Designing A Generator From A Predetermined Power Output

[BBT723]

Hello All.

I have spent the past few weeks working on a simple generator and I have come to a point where additional math and science are required.  My approach is currently paused until I get some advice, which I am hoping to get from my fellow Fieldliners'.  So to lean on you all, I have a question (and some follow-ups) I would love some answers to.

Is it possible to design a generator based on a predetermined power output?  Say I want to build a generator that can produce 1kW.  Can I start with that information and go backwards?

For example and hypothetically speaking, I want a 1kW disc-style generator.  Since I want it to produce 1kW, I will need X number of coils and X number of magnets.  The coils need to be X gauge, have X turns and be X size.  The magnets need to be X grade and be X size.  The coil/magnet spacing needs to be X and the rpm of the coil or magnet needs to be X.

I'm not sure if it is feasible or even possible, but I thought the question was worth asking.  I wish there was a program that could generate (lol) a generator like this.  I would even take an excel file.  I have limited resources on learning about this.  I'm sure you are all aware that when you search the word generator on YT, all you can see are free energy devices.

Thanks in advance for your time.

[bigrockcandymountain]

The first question will be 1kw at what voltage? And is it ok if it is a 3 phase alternator rectified to dc?

[BBT723]

I guess I should’ve included the question of what’s more manageable.  Is it better to design around a higher voltage or a high amperage?

[MagnetJuice]

Welcome to the forum BBT723.

Yes, it is possible to design a generator based on your desired output power.

You can estimate each magnet output in watts according to the size and magnetic strength. For example, a neodymium magnet of N42 strength that is 2 x 1 x 1/2 inches in size has the potential to yield about 45 watts. Let's say that you have 24 of those magnets, (2 rotors with 12 magnets each) That could give you an alternator with about 1000 watts output.

Next, you would need 9 coils to build a 3-phase alternator with the 2 rotors of 12 magnets each. Then you choose the gauge of the magnet wire according to your desired voltage, whether it is 12, 24 or 48 volts output. Those 3 voltages are the most common because most people feed the rectified DC voltage output of the alternator into an inverter that converts it to 120 or 220 Volts AC.

The wire gauge that you choose for the coils depends on the total output power and on the voltage that you choose for your alternator. The higher the alternator output and the lower the voltage, the thicker the wire that you need to use.

For example, for the above alternator of a 1000 watt output, your wire size should be, 13, 14 and 15 gauge for 12, 24 and 48 volts respectively.

The number of turns per coil is determined by the desired RPM that you want your alternator to run. A higher number of turns will produce a higher voltage at a predetermined RPM.

Ed

[BBT723]

Thank you so much for your reply! These confirmations are much appreciated. Do you by chance have some links for me to dive in to? I’d love to dig deeper into these relationships and begin a rough design!

[MagnetJuice]

BBT, when I get a little free time, maybe tomorrow, I will search the Forum for some useful old posts that can be helpful to you.

Right now, I am taking advantage of good weather here and doing some work outside that is way overdue.

Ed

[BBT723]

Don’t worry about that brother! I appreciate the offer! I can look myself, you enjoy the nice weather! Thanks again!

[MagnetJuice]

BBT, here are some good posts you can check. Maybe you already found them, but I am posting anyways for the benefit of others too.

On the post below, there is an Excel file you can download. I don't know if anybody tried it, but the guy that create it, Menelaos (Max), knows a lot about alternator design. Wouldn't it be great if you can eventually perfect that Excel file and made it available for everyone here to use?

https://www.fieldlines.com/index.php?topic=143174.0

In the post below, there are 2 formulas or equations, one from Ed Lenz from windstuffnow.com and the other from Hugh Piggott from scoraigwind.co.uk. They are a bit hard to decipher so if you need help with it let us know. By the way, you can buy Hugh's book from his website. You can get it in digital form or paper; it is loaded with very good information.

I have my own equation; mine is a combination of Faraday's law of electromagnetic induction and the one from Hugh Piggott. It is a lot simpler to use and uses imperial units instead of metric. I built an alternator using my equation and it was very close to the predicted values. I still want to perfect it a little more to make it more accurate, so I need to build another 2 alternators to test it.

https://www.fieldlines.com/index.php?topic=138646.0

In the post below, there is another useful equation from Hugh and a good interaction by Flux. He was a very helpful and knowledgeable user that sadly is no longer with us.

https://www.fieldlines.com/index.php?topic=137269.0

Happy learning!

Ed

[Mary B]

way back in the dark ages of this site there was a spreadsheet called number of turns that was useful to predict voltage per coil. I no longer have a copy(or if I do I don't have a clue where it is on the hard drive!)