Hydro-newbie questions

[XeonPony]

it is a good distance back to the house (~100m) so I was thinking 240/400v ish, then step down to 24v.

XP, if you go back to the first page you will see the OP is charging batteries not trying to run hydro direct like you have been doing. I have found in my systems if you keep the volts/freq ratio near what the motor was designed for it runs cooler (more efficient)

In that event you are most certainly correct, How ever keeping the voltage synch'd to the rated frequency this is all ways true whether direct or battery charging, I was not aguing that at all. 

For the others  Poles = (120*F)/RPM
more use full how ever is finding what frequancy to expect at what rpm  F= RPM/(120/Poles) so you can figure out what F is based of the various shaft rpms

[mab]

Hi folks,

Still trying to get the end plate off the motor (to remove the brake mechanism) at the moment - it doesn't want to pull off and I don't want to use excessive force or I'll have to find a new bearing.

I suspect this is a fast motor as is - (the main winding is in two parts 180° apart - 2 pole?) even on nominal 50Hz. the stator has 24 iron 'pole' pieces so would lend itself to being re-wound I suppose, but am not ready to do that (been reading (Zubbly's) old posts on using induction motors).

[equiluxe]

A very good book on the subject is "Motors as Generators for Micro-Hydro Power" by Nigel Smith it is published by itdg publishing. ISBN 1-85339-286-3. It gives full details on how to convert induction motors to generators and shows how to calculate the correct capacitance for excitation, also gives details and circuitry on the required control gear. Apparently you can get in excess 80% efficiency with induction motors when properly set up. Three phase motors are best connected in the c-2c where you have 2 capacitors across 2 phases and none on the other the load comes of the c phase the 2c phase has twice the capacitance of the c phase, this will give 80% efficiency. itdg or Intermediate technology Development Group is not for profit organization that creates technology for third world countries they are at Myson House Railway Terrace Rugby CV21 3HT UK. I bought a copy a few years back when I had the job of restoring a Victorian water turbine,  it is well worth having if you want to get into or are already involved in small scale hydro power   

[thirteen]

MAB Some motors have one end that has a snap ring that holds the bearing in place and are there to keep one bearing in place while the other one is used for exspansion. so you might have to take the other end off to get things apart. If I am reading things correctly. But by this time you probably have already gotton the end off. Just a passing thought.

[mab]

MAB Some motors have one end that has a snap ring that holds the bearing in place and are there to keep one bearing in place while the other one is used for exspansion. so you might have to take the other end off to get things apart. If I am reading things correctly. But by this time you probably have already gotton the end off. Just a passing thought.

Just a few days ago.  in the end I just used a puller - there was no snap ring but the ally of the end plate had been punched to hold the bearing. my guess is the bearing was fixed into the end plate and the rotor then pressed into the bearing.

equiluxe - I might just get that book - though I'll probably try trial & error on this motor to start with.

I'm just wondering (as I need about 1200rpm) how easy it would be to re-wind this motor for lower rpm (and maybe 3ph). would the rotor still be suitable as it is?

m

[equiluxe]

You actually need to be faster than the rated moto speed by the same amount as the slip factor so if the speed of the motor is 50 rpm slower than the phase speed you need to be 50 rpm over in order to use an induction motor as an alternator.

[XeonPony]

You actually need to be faster than the rated moto speed by the same amount as the slip factor so if the speed of the motor is 50 rpm slower than the phase speed you need to be 50 rpm over in order to use an induction motor as an alternator.

nope I was 1600rpm under and mine worked just great! mind you it was a 60hz unit and I was geting 44, but that was expected.

You are correct if you want the frequencies to match how ever!

[equiluxe]

Yes I did rather make the  assumption that the correct frequency for the area would be wanted but of course if a battery is being charged that would be of no importance other than efficiency of operation of the machine and keeping the coil currents  low.

[XeonPony]

Yes I did rather make the  assumption that the correct frequency for the area would be wanted but of course if a battery is being charged that would be of no importance other than efficiency of operation of the machine and keeping the coil currents  low.

Now days all most nothing cares about the frequancy due to most things run via switch mode suplies that just rectify it all to DC, even the flourescent compacts don't care so so long as you understand the idea the off side frequency is a  moot point. I ran every thing striet off mine with no issue what so ever.

[mab]

Is it just my local suppliers or are motor run capacitors quite expensive?

 - unless I can find some 2nd hand ones it may be cheaper to buy neos and modify the motor into a PMA. 

m

[XeonPony]

Is it just my local suppliers or are motor run capacitors quite expensive?

 - unless I can find some 2nd hand ones it may be cheaper to buy neos and modify the motor into a PMA. 

m

Well here for an Oil filled metal canned run capacitor at 50Uf it will set ya back about 50 cad dollars. 

If you go to a wrecking yard or dump with a socket set and screw driver set in a good days hunting you could usualy find more then enough to get started!  Old Grow lamp balasted will have a big 15 to 25Uf one on them.

[equiluxe]

I would think that magnets have got to far more expensive than a few capacitors look on ebay for motor run capacitors ( I have found some here in the UK from 99 pence to ten pounds so you need to shop around )or look for florescent lamp ballast capacitors if you cant get high enough voltage put two in series this will halve the capacity but then put another two alongside in parallel.   

[Basil]

Try AC repair shop.   They gave me a box full free.

[mab]

Thanks for the suggestions ( I have a couple of old type fluorescents in the shed  - I'd forgotten they have caps).

If you go to a wrecking yard or dump with a socket set and screw driver set in a good days hunting you could usualy find more then enough to get started!  Old Grow lamp balasted will have a big 15 to 25Uf one on them.

Alas the nanny state is making this increasingly difficult:- most dumps and scrapyards are now reluctant to let folks dismantle stuff - they might hurt themselves; or take stuff away (apparently, if I take an appliance away and plug it in and electrocute myself, they (the dump) might be liable  ).

mab

[mab]

Well I've sort of given up on the 1ph motor - it was a 3000RPM sync speed anyway (50Hz) and trying to make it run at 1250rpm would require more capacitance than I've managed to acquire (at least I couldn't get it to work) - besides, it would end up running ~20Hz which might be a tad low even for electronic psu's.

I've managed to acquire a couple of 3ph 1500 rpm motors - one's 3HP 400v/4.6A delta; the other's 2HP 420v/3.4A wye. I'm thinking one of these would work better at 1250rpm (optimum (theoretical) runner speed)?

Though I don't really want to run at 400v...

These motors are HUGE compared to the 1ph 2kw rated motor - the pic shows the 1ph 2Kw next to the 3 Ph 3Hp - but maybe it's 'cos they're older?



m

[equiluxe]

The 3 phase motor you show is an old style industrial electric motor dating back possibly as far as the 1930's but most likely 50's. They built electric motors back then to run for years without trouble, the BS rating used to state that the motor shall not have more than one degree temperature rise in ten hours while running with a fifty percent overload, not something you will find these days. The other motor you show is a modern washing machine motor or some such, they are designed for intermittent use and a short life.

To get 240 volts with the star wound motor (often referred to as wye on these pages) reconnect inside the junction box to delta, then wire the capacitors in the C-2C fashion, one winding has about 50 micro farads the other will have twice that and the third nothing at all you extract the power from the C phase (winding with the 50 micro farad across it).There is no problem with unbalanced loads as the unbalanced capacitance takes care of that.

[mab]

These motors do seem well made and the bearings still seem good - and they have grease nipples to keep them good  .

Annoyingly, the 2hp motor (400v star) only has 3 wires into the junction box so I'll need to dismantle it to find the star point - assuming it isn't buried in the windings  .

I assume it only needs to be re-configured star to give a 240v nominal output? or does it need to be in star configuration for the C-2C excitation to work?  I'm only curious 'cos I was idly considering running at 400v and converting down to reduce cable losses - but 240 would be much simpler for using the power directly (and I won't need 600+v caps).

Thanks for your help.

m

[equiluxe]

If it is delta at 415 Volt turning it into star will up the voltage phase to phase to somewhere in the region of 700 volts if it is star wound for 415 volt you can reconnect it to delta for 240 volts.

[mab]

Thx - so I could use it in star if I wanted the higher voltage.  (probably won't though)

m

[mab]

Yet another question:-

I've found the star point on the 2hp motor so I can rewire it Delta 240v 

trouble is, I'm finding it difficult to see which wires go where, so how do I know I've connected the phases correctly?

I've now got 6 wires: the original three that went to the the phases in star configuration (now labelled P1, P2 & P3); and three new wires I've labelled S1, S2 & S3 - the numbers correspond to the P wires.

I'm thinking I should connect them P1-S2, P2-S3 and P3-S1 ? Does that sound right?

Is there an easy way to check I've got it right (I don't have a 3Ph supply)?

thx

mab

[equiluxe]

Try connecting each set of coils to 12 volts in turn always using the same polarity to do so you can then check the magnetic field s of each coil either giving a North or South at the same relevant point with a compass. This will show you the direction of winding's using the right hand rule where if you place your right hand on a coil such that your fingers point in the direction of current flow    ( positive to negative as this trick originates from the early days of electricity) along the turns and with your thumb outstretched your thumb will be pointing to the magnetic north.

[mab]

Thx EQ, although when I asked for an easy way I was hoping it might be an easier way than that 

I think I'll need to draw myself some diagrams and work out what the 'right way' should look like.

m

[pavshinAN]

I think that is what  is done on the garbogen wind turbine.
Chris

[mab]

Well, It's now wired 240v delta, and it works as a motor (connected 240v across 2 wires and gave it a spin to start).

I tried connecting 50uf and 100uf as per the C-2C technique and have tried spinning up (with just a voltmeter connected across  the 50uf) using a hand drill - Success!    It starts generating (well below 1500rpm - probably 250 - 300rpm) and puts out ~60volts - unfortunately my hand drill doesn't have the oomph to get it over 100v (I was driving it direct 1:1).

So my next newbie (stupid) question(s):

I'm a bit hazy on how to control the voltage - there's the fixed load system - where you have a (largish?) fixed load permanently connected:-
Will it start up with a load connected? - I though you shouldn't start/stop with loads connected as it demagnetizes the rotor? if you start up without the load, doesn't the voltage go very high?
what proportion of the generator output does the fixed load have to be?

I'd like to use a controller, (when I can make / acquire one) but initially a fixed load system may be the way to go - unless I can get a IGC quickly (any links to readymade & cheap controllers or simple controller circuits greatly appreciated). I'm currently googling but only found general ideas rather than circuits so far...


Also, given that the drill couldn't get it up to speed, will the pelton runner have enough torque? or do you spin up without the caps connected?

As I don't have a means of test running other than the drill, I guess I need to start to set up with the pelton wheel (still haven't bought the penstock so it's all still to do).

incidentally, I did find that book online as a pdf Equilux:-
http://www.frenchriverland.com/Motors_As_Generators_N_Smith_UK_1994.pdf
free is always good 

m

[equiluxe]

As I understand it, out in the wilds they start these machines on load and stop on load when required. As the winding's always have the capacitors  in circuit and one is unloaded at all times as is the coil without the capacitor there is no problem with demagnetization. I do not know what size of electric drill you have but it is likely that it will have far less torque than the water turbine so there should be no problem with run up if there is it would mean that you turbine is too small for the motor that you have.

[mab]

Good - I can set up with a fixed load then and worry about a controller later.

As for the torque of the pelton runner; I did a crude calculation and it should indeed produce a lot more than the hand drill - which makes sense.

thx