1/2 hp output numbers after spliting the coils

[Devo]

I took the 1/2 hp induction motor with 4 curved #29 mags . I used the stock coils except I took the leads out from each coil individually so I could control how I wire it.

As was suggested to me I spilt the coils so that I ended up with 4 sets of 2 coils , I than ran these 4 sets into 4 bridge rectifiers & was quite suprised with the increase in performance.

at 210 rpm 18.0 volts open/2.1 amps at 13 volts( 27.3 watts)

at 280 rpm 25.3 volts open/5.6 amps at 14 volts(78.4 watts)

at 450 rpm 38.5 volts open/11 amps at 15 volts (165 watts)

at 680 rpm 61.0 volts open/17 amps at 16 volts then drill press cut out-at least 272 watts

I have a few questions , am I getting the same output power as before when the drill press cut out but now less is into heat loss thus the better output numbers?

Also the thicker outside wires both had 2 wires going into the main leads before I started hacking the coilsd apart is this normal it kind of confused me for a bit?

When I rectified the thin & thick wired coil individually 1 came out at 9 volts & 1 at 7 at about 220 - 250 rpm , I am tonight putting 8 mags on the rotor so I have nn ss nn ss to see if I can get individual rectified out put near 12 volts by 250 rpm .

Then I will rectify all 8 coils seperately & parallel them all to see the output.

Wow is it hard to glue 2 mags of the same polarity side by side! , I am going to have a small 1/8 space between them.......

Devo

[willib]

I am a little confused ,

 you are using glue to hold the magnets in place.

but you are sticking them to metal , right?

[Devo]

yes that is correct

[ghurd]

Less power is lost in the ohms of the coils. More power can get out of the alternator.

Did you get the magnet count doubled and tested?  

My bet is a 75% jump in voltage and power. How did it really do?

Too late for this trick?

I have a trick for getting the 2nd set of same pole magnets on closer together.

Weaken the field strengths by shorting them to the next magnet of the other pole.

Simple.

Use soft iron bent to fit from one glued magnet (N) to the one glued one next to it (S).

Use another piece of soft iron from the magnet being glued (N) to the other one next to it (S).  The N & N don't argue quite as much if they are busy somewhere else.

A couple additional layers of iron will help a little more.

I have used cheap coat hangers or 'farm' wire in many pieces. But my favorite is pieces of microwave transformer laminations, because it is here, takes less pieces, and it bends very easy.

Be careful the glue does not reach the iron, like JBWeld will want to.  Maybe electricial tape on the iron would add a little piece of mind.

Not as good as a cage or fancy jig, but it helps a lot when doing it by hand!

Yes. Remove the iron after the glue has cured.

G-

[Devo]

I am doing the 8 mag & will post the results , I have glued them on with gorrilla glue 3 times but the darn thing goes in with such force when 8 mags are on the rotor that one always hit's the lamination & breaks loose

I have the glue "setting" again for the 4th try. I can't believe how hard it is to get the rotor back out of the motor with 8 #29 mags on it , I have a scar on the side of my belly from the pry bar to prove it -lol OUCH!!!

Devo  

[ghurd]

Not sure it will help. I do it with smaller ones.  Wrap the rotor in 2-liter soda bottle plastic, like a large funnel.  Slips right in. Usually.

Make sure OD with the plastic is a little smaller than the hole ID. Removing a half way in, force fitted rotor is a bugger.  :/

G-

[Devo]

Must have been near saturation with 4 mags ,there was some improvement but not until about 600 rpm , I didn't take it much higher because the battery bubbled crap out at 680 rpm , I will maybe add another battery tomorrow.

210. rpm open 12.5 volts /.05 amps into a battery at 13 volts(not sure how)
     
280. rpm open 17.4 volts /3.3 amps at 14 volts(46.2 watts)
     
450. rpm open 26.8 volts/11.8 amps at 16 volts (188.8 watts)
     
680. rpm open 42.5 volts/20 amps   at 17 volts (340 watts)
     
     

I did these tests using a 10 amp multi meter when it hit 20 amps it blipped the meter to 1 so I put an old 30 amp ammeter on it out of an old lawn tractor , it sat steady at 15 amps 17 to 18 volts so I am not sure which is more accurate but the multi was used on all other tests so I went by it's 20 amp reading to keep the tests the same.

This time at 680 rpm the drill press did not shut off but the battery boiled out the vent in short order.

I think it would out perform at higher rpms (680 & up) but it seems more cost effective to split them into 2 coils & use 4 bridges & 4 mags-you get better low wind power & pay for 4 less bridge rectifiers & 4 less mags as I picked up a motor for 5 dollars,those 4 extra mags & rectifiers would make more power in another motor.

Then again if you wired it with one of those star delts type switches it may be fun to have the bigger amps at high rpm & still get the low power .

Single coil output was 9.1 at 210/12.9 at 280 for the thicker coils & 7.5 &10.8 respectivly for the thinner.

I am thinking of trying a set of Arts 8 foot blades on this.

Devo

[Flux]

Did you notice any difference in the iron loss drag when you turn it with the extra magnets.

I just mean the drag bit ( not cog if there is any).

Flux

[Devo]

It is quite a bit hard to turn with the 8 mags on it Flux.

Another thing to note is I just lathed down the original shaft's soft metel enough to fit the mags in but not right to the steel centre. So performance with 4 mags might be even better with the mags being on solid steel.

I have a few more hours of work today then I am going to mess with it some more & see how it performs up in a higher rpm , I may get a new 30 amp meter from the farm supply place today & see how it performs.

I will try to get some batteries for my camera as well.

Devo

[anchor1]

Devo try using that heavy black cloth duct tape to hold the magnets on for testing .I have done it lots of times even to a 1000 rpm without it letting go.Clean the magnets first with a wax and grease remover then wrap the tape around overlapping on a magnet and cut through both tapes on the centre of the magnet.Also it protects the magnets when they go in. I've never had one fly off yet,the magnets did slip once on the rotor at about 800 watts no damage at all just scuffed them a bit ready for the glue  (locktite 3805 is the glue i'm using to finaly glue them down.

[Flux]

Thanks. It would be interesting to actually know how much that iron loss comes to, it's something that never gets discussed with these motor conversions.

If you have a lathe big enough, any chance that you could hold the shaft in the chuck and measure the torque needed to hold the stator with a spring balance at a known radius. From this and the speed we could find the no load iron loss.

You will increase output at high speed even when the iron is saturated as the air gap in the teeth will still see increased flux and you will also reduce the effect of armature reaction. There is no doubt a good balance somewhere between no load iron loss and maximum possible output. It may be that too much magnet will affect the trade off between low and high wind performance.

This iron loss will definitely affect start up but every one seems to think that cog is the total issue.

Flux

[Devo]

I will look for a spring scale today , what if I ran my drill press through the killo watt meter to see the difference in power the drill needs to run it at open voltage would that work?

Devo

[Devo]

Ok fellas I went & got a brand new 30 amp ammeter from a farm supply store (for a tractor).

At 680 rpm on my drill press it read 22 amps 14 volts in the battery(308 watts)

I decided to wire the motor back as 2 coils in series bridge rectified as before but now I have 8 mags to see if there was much difference , it was a big difference , it has me wondering if I should rewire them all as single coils with 8 bridges because maybe I had something wired wrong.

Here are the new "split coil" Numbers

210. rpm 53.3 open volts / 11.5 amps at 13 volts(149.9 watts wow)
     
280. rpm 74.5 open volts // 17 amps  at 13 volts (238 watts)
     
450. rpm 114.1 open volts/ 25 amps at 13 volts this cut out the drill press
     
     

(325 watts at 450 rpm !!)

680 rpm 181.4 volts open//drill press wouldn't drive it

These numbers are way higher , I could try it in 48 volts to see what I get , Shouldn't my open voltage for single coils be 25 volts at 210 rpm & not 12 if I get 53 with 2 coils in series?

I am thinking I need to rewire all 8 bridge rectifiers again & see what I did wrong

Devo

[ghurd]

Hi Flux,

I can tell you, from what I have done, that they seem to hit a peak amps. Not so much peak watts.

Much like a large stepper motor... Say 1A at 12V and almost 1A at 48V... If you know what I mean.

I have no way of accurately measuring iron losses or inductive reactance.

My guess is inductive reactance is a far larger problem than iron losses. Low RPM voltage is the least of my troubles.

This is very old news, but I believe it could be relevent.  More so given a recent statement by possibly(?) Zubbly or TomW, saying something about amps peaking out, while voltage was less of a problem.

I believe I hit the amps wall with that ugly 250W 3600RPM 3-Ph Hard-Drive magnet unit.

An old post by Jerry...

http://www.fieldlines.com/story/2005/4/16/42254/0713

G-

[Flux]

Check your new ammeter against your multimeter at about 10A and see how they compare.

Most of those vehicle things are indicators to show if you are charging or discharging I wouldn't vaguely trust it without checking.

Scoop does something strange with columns of figures. The first figure seems to vanish. I can't understand the speeds in your results.

Perhaps if you add another number to the front, when that disappears it will leave the rest making sense.

Your open circuit voltages look way too high for charging 12v with decent efficiency, looks as though you need more parallel circuits.

Flux

[Flux]

Induction motors are so difficult to calibrate as dynamometers that at best it would only give a comparison between iron loss with 4 and 8 magnets.

You may be able to mount the stator of your alternator to turn on a bearing as a guide at the bottom and drive from the chuck and measure the torque to hold the stator from turning, same as with a lathe.

Flux

[Devo]

All my speeds are done using a belt driven drill press & many of the speeds are stamped incorrect.

When I wire it yesterday & got the high voltage I must have had one set parallel & one series or something , anyway after rewireing it a few times here are some results compared against each other

Top results are 4 mags  4 coils in each set split into 2 sets of 2 coils in series run into 2 bridge  rectifiers.Total 4 bridge rectifiers

bottom results are 8 mags wired the same

210. rpm open voltage=18 volts or 2.1 amps at 13 volts(27.3 watts)
     
210. rpm open voltage=25 volts or 6 amps at 13 volts (78 watts)
     
280. rpm open voltage=25 volts or 5.6 amps at 14 volts(78 watts)
     
280. rpm open voltage=34 volts or 10.8 amps at 13 volts(140 watts)
     
450. rpm open voltage=38 volts or 11 amps at 15 volts(165 watts)
     
450. rpm open voltage=forgot to check or 15 amps at 13 volts(195 watts)drill press cut out
     
     

Then I have these sets of figures

the top set is each coil individually bridge rectified then all 8 parallelled(total of 8 bridges)

the bottom is 2 coils attached in parallel then bridge rectified with 1 rectifier(total of 4 bridges)

210. rpm open voltage=12.5 volts or .05 amps at 13 volts
     
210. rpm open voltage=12 volts didn't check amperage as it's below cut in voltage
     
280. rpm open voltage=17.4 volts or 3.3 amps at 14 volts (46.2 watts)
     
280. rpm open voltage=17 volts   or 3.8 amps at 13 volts (49.4 watts)
     
450. rpm open voltage=26.8 volts or 11.8 amps at 16 volts (188.8 watts)
     
450. rpm open voltage=26   volts or 13.5 amps at 13 volts (175.5 watts)
     
680. rpm open voltage=42.5 volts or 20 amps  at 17 volts (340 watts)
     
680. rpm open voltsge=42 volts   or 18.5 amps at 14 volts(259 watts)
     
     

So as has been stated before it seems on an induction motor with single phase style windings more bridge rectifiers gives you a little more power at the higher rpm range & about equal at the low rpm (210)

Flux I haven't found a spring scale yet , I still would like to parallel all 4 coils then run 1 bridge for each set of 4 to see how it compare & I would also like to rectify all coils again but then run sets of 2 in series then parallel those with the other 2 basically the same as the bottom set of top tests but with 8 bridge rectifiers.

Is there some kind of switch I could buy that can detect when I am at about 600 rpm & than switch me from 2 coils in series parallelled to all coils parallelled? This seems to be about where the parallel output over takes the 2 series & it is also much easier to turn at that rpm which should free up more power.

Thanks for all the input & advice guys this little 70 watts conversion is now pushing 300 watts out of my drill press just from some wireing changes & advice.

Do you think there would be any benefit to rewiring it in 48 volt( all 4 coils in series ,both sets parallelled)  & testing through 4 batteries?  

[Flux]

48v would suit that motor quite well.

Sorry I can't make any sense of your speed figures, I only get 10, 50 or 80 and these must have something in front as you mention 210.

Maybe some browsers don't screw this up, but Gates's thing looses the first figure somehow.

Flux

[Devo]

they are always in this order

two hundred & ten rpm

two hundred & eighty rpm

four hundred & fifty rpm

six hundred & eighty rpm

I can see them ok on my end, not sure why they are not good for you so I typed them -lol.

Devo  

[oztules]

There's nothing wrong with your figures from here Devo ...I'm running linux ephiphany browser. Must be the MS thing that Flux is running.

Its ok in Mozilla, and Konquerer also.

[Flux]

Thanks

That makes sense now. I can see that you are not saturated with 4 magnets but it almost certainly is with 8.

You could use series parallel connection to obtain the best low and high wind results in much the same way as star delta. The switching can be done with one simple relay.

Group your bridges into 2 groups that you want to connect in series or parallel and try this circuit.

With the relay closed you have a series connection. with it open the groups go in parallel via the diodes. For least loss use schottky diodes, but you won't notice the different with ordinary diodes.





Flux

[Devo]

what tells the relay when to open & close?

Devo

[Flux]

The best thing to use is a speed signal derived from the frequency of the ac line volts.

Commanda has a circuit that uses a 2917 tacho chip to do this for star delta switching.

You can use battery current as a signal but it needs time delays and backlash to keep it stable as the current drops at first until the prop picks up speed.

If you don't like electronics it is possible to make mechanical speed switches.

Flux