PMG construction manual

Contents	page
1. Introduction	2
2. List of materials and tools	6
3. Jigs and Moulds	8
4. Stator construction	23
5. Rotor construction	29
6. Assembly	34
7. Testing and connecting	39
8. Additional information	47

This manual was commissioned by Dr Smail Khennas Senior Energy Specialist Intermediate Technology The Schumacher Centre

 

On site assembly in Peru

 

1. 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

12V BATTERY

STATOR

FRONT ROTOR

1. EXPLODED PMG

REAR ROTOR

SPINE

The PMG (see diagram 1) consists of :-

• A steel spine and shaft.

• Astator 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.