Why don't we see more servo motors being used as generators?

[makenzie71]

Just a curiosity.  Someone posted one on Facebook cranking out a little usable voltage just turning it by hand.  Albeit it was a large motor that would be quite expensive to buy new, but there's a few used ones on eBay for not a lot of money.  Seems like all they would need is a mount and a rotor to make some juice.

Is there a reason why they're not used much?

[DanG]

http://web.archive.org/web/20010601000000*/http://www.fieldlines.com

You'll be in good company once you've finished reading what is there ^^

[JW]

I remember Forcefield magnets, it was sold out by the Dans several years ago.

[makenzie71]

http://web.archive.org/web/20010601000000*/http://www.fieldlines.com

You'll be in good company once you've finished reading what is there ^^

That just takes me to the 2001 snapshot calendar for fieldlines...unless you were just suggesting i read everything ever posted here :p

[DanG]

...unless you were just suggesting i read everything ever posted here

yuppers, it's what Dreams are made of...

[mmurray70]

I think a surplus servo is a great idea. This makes way more sense to me then messing with F&P or axial flux generators. There are a Ton of these on e-bay for great prices if you look around. Do some homework on what electrical specs you need. I bought a medium sized fanuc motor last spring with intentions of building a turbine, but ended up getting really busy at work after and I havent built it yet. Also got a little discouraged by the lack of good blades available.

Your onto a great idea. My servo made decent power, I tested it in my lathe. I posted results of that on here if you want to do a search. Note that the one I had was chosen for its fairly high voltage output as I was planning on doing resistance heating only. This would not be a good choice for typical battery situation.

[SparWeb]

Here you go:

https://www.fieldlines.com/index.php/topic,146090.msg997655.html#msg997655

The member 97FishMt posted regularly, so there's more to find than just that thread about the servo setup.

[Adriaan Kragten]

Just a curiosity.  Someone posted one on Facebook cranking out a little usable voltage just turning it by hand.  Albeit it was a large motor that would be quite expensive to buy new, but there's a few used ones on eBay for not a lot of money.  Seems like all they would need is a mount and a rotor to make some juice.

Is there a reason why they're not used much?

For a motor, it is no big problem if the armature has preference positions. But if you use a PM-motor as generator, you don't want preference positions because strong preference positions result in a high starting wind speed if the rotor of the wind turbine has a low starting torque coefficient. So not all PM-motors can be used as a generator for a wind turbine for this reason. An other reason might be that the generated voltage for a certain rpm is much to low if the motor is normally used at a low voltage.

[JW]

Here is one of the sch built for this.

https://www.google.com/search?sitesearch=https%3A%2F%2Fwww.fieldlines.com&q=97FishMt


This feature is a way to trace any users posts  in this case it was 97FishMt. at the bottom of the home page is a way to google search the site.

[makenzie71]

Yeah i've actuaLly found Several examples of them being used...i was seeing them before I asked here.  I was asking because they seem relatively inexpensive, powerful, and readily available.  I just assumed there was some reason why not everyone was jumping in them.

[SparWeb]

There are some reasons to be reluctant.
One is the V/r ratio isn't always obvious.  Or good for the wind-turbine range.
These are e-bay ads: some are good some are bad.  You can't always tell what you're getting.
Some servos have good bearings, some won't. Another thing that might be hard to predict.
Servos often run for short bursts for a few minutes/hours at a time.  Wind turbines must spin 24/7 for years.
You have to do your research by looking up the manufacturer's data and applications for the particular servo you like, before having confidence that you're going to get something useful.

[mmurray70]

There are some reasons to be reluctant.
One is the V/r ratio isn't always obvious.  Or good for the wind-turbine range.
These are e-bay ads: some are good some are bad.  You can't always tell what you're getting.
Some servos have good bearings, some won't. Another thing that might be hard to predict.
Servos often run for short bursts for a few minutes/hours at a time.  Wind turbines must spin 24/7 for years.
You have to do your research by looking up the manufacturer's data and applications for the particular servo you like, before having confidence that you're going to get something useful.

It is a little bit of a gamble, but most will work just fine. These AC servos are usually built very well. They typically outlast whatever they are used on. You see old CNC machines that were used everyday for 30+ years and servos never touched. Kind of amazes me. Some operate at pretty high rpms too.

Another thing to keep in mind too, the current ratings on these are continuous. And they live deep inside machines with absolutely no airflow on them, covered in grease, dust and metal chips and they run just fine. So should be fairly safe running considerably higher current then their rating. Probably double.


 

[SparWeb]

Thanks Murray!
Right - you've had a go at servos, too: https://www.fieldlines.com/index.php/topic,149721