Alternator motor conversion.

[wfouri]

So I have a few questions.

I have like so many people blown a motor or two, and can't afford buying expensive replacements.

A little background, I built an electric trials motorcycle, using an old "fantic key roo" frame, bit heavy but strong. Threw in an 25kw outrunner motor. Definitely doesn't produce torque. Paired it to a kelly kls-d motor controller, capable of 200A constant. Running 48v 44ah lithium cobalt batteries, high discharge rate, can do 500A. This motorcycle was ment to produce torque and used for just silly things.

The motor didn't make it through the testing phase, I was still running current around the 100A mark and it just smoked the motor.

So now I am considering joining the crowd in converting an old alternator, theoretically it's possible. I am however unsure of how effective it would be or how long it will last. The windings on a normal Automotive alternator are rather thick and you can find once rated above 100A of the older types.

So basically you strip the Alternator and turn it into an hybrid induction motor. You remove the rectifier and connect the phase (stator) wires to your standard controller, the rotor or field wires you want to connect to a DC speed controller to be able to vary the current going through the field, more current means more torque, but less speed and high losses, you just need it to start the motor and get low down torque. Since alternators usually work on demand, meaning that the regulator usually varies the field depending on the charge rate required to charge a battery and run all the lights ex.

So the hard part is how does one vary the field?? An idea I am toying with is just to take the potentiometer from the DC speed controller and building it into the twist grip, but its less than ideal, and you require a second pot inline to be able to tune the motor to be at its sweet spot at full throttle. Another option could be some sort of sensor on the rear wheel, to reduce the field as the wheel speeds up. Can a pas sensor be used for this? Does anyone have an idea of how that would be connected?

Controlling the stator is the easy part, just fit hall sensors to the motor, and connect the wires as per usual. It's controlling the field that seems to cause some difficulty.

Would like to hear some opinions and advice.

 

[Skalabala]

Alternators do work but I think you will struggle to get 1kw out of it.
Will also need a huge reduction as it will be spinning 10000rpm+

 

[IanFiTheDwarf]

I tried modding an alternator as you describe and had it running for a little while with an rc brushless speed controller. For the rotor field I just connected a car headlight lamp in series and connected directly to 12v it worked for a while until something went and I lost a phase on the controller or a winding on the alternator/motor.

My plan was toswitch between different filaments of the lamp or resistors eventually for different gears ie two in parallel for highest current and torque but low speed a single filament for mid gear and two in series for top.

I never got round to fitting the motor to anything before it died and haven't tried again but when it worked it was fairly slow, probably not much over 1000rpm if that

I might get back to it when I eventually finish building my workshop.

 

[wfouri]

Good to know it does work. I was hoping to hear from some more people who have tried this conversion, and what results they had.

IanFiTheDwarf- what kind of torque did you get at a 1000rpm? What was your input voltage?

My opinion is to try and use a 24v alternator that is rated over 100A, as in some trucks or aircraft. Standard 24v Aircraft alternator is around 70A on small aircraft. This should be a good find. More likely an old truck alternator would be easier to track down.

I will try and run it at 48v using my kelly kls-d motor controller, and a standard DC speed controller I got from banggood.com for the field. I will have to fit hall sensors to the alternator to make it work, but this should be a fun experiment.

I first have to find a suitable alternator.

Has anyone else given this conversion a try?

 

[spinningmagnets]

You might find some link to past experiments over at http://www.otherpower.com (DIY wind-generators, etc), and their forum http://www.fieldlines.com/

Just Googled this: http://www.alternatorconversions.com/

https://endless-sphere.com/forums/viewtopic.php?f=10&t=15057

 

[Ianhill]

Spinning magnets you look like Michael Keaton in your profile pic by there, Iam the batman !
I got to say it beetlejuice beetlejuice beetlejuice damn no ones here :lol:

Running an alternator as a motor can be done, plenty of good vids on YouTube but its efficiency can be low and its rotor current needs to be messaged to get it to spin fast lots of current on both winds fight each other and create more waste heat so the rotors current is key, like mentioned though 1kw + underload and your doing well with a stock 55amp alternator not sure on the 100+amp modern units.

It would be great if we could all put our minds together in one thread and make a simple diy motor plan that would be simple to make and gives us all access to something thats easy to power cheap and efficient while learning some of the princables even recycle a thing or two.
I wonder if the ferrite in speaker magnets has its poles arranged correctly to be used In the rotor of a reluctance motor be even cheaper then just cut it into four pieces and make the stator around that, make a simple die to press out thin sheets of iron for all the laminates, aluminium can to place it all in

Could something like this be powered with just a sensored controller and hall sensors my mind is saying yes but it sometimes plays tricks.

 

[Ykick]

Here's a golden oldie - https://endless-sphere.com/forums/viewtopic.php?f=30&t=16328

RCG had a lively thread on this deal and I'm sure plenty of others - https://www.rcgroups.com/forums/showthread.php?t=905411&page=64

Sooner or later the name R a n d y D r a p e r will come up....

 

[IanFiTheDwarf]

Im not sure how much torque I was getting, I remember it being a bad idea to try and load it with my hand but that about it.

I was planning on using 24v but I dont remember if I got to that but I defenately tried 12v first.

I wouldn't wory about trying to find a 24v alternator. Theres a good chance the windings are the same just a 24v regulator. Without a regulator you can get over 50v from a 12v alternator. The most important thing to look for is thin laminations which will help efficiency.

An old workmate of mine made a water turbine generator with a car alternator with the regulator removed and had it charging a bank of old forklift batteries, he had a contactor switch in a bank of old oil heaters in a cow shed to stop the alternator cooking the batteries. The cows loved it.

he had issues with the rotor winding so reolaced it with permanent magnets from magnatrons, we worked with radar so had a few old ones lying around at work but microwave oven magnatrons have an almost perfect magnet on them. I think you need two and take great care removing it as there is a byrillium disc in the magnatron which is highly toxic.

I remember seeing somewhere online a converted alternator on a motorbike that could spin the back wheel so high torque must be possible.

 

[Ianhill]

If I was to run one I would find a decent rated one, break the connections in to two group stator and rotor, the rotor is a simple DC coil powered through the slip rings I would use a 10amp 18khz 12v pwm controller to energize this coil.
Then the stator is effectively a 3 phase motor terminated in wye so you need to identify the the start of each phase and and feed them with a non sensored controller around 48v 30amp mark or 1500w.
To start the motor place max throttle on the rotor then rev the three phase controller when up to speed dial back the rotor current to get more speed out of it

 

[wfouri]

Thanks guys,

There is really a lot of good info here. Think I will definitely give it a go. I rewound my 25kw outrunner motor that I originally intended for the motorcycle to a lower KV, using 0.8mm wire 7 turns and 8 parallel. But tested this today and it seems that I have created a different kind of monster, seems I will only get 2000rpm max at 48v but producing much more torque.

I will try it again in the motorcycle, but this time if it doesn't produce the torque needed it's getting replaced with a alternator-motor. Have already bought a good old alternator, ordered a DC speed controller and hall sensors to do the conversion.

I will work on a plan to make the field voltage automated, sort of a torque on demand idea and more speed when you need it.

 

[Hillhater]

I know there are lots of vids and forum threads about these Alternator motors, but using the old yourstick of ..."if its anygood, we would all be using them"...i have my suspicions as to the practicallity of the idea.
Especially here , on this forum, with more than its fair share of motor builders and tinkerers !
I guess, if anything, they end up as low power/weight, low efficiency, devices that are probably difficult to control ?

 

[Punx0r]

If the motor overheated then it doesn't matter how you rewind it, it will never produce the torque you require without overheating. The only thing you can do is to increase the gearing and spin it faster, so the torque requirement at the motor is less.