1 HP Conversion

[FishbonzWV]

Greetings all,

Just finished testing a motor conversion.

It's a 1hp, 3phase motor with the 6 coil configuration.

I had to open up the wye point and bring out the other three leads.

I used a set of 29's and a set of skewed "29's" on the rotor. I settled on using this combination because the distance between teeth is 5/16 inch and the skew of the mags is the same. Cogging is minimal.

I chucked it up in the lathe, connected up the test rig, and hooked it to a couple of tired old GNB M836VG27's.

Using the test rig I can change from delta to wye to jerry rig easily so I tested the output all three ways.

The lowest speed of the lathe is 133 RPM and I didn't test over 315 RPM because the meters would peg. The batteries were at 12.3V. DC voltages are listed as open.

       Jerry Rig      Delta       Wye

 RPM   DCOV  Amp   DCOV  Amp    DCOV  Amp

 133   13.5  0.2    11.3  0.0    20.4  2.0

 148   14.9  0.8    12.7  0.0    22.9  2.7

 172   17.3  2.0    14.9  0.9    26.6  3.6

 225   23.0  4.9    19.7  4.0    35.1  6.0

 251   25.7  6.0    22.0  5.4    39.3  7.0

 291   30.3  7.9    25.6  7.6    45.5  8.0

 315   32.3  9.0    27.8  9.0    49.2  9.2

I'm pleasantly surprised with the output of this little one horse.

[GeeMac]

Excellent conversion. I envy your talent.

[pvale]

I am beginning to think, from things I've read here, that despite the resistances on a standard motor being too high, the close gap between the stator and rotor gets a bit better efficiency than an axial with a larger gap. Not to put the axial machines down or anything, but it seems a correctly done motor conversion has the potential to be as good as the axial flux machines. I might explore this route for my first machine. I have not read all of the Zubbly posts yet, but he was the undisputed master at motor conversion. I have a couple of small motors that may fill the bill for a first time thing. Thanks for the look-see at your successful conversion.

[Jerry]

Now if you can rig it, a prime driver power requierment would be intresting.

I did this with a 2.5 HP dc motor, a DC power supply and a large Variac.

Now you can compair star, delta and jerry rigged as far as power requiered to produce X amount of power.

Jerry rigged and delta are simular scheems. In thirory they'll produce more amperage but less voltage then star.

So it would be well worth testing jerry rigged and delta at 12 volts and star at 24v.

Then compair wattage figures at same RPMs. Also then compair prime driver requierments.

Great setup, very good work all around.

I did a long armature 6 pole. It used 2 rows of 6 #29s slightly scewed between rows.

It had very littel cogging. A thum and for finger would spin the 5/8" shaft.

With 7ft blade it did 2025 watts at 30 mph.

Again great work.

                               JK TAS Jerry

[Flux]

I take it that you have given volts open circuit and current into the 12v battery.

The power out is very similar in each case but obviously the efficiency is going to be very different. The star case is going to be quite inefficient.

To be of any real use I agree with jerry, you need to measure input power to have any idea how it is going to match a set of blades.

That set up in any form seems very low speed for 12v. I don't think you have the capability to load a size of prop that would suit a cut in of 130rpm. For a more modest size of prop then the cut in is low for 12v even with Jerry connection. the star has no chance below 24v.

You have used just about the best magnet set up possible and if you can get the loading and prop size matched properly you should have a good machine.

Flux

[SparWeb]

Me too, I want to say congratulations, and thank you for the test data.

Do you have the motor shaft chucked into the lathe such that you can move the body around freely?  Within reason it could be left free to rotate without wrapping up the wires.  If so, you can use a spring scale hooked through a mounting hole or the connector box.  The force of the spring scale holds the body of the generator from turning as you run the lathe.  This gives you a measured force at a measured radius.  F*L equals torque.  Multiply by lathe RPM and the appropriate conversion factor and you get power.  That would be the input power.

With those numbers, the door to matching the prop is wide open to you.

Did the lathe slow down as you loaded the generator?  If so, see if you can measure the actual speed, not use the nameplate speed, for more accurate results.

Thanks again.

[FishbonzWV]

Thanks for the comments everyone.

The lathe is too small for the motor to be chucked up in it. I had to use a flex coupling to test as it is. If it was large enough I could rig up a DeProny brake.

So, my thinking is the cheapest alternative would be to use a clamp on ammeter on one leg of the 220V lathe drive motor. Maybe test amperage on each speed as open circuit, then load it into the batteries and get a reading. The difference between readings should tell me the power usage.

Am I anywhere correct with this reasoning or is there more math involved?

Bonz

[Flux]

If the drive motor is an ordinary induction motor the line current will not be much of an indication of load, the power factor tends to change more than the current.

All you could do would be to mount a bar in the chuck and make a prony brake by clamping bits of wood round the bar. That way you may be able to get a comparison between motor current and torque and then use this to find the alternator torque.

Flux

[FishbonzWV]

Okay,

I see it's back to the drawing board to figure something out to support the motor.

And research the Prony a little more.

Thanks

[Ungrounded Lightning Rod]

Interesting test results.  You're showing higher voltage and current for Jerry-rigged than for Delta.

For a three-phase if the waveform is sinusoidal (or close to it, or any of a number of compatible waveforms) the voltage should be the same but delta should provide more current.

What this says to me is that the waveform is so far off sinusoidal that you have significant circulating current in delta and this is dropping the voltage (and burning power heating the mill, too).

Which is not necessarily anything wrong with the conversion.  B-)  It just means you'll want to do a few things:

 1) Check that the coils are all intact:  Does each phase, working alone, produce the same voltage and current as its brothers.

 2) Check how you're connected for delta:  Are you paralleling two sets of diodes in delta so diode drop doesn't unfairly distort the results?  (Using bridges:  Tie the two AC lines of each bridge to form one parallel set, for best balance.)

Presuming neither of those shows a problem:

 3) Use Jerry-rigged rather than Delta if you want to do a high-speed mill or a delta-wye switch.

A nice thing about wye-jerry switching is you only need two contacts, shorting together the wye point without changing the rectifier configuration.

A downside to Jerry-rigged is that, if you want your rectifiers at ground level (which you DO if you want to do short-the-mill furling) you need six drop wires rather than three.  (If you put the diodes up the tower you only need two, of course.)

[FishbonzWV]

Threw this together in about an hour.

Motor shaft rides in oilite bushings inserted in the wooden sides.

Lucky I had a 5/8 rod and the bushings handy.

Now I need a spring guage.

Tomorrow.

[FishbonzWV]

ULR,

For Jerry rig I used the three individual rectifiers, for delta and wye I used the three phase rectifier.

I also ran each set of coils through the AC ammeter, they were all very close.

Static resistance was checked and double checked with my Fluke 77.

I have several of these motors so I dug into the windings on one to find out how they are wound. What surprised me was the outside set of coils had more windings than the inside set. I went through a trial and error period, hooking up all combo's of coils. What I came back to was the original wiring with the Wye point separated.

What I noticed with the results is that they all ended up pushing 9 amps at the top.

This could be the limit it is capable of.

I'll get a spring guage tomorrow (hopefully no honey do's will get in the way) and rerun the tests.

Thanks

Bonz

[Flux]

Your set up for torque should work fine.

I have a feeling that 9A is going to be close to your limit with star connection, the resistance is too high and although I haven't plotted your results butI suspect the curve turns over and you are becoming reactance limited.

In Jerry connection your output is limited by speed and if you raise the speed then the current will go up to at least 1.7 x the 9A.

If you can increase the speed even more you will be able to maintain the 9A star into 24 or perhaps 36 or 48v so the power will still go up. You should be able to hold the higher current with Jerry connection at 24v or perhaps 36v if you get the speed up.

The thing about these motor conversions is that they need speed. A 2M prop would probably suit it well and for that you could cut in at something over 200 rpm and in a good wind then 800rpm is not out of the question. That gives you potential for at least 3 times what you have measured at present and you may even do more than that.

Motor conversions are not particularly good in very light winds, don't try to optimise it for much under 10mph or you will very seriously compromise the high wind output where these things come into their own.

With any load including rectifiers or other non linearity delta performs badly. Jerry's connection is unorthodox but it works. I have never seen it in any other application but for wind turbines my advice is to forget that you ever heard of delta.

If you can't get the voltage match in star then use Jerry connection and put up with the extra leads. I really don't know why people don' have a go at star/Jerry connection especially with these motor conversions, the switching is so much easier than star/delta.The widening of the speed range gives the potential to greatly increase output.

Flux

[ghurd]

I tend to get about the same kind of numbers as Bonz's tests with Jerry and Delta.

Sometimes the open voltages are almost the same, but the output with Jerry is always higher.

My power output tests may have been a bit skewed because Jerry is more efficient (I believe), so it would not have loaded the 'prime mover' (usually a cordless drill for my little stuff) as much, resulting in a little higher RPMs.

Nice job Bonz!

G-

[FishbonzWV]

Whew,

Here's the data from the spring test.

It's wearing me out changing the lathe speeds...my hand is sore!

The volts and amps are basically the same and I researched the formulas but I couldn't determine what unit of length to plug into them. Thinking back on it, I guess I could have made it easy by using a foot long lever. :-(

My spring hook up was 5 inches from the center of the shaft.

        Jerry     Delta

 RPM   AMPS POUNDS  AMPS POUNDS

 133    0.2  0.0    0.0   1.0

 148    0.8  1.6    0.2   1.4

 172    1.9  3.4    0.8   2.4

 225    4.6  7.6    3.9   7.0

 251    6.0  9.8    5.4   9.0

 291    7.8 12.8    7.6  12.2

 315    9.0 14.0    8.8  14.0

I also kicked the speed up and checked open voltage. I hooked up a car ammeter that went from -30 to +30 amps but it is a really cheap one but the needle went to about 15 at 407 RPM.

 352     36.1

 407     41.9

I didn't fool with star YET. I didn't feel like reconfiguring the battery bank today.

I'm tired!

ULR,

I did put the AC meter on each leg of the motor, all amps were spot on, so I don't think there is any mismatch of the coils.

P.S.

One thing I thought was strange was the delta pressure at no cutin...1 lb.

I thought it might have been the 3 phase rectifier so I ran them delta through two bridges... same 1 lb. Jerry connection didn't move the gauge.

[Flux]

This all makes sense.

Taking the Jerry case I have worked out the input power for three speeds.

for 172 rpm      34.5W

For  251 rpm     145W

for  315rpm      260W

You can compare these with the output figures into the battery and you drop from about 77% down to 48% and that seem quite reasonable.

I haven't cheeked delta but the figures are worse so why bother.

The torque figure for delta will be from the 3rd harmonic circulating within the delta. Jerry connection will block any circulating current below rectifier conduction and give an easier start up.

Flux

[FishbonzWV]

Thanks Flux

[SparWeb]

Don't forget that series-to-parallel switching is also a viable choice (especially if one has only 3 wires in the tower).  It does require more relay contacts, but also avoids the delta-related circulating currents.