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Old portable permanent magnet generator
By Guiney, Section Wind Posted on Mon Sep 14, 2009 at 09:48:26 PM MST
What speed needed for 50Hz

Hello,
First post here. I have been given an old engine driven generator that uses a permanent magnet rotor and two stationary coils. It's a McCullagh 'MightyLite'. Made in California. The engine is broke.
I cannot find any info. on the machine to tell me what engine revs should be to give 50 Hz (or 60 Hz).
In order to get 50 Hz from this generator what speed do I need to rotate the generator at?
I am going to guess 50Hz X 60Sec / 2 = 1500 rpm??? 3000rpm seems too much for the engine to be doing (guess).
The coils are connected in series but they appear to be wound in 'opposite' directions. (Since each winding will always have an opposite pole going accross it, this is the correct way to connect them...I think)
Would this device be suitable for connection to a wind turbine? I guess not unless with a gear box and then you
have to drive the gear box (lose energy).
This information is no doubt already on the board but I am dammed if I can find/figure it out.
See the attached drawing of generator.
Thanks
Guinney
[IMG]http://i628.photobucket.com/albums/uu10/guiney12/generator.gif[/IMG]

Old portable permanent magnet generator | 5 comments (5 topical)

Re: Old portable permanent magnet generator (3.00 / 0) (#1)
by Ungrounded Lightning Rod on Mon Sep 14, 2009 at 04:18:54 PM MST

Sorry but I can't make heads or tails of the diagram.

If you've only got one north and one south pole ("two pole") it will be 3000 RPM for 50 Hz, 3600 RPM for 60 Hz. If you've got two each it will be half that.

A lot of inexpensive direct-drive alternators do run the engine at 3600 RPM and use a two-pole alternator. It cuts the life of the engine compared to a four-pole design but simplifies the alternator.

Re: Old portable permanent magnet generator (3.00 / 0) (#2)
by Airstream on Mon Sep 14, 2009 at 04:30:29 PM MST

It's a McCullagh 'MightyLite'. Made in California. The engine is broke.
I cannot find any info. on the machine to tell me what engine revs should be

Computer anything requires letter perfect input, garbage in means garbage out.

"McCulloch Mite-E-Lite"

http://www.smokstak.com/forum/showthread.php?t=65729 <-- a quick search revealed one alternator hint to keep from damaging it on reassembly...

Google Search "McCulloch Mite-E-Lite generator -chainsaw" yielded 2200 hits...

3000 RPM is a good bet for 50HZ - gearbox would eat a lot of horsepower, serpentine belts would probably be least parasitic... but its' a losing situation for wind power - it might be ideal to "add-on' to a lawnmower type Automotive alternator DC power rig to have AC and DC flavors available...

Re: Old portable permanent magnet generator (3.00 / 0) (#3)
by Guiney on Mon Sep 14, 2009 at 05:59:28 PM MST

Thanks alot for replys.
Mite-E-Lite it is!
I came accross an exploded diagram (similar to the one I have) at the link below on page 119.
http://books.google.ie/books?id=EiEDAAAAMBAJ&pg=PA109&lpg=PA109&dq=McCulloch+Mite-E-Lite +generator+-chainsaw&source=bl&ots=ujqmD_4Cgk&sig=vEhgA9ZmypDmw6LzmL9xdPJBEs4&hl=en& amp;ei=w9SuSvz9AcKj4gab75nqBw&sa=X&oi=book_result&ct=result&resnum=32#v=onepage& q=&f=false

Rather long URL that may wrap around.
My bad diagram is inclined to make the generator look 'three dimensional' when it should in fact look more flat.

3000 rpm it will need to go at to give 50Hz

Thanks again

Re: Old portable permanent magnet generator (3.00 / 0) (#4)
by bob g on Mon Sep 14, 2009 at 06:56:19 PM MST

talk about wierd,, i was at the library today killing about an hour
and found a book on small engine driven gensets, and this exact unit caught my eye
because of its rather unusual design.

too strange!

bob g

Re: Old portable permanent magnet generator (3.00 / 0) (#5)
by Flux on Mon Sep 14, 2009 at 11:56:54 PM MST

Yes it's 2 pole and ran at 3000rpm on the versions here in UK. For Canada it would be 3600rpm for 60 Hz.

One of the few commercial air gap alternators. OK for engine use but for wind power I don't know how it would work out. It may work reasonably well for 24v but will be big and heavy for the power out and single phase really restricts it to a tiny machine.

3000 rpm at 240v ( 320v peak rectified) would cut in at 24v at something like 230 rpm.

Flux

[ Parent ]

Old portable permanent magnet generator | 5 comments (5 topical)

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