Baby Blue Motor Conversion

[SparWeb]

I promised to post about this one a long time ago.  Then I started to hijack a thread with Adriaan when his ideas gave me inspiration for this project.  So it must be time for me to start posting about this new project I am planning.

Let me start with the long story:  I once before stopped in at one of the few shops in Calgary that still re-winds motors.  The previous time I visited was many years ago, during my first motor conversion project. Then, I explained what I was doing, and got some advice about a safe way to get the magnetized rotor inserted safely and without damage.  I believe we discussed other things but it was over 10 years ago.  Earlier this year (just before we all got locked up, in fact) I paid him another visit, both of us more than 10 years older but still doing the same things.  He still had a giant pile of old motors in a corner of his shop, most of them single-phase and fractional HP, so I just struck up a conversation about what I had been doing, how his previous advice had helped, and so on.  He was genuinely interested, then went to his junk pile, shifted a few and revealed....   this....



It is seriously brand new.  I don't think a single Amp's ever been passed through its wires.
It's almost a shame to cut it apart!
He was prepared to give it to me for free, but I had to at least give him coffee money for a month for something like this.

[SparWeb]

Some more pictures.  It's very pretty!

[SparWeb]

A recent thread started by Adriaan Kragten: https://www.fieldlines.com/index.php/topic,150222.0.html has given me some new ideas that look very helpful for these kinds of motor conversions.

Here's a diagram of the rotor's cross-section.  This was done in a program called FEMM (Finite Element Magnetic Modeling).  The program FEMM is great and free.  It quickly generates simulations of the fields inside the materials in the motor.  I can use it to predict the results of any conversion process, and especially to compare several design options.

[bigrockcandymountain]

Wooo this is going to be great.  You definitely scored big picking that one up. 

You are going to hit 24v at a very low rpm.  That means large diameter. 

[ruddycrazy]

G'day Sparweb,
                         Not sure how your going to do the magnets, now with my 4Kw conversion I used 22 off 16x13 N50 grade round neo's in each pole and put them on a 10 degree skew to cancel the cogging. Now this would mean machining up a whole new rotor and counter boring in individual pads for each magnet to sit on. Believe me it is scary putting 22 N50 grade neo's all the same pole in beside each other but if bery careful it can be done. once the pole is in make up a dam and put in some epoxy to keep the magnets home and move onto the next pole. Once all 4 poles are done make up a mold and epoxy it. Leave for a week to fully cure then machine to OD.

                     Now what I like to do with the rear bearing is use a 5 series double row ball bearing as the rear bearing takes a hammering from the blades as you would already know.

Most of all have fun building this one mate and it should be a ripper of a conversion.

Cheers Bryan

[wbuffetjr1]

Does this new thread mean you are committed to starting it??

[gsw999]

Is this the same sort of motor they put in the "prairie" turbines with the 4 long wooden blades.

[Adriaan Kragten]

If you want to use the standard winding, you can chose for a 4-pole or for a 6-pole motor. I have used 4-pole motors for my older VIRYA designs. The problem with 6-pole motors is that the rectified open DC voltage at a certain rotational speed is about a factor 1.5 higher than for a 4-pole motor if the same Bl value is realized. If you want to use the generator for 24 V battery charging, the voltage is much too high if you use a 6-pole motor, even if the winding is rectified in delta. You can modify an existing 230/400 V winding into a 115/200 V winding by connecting the first and the second layer in parallel in stead of in series. In this case the voltage is a factor 2 lower. This procedure is explained in figure 2 of my public report KD 341. So it might be possible to use a modified winding of a 6-pole motor for 24 V battery charging but correct matching also depends on the diameter and design tip speed ratio of the chosen wind turbine rotor.

You want to use the original armature but this armature contains aluminium short-circuit bars and these bars will restrict the magnetic flux which is flowing in the armature. It might be that this restriction is that bad that even with the standard winding, the generated DC voltage isn't too high. 

[bigrockcandymountain]

Nope, not the same as prairie turbines.  They were a 7.5hp 1720 rpm motor with a gearbox attached. 

I think this will be good for 24v based on what i have seen with my 5hp.  The reason being, it has a huge frame and shaft, so up to 5m diameter is probably possible. 

5m dia at tsr 7 and 5m/s cutin speed is only 133rpm.  Using thinner magnets and only on the N poles will have you somewhere in the ball park.   (My 5hp hits 24v at 80 rpm with 1/4 thick magnets and both poles magneted.  2Y connected)

If not, you can drink the mppt cool aide and buy a classic so your voltage can run higher than battery.  At 24v though, that limits the watts pretty low unless you use 2.

[mbouwer]

Nice project,
Do you already have an idea about the the rotor?
I think shaping is possible with a milling machine. Starting with solid iron.
But with a pipe as a mould, perhaps it's also possible to form the rotor from a number of welded strips.

[SparWeb]

Lots of questions - thank you everyone.

I want to start this build, I just can't claim that I have a complete plan on how to finish a whole turbine, yet.  More specifically, as soon as this motor came into my hands, I knew I had a fantastic candidate and I'm sure I will put it into a turbine if I can.  Since my Baldor 3 HP conversion was such a success, it may be difficult for me to actually match or beat it, both in ruggedness and in match-up to the rotor for performance.  After examining this bigger Baldor, the ruggedness shifts up a level because the matching rotor will be much larger. Probably not 5 meters as BRCM suggests, but 4m ought to be possible.

I am not concerned with matching voltage to a particular battery stack.  This motor has adequate wiring provisions for combinations of series and parallel connections to shift its range of operation as I need to after conversion.  If that range is not sufficient, the wiring is accessible and I could separate the star-point to re-connect it in Delta.  I have previously experimented with a delta-connected motor-conversion and it became much hotter when I performance tested it.  I regret not taking temperature measurements during those tests.

The size of this machine could represent a step-up change in my use of wind power at home.  My current 2.4m turbine is capable of producing 1000 kWhr per year, which is 1/8 of my total household usage.  It's not big enough to justify the hassle of grid-tie, so it maintains a back-up battery.  A 4 meter turbine will produce much more.  I would either need to grid-tie, or sell the machine to a willing buyer.  I could also adopt parts of both those plans, investing in the infrastructure to loft the turbine in order to do performance testing before trying to sell it.  And it would need a bigger diversion controller - MPPT is almost unavoidable at that size.

I've never really envisioned myself as a wind-turbine "manufacturer".  I have some reluctance to turn my hobby into a business.  Go looking for small wind turbine manufacturers that have NOT gone out of business.  There aren't any.

So I don't have any firm long-term plans, just opportunities to try things if they come.

[SparWeb]

Some other practical matters about converting this motor:

I don't have a milling machine, but I do have access to one at work.  If I pick the right time and somebody owes me a favour, I can get the machine for the hours I would need to get this done.  I'll need to prepare myself in detail before using their machine for my work, making sure that they have tooling suitable to what I need.

The plan is to mill 3 large troughs through the existing rotor.  The rotor would be horizontally mounted so that the cutter will cut long slots in it.  I would use an indexing chuck to rotate it accurately.  The mill would be set up with a vertical cutter that I can plunge into the side of the rotor and cut from end to end - but not break through the ends.  There are end castings that will hold the rotor together during the milling operation.  After the first slot, the rotor would be turned to an indexed position 11 to 12 degrees from the first trough, and another pass cut.  When 5 passes were made, the troughs would actually form one large channel that covers 1/6 of the circumference of the rotor.  At the bottom of the channel would be 5 long, flat surfaces.  Then I'd advance 120 degrees, repeat, another 120 degrees, repeat, and that would give me the 3 wide troughs for 5 rows of magnets in each trough.

Since coming up with this plan, I've thought about the consequence of not altering the rotor on the S poles.  I am starting with an induction motor, here, and hiding in the interior of the rotor is a sequence of aluminum bars that develop their own field through induction from the main windings.  That effect could continue to operate if I don't cut through these bars.  I don't know how strong the effect will be, or if the other cutting with interfere with it, or if a careful selection of the location where I mill the channels could enhance or eliminate this effect. 

There's a lot I don't know about induction motors.

[SparWeb]

And looking farther ahead (too far...)  The price of cedar has doubled this year, in case nobody noticed. 
If I get to the end of the conversion with successful results, which may happen by next year, would the price of lumber have come back down by then?
Don't ask me to work with some other wood, or (worse) fiberglass, please.

[bigrockcandymountain]

I bought spf cull lumber last year or maybe 2 years ago for $4 per 16' board.  Mostly 2x6 with some 2x8 and 2x4. Even some 18' 2x8.  I have a small pile of clear stuff i will use for my blades 3.0.   Use spruce.  You'll love it.  Except it doesn't smell nearly as nice as cedar. 

I really do expect the price of lumber to drop fast this winter.  It is in the territory of stupidity right now.

I built a hot wire foam cutter for some insulation i was cutting.  The thought crossed my mind that i could do a foam core fiberglass set.  Then i thought how much i hate composite/glass/plastic etc. 

[Adriaan Kragten]

Some other practical matters about converting this motor:


Since coming up with this plan, I've thought about the consequence of not altering the rotor on the S poles.  I am starting with an induction motor, here, and hiding in the interior of the rotor is a sequence of aluminum bars that develop their own field through induction from the main windings.  That effect could continue to operate if I don't cut through these bars.  I don't know how strong the effect will be, or if the other cutting with interfere with it, or if a careful selection of the location where I mill the channels could enhance or eliminate this effect. 

There's a lot I don't know about induction motors.

The aluminium bars in the armature only guide a current and so only make there own magnetic field if the armature is rotating slower or faster than the rotation of the magnetic field of the stator. This is the situation for use as an asynchronous motor or for use as an asynchronous generator. But if you use permanent magnets for the north poles, it becomes a synchronous generator. So now the magnetic field of the armature rotates with the same rotational speed as the magnetic field which is created by the currents in the stator winding. This means that no current will flow in the aluminium bars of the south poles and so no magnetic flux is created in the south poles because of this effect.

Normally these aluminium bars in the armature are twisted such that at the ends, they just overlap one stator pitch. This is done to flatten torque fluctuations. At the outside of the armature you see only small aluminium strokes but that is because the slots for the aluminium bars are only small at the outside of the armature. At the website of Kienle & Spiess, the armature slots are specified for a certain stamping and you can see that these slots are tapered and that they are widest at a point only some mm below the outside of the armature. If you mill grooves in the armature which are in parallel to the armature shaft, you will certainly cut these aluminium bars at the bottom of the grooves (except if the grooves are very deep). So at the bottom of the grooves you will see inclined strokes of aluminium which don't guide the magnetic flux of the magnets. At the widest point of the slots, the width of the iron is about a factor 0,53 of the pitch in between the heart of the slots. So there will be a large part of the bottom of a magnet which will touch no iron. I think that using the existing armature in stead of using a new massive steel bar will cause a strong reduction of the magnetic flux and so also cause a strong reduction of the maximum torque level and the generated voltage per turn per coil. But you can try it and if the result isn't acceptable, you can try a massive steel armature afterwards.

[gsw999]

Nope, not the same as prairie turbines.  They were a 7.5hp 1720 rpm motor with a gearbox attached. 

I think this will be good for 24v based on what i have seen with my 5hp.  The reason being, it has a huge frame and shaft, so up to 5m diameter is probably possible. 

5m dia at tsr 7 and 5m/s cutin speed is only 133rpm.  Using thinner magnets and only on the N poles will have you somewhere in the ball park.   (My 5hp hits 24v at 80 rpm with 1/4 thick magnets and both poles magneted.  2Y connected)

If not, you can drink the mppt cool aide and buy a classic so your voltage can run higher than battery.  At 24v though, that limits the watts pretty low unless you use 2.

Thanks for the answer , I remember seeing the prairie build video that was a hell of a big motor on that thing, also you gave me some good info with regards to a midnite classic , no one ever explained to me why they work so well and from what you said that makes a lot of sense, are there any cheaper options?

[gsw999]

And looking farther ahead (too far...)  The price of cedar has doubled this year, in case nobody noticed. 
If I get to the end of the conversion with successful results, which may happen by next year, would the price of lumber have come back down by then?
Don't ask me to work with some other wood, or (worse) fiberglass, please.

(Attachment Link)

Prices for stuff like this will continue to go up up and up due to the climate change agenda , buy some now if you can , I'd be very surprised if the price came down.

[wbuffetjr1]

Lots of questions - thank you everyone.

I want to start this build, I just can't claim that I have a complete plan on how to finish a whole turbine, yet.  More specifically, as soon as this motor came into my hands, I knew I had a fantastic candidate and I'm sure I will put it into a turbine if I can.  Since my Baldor 3 HP conversion was such a success, it may be difficult for me to actually match or beat it, both in ruggedness and in match-up to the rotor for performance.  After examining this bigger Baldor, the ruggedness shifts up a level because the matching rotor will be much larger. Probably not 5 meters as BRCM suggests, but 4m ought to be possible.

I have looked through your old posts but couldn't find the specs of your original Baldor. Can you post a comparison of the two motors?

[bigrockcandymountain]

As far as I know, there aren't any off the shelf cheaper options for mppt with wind.  The other nice thing about the classic is it has 2 aux terminals so you can set up safety shutdowns, manual furling control etc. I have one wired to kick on a ssr to heater elements when the voltage spikes during gusts.  It keeps things much better controlled than a controller alone.

I understood the lumber price was due to everyone renovating during lockdown and supply issues caused by the same lockdown.  Lots of demand, short supply.

[SparWeb]

Thank you Adriaan!

From K&S website: