El cheapo 230 volt alternator

[starfire]

using a 5hp 3 phase 8.5 amp induction motor.
Today I had a quick play with the concept.
 By spinning up a 3 phase motor with the Petter, it quite happily generates 50 cycle power at 1500 rpm. or 60 hz at 1800 rpm.
These motors are very cheap and and easy to find, can often be found at a scrap dealers at scrap prices.... working out much  cheaper than buying a dedicated generating  head.... important as I spend all my spare cash on drugs, alcohol and cigarettes, or so i have been told.....
Each motor is a little different in the capacitors required to get it working properly, but a bit of fiddling will get the best performance.
The output voltage/current is taken from one phase, the other two are capacitance loaded to "bend" the magnetism so the rotor is at maximum magnetic potential as it tranverses the poles, making it self starting and self sustaining.
Many, if notall  of the Chinese generators now use the exact same principal, although with actual rectified windings on the rotor, rather than a squirrel cage.
Mine ended up Delta connected  with a 40 microfarad and an 80 microfarad capacitors  on the two legs.  It manages 2 kilowatts with a 10 percent voltage change from zero to full load. At 2.5 kilowatts, it quits  generating ..... quite a nice safety  feature... cannot be overloaded.
By varying the engine speed, on my example the frequency can be altered from 30 hz to 80 hz, possibly an easy way to run induction motors as variable speed motors in the future., although the voltage varies considerably as well without recalculating the capacitance values for the changed speed.
Theres a little on the internet on how to do  this , google induction motor to generator, so wont repeat it here other than to include a link that decsribes  the capacitance values and another to claculate the caps to balance the current in each winding for maximum efficiency. Im pretty excited about this, the motor cost me just $13 nz
The beauty of using a motor as a generator, is price, availability, and reliability, no brushes or slip rings, and usually these industrial motors are completely sealed as to be moisture proof. Looking on the scope, it puts out a very nice undistorted sine wave, and NO radio interferrence, a result of not having brushes.

capacitance calculator:

  
http://users.telenet.be/b0y/content/gen_techin/capacitor%20values.xls

and to fine tune for max performance:

  http://www.mdpi.com/1996-1073/5/9/3534/htm
 
I wont know for sure how well this will perform until i get a more permanent installation and have a good fiddle, run a few appliances, and electrocute myself a few times,  but right now its looking very promising.... ill keep you informed.



  

[mikenash]

fascinating

[BruceM]

The capacitance must change according to load, which makes this approach somewhat less appealing. 

[starfire]

The capacitance must change according to load, which makes this approach somewhat less appealing. 

If you check out the second limk i gave, this is not the case....

[dieselspanner]

So,

A synchronous motor connected by a belt to a 6/1 and geared to turn at 'no load' speed with the Lister running at 550 rpm would act as a starter, then as the Lister over rev'd it would overdrive the motor and back feed the grid, either rewinding the meter or 'clocking up' credit at a rate agreed with the power company...........

Or not........

I started off wondering how a constant load could be applied to a genset using a 3 phase motor, and what you could do with the excess power as the domestic load fluctuated without using complicated control equipment

As I'm sure most of you have realised by now I ain't the most with electrical generation so if some one would expand on this theme I'd be grateful. It comes of reading threads like this and having 10 minuets in the bath before SWMBO finds out where you are!

Cheers Stef

[starfire]

Hi Stef,
The easiest way to constant load a stationary engine is by using car alternators to charge battery banks, and then convert the DC into the AC current and voltage for your house. No control equip required. To suppliment a grid connection, this motor  idea will work great, thats how wind turbines do it, it automatically will synch to the mains, the grid will also be seen as a constant load to the engine.  If just supplying  your own homes, its not such a worry with voltage and frequency changes/ fluctuations  from a poorly regulated supply, most electronics have whats called switched mode power supplies internally, meaning the AC is converted straight to DC then chopped up via a PWM to output the correct voltage to the equipment. CFLs too rectify the AC, and are happy with any voltage between 80 to 260....AC or DC. For the same reason, frequency really isnt critical unless you have an old fashioned electric clock, or a speed critical induction motor driving something, llike an old vinyl record turntable for instance. Most of the  higher  powered devices like vacuum cleaners and workshop tools use brushed motors, these also are happy with AC or DC at any frequency and with  wide voltage variations. The later inverter type welders also directly convert the AC into DC before chopping it into a lower  voltage.
Another  huge advantage with generating 3 phase power, it opens up the huge range of cheap high hp electric  motors,  and surplus industrial equipment.
Check out the price difference between a single phase 2 hp motor and the 3 phase equivalent....


Heres the motor Im messing with.....

   


 

[starfire]

Just a thought. To help understand how this works, think of riding a bicycle with fixed pedals. If you try to pedal faster than the bike is moving, you are acting  like a motor, accelerating the bike.. If you try to pedal slower than the bike, then the pedals will push against your feet, then you become the generator,  absorbing power from the bike. If you pedal at the same speed as the bike, nothing happens, you are then synchronised.
This is what is called "slip", and is why an electric motor develops most torque at standstill.... when the slip is greatest.
So, grid connected, the loading of the generator increases with slip, this loads the drive engine, slows the speed, the load decreases, engine speeds up, load increases..... a happy medium is reached eventually where everything remains constant.
At less than 50 cycles, (1500 rpm) the motor will take power from the grid and act as a motor, at 50 cycles (1500 rpm) will niether absorb of generate power, its synchronised, it will free run, and when spun above 50 cycles will feed power back into the grid automagically, no other controls required.
Without a synchronising grid connection, the motor will generate any frequency depending on speed of rotation and capacitor values.
Thats induction generators in a nutshell.

[BruceM]

Um, the two charts in the second document clearly show vary different capacitance values for different loads.  You might be able to find a value that works with acceptable voltage variation for two different loads if they aren't too far apart.

[starfire]

Bruce,
Yes, that linear part of the operating curve is very short........
To date, my experiments indicate a +'- 3 percent voltage change if I keep the output current considerably less than the skewed reactive current through the caps, in other words, a small part of the total. This gives me 1.3 kW  max into a resistive load. To push 2kW, the voltage variation increases to  +/- 8 percent, at 250v nominal, we get 265 no load, 235 full load, although this is due in large part to the lazy governor on the Petter.   If i load all three phases with  proper 3 phase tools, this variation i expect to be less, although, with only 5hp driving it, this 2 kW would be close to the limit anyway.
 Given my house already runs on clean inverters, the "shitty" power is more than adequate to power my workshop tools like grinders, drill press, compressor etc. Power factor issues not incuded in  the above...
 And, the price is right.... this will retire my standby petrol geny i use for the big jobs now.  Of course, when i repair the AV2, all this will change.
There is more internet info if you look up "rotary 3 phase converter" which is a very similar concept.
I love doing stuff like this..... fascinating.

[EdDee]

Hey Starfire,

Have you considered running the IG as an internal "net metering" type setup? ie couple it to the output of your inverters to boost the available power, the inverters do the frequency coupling etc....? (extends battery life by lowering drain, rather than charging....)

Just a thought....

Ed

[starfire]

And Glort had the temerity to castigate me for my shitty wiring...... sheesh. Something about stones and glass houses?
Ed, I think we think alike...
What I did today......
I rectified the three phases from the IG, giving me 310 volts DC. This I dumped into the input circuitry of a Strata inverter welder. I repair these for a living so I have several laying around. With a small mod to the PWM, its outputting  56 volts DC at up to 180 amp, just right to charge a 48 volt battery bank these welders normally sit at 47.
Using all 3 phases, this evenly loads the  IG, and gives a constant load to the engine.
 The DC  inverter welder has to be the cheapest high current adjustable battery charger you can get.
Now, I dont have a 48 volt mains  inverter, but I do have the 12 volt sunlite. This is a low frequency sine wave design using 50 Hz all the way through, so it uses a normal iron core transformer. All I need to do is to add  4 x the windings to the primary, this will let it run on 48 volts and the 240 volt AC output and AVR circuitry will stay the same.
Its current , not voltage that kills mosfets, so instead of seeing 160 amps as they currently do on 12 volts at 2000 watts loaded, the current will reduce to 40 amps at 48 volts ... so  they will breathe easy.

So, what I hope to have running this time tomorrow night :   

250 volts AC from the IG, all 3 phases rectified to 310 VDC then into the inverter welder, then an output of 56 VDC into a battery bank of 48 volts.
The 48  VDC then into the sunlite, 2kW 240VAC 50Hz  into my house.
Advantages being constant engine load, constant IG voltage, even phase IG balance, low current demand, pure sinewave power and good AC voltage regulation, certainly better than a AVR or mechanical governor can provide. The Sunlite may even supply more than the rated 2kW depending on transformer saturation  with the much reduced input current. .
And, all low cost. 
Its fun to use wot u got.
I also need to tidy my toxic waste dum... er.... fuel storage area, while the rain has stopped , like 30 odd 44 gallon drums of assorted oils, kero and paint thinner.....

[gusbratz]

.  The load is imbalanced but in my experience, much to the protest of many on forums etc, the motors don't give a dam.  They are heat sunk and cooled for 3 times the load and you are only driving them to 1/3rd capacity, T
https://www.youtube.com/watch?v=HUE1RQRAXlg


[/quote]

glort,I  wathced your link and just realized you are the oil the  burner guy! i watched all your vids and really enjoyed them, tried sharing my excitement with my co-workers but they have no imagination. I even tried making an oil burner like yours to fire an aluminum foundry i want to build. The burner was a total failure and didn't work like yours. not sure what i am doing wrong. maybe I just didn't try hard enough to get it going. any way back to the topic at hand about bi-phaseing motors. people come to my house and seem all my 3phase stuff and say wow you have 3 phase here! no, i just use little cheap static phase converters to start them then i run them on 2 phases. oh and their faces drop and they lose all interest like it doesn't count and i am a fraud. i counter with well you know it's just like 2/3 of the rated power and seems to work good. "oh but isn't it bad for the motor" well the f@$*ing thing was in the dumpster at work so i would say that may have been worse for it. besides it has run my stuff for thousand of hours with the only problem being capcitors blow if you start and stop it too often. i always thought backfeeding the grid with one set up as a generator would be a snap because to sync it to the grid all you would need to do is start it as a motor. then useing it as a motor start the engine. as soon as the governor starts pushing it would slip right into generate mode. 

[starfire]

Just to butt in here, if you are after a safe waste oil burner for inside your house, this is my version. It  works very well, uses around 1 liter/hr , no smell, no smoke and fully controllable. The oils runs  down the vertical air tube on a wire, so no carbon buildup or blockages , the air can be throttled to adjust temperature. Water injection is added on those really cold days to increase the burn, hot oil and water atomises really well...... so no air compressor or fan needed.  Global warming has increased significantly since I built this 5 years ago.... a good indication of its effectiveness.
Main body is a car type LPG tank, air tube is a length of 3 inch car driveshaft tubing, a ball valve adjust the drip into a wheel hub boss, and from there runs down a wire to drip on an old fire brick sitting in the bottom. Chimney is 6 inch diam stainless. An access  door allows for the occasional cleaning. The holes at the base were drilled to monitor the flame colour, they are not required , i left them there for visual ambience. Oil is gravity fed from a 20 liter plastic drum. Corrugated iron is great as a heat barrier, the air flow ensures the iron stays cool. Its also quiet when running but goes into rocket mode when water injected....






 

[starfire]

Lets see Glort,
You complained  about my messy wiring despite it being a temporary fix, my  alternator, my car,  my mismatched battery bank, my choice of belts, and even my dirt floor!! You complained I had no clamp meter, despite having more accurate shunt meters, no rev counter despite monitoring AC frequency direct with a counter that can also measure  belt slip.
 Oh wait, you even  have a complaint with my test procedures, and the accuracy of my independently calibrated test equipment
You complained  I waste  money on drugs, booze and cigarettes even though I dont smoke, drink or take drugs.  You now complain I  sell dodgy products online..... just what are these products?. Have you bought one? Bloody hope so. Can I sell you another, whatever it was,?  Swap you for an alternator?
You are obviously the  unhappy one Glort, and becoming more so by the day.
Heres a part photo of my fuel storage facility, pre the  tidy up.  I would like you to share your valued opinion on this, I am  very sure you will have one.   

   
 

Edit   
 Oh, I see, you do have an expert opinion already on my storage facility, without even seeing it!!, as well as my oil burner!!! That didnt take very long at all. Thank you so much, you are awesome.
Have you thought to enter Australian politics at all?
You may just get the vote....
Did I mention the infra red oil shutoff valve...... the fly ash seperator?
Lets not worry too much with detail.
Or logic...

Todays big alternator upgrade cannot be completed, I need pulleys and belts, and its a long weekend here in NZ, so no shops open  until Tuesday,  bugger.

[starfire]

And, here we have the oil burner surround incorporating a temperature controlled fan  to circulate the heated air. These pics were taken during maintenance after a 3 year trouble free run. And, yes, it did get painted...
Glort, I will no longer respond to you, you are a total waste of my time