TheBackShed.com

Forum Index : Windmills : Bryans 4Kw Motor Conversion

Author

Message

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 1609

Posted: 08:31am 06 Dec 2025

Copy link to clipboard

Print this post

Well guy's this was one forum where I didn't document this build and every other forum where I did is now gone so no pictures from the build.

I have been talking with the Electrical Engineer at work about my inverter build and the high currents involved etc so I thought to ask the question about slip rings and the high currents that will be there with this motor conversion.

I machined up a new rotor and put 22 N50 16x13mm round magnets on each pole for 88 neo's in total and only broke one magnet along with a sore finger for a week after a brain fart. Then potted with epoxy and machined for a 2mm clearance from the lamination's on diameter.

I did a one wire test and found off memory 30 turns where I went 3 inhand 1.2mm wire was used along with sore fingers after.

Doing a lathe test was fun at 240 rpm cutin saw a flash of 90amps then my VFD complained of over current. So with a 2hp 3 pahse motor and a programmed VFD this conversion acted like a break.

I had a 100amp 3 phase bridge rectifier going into 2 truck batteries in series for 24 volts and on the third test where the same 90 amps was shown on the clamp meter the bridge rectifier let out the magic smoke.

So for years the conversion has sat there and the talk about 460 amp brushs for the slip ring has me thinking time to design and make the slip rings up and finally get this project going again.

Now for the blades I'm going to carve up some red gum to use as I do have a few big dead gumtrees for the donor wood.

There is a story to tell and a long road before this motor conversion is in the air procuding power.

Regards Bryan

Godoh
Guru

Joined: 26/09/2020
Location: Australia
Posts: 596

Posted: 08:30pm 06 Dec 2025

Copy link to clipboard

Print this post

Hi Bryan, so from the beginning of the story, you are using the motor as a generator for a wind generator?
The current (460 amps) should be possible with slip rings, but i am wondering why you didn't wind the stator for a higher voltage and use a transformer at the battery end to drop the voltage back down?
If I were looking for a large set of slip rings, then i would go to a scrap metal yard and look for an old three phase slip ring motor.
That way you would get the slip rings as well as the brush gear you need.
I am also wondering how you calculated that you need 460 amps for the slip rings.
That is a very high current to be trying to draw from a small motor like a 4kw three phase motor. I would think the motor would get too hot if you tried to pull that much current from it.
Good luck with the project
Pete

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 1609

Posted: 10:02pm 06 Dec 2025

Copy link to clipboard

Print this post

Hi Pete my first motor conversion was that new 1/2hp motor which used the offset method for the magnets and I did put that project on this forum. It did run for many years with those 3 metre oregon blades I made that did fail in spectacular fashion with a bit of them still stuck in my shed roof.

Now for decades I was a member of the fieldlines forum where a member called Zubbly came up with this idea that just worked. Oztules did say the motor conversions are bullet proof and won't burn out as the max current will be limited to what the wire can produce then the eddy currents kick so the current will decrease.

The 460 amp figure was just a figure the engineer came up with as he had used them before as I did ask the question about high current brush's.

Now the best site is ontop of the hill which is around 100 metres from my shearing shed so a long cable run will have to be done. Now whats the bet the site I choose is solid rock about 1/2 a metre down so I will have to buy a rock breaker to go on my mini excavator to get to the depth of the hole for the base.

I do intend to make this a downwind turbine and I will be putting a disk brake on so the max speed can be controlled and that 10,000 amp 240 volt switch I have here will be used to short out the turbine. Why use that heavyduty switch well I do have it here and it may aswell get used.

Basically the rule for motor conversions as one is limited to the nameplate so around 4Kw will be the max the turbine can produce. Going over kill on making everything is the way to go so the turbine can last many years.

Regards Bryan

Godoh
Guru

Joined: 26/09/2020
Location: Australia
Posts: 596

Posted: 11:01pm 06 Dec 2025

Copy link to clipboard

Print this post

Hi Bryan I saw some of zubbly's stuff years ago.
I dont know what voltage you are planning to generate with the turbine, but I cannot see any way that you will get 460 amps from a 4kw motor.
Especially as you say you would the stator with 3/ 1.2mm wires
If you were to run the generator for 24 volts output then I would expect the maximum line current you would get would be 100 amps.
Even then that would be way too much for the windings you have. 1.2mm wire would be good for about 10 amps, so 3x1.2 would really only be good for around 30 amps. Even at that current the motor would get very hot.

Bryan1

Guru

Joined: 22/02/2006
Location: Australia
Posts: 1609

Posted: 12:52am 07 Dec 2025

Copy link to clipboard

Print this post

Well I found 3 off 76.1mm diameter brass disks so I'm now on setting up my toolroom lathe so I can face the disks true and 75mm diameter will be the size of the slip ring.We have a heap of poly carbonate round lengths at work so I'll get the separators parted off for me by the guys in the toolroom.

Pete that 460 amps is just a figure and like I said by building with plenty on overkill will ensure it runs trouble free.

The engineer did say he needed a diameter to work with so 75mm it is and I'll find more out tomorrow at work.

Print this page

To reply to this topic, you need to log in.