Author Topic: Proper Copper Shopper (so I don't come a cropper)  (Read 1706 times)

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Andy from the cross

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Proper Copper Shopper (so I don't come a cropper)
« on: January 05, 2017, 11:29:41 AM »
Hi folks :)
I'm about to splurge on some copper wire and looking for some advice before I order.
The plan is to run a small engine on methane to turn the dual-rotor, 12 pole 9 coil PMA at something like 900 rpm.
Magnets are N52 50*25*10mm, and sketched out as a 350mm dia rotor would indicate the maximum coil size is 120*100mm (100mm across the 40 arc).

A couple of designs i've seen have used 1.6mm wire in the coils, would that be appropriate in this build? Each phase will be rectified separately and combined into an inverter.

Your thoughts, suggestions etc are appreciated. Thanks in advance :)

joestue

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #1 on: January 05, 2017, 12:45:27 PM »
how much shaft hp are you expecting to get?

at 900 rpm a motor conversion would make a lot more sense. also don't throw out winding a synchronous motor from an induction motor. if you can find an angle grinder you can cut the slots in the core needed to fit the coils.

electrondady1

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #2 on: January 06, 2017, 06:25:48 AM »
@900 rpm on a drive motor you could drive an automobile alternator.
in a dual rotor you would need to take measures to secure your mags in place at that speed.
you can do a test coil with fine wire to determine the number of turns  you want to get the voltage you want at that speed. then the challenge is to fit that many turns of fat wire into the available space

 can you describe your methane source and how you feed the engine ?

Andy from the cross

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #3 on: January 06, 2017, 02:17:28 PM »
Okay, 900rpm is guesswork for now, i'm still looking for a suitable motor - a propane forklift engine would be ideal. Let's call that a maximum speed...

I could use alternators or induction motors, but i'd rather create something from scratch.
Anyway, i'm just thinking ahead (or getting ahead of myself...), I have got me some rotors to build.

electrondady1

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #4 on: January 07, 2017, 06:02:06 AM »
do you have your rotors and magnets already?
if so, check out dan b's posts were they band the edge of the rotors.
another popular method is to drill and insert steel pins along the edge of the rotors to keep the mags in place.
most of the alternators built on this page are for wind mills that turn significantly less than 900 rpm.
some mags come with counter sunk mounting holes.

Ungrounded Lightning Rod

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #5 on: January 07, 2017, 03:07:41 PM »
What do you intend to use this for:  Powering your house long-term?  Fill in for battery charging in an R.E. house when the sky is cloudy and/or the wind is clam?  Campground?  Welding at a job site?  Just the fun of making an electric machine?

Will it be used occasionally or a lot?  How long does it have to live - or go between shutdowns or overhauls?  How critical are the loads, i.e. what happens if it shuts down or breaks at an unplanned time?  What are the load you'll put on it?  What is their preferred input voltage and frequency-or-DC?  How much power do you need from it?

This will make a BIG difference in the choices you'd want to make and/or the advice you'll get here.

For instance:  For appropriately sized moderate loads used intermittently, an auto-alternator based system might be fine.  But for continuous use the bearings might go through an automotive alternator's expected lifetime in a year or less - and typical alternators aren't designed to last longer than the vehicle they're intended for, so a converted motor (with bearings designed for years of continuous use at substantial RPM) or some other solution would be preferred.  (And that might save you the rewind and copper purchase, too.)

Andy from the cross

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #6 on: January 07, 2017, 07:48:13 PM »
Thanks for the input :)

There is a plan, it goes something like this...
1- Build PMA
2- Source and prepare a motor
3- Test on propane
  (If the digester is not operational at this point, continue using propane as fuel)
4- Connect to home supply with a grid-tie inverter.

Timescale: up to two years - i'm in no rush :)

If it exceeds my expectations, I will probably be 'feeding in', running most of the time.
If it meets my expectations, I don't intend to feed in, but to power the home intermittently - light/medium loads.

Backup plan:
Provide power to the shed and lv lighting in the garden.
_

However it turns out, I will have enjoyed creating it, learned new things, and put into practice the things I haven't already forgotten...
_

I have the magnets, I confused myself trying to decide on which size copper to achieve enough volts and amps to run a good size house minus kitchen appliances.

I have been thinking about how best to ensure the rotor integrity at high rpm... i'm wondering if I might be able to get an offcut of >350mm dia. stainless steel pipe with a decent wall thickness, which would also become the mould outer edge...
Occasionally, there is a plus side to living in the 'steel city' :)

Thanks again :)

joestue

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #7 on: January 08, 2017, 12:00:16 AM »
I highly recommend building the motor and get it running on methane, and measure the shaft hp available before building a pma.

Andy from the cross

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #8 on: January 08, 2017, 01:24:55 PM »
Right, that's my shopping list rearranged. Now, imagine I have no idea how to measure horsepower and you have to spell it out real clear to some noob who is going about it all ass-backwards ;)

electrondady1

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #9 on: January 09, 2017, 06:54:03 AM »
 ;D  1h.p. =750 watts.
it's becoming  a chicken or egg thing now .
but what ever way you go first you don't want the mags to fly off.



Andy from the cross

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Re: Proper Copper Shopper (so I don't come a cropper)
« Reply #10 on: January 09, 2017, 03:39:18 PM »
;D  1h.p. =750 watts.
it's becoming  a chicken or egg thing now .
but what ever way you go first you don't want the mags to fly off.
That much at least I am 100% certain of. I will be taking safety seriously.