Bakersfield College Engineering B47

A simple motor has six parts:  Armature or rotor  Commutator  Brushes  Axle  Field magnet  DC power supply of some sort

Magnets:  Attractive or repulsive force Two Magnets:  Armature – rotating portion of the motor – electromagnet  Field Magnet – permanent magnet

Simple Electromagnet  Wrap 100 loops of wire around a nail  Connect to a battery  Nail becomes a magnet  Add an axle  Effect of the laws of magnetism  Flip the electromagnetic field by flipping the battery

Armature  An electromagnet made by coiling thin wire around two or more poles of a metal core. The armature has an axle. Commutator  Pair of plates (for example, metal foil) attached to the axle. These plates provide the two connections for the coil of the electromagnet. Brushes  Flipping the electric field is accomplished by contact between the commutator and the brushes (metal contacts).

Notes  As the armature passes through the horizontal position, the poles of the electromagnet flip. Because of the flip, the north pole of the electromagnet is always above the axle so it can repel the field magnet's north pole and attract the field magnet's south pole.  This is a two-pole motor. If the electromagnet is at the balance point, perfectly horizontal between the two poles of the field magnet when the motor starts, you can imagine the armature getting "stuck" there.  Each time the commutator hits the point where it flips the field in a two-pole motor, the commutator shorts out the battery (directly connects the positive and negative terminals) for a moment. This shorting wastes energy and drains the battery needlessly.

Step 1: Building the Electromagnet Tape the lag screws to the axle Wind the wire around the bolts -Windings 4 layers thick -Leave 6” tails Test the Electromagnet

Step 2: Building the Commutator Affix foil tape to the dowel -Leave ¼” gap between contacts Place stripped ends of wire under foil tape Break in foil must be perpendicular to electromagnet

Step 4: Forming the Brushes Use the brass sheet - ¾” wide by 3” long Wind around nail Form it to shape shown

Step 5: Assemble the Motor Insert bottom brush Insert rotor assembly Insert top brush Use rubber band to hold brushes against commutator