Generator - Motor

These guys have a huge amount of info, check them out!

http://www.build-a-windturbine.com/caddownloads/caddownloads.htm

plans and all

Hi,

look for the principles of PMDC motors. These can be used without modification as generators as the motor-constant = voltage/speed is equal to the torque/current ratio. (friction is neglected).

So one motor/generator can be used at different speeds, voltage is going up with speed, current should be held constant (constant torque) so power will go up linear with speed.

So to adopt an existing motor is an easy approach.

If you choose to build everything yourself: then first step will be to refrain from AlNiCo magnets - too difficult in magnetising after mounting.

Next select either FeNdB-magnets (cheap but temperature sensitive) or SmCo-magnets (expensive but able to work at higher temperatures).

Then select a construction that is existing in the motors you have found - most likely the axial version as this is easier in small number production and better adapted to magnet data.

Then select the airgap to be the same as the magnet length, this will give 50% (...30%) of the magnets Br (the remanent flux density) inside the airgap.

Then think about the coils (in the construction selection step you shall have decided on size and number). Make the coil from big sized wire and half the diameter of the wire.
The principle data will not change much, only the voltage will change. Wire dimension is only for adopting to an existing or specified voltage.

I have a complete tutorial on magnetic circuits but this is handwritten and in German it took typically 3x4hours to explain to students in precision engineering.

(The electrical engineers don't like electro-magnetics the mechanical engineers are worse the physics may be able to do Maxwell's equations but not to simplify to build a motor, so prolonged learning and training is necessary. I never found a book that is showing clearly these simplified basics of coils and currents in permanent magnetic fields.)

Some coils I have designed and built as prototypes are shown on my website.

What is missing (also in commercial generators) an adoption to different wind speeds to extract at any time the maximum amount of energy: this would require a servoed variation of magnetic flux density.

RHABE

It may be a good idea to refer to a design book.You are practically asking the forum for a design and space is too small.There are very good softwares available for these designs.One point I would like to state 3000 rpm winding bracing needs special attention as otherwise u can see the rotor winding opening out like a lotus.

Thx everyone so far for the comments. It seems to be a trade secret on how to work it out as the response is not what I had hoped for. Could anyone tell me what a software package is called that can do this, or what reading material I could use? The wind turbine material was very interesting but it still does not explain windings and magnet ratios. The searches on the net is not much use either.

Hi Conrads,

it seems to be not very useful to buy a software package as these are costly and only usable if you have done a lot of work before.

So I would recommend once more:

1. look at existing PMDC motors and decide which type to copy

2. design your magnetic loop so that you have an airgap equal to magnet length and a cross section of iron flux-paths so that flux-density is below 1.5 Tesla,

3. play with coils: how to do the mechanical work of winding, what is the resistance, what is the RI² loss, what is the torque/current,

Then ask more questions (you will have learnt at that stage) and I will be glad to answer these.

RHABE