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Author Topic: A DC bank Manager,  (Read 8142 times)
biff
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« on: January 12, 2016, 07:02:47 PM »

Well Yes,!
        You could call it that but it is really a breed of an inverter generator. The lump is a 120volt x 2kw permanent magnet generator which used to drive a wind turbine. With the Hub and blades removed and a pulley fitted ,I planned to belt it to a small pulley on the engine crankshaft. However, my first attempt using a 150mm pulley on the pmg was a serious miscalculation because the figures meant that the pmg would be running at a speed 5 times greater than what it was designed to run at, so that was a non runner,so to speak.
  So today, I managed to find a bigger pmg pulley that will slow things down considerably .
 The engine runs at 3000rpms normally but there is a sweet spot around 2,000rpms, I think that it will still run fast enough to cool itself.
 The new pmg pulley still turns at 600rpms while the engine is turning 3000rpms, however,throttling back to 2,000rpms should give me the required 400rpms that will deliver the 2kw from the pmg.
 The rpms are easily controlled by a lever on the side of the engine. The governors on the pump will hold that rev so when the load comes on,the engine picks up to match it. This is the same principle of the small petrol suitcase inverter generators. ( I think).
  The lump of course is three phase and the juice will be rectified and delivered into the Battery bank with one of my normal 120vdc wind turbine controllers which of course looks after the voltage range as well and diverts to dump and correct any little surges.
  The whole idea is about economy and charging the bank with a realistic amount of power. The present conditions of the generator is good and delivers a pleasent 3kw of nice clean electricity when
required, It remains to be seen as to how this will turn out. There is no point in modifying the generator chasis until it proves itself. There is a large built in fan in the new pmg pulley which will help to pull the heat away from the top of the engine and also cool the pmg. I am told that it will create a drag on the engine but I will just have to wait and see.
  The electronics side of things are pretty well looked after, It is just a question of getting the engine to run comfortably at that lower speed without overheating.
                                                                       Biff
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biff
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« Reply #1 on: January 12, 2016, 07:18:13 PM »




   There is nothing definite about this project. For a while I changed tack and planned a separate unit that would have a system of pulleys and belts to step down to the required 400rpms, It could be driven of a small pto on the crankshaft using an adapted front wheel drive unit. This would mean that I could wheel it up to the geni and just connect up the drive to the generator crankshaft. Which would mean that I would be able to use this generator for ac house supply if needed without removing the belt to the PMG.
   But the present method seems to be simple, Roll Eyes
                              Biff
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Billy
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« Reply #2 on: January 12, 2016, 08:11:06 PM »

Ooh Biffffff,  I like it. Grin

That large pulley looks suspiciously like the one off my compressor. I'll just check to see if it's still there!
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Stochengberge
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« Reply #3 on: January 12, 2016, 08:23:32 PM »

Or washing machine...

SB.
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On the North Downs of Kent with 3.2kWp facing 12' west of south @ 33', 36 x 58mm Thermal tubes on an east / west split, 300ltr triple coil DHWC and an 8kW to water WBS.
guydewdney
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« Reply #4 on: January 12, 2016, 10:08:42 PM »

pedant mode

its rpm not rpms

you say 'revs per minute' not 'revs per minutes'

bloody americanisms coming over here stealing our jobs....
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biff
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« Reply #5 on: January 12, 2016, 10:37:46 PM »

Aye Billy,
         It is indeed a compressor pulley, I wanted one that was able to pull or push air and that seemed to fit the bill.
   OK Guy, Point taken about the rpms,  Grin
                                Biff
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oliver90owner
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« Reply #6 on: January 13, 2016, 02:52:21 AM »

The prime mover?  Guessing diesel of 4 to 5 horsepower?

Generator cooling?  It is no longer in a gale force wind?  Drawing hot air from the engine to cool it?

Another pedant.  That generator never drove any turbine.  Try the other way round!

Diesel engine? Needs to run at about 85% load if you want it to 'flourish'?

About economy?  Items need to be matched carefully?

Just a few things to consider before letting any smoke out....

Final thought..... a Lister CS (water cooled) would be an ideal prime mover, but you wouldn't be wheeling it around too much!
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fourfootfarm
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« Reply #7 on: January 13, 2016, 10:19:51 AM »

I've got a scrap lawn mower and 24v alternator waiting around to do much the same thing. We shall see if I ever find time to do it though.
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Outback FM60. EPsolar 30a MPPT and a bunch of Tristar 45's. Hodge Podge of solar ~ 4500w. Various generators and 1000ah 24v forklift battery.

Turkish Turnip
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« Reply #8 on: January 13, 2016, 10:34:44 AM »

Biff is this something you are going to link to the generator that you have shown in the photo ??
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biff
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« Reply #9 on: January 13, 2016, 04:48:45 PM »

Hi GG,
       Yes,the plan was to drive the PMG of a  pulley on the engine crankshaft but the gearing is very far out, 3000. to 400. snow
      I did have a similar set up some 4 years ago with a bell mixer motor which melted after 30 minutes ptoviding .5 of an amp@130volts. The bell mixer motor was 400watt so I was expecting a little too much. There are a lot of things against linking the PMG to the diesel generator and already I am starting to have second thoughts.
 I remember years ago searching for a 2kw motor that would direct drive @: 400rpm. (thank you guy Grin) but I just could not source it and settled instead for the bell mixer motor. I might have another go tomorrow . At the moment, there seems to be a lot of hassle with big wide pulleys that would need to be caged in,. Hmmmmm
                                                          Biff
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guydewdney
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« Reply #10 on: January 14, 2016, 12:24:21 AM »

the wind turbine things i bought ages ago were about 2kw and 400rpm......
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knighty
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« Reply #11 on: January 14, 2016, 01:00:30 AM »

you could use a 3 phase motor as a generator, feed that into a transformer, and then feed that into a rectifier ?

not sure what voltage you'd need out of the transformer, about 80v ?
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biff
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« Reply #12 on: January 14, 2016, 10:18:37 AM »

Hi Knighty,Guy
           The PMG is a 2kw @400rpm and off a wind turbine. The plan is to have a yoke that can charge the bank when there is no sun or wind. This was the reason that i was trying to match the 400rpm gearing of the turbine to the 3,000 rpm of the engine. The generator engine delivers it,s 3kw at 3,000rpm but the voltage drops drastically when you throttle back to 2,000rpm, so in this case you either have one or the other. It is working out now at the moment that I need a pulley like the one on a washing machine to get the correct gearing. Again it would have to be caged and would involve a whole load of hassle.
 I will begin my search today for a 1.5 to 2kw single phase motor that can be easily geared to the present pulley on the pmg which is a 150mm A. I would prefer a direct drive set up with rubber bushings on the shaft. I am covering old ground here (accidentally). The very very few times that we have to start the generator in anger was always accompanied by a few washes in the machine or a load of hoovering or a load of electric fires to keep the geni running happy. A 1.5kw motor would seem to me to be a nice load on our silent running geni (5kw) and would soon top up the bank in a few hours.
  So it looks lke an electric 1.5kw or more, motor to drive the pmg is the way to go. Certainly a lot less hassle.
  In all the time i have been off grid with out 2kw bank,the only time it was charged from another source other than the solar and the wind, was the small 400watt bell mixer motor which melted. I had other reserves in the 48v shed system,the original 1200ah x 12volt system but these were dismantled when I reorganised the whole house system last summer. So our 120vdc house system is the one that runs everything, shed and all.
  I could be wrong in saying that I do not foresee any problems with the electronics . Once the PMG gets turning it feeds and ordinary wind turbine controllers which feeds into the bank. I can let the other controllers divert to dump into 2 x 138dc immersions but hopefully see a way of regulating that side of it. This will have to be able to sit in a dry place for long periods of time (4 months at a time at least) and then be able to get going at a moments notice. I think the idea is good enough.
                                                                    Biff
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biff
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« Reply #13 on: January 19, 2016, 10:02:01 AM »

One would think,
                That I had given up on my 120volt dc generator/charger but,no, I am still struggling along.
 I examined a number of alternative methods of powering the actual PMG itself and came to the conclusion that a simple single phase motor was the only way to go.
 Sadly, direct drive of the crankshaft is a non runner because the rpm on the engine might not match the PMG and shutting down the PMG without shutting down the engine(still driving the generator) could be a load of hassle. The generator,which would be powering the house also would have to sit on 3,000rpm steady.
 I could invest in an 8pole motor,with low rpm and good torque but 8 pole motors are like hens teeth in this part of the world.
 I was reluctant to go for a much larger pulley on the PMG but after a good think about it, i decided to start hunting for a 18" Vbelt pulley. What can I say.Huh Even compressor pulleys are not that big.
 So now I am enquiring in the industrial washing machine world and hope to come up with something that will do the trick.
 The electric motor with the 75mm pulley is not a problem. I will have to have the lot on the floor, in front of me before I will know what kind of cage or support stand to build.
 I am not happy about the big pulley but there is no alternative,without going to all sorts of bother.
 What ever, I build, will have to be simple and easy understood. The energy generated will feed into one of my wind turbine controllers,with the excess being redirected to the house immersion heaters.
 There will also have to be a sizable fan to keep the lot cool.
  None of this is impossible, yet it is never as straightforward as we would like it to be. If it were, there would be no fun in it and we would be tripping over works of genius.
                                                                                         Biff
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biff
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« Reply #14 on: January 20, 2016, 06:14:08 PM »

  Starting Mr Changfa without the starter or rope can be quite exciting, especially if he has not been going for over 8 years.. But he went,eventually,with me sitting on the red one and pushing back on the yellow one with my two feed,till it fired up and filled the place with smoke. People were supposed to pull start these babies. freeze

   10.5kva,, he he he..et es ia velly good joke.

. Mr Lister sat for quite a few years and a dab of 2 stroke and half a turn sent him skating around the floor with me trying to wrestle the handle of him,
 All food for thought.It is still possible to wrestle up some combination to power the PMG of one of these.
                                                      Biff
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