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Connecting small generators in series? Answered

Hi all,

I'd like to make a bunch of small generators, like Pleech turbines, for example. Each one might only be producing a couple volts and however much power. What is the best way to connect them together to get their combined power?

I was thinking that I could just give each generator its own rectifier, and then connect everything together in series. Would that be efficient?

My circuitry understanding is a little limited, so a simple solution that is 90% efficient may be better than a complicated solution that's 100% efficient.... :)

Thanks for any suggestions!

Discussions

0
user
shomas

1 year ago

In summary you can do it, but you will probably have to down grade the expected wattage from each generator due to reactive load between generators. You will also want to pay close attention to the phase angle between generators to keep a smooth voltage and torque on the prime mover.

An additional note. in the link below I set low voltage drop across the diodes. but in normal diodes there is a a voltage drop of about .70o something milivolts. each bridge rectifyer always is always passing current through two so each bridge will drop about 1.6v. Meaning you loose power in each series connected bridge rectifier.

Here is something you can play with

http://tinyurl.com/lwyc5bt
You can play with any value voltage resistance inductance, and phase angle.
The transformers representing the generator's coils with their inductance and power being supplied from an alternating magnetic field. The resistor in series represents a coil's internal copper resistance. Here I have the three generators out of phase by 120 degrees from each other to limit torque ripple.


Now normally, as you can see on the left, even AC power from a single source is generally always negative, or power is drawn from the source, unless the load has any inductive or capacitive reactance. As you see in the series connected motors, positive power means power from another generator is being channeled through the first series connected generator. Additionally, look at the amount of wattage in the first series connected generator has a lot more watts being drawn from it. It seams to me that power is being absorbed into the coils from another generator and reflecting back out. This might be a concern when considering how much to load the generators.

It seems reasonable, I'm not the guru or anything but reciftying will cause a minor voltage drop, I think it's 0.6V with silicon diodes, though that needs check, also I'm not sure how AC works in series, it may be possible to do another system or have a single rectifier, I do like this idea since those little things don't provide much voltage usually, I'm thinking of making a big turbine or some such soon so this stuff interests me...

One of my worries is that the generators that are not producing enough power will impede the current that is being produced by the other generators. The generators may even start trying to act as motors. Would this be a real problem? Would there be a clever way to prevent it?

Again diodes, these prevent the flow of electricity in one direction, making it one way, a diode rectifier should function as an anit reverse anyway...

The problem I see with interconnecting the generators is the phase shifts, for simplicities sake, imagine you interconnect two generators that are 180 degrees out of phase, the output will be zero. Now complicated the problem by having multiple generators all at different frequencies and amplitude and phases.

Generally its a good idea to have three single phase generators out of phase by 120 degrees. Else you will pulse torque back to the prime mover very strongly if you align all the phases up in the same direction. 180 degrees out of phase is indistinguishable from 0 degrees after rectification. http://tinyurl.com/lwyc5bt

I knew there was something I was forgetting, that also ruins the single rectifier idea... the problem it that diode rectifying is not a good thing on small things where every little volt counts...

You will still momentarily cause the generators to motor. Look at the positive power flow. http://tinyurl.com/lwyc5bt

"The generators may even start trying to act as motors. Would this be a real problem? Would there be a clever way to prevent it?" No. http://tinyurl.com/lwyc5bt This is probably a better representation with the the transformers representing the generator's coils with their inductance and power being supplied from an alternating magnetic field. The resistor in series represents a coil's internal copper resistance. Here I have the three generators out of phase by 120 degrees from each other to limit torque ripple.

Now normally, as you can see on the left, even AC power from a single source is generally always negative, or power is drawn from the source, unless the load has any inductive or capacitive reactance. As you see in the series connected motors, positive power means power from another generator is being channeled through the first series connected generator. Additionally, look at the amount of wattage in the first series connected generator has a lot more watts being drawn from it. It seams to me that power is being absorbed into the coils from another generator and reflecting back out. This might be a concern when considering how much to load the generators.

0
user
PKM

10 years ago

I have a gut feeling that connecting them in series wouldn't work very well, because the coils in any one generator would be driven by the power from the others, which would turn the coils into electromagnets, which would impede the rotors and make them cog or even stop, and it would all be messy. AFAIK you could connect them in parallel, however, each with their own rectifier before their wires join together, but then you have a serious voltage drop (if each only produces a few volts it's a significant % of the total power) and resistive losses from having a high-current low-voltage power supply. Long story short, I believe series wouldn't work properly and parallel has major inefficiency issues (try saying that quickly) unless you can find some suitably low-voltage-drop diodes.

I was still unsure, so I made a little circuit using the circuit simulator, were I created three AC sources, each with their own smoothed rectifier, and connected them all together in series. I then replaced one of the AC sources with a resistor (a load) -- see image (ignore the three extra resistors in parallel with the caps, they were bleeder resistors, but are obviously too small).

It looks to me like it would be ok after all -- the current prefers to go through the low-resistance diodes in the rectifying bridge rather than going through the load. So it seems that having a stopped generator in series with everything else is not much worse than having no generator at all.

Does that seem right to you (or anyone)? My circuit is probably simplistic, but is it roughly accurate? Am I making a mistake somewhere?

Thanks!

rectifying circuits.png

(forehead smack) Of course, I forgot if it has a bridge rectifier then it is kinda 'perpendicular' to the DC circuit. In that case I suppose the rectifier will mostly bypass the generator. My concern then would be the generators might do weird things with the bias voltage of the diodes, I don't know enough about diodes but I have a sneaking suspicion you could still get current through the generators, but it wouldn't be as bad as I previously thought. This is stretching the bounds of my electrical knowledge now...

No they wont bypass the generators. http://tinyurl.com/lwyc5bt This is probably a better representation with the the transformers representing the generator's coils with their inductance and power being supplied from an alternating magnetic field. The resistor in series represents a coil's internal copper resistance. Here I have the three generators out of phase by 120 degrees from each other to limit torque ripple.

Now normally, as you can see on the left, even AC power from a single source is generally always negative, or power is drawn from the source, unless the load has any inductive or capacitive reactance. As you see in the series connected motors, positive power means power from another generator is being channeled through the first series connected generator. Additionally, look at the amount of wattage in the first series connected generator has a lot more watts being drawn from it. It seams to me that power is being absorbed into the coils from another generator and reflecting back out. This might be a concern when considering how much to load the generators.

http://tinyurl.com/lwyc5bt This is probably a better representation with the the transformers representing the generator's coils with their inductance and power being supplied from an alternating magnetic field. The resistor in series represents a coil's internal copper resistance. Here I have the three generators out of phase by 120 degrees from each other to limit torque ripple.


Now normally, as you can see on the left, even AC power from a single source is generally always negative, or power is drawn from the source, unless the load has any inductive or capacitive reactance. As you see in the series connected motors, positive power means power from another generator is being channeled through the first series connected generator. Additionally, look at the amount of wattage in the first series connected generator has a lot more watts being drawn from it. It seams to me that power is being absorbed into the coils from another generator and reflecting back out. This might be a concern when considering how much to load the generators.

0
user
shomas

1 year ago

http://tinyurl.com/lwyc5bt This is probably a better representation with the the transformers representing the generator's coils with their inductance and power being supplied from an alternating magnetic field. The resistor in series represents a coil's internal copper resistance. Here I have the three generators out of phase by 120 degrees from each other to limit torque ripple.

Now normally, as you can see on the left, even AC power from a single source is generally always negative, or power is drawn from the source, unless the load has any inductive or capacitive reactance. As you see in the series connected motors, positive power means power from another generator is being channeled through the first series connected generator. Additionally, look at the amount of wattage in the first series connected generator has a lot more watts being drawn from it. It seams to me that power is being absorbed into the coils from another generator and reflecting back out. This might be a concern when considering how much to load the generators.

Rather than mini-turbines, you might consider building wind belts. They are less expensive and more simple to build and you can easily add more and more of them to your system. I believe there are Instructables available that show how to build them.

Good luck.

I want to join a few of these together, and I want to know if I join all the positives, and all the negatives, will it give me a combined wattage, at the same Voltage?

Will i need diodes on each one to stop the current flowing into the next one?
Would a solar combiner box do the job (some have built in diodes)?
What is the PSI of a standard water tap on a 1/2 inch pipe?

http://www.ebay.co.uk/itm/190880105597?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649 is the product I will be using.

I would like to know to this answer too you could use voltage diodes, some only drop the voltage by 0.2 or less