What makes a generator powerful? - Page 1
Forum section: electronics / beginners

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 02, 2016, 06:52:05 pm
content: HiIs there any pages or videos explaining what sort of combination of magnets and windings you need for a generator to generate the right power, or a sort of formula to work it out?I want to make my own windings to generate at least 12V 5A DC with minimum torque possible such as a low pressure impeller.Thanks in advance.

author: hayatepilot
author_rank: Frequent Contributor
timestamp: March 03, 2016, 01:54:54 pm
content: This is like asking "I want to build my own car, what tyres do I need to drive as fast as possible?"Generators are a HUGE topic and one cannot say use this wire diameter with X turns and use those magnets...If this where the case, many, many engineers would loose their jobs.You will need to find those things out by trial and error. But the stronger the magnets (->neodymium) and tighter the windings, the better.I wouldn't bother winding your own generator and just buy a RC brushless motor in combination with a 3phase rectifier as a generator. You have to choose the rpm/volts of the motor so that you achieve your desired speed.Greetings

author: danadak
author_rank: Super Contributor
timestamp: March 03, 2016, 02:57:54 pm
content: Google "dc generator winding techniques", quite a few hits on solutionsand considerations.Regards, Dana.

author: DenzilPenberthy
author_rank: Frequent Contributor
timestamp: March 03, 2016, 03:48:53 pm
content: Go to a scrap yard and buy a car alternator for £5. If your system does not contain a battery which can supply initial current to the field windings in the alternator then you will need a '1 wire' or 'self exciting' type.

author: senso
author_rank: Frequent Contributor
timestamp: March 03, 2016, 04:05:41 pm
content: With those power requirements, a small brushless motor for RC/quads/planes will fit the bill.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 06, 2016, 08:13:53 pm
content: Quote from: danadak on March 03, 2016, 02:57:54 pmThanks for the reply it did bring up some useful information .also I found these articles :http://www.free-energy-info.com/Chapt2.htmlhttp://www.6pie.com/howtowirecoil.phphttp://www.6pie.com/faradayslaw.php

author: LordHexahedron
author_rank: Contributor
timestamp: March 06, 2016, 08:18:06 pm
content: I wouldn't trust any site that has "free energy" in its url, the other two links seem pretty ok though

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 06, 2016, 08:20:30 pm
content: Quote from: LordHexahedron on March 06, 2016, 08:18:06 pmWell even so its information was very useful anyway.

author: LordHexahedron
author_rank: Contributor
timestamp: March 06, 2016, 11:35:52 pm
content: I suppose it could be, I only skimmed it and didn't see much useful data there.In any case, doing the windings yourself isn't necessarily the best option as pointed out - don't get me wrong, it's a brilliant learning experience and if all you have are magnets, misc junk, and a whole lot of copper wire it's doable if you can't get anything else.

author: IanB
author_rank: Super Contributor
timestamp: March 06, 2016, 11:47:43 pm
content: Quote from: abdullahseba on March 02, 2016, 06:52:05 pmOn reading your post, it is not clear that you understand power balances.For instance, do you understand the following two equations?1. (Power out) = (Power in) - (Power losses)2. (Power in) = (Torque) x (Speed)From the first equation, if you want to generate 12 V at 5 A, that is 60 W. So your low pressure impeller must generate at least 60 watts of power, and more than that if you allow for losses.From the second equation, if you know the torque of your low pressure impeller, then you know what speed it has to run to generate at least 60 watts. If the torque is low, then the speed is going to be very fast.You will notice that magnets and windings do not appear in any of these equations. Only after you have answered questions 1 and 2, and maybe considered other mechanical considerations like a gearbox, only then do you start to consider how to design your generator.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 07, 2016, 10:52:58 am
content: Quote from: IanB on March 06, 2016, 11:47:43 pmThanks but been an experiment I don't have such figures.

author: G7PSK
author_rank: Super Contributor
timestamp: March 07, 2016, 01:25:50 pm
content: To calculate the EMF you need the total lines of force per pole, the rpm, total number of conductors, the number of poles and the number of parallel circuits.See the attached scan from a 1920's book I have.

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 07, 2016, 03:12:03 pm
content: Quote from: G7PSK on March 07, 2016, 01:25:50 pmthanks for the pic. its funny because I forgot completely that I've got a book called electricity and magnetism from 1912 Ill have to look at it.

author: IanB
author_rank: Super Contributor
timestamp: March 07, 2016, 06:34:20 pm
content: Quote from: abdullahseba on March 07, 2016, 10:52:58 amIt seems like you still don't understand.You asked, "What makes a generator powerful?"The answer is: "Feeding lots of power into it."You say you want to get at least 12 V and 5 A out of it. You cannot do that unless you put more than 12 V and 5 A into it.Here is what you asked:Quote from: abdullahseba on March 02, 2016, 06:52:05 pmThere is no magic you can do with magnets and windings that will make the generator generate the right power if you do not feed sufficient power into the generator to start with.Do you really understand this?

author: abdullahseba
author_rank: Frequent Contributor
timestamp: March 08, 2016, 09:58:08 am
content: Quote from: IanB on March 07, 2016, 06:34:20 pmCourse I understand. If there was I'd be the first to build a perpetual motion generator. You cant simply put what you want in and expect to get it out unless you have a hundred percent efficiency which is impossible. All I wanted to know was WHAT makes it powerful and as someone already said stronger magnets tighter winding's. I don't want a bad design where I put lots of power in and get 1% of it back or something like that.The power input in my case was an impeller and I wanted to know how many wingdings I need to get 12V 5A out of it .If I didn't know my design might end up needing a lot of unnecessary torque and speed which I don't have.