Results of a 1/2 hp conversion using #29 mags

[Devo]

This motor was a 1/2 hp 1725 rpm 110 volt ac motor.I turned the rotor down & put 4 #29 mags around the rotor n s n s.Using the stock coils I put each pair of 4 coils through it's own rectifier

  When I tied the recifiers in series I got these results  

 210 RPM open voltage 34 volts / 2.85 amps into a battery at 13.1 volts (37watts)

 280 RPM open voltage 48 volts / 5.4 amps  into a battery at 13.2 volts (71watts)

 450 RPM open voltage 74 volts / Drill press wouldn't drive it -it cut out at 7.5 amps,13 volts unsure of actual # (need bigger drill press)

  When I paralleled the bridge rectifiers I got these results

 210 RPM open voltage 26 volts / 2.45 amps into a battery at 14 volts (34.3watts)

 280 RPM open voltage 36 volts / 6 amps into a battery at 13.2 volts (79 watts)

 450 RPM the ammeter would hit 9 amps for a second into batteries at 14 volts & the drill press would shut off...(need more power..)

  Using this info can I figure out what the wattage would roughly be at higher rpms?

I realize the 450 rpm stuff is useless...

Devo

[drdongle]

Your values for paralleling the outputs doesn't sound right. Does each output work independently? that is winding 1 and rectifier 1 give an output and winding 2 and rectifier 2 give an output? The voltages should be similar and the current should double when in parallel.

[henjulfox]

The output of my conversion, RPM vs Amps was pretty linear. You should be able to take the points you have and draw a straight line to predict higher RPM output. As I understand it, it will top out at some point and level off. I had the same problem as you - not enough drive.

You may need to assume less RPM than you have listed. Driving the generator pulls down the RPM from what is listed on the drill press.

Output numbers look good. Not that much lower than my 1 1/2 HP conversion.

-Henry

[Devo]

yes both windings are bridged seperately but they have a different resistance as on set of 4 coils is much thinner than the other , I never did try just the output on the thicker coils by themselves-maybe tommorrow after work.

I started carving a set of 8 foot blades tonight for it , maybe to big but it should cure any cogging issues (I hope) , what size blades are most people running that have done a 1/2 hp conversion?

Devo

[drdongle]

Sounds like one is the run winding and the other is the start winding. As long as you wire them in phase you can use just one bridge rectifyer for both. The start winding will put out less then the run.

[powerbuoy]

Also, you cannot count on starter and main coils having the same number of turns. You'll receive different voltages. I would take the cois out and rewind it.

[dinges]

Personally I'd lay the motor aside and first do a magnet-only conversion on another motor, where you don't have to replace the windings. There's already enough things to get right just minding the magnets. What size magnets, how many, how skewed, how to mount them, etc. Playing with windings (how many turns, how thick, etc.) would complicate matters a bit more.

Just my opinion.

BTW, if it's a learning experience you're after, read everything written by Zubbly on motorconversions. You'll learn a lot there and with little effort.

[Devo]

I am quite happy with the output for 4 mags...I realize it would be better if it was rewound but for a little camper genny it will do fine.

I have tried using one bridge rectifier & wireing it as a 2 phase , the voltage is the same or very close to the paralleled open voltage but the amps through the battery where significantly lower.

I am on the hunt for a bigger motor with better wireing for a conversion...

Thanks for the input

Devo

[Flux]

You were doing the right thing by using one rectifier on each winding and paralleling them.

There is no sensible way to use both windings with one rectifier.

You have a low cut in speed, if you have another battery, try it into a 24v battery and it will most likely work better.

If it does then you can reconnect both windings series /parallel to get it back to 12v, or use separate rectifiers for the half sections of the winding as Jerry does.

Flux

[drdongle]

Actually if you look back at a bunch of Jerrys earlier conversions that is just what he did and quite successfully, as long as they are in phase and put out the same voltage you can wire them in parallel ( just as in multi voltage 3 phase motors). Ther original post suggests that both windings put out similar voltages.

[Devo]

I got confused on what jerry was doing before, Do I take 1 set of 4 coils & split it into 2 sets of 2 coils each with it's own rectifier so that I end up with 4 rectifiers all parrelleled to get the cut in on target? just a little confused as to exactly what he was doing , I have read through his posts.

I never thought about 24 volts I always get 12 & 48 stuck in my head , thanks Flux I will try that tonight after work

Devo

[ghurd]

Jerry splits up the coils IF the voltage is too high for the RPMs.  At 210 RPM, 34V is too much for a 'normal' 12V machine, so I expect it would stall badly.

"Do I take 1 set of 4 coils & split it into 2 sets of 2 coils..."

That is what I would do next.  Sounds like it would work best for 12V, but the cutin may still be a little low.

Seperating the series coils into parallel coils also reduces the coil resistance, meaning more output and less internal losses.  The difference can be quite dramatic.

G-

[kitno455]

i have not seen a photo, but arent the start windings and run windings offset from one another? it would seem that you would have to have them on two different rectifiers, they are not in phase. putting the output in parallel is exactly what jerry does?

allan

[ghurd]

I was talking about one set of coils, be it start or run coils.

If there are 4 series coils in the start or run windings, often it is better to seperate them into 2 series coils, paralleled with each other.

Often the starts are wired with more turns of smaller wire, giving a much higher voltage than the runs.

I have a small one that would be best if all 4 start coils were seperated from series and then paralleled, but I can't do it because of the teeny-tiny wires. At a good running RPM as it is, the starts make about 60V open, but only ~150ma into a 12V battery. Would probably do 1/2 amp if the 4 in series start coils were 4 in parallel.

The run coils are only half as bad, but I still can't find the wire between the coils to do any seperating.

I don't think it is a good idea to mix starts and runs in series or to the same rectifier, if that's what you mean. They are 90 degrees out of phase.

Just parallel the outputs of each rectifier to the battery.

G-

[Devo]

Here are the results for 24 volts

210. rpm      .65 amps 24 volts   (15.6 watts)
     
280. rpm   1.6 amps at 26 volts   (41.6 watts)
     
450. rpm  5.05 amps at 28 volts   (141.4 watts)
     
     

Quite an improvement already , now to split the coils & try 12 volts again

Devo