Ask : can i turn a motor from a fan to a generator ?

I have a motor taken from a fan ( picture ) i want turn it into a generator. Can i do that ? My teacher said that the motor taken from a fan could not be turned into a generator. And if it is possible, how to do that ? thank you a lot

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I think know that motor it is an induction motor and you would need to change the armature to convert it to a generator. You can cut notches in the armature and attach permanent magnets to the armature then rectifiers to the coils, it would be a lot of work though.

I can't really see and details of the motor to make a judgement, but if the motor has no magnets than most likely it won't work as a generator without massive modifications.

Depending on what power you nee scoote motors or those from electric treadmills are often a good start.

Some waching machines also use a motor that looks like a big ring - perfect to make a generator as it can berewired for most voltages you might need.

A bit late to the discussion but would not a microwave motor be an excellent choice since it has a low KV. Around 3 - 4 RPM at 120 V?

Toga_Dan2 years ago

generally, a dc motor will work as a generator. an ac motor cant.

Wrong!

These big round washing machine motors are 3 phase AC - but they use permanent magnets.

Same story by the way for most ceiling fan motors, although they are a mess to rewind...

it is good to know about the exception to the rule. would you agree that most ac motors are induction motors with no perm magnets?

re. ceiling fans, are u saying they must be rewound to be used as a generator?

Yes, most AC motors don't use permananent magnets.
But for certain application it does make sense to go back to motors with magnets.
If you know where to look it can save you a lot of trouble and money.
Some ceiling fans use magnets in the outer ring and a set of 3 coils fixed on the inside.
Although they would procude electricity like this right away it makes sense to take all the windings out and to replace them with something that matches the needs.
Lke for most solar system using around 50-55V to feed the battery charger.

i definitely agree that a motor with magnets will be the easiest to use.

if you rewind a motor/generator, how would u choose wire size, # of windings etc for a given purpose?

Not that eas to answer but I will try to explain my way of checking:

1. The amps you need determine the gauge of the wire.

That does not mean you can get 50amps @ 240V from a small 100W motor!

It all has to fit back onto the original coil packs.

2. Let the motor/generator run as it is with the speed you estimate it will reach in your setup.

Measure the voltage on the output.

The difference between windings and voltage will determine how many turns you need for the rewinding.

Example: Generator spins at 600 revs and produces 80Volts and has 140 turns on each coil block.

You need around 50V to charge your batteries.

80V/140 turns * 50V = 87.5 turns to get 50V instead of 80V.

To compensate for losses you would make 90 - 92 turns.

3. Three phase back to single phase...

Most wasching machine motors that are suitable have the same problem as every other good sized motor, they run on 3 phases and not just one.

A very common misconception is that you need a single phase motor to turn it into a useful generator.

The fact is that really only matters if you need AC output and for that you really want to match the 50/60Hz mains frequency, which needs a lot more additional electronics to regulate.

Best option is to rectify the voltage from the generator to get a stable DC and to use this to charge batteries.

The batteries either run the devices directly or if AC is used an inverter goes on the batteries.

4. How to actually rewind...

http://www.bavaria-direct.co.za/models/files/CD-R_...

If you check the image ignore that the windings are on the inside and not the outside, it does not matter for the exercise.

Each color is for one phase of the AC.

You can see they go 1 ,2, 3 around the coil pack.

There will be one or magnets that always align north to south over two corresponding coil packs.

E.g.: North on pack 1, then south will be between 5 and 6.

So you see if the thing is spinning that the position of the magnet will correspond with the output wave form if you assume max is directly over the coil when the magnet is on top.

You want to keep the direction of the winding on the coil itself as well as how it goes around in the motor!

So if the coils are wound clockwise you will rewind clockwise.

If the next coil of the same wire is to the left you will rewind this one next and continue until the first phase is rewind.

Do the same for the remaining phases.

5. Considerations...

Depending on the motor the rewinding can be quite painful if you make mistakes, so take your time and take notes.

You will need a certain amount of turns to get an effective generator.

This means that you have to keep in mind that replacing 200 turns on a coil pack with just 20 might work in theory but in practice can result in poor performance as the 20 turns can't produce a strong enough magnetic field.

As a rule of thumb expect around 20% less output at the same speed if you use a motor as a generator - this is bad and in most case you will see better but it helps deciding on the right motor.

So if you have a 100W / 240V motor it uses about 450mA of power, rewind to 50V as a generator and you might get around 2A out of it - 100W stay 100W.

Yes, most AC motors don't use permananent magnets.
But for certain application it does make sense to go back to motors with magnets.
If you know where to look it can save you a lot of trouble and money.
Some ceiling fans use magnets in the outer ring and a set of 3 coils fixed on the inside.
Although they would procude electricity like this right away it makes sense to take all the windings out and to replace them with something that matches the needs.
Lke for most solar system using around 50-55V to feed the battery charger.

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