Introduction
This manual describes how to build a 'permanent magnet generator' (PMG). We can
also call it an 'alternator', because it generates alternating current (AC). It will not
generate 'mains voltage' or 'utility power' AC. It generates low voltage, 'three phase'
AC, and then changes it into 'direct current' (DC) for charging a 12 volt battery.
What this PMG is made of
1. EXPLODED PMG
REAR
ROTOR
SPINE
SHAFT
STATOR
FRONT
ROTOR
RECTIFIER
12V
BATTERY
The PMG (see diagram 1) consists of:-
• A steel spine and shaft.
• A stator containing coils of wire
• Two magnet rotors
• A rectifier
The stator contains six coils of copper wire, cast in fibreglass resin. This stator
casting is mounted onto the spine; it does not move. Wires from the coils take
electricity to the rectifier, which changes the AC to DC for charging the battery. The
rectifier is mounted on an aluminium 'heatsink' to keep it cool.
The magnet rotors are mounted on bearings, which turn on the shaft. The rear rotor
is behind the stator, and enclosed within it. The front one is on the outside, fixed to
the rear one by long studs which pass through a hole in the stator. The wind turbine
rotor blades will be mounted on the same studs. They will turn the magnet rotors,
and move the magnets past the coils. Magnetic flux passes from one rotor to the
other through the stator. This moving magnetic flux is what produces the electric
power.
PMG manual
page 4
June 2001