magnets tend to rotate so the north pole of one magnet aligns with the south pole of
the other.
Electric energy stored in a battery can be converted to mechanical energy by an
electric motor which uses electro-magnetic fields to rotate an output shaft. Model
motors come in two basic varieties, “brushed” and “brushless”, which differ in terms
of how electric current gets to the copper coils or “windings” inside the motor.
Brushed motors
O-Brushed mo tor op er a tion
In a “brushed” motor, electric current flows through carbon brushes that slide on a
copper commutator ring attached to the motor output shaft as shown in Fig. 3-1. The
commutator ring generally has three segments attached to three coils of copper wire
each wrapped around an iron core. The motor shaft, commutator, coils and iron core
are collectively referred to as the motor “armature”.
As the armature rotates, the brushes conduct current to each segment on the
commutator and through one coil after another. The energized coils produce
magnetic fields that pull the coils toward permanent magnets mounted on the inside
of the motor body (also called the motor “can”). As each coil passes a permanent
magnet, the brush associated with that coil slides onto the next commutator
segment. This de-energizes the coil and energizes the next one in sequence.
Op er a tor's Guide
Electric Motors
LITE MA CHINES
3-3
Figure 3-1.
