9806Views18Replies

Author Options:

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

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

18 Replies

user
Josehf Murchison (author)2016-03-02

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.

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)2014-11-13

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.

Select as Best AnswerUndo Best Answer

user
JamesH261 (author)Downunder35m2016-02-28

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?

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)2014-11-25

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

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)Toga_Dan2014-11-26

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...

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)Downunder35m2014-11-27

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?

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)Toga_Dan2014-11-28

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.

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)Downunder35m2014-11-28

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?

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)Toga_Dan2014-11-29

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.

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)Toga_Dan2014-11-28

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.

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)2014-11-27

http://en.m.wikipedia.org/wiki/Induction_generator

how to use an induction motor as a generator. seems i was mistaken in sayng it wont work.

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)Toga_Dan2014-11-27

People seeking "free energy" often get confused by the motor types and if/how they can be used as a generator.

If you want it easy take a motor that uses permanent magnet, no matter if AC or DC.

And those waching maching motors (at least the big disc type) make excellent generator for small power needs.

To get serious with the power a more decent motor is needed but I think for home projects it would be overkill to build 5kW generator from an old motor.

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)Downunder35m2014-11-27

i dont think anyone mentioned free energy. mechanical energy in, power out.

need an example of power generation without permanent magnets? look under the hood of any automobile. Sure, a permanent magnet motor is easier, but not the only option.

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)Toga_Dan2014-11-28

Free enrgy in "" - meaning you don't have to pay for it as it is generated from freely available sources, like sun, wind, firewood...

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)Downunder35m2014-11-28

ah, yes. hehe. thought you meant free, like running engine on water, perpetual motion, etc. :P thx fo clarifyin.

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)2014-11-26

i recently came across an online pdf stating that even an induction motor like this could be used as a generator if you just connect the right capacitor, and apply an initial outside voltage to magnetize the rotor. I'm not sure if i believe this, but it might b worth playin with.

one might also drill holes in the circumference of the rotor to inset permanent magnets.

Select as Best AnswerUndo Best Answer

user
Downunder35m (author)2014-11-25

I found that sertain washing machines use a big round motor that has a magnet ring to spin the drum while the coil windings are organised like in a wind farm generator already.

If you salvage the entire unit with the bearings and all you can put a nice fan blade on and start generating 3 phase AC right away.

Add a rectifier and regulator to get stable DC.

If you need different voltages the coils be be simply re-wound to single phase, two phase, three phase in basically any voltage.

Only limit is the size of the coils so don't expect to generate kilowatts ;)
Here are some pics of the item in question (sorry if the images don't show up but was too lazy to host them on my PC first):

http://www.sustainability.fm.uwa.edu.au/__data/pag...

https://cdn.instructables.com/FQ0/AY2A/HCJOEM9N/FQ0...

Select as Best AnswerUndo Best Answer

user
Toga_Dan (author)2014-11-25

an easy way to test a motor: connect the wires to a voltmeter, spin the motor with a drill. does it produce voltage?

Select as Best AnswerUndo Best Answer