Cascade-Gen

[Vizier87]

Hi guys,

I'm wondering: is it possible two combine two identical DC generators to produce twice or less output power? I imagined that it would be impractical to combine the terminals directly, so there might be a converter circuit which simulates the output of a battery, and these output terminals can be combined in series with other converters and produce an effect similar to combining batteries in series?

If you guys are wondering the "why" part, I've got small 30V-10V generators I built myself using scraps from hard-drives, and plastics from broken appliances. Here's three of 'em:

**broken link removed** 30V

**broken link removed** 10V

**broken link removed** 10V

All rated at 3000 rpm, no load. I imagined that it might run at lower speeds, but I tested 'em by connected them to a drill shaft, and see the output.

 

[dknguyen]

I don't see why you couldnt connect them in series for more voltage. Or parallel for more current. You'd want low value resistors on the lines though so the generators wouldn't back feed into each other due to non-identical voltages on a parallel connection.

 

[Vizier87]

Thanks for the reply. How about if I connect them in series after they've been diode-rectified?

 

[Hero999]

You need diodes to prevent back feeding, resistors will just waste energy.

Connecting them in series is probably the most efficient way but if one of them is not turning it will be fed from the other one causing it to behave like a motor.

 

[Vizier87]

series with rectification from each generator or directly connecting them in series?

 

[Hero999]

series with rectification from each generator or directly connecting them in series?

That won't prevent back feeding.

To prevent back feeding when the generators are in series, you need to connect the diodes in reverse parallel with each generator.

 

[Vizier87]

er.. can you complete the block diagram on what you meant? I'm still "blurred".
**broken link removed**

thanks uncle Hero.

 

[Hero999]

Assuming the generators are AC, connect them up like this.

Obviously, diodes will not work with AC voltage.

 

[Vizier87]

Assuming the generators are AC, connect them up like this.

Obviously, diodes will not work with AC voltage.

Thanks uncle.
Er, is there a typo? A bit confused here, but what do you mean by 'not working with AC voltage'? I thought it'll just cut off 0.7V from the AC output, ain't it?

 

[Hero999]

No, worse, it'll short circuit every half cycle, if it's AC.

EDIT:

Yes it was a typo, I meant: assuming the generators are DC, connect them up like this.

 

[bryan1]

Looking at the output shaft on those motors as soon as the blades are connected and the wind starts they will bend like a banana. Also putting wind generators in series will never work as it will be impossible to get them synchronized. I reckon the best way to connect them up is use some gearing on the shafts of the motors and have a lay shaft for the blades. Put each motor in parallel with a blocking diode on each positive lead. At best doing it this way you might be lucky to see 5 watts at 12 volts.....

 

[Vizier87]

Looking at the output shaft on those motors as soon as the blades are connected and the wind starts they will bend like a banana.

Here in M'sia bananas are abundant and inherent to the M'sian culture significantly, mentioning it like that with our language culture is seriously really funny. I got my laugh of the day.

I'm gonna build a new one anyway, I've got a new stash of hard-drive magnets, extracted and waiting for the next tinkering. I'm gonna use my ex-printer shafts, they're IMPOSSIBLE to bend with pliers but only 2mm in diameter.

So you support Hero's config. as well? Any more modifications for the figure?

 

[Hero999]

I don't know what's wrong with me, I made the same typo on my post that was supposed to correct it.

I meant: assuming the generators are DC, connect them up like this.

I've edited my previous post.

Do not connect diodes in parallel with AC generators, they will blow up.

 

[Vizier87]

got it, thanks uncle. I have 5 pairs of neo-mags now... Battle Stations!!

 

[bryan1]

Visier what size are these HD magnets ? if they are the old ones and a good size then a small dual axial flux generator will be the way to go. They are an air core genny so no cogging and even a small one will output a heap more than a small radial genny. To find the amount of copper you need just wind a single coil and measure the voltage then multiply the voltage for the amount of turns.

I canned my 4kw motor conversion as the cost and work involved wouldn't of produced the same output from a dual axial genny.

Cheers Bryan

 

[Vizier87]

Bryan, it's ViZier btw. Hehee.. yea the magnets are from the REALLY old ones, twice the size of the standard PC HDD, with a 1.5 GB space.
Here's the armature design I used for the 30V one:
**broken link removed**
It seems to be quite good, here's a 15 sec-vid:

 

[Hero999]

Have you tried you power anything larger?

You don't need much power to light a couple of LEDs.

 

[Vizier87]

well... The LEDs burned out if I try to turn it faster. I'm not sure how much power is produced, but that is just a demo generator. Like I said, I'm gonna build a larger one. The transformer in my box needs to be dismantled though for the coils.. it's hard work.

 

[Hero999]

Did you not use a series resistor?

No wonder the LEDs burned out.

 

[tcmtech]

Seems like a lot of time and effort is being put into a design that can be easily topped by a common DC motor in an old piece of office equipment.

Given a rough estimate of the size of your big motor I can say I have old copier drive motors of similar size that can produce around 100 watts at 3300 RPM (20 volts @ 5 amps).