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AC or DC Motor as Generator

PostPosted: Mon Oct 12, 2009 9:58 am
by mobile
Hi all

I am doing some research before I start my project. I will not be building a generator but will be taking advantage of current technology.

Fact DC
Using DC motors to generate electricity requires inverters to convert to AC and to make a AC sinewave however the cheaper inverters do not create a true sinewaves so you cannot inject this AC directly into your DB board unless you buy a very expensive inverter which can range from R3000 up to R15000 and more

Fact AC
Using a car alternator you can produce a pure sinewave which theoreticaly can be injected directly into your DB board however the rpm's required to use an alternator is extreamly high from what I have read.

Now my questions

1 What is better? A DC motor or an AC motor. " I believe that DC would be better.
2 What are the best ? DC motors to use eg, wheel chair motor,
3 What are the best ? ACmotors to use eg, weed eater motor, car alternater

As children growing up we had little cars with a weighted balanced wheel. rubbing the cards wheels would generate energy in this wheel and when you put the car on the ground it would drive for some distance before stopping.

Can we not apply this theory to the wind turbine? I know that it would make it difficult for the wind to start it up however would it not assist the turbine in keeping a constant speed under low wind conditions. Just an idea. What do you guys think

Re: AC or DC Motor as Generator

PostPosted: Tue Oct 13, 2009 3:09 pm
by windgat
My 2c:
Forget AC motors, unless you rectify to DC.
You want a low RPM high power motor with minimal cogging. Eg. perhaps something like a 24V 400rpm motor

Inertia (momentum) does not help at all. I can't see any point in, for e.g. adding weights to the blades. You want power from a turbine generator, not momentum, so when using DC and batteries, keeping a constant speed has no advantage.

Re: AC or DC Motor as Generator

PostPosted: Thu Oct 15, 2009 7:28 am
by mobile
Hi windgat

Thanks for the reply.

Do you know if anybody has tried this with weights at the tips of the blades?

Would it not also help for torque then?

I think I am going to look into wheel chair motors as they are 24v and are low rpms or even treadmill motors.

Re: AC or DC Motor as Generator

PostPosted: Thu Oct 15, 2009 5:31 pm
by windgat
I know of one person who was talking about weighting the blades. He has been very quiet since then. The physics of doing that makes no sense to me.

Sounds good, as long as they are really low RPM, and not just geared down to be low RPM.

Re: AC or DC Motor as Generator

PostPosted: Wed Jul 14, 2010 9:20 pm
by Whadda
Hi, does anybody know where in S.A one can buy a permanent magnet DC motor to charge deep cycle batteries. I have read extensivley on this great forum and saw somebody used a treadmill motor (did find people servicing treadmills and as soon as I explain my use, they disappear) also wheelchair motors and the same happened.

Thanks

Re: AC or DC Motor as Generator

PostPosted: Wed Jul 14, 2010 11:46 pm
by windgat
Hi Whadda. A lack of success going down that path is what led me to make my own coils and magnet plates...

Re: AC or DC Motor as Generator

PostPosted: Sat Jul 17, 2010 6:31 pm
by Whadda
Dankie Windgat, let's day I am somewhat constrained in the diy department. Got hold of 1 or 2 sources in the meantime, but pricey.

Loop mooi.

Re: AC or DC Motor as Generator

PostPosted: Sun Jul 18, 2010 9:42 am
by windgat
Please keep us informed of what you find...

Re: AC or DC Motor as Generator

PostPosted: Mon Sep 06, 2010 11:15 am
by Whadda
Hi Windgat, have you perhaps had time to look at my Starwars machine under General? Would you buy it for R1000 and can I rewire the burnt wire section or will I have to redo the whole thing?

THANKS!

Re: AC or DC Motor as Generator

PostPosted: Mon Sep 06, 2010 7:49 pm
by windgat
See my reply to that post...

Re: AC or DC Motor as Generator

PostPosted: Sun Feb 06, 2011 6:06 pm
by L1508
DC definitief daar is beskikbaar 24 Volt baie lae R.P.M. ( 64 ) lae amps is wat jy nodig.Lukas

[DC definitely. There are 24V very low R.P.M. (64) low amps ones available. Low amps is what you need]