Alternator speed (slow speed alternators)

[Proper Job]

Is the 'running rpm' for alternators 'common' across all manufacturers?

 

I need to invest in a 24v alternator for the Ailsa Craig. It has a tick over speed of 200 - 250 rpm. Max speed of 1200rpm. It will probably spend most of its life at 6 - 800 rpm.

 

Getting the right pulley size for the crank obviously depends on the alternator pulley size, but what is the speed range for the alternator? There must be a minimum speed, best operating speed and a maximum over speed.

 

Is this common or will I have to pushase an alternator and then pulley up to suit one I have manufacturer info?

[chris w]

Is the 'running rpm' for alternators 'common' across all manufacturers?

 

I need to invest in a 24v alternator for the Ailsa Craig. It has a tick over speed of 200 - 250 rpm. Max speed of 1200rpm. It will probably spend most of its life at 6 - 800 rpm.

 

Getting the right pulley size for the crank obviously depends on the alternator pulley size, but what is the speed range for the alternator? There must be a minimum speed, best operating speed and a maximum over speed.

 

Is this common or will I have to pushase an alternator and then pulley up to suit one I have manufacturer info?

 

You will typically need about 2000rpm alternator speed to get at least 60% of the nominal current output and as much as 5000rpm alternator speed to get the full rated output. This is for a "normal" star-wired stator. If the stator is rewired as a delta connection, you can get very high current output at far lower revs. Snibble is the king of this.

 

Chris

[Timleech]

Is the 'running rpm' for alternators 'common' across all manufacturers?

 

I need to invest in a 24v alternator for the Ailsa Craig. It has a tick over speed of 200 - 250 rpm. Max speed of 1200rpm. It will probably spend most of its life at 6 - 800 rpm.

 

Getting the right pulley size for the crank obviously depends on the alternator pulley size, but what is the speed range for the alternator? There must be a minimum speed, best operating speed and a maximum over speed.

 

Is this common or will I have to pushase an alternator and then pulley up to suit one I have manufacturer info?

 

 

There is some variation between makes & models, you ought to be able to get the info from the makers.

Leece-Neville, whose products have become popular for those wanting a higher output than the standard 'car type', publish info on their website but their range is rather daunting.

eg:-

http://www.prestolite.com/literature/alts/PP1138a_mda.pdf

 

Probably best to talk to a supplier first to find what they can offer from stock, then check the details.

 

I don't know where you are, but I've always found G E Middleton in City Road, Manchester to be very helpful. I believe they will do mail order, they advertise from time to time in the waterways press.

 

Tim

[DHutch]

Our engine runns between about 50 and 320rpm, crusing speed of around 150/200.

- We ended up geting an alternator that is rewound to charge at lower speed. It has done about 30amps (24v) at 800rpm on a bench, still rising.

 

 

Daniel

[chris w]

Our engine runns between about 50 and 320rpm, crusing speed of around 150/200.

- We ended up geting an alternator that is rewound to charge at lower speed. It has done about 30amps (24v) at 800rpm on a bench, still rising.

 

 

Daniel

 

Do you happen to know if it's a delta winding configuration?

 

Chris

[Sir Nibble]

You will typically need about 2000rpm alternator speed to get at least 60% of the nominal current output and as much as 5000rpm alternator speed to get the full rated output. This is for a "normal" star-wired stator. If the stator is rewired as a delta connection, you can get very high current output at far lower revs. Snibble is the king of this.

 

Chris

Other way round Chris, the low speed mod converts delta to star.

QUOTE(Dhutch @ Oct 17 2007, 10:07 PM)

Our engine runns between about 50 and 320rpm, crusing speed of around 150/200.

- We ended up geting an alternator that is rewound to charge at lower speed. It has done about 30amps (24v) at 800rpm on a bench, still rising.

 

 

Daniel

 

 

Do you happen to know if it's a delta winding configuration?

 

Chris

 

Dan's alternator is a Butec A60 from a leyland leopard coach, as standard they are delta wound, and I would bet that the "Rewind" consisted only of reconnecting to star, these are dead low speed units anyway.

I would suggest that you search out one from a commercial vehicle scrappy, or I could price one up, I may have enough parts lying around to build one! Good reliable unit, good low speed characteristics, good output.

[chris w]

Other way round Chris, the low speed mod converts delta to star.

 

Oh, I thought most standard alternators were star anyway. Am I incorrect in thinking that Snibble?

 

So, what you would advocate is to start in star config and then (through circuitry) switch to delta running at higher revs?

 

I had assumed that because delta gives higher current at a lower voltage that this would be ideal to get a higher current at lower revs and then switch over to star config at higher revs. Je suis confusé, aidez-moi s'il vous plait.

 

Chris

[Sir Nibble]

Oh, I thought most standard alternators were star anyway. Am I incorrect in thinking that Snibble?

 

So, what you would advocate is to start in star config and then (through circuitry) switch to delta running at higher revs?

 

I had assumed that because delta gives higher current at a lower voltage that this would be ideal to get a higher current at lower revs and then switch over to star config at higher revs. Je suis confusé, aidez-moi s'il vous plait.

 

Chris

Blimey Chris, you are the LAST person I would ever have expected to have to say "do the maths" to! Yup, delta for higher current, star for higher voltage. But at low speeds it's voltage that we are missing. Each individual winding will have it's own emf of course, in star that's multiplied by root 3, yes? so at low speed the voltage exists to drive the current, although less current is available. At higher speeds the individual windings are producing sufficient voltage so back to delta and now Current is multiplied by root 3 over what it was in star.

"Standard" alternators can be either delta or star at the designers behest, sometimes a 24V stator is only a 12v stator swapped from delta to star, (CAV AC5, and, you guessed it A127).

Edited October 18, 2007 by snibble

[chris w]

Thanks Snibble. Actually I understand the maths and where the root 3 comes from, but was having a Saga moment. I was totally missing the point that at low revs we don't have much voltage and therefore need star config.

 

So, if I understand you correctly, if I could (electronically) switch my A127 into delta at high(er) revs, I could get significantly more current from it or, you seem to indicate, that an A127 is in delta anyway? I realise the power will be the same in both configs.

 

Chris

Edited October 18, 2007 by chris w

[Sir Nibble]

A127 is delta. I will gladly talk more about stator mods when this damn vulcan is airbourne!

[Timleech]

"Standard" alternators can be either delta or star at the designers behest, sometimes a 24V stator is only a 12v stator swapped from delta to star, (CAV AC5, and, you guessed it A127).

 

Interesting (to some )

 

There used to be a 'low speed' version of the AC5 available, I'm not absolutely sure whether it was a CAV offering originally but later available as someone else's mod. Any idea how that was done?

 

 

Incidentally I've got what I'm fairly sure is a 'new' 24V AC5 here, I wonder whether that might suit the OP's purpose?

 

Tim

[Sir Nibble]

Interesting (to some )

 

There used to be a 'low speed' version of the AC5 available, I'm not absolutely sure whether it was a CAV offering originally but later available as someone else's mod. Any idea how that was done?

Incidentally I've got what I'm fairly sure is a 'new' 24V AC5 here, I wonder whether that might suit the OP's purpose?

 

Tim

Yes there was a slow speed AC5 for Garder engines, but I can tell you from experience it's no slower than the Butec. A CAV AC7 would meet the case nicely but is less likely to be cheaply available, similarly the AC203 (but usually 80A). Do you have any details of the AC5 you have? They came in 12 and 24V with outputs from 30 to 60A, with or without internal regs.

[Timleech]

Do you have any details of the AC5 you have? They came in 12 and 24V with outputs from 30 to 60A, with or without internal regs.

 

 

I'll check later, but I do know it's not an AC5R, but it does have the 'marine' shroud on the back.

 

Tim

[RLWP]

I will gladly talk more about stator mods when this damn vulcan is airbourne!

 

OFF TOPIC, but, is this your Vulcan then? http://www.tvoc.co.uk/

 

Richard

[Sir Nibble]

A127 is delta. I will gladly talk more about stator mods when this damn vulcan is airbourne!

Righto! The more turns in a stator winding, the more the voltage. The fewer turns the more the current. I am intending sooner or later to wind a stator with tapped windings to experiment with. Is it better to take one turn off and connect star for better low speed performance? or put a turn on and connect delta? Idealy, what I would prefer is a longer stator, since the length of the conductor rather than the winding turns is what gives us the voltage, but winding turns knock back the current. I have welded two A127 stator cores together for this, but I'm stymied until I can make a longer rotor which I'm not really tooled up for. If I can get this together it should not be too difficult to produce a unit to make around 60A at tickover. What I'm aiming for is to hold up a bit of metal and say "This, is a purpose built narrowboat alternator".

[Timleech]

Do you have any details of the AC5 you have? They came in 12 and 24V with outputs from 30 to 60A, with or without internal regs.

 

Just checked, I was wrong, it's 12 Volt.

 

I do have somewhere, in theory, a 24Volt AC5 but it's of unknown parentage plus I can't lay my hands on it just now.

 

Tim

[DHutch]

Other way round Chris, the low speed mod converts delta to star.

Dan's alternator is a Butec A60 from a leyland leopard coach, as standard they are delta wound, and I would bet that the "Rewind" consisted only of reconnecting to star, these are dead low speed units anyway.

I would suggest that you search out one from a commercial vehicle scrappy, or I could price one up, I may have enough parts lying around to build one! Good reliable unit, good low speed characteristics, good output.

Yeah, sounds about right.

 

I dont know a huge amount about it, as I didnt even speak to the guy who supplied it myself, and my grandad who did recall much of the details.

- However i do beleve that it is off a coach, giving it a slowish, 24v base.

- And i also know (or atleast have assummed) its wired as a star, as i cames with a flying lead marked 'startpoint'. Which we dont use.

- Its the same from the outside as the one we had fitted previously, bar the fact that's its about 30mm longer in the middle (more iron).

 

So yes, I expect it is exactly as you describe, and has not actually had the windings themselves replaced/rewound just the topology changed to star.

 

 

This is the best photo i have to hand, taken before we had fitted the new belts.

- After it ended up like that after one winter, i got some grease and wd40 rubbed into it as well!

- The sterling gadetory isnt wired up either, never has been. Maybe one day we will play with that...

 

 

 

 

 

Daniel

[Proper Job]

I'm getting a little confused (especially when the square roots came in to it).

 

I need to try to find a:

CAV AC7 or AC5 ?

or a Butec ?

 

I have found a Butec A100 set up (Leyland National?) on line:

Alternator £220

Charge loom £100

Regulator £30

 

Not knowing much about the cost, is this reasonable? Should I bite his arm off at this price?

 

How difficult would it be to source one via a breaker? I'm not in a massive hurry.

 

Cheers

[Timleech]

I'm getting a little confused (especially when the square roots came in to it).

 

I need to try to find a:

CAV AC7 or AC5 ?

or a Butec ?

 

I have found a Butec A100 set up (Leyland National?) on line:

Alternator £220

Charge loom £100

Regulator £30

 

Not knowing much about the cost, is this reasonable? Should I bite his arm off at this price?

 

How difficult would it be to source one via a breaker? I'm not in a massive hurry.

 

Cheers

 

At that price, I would have a word with someone such as Middletons to see what they can offer new. The Leece-Nevilles they've supplied to me and others, admittedly 12 volt, are fairly low-speed, high output current also higher charge voltage than some of the older models (reckoned to be a good thing for modern batteries & you shouldn't have any need of a fancy charge controller)

 

 

Tim

[chris w]

[/url]

 

Daniel

 

What are the two (old) Sterling boxes? I can't read the text on them.

 

Chris

[DHutch]

 

 

What are the two (old) Sterling boxes? I can't read the text on them.

Chris

The yellow box on the right is a Sterling "alternator power booster" which is 15yo and not yet been used, however i beleave it allows a battery sensing set up.
- The red fronted ali fined box is the alternators regulator (external reglaor) and then as i mentiod above, the ampmeter is disconected, and the switch placed in the field ciruite to enable the alternotor to freewheel. There is the a simular ampeter, and the 'ignition' switch which are just above the set up and the wheelhouse floor.

Also if you click and enlarge it, you can read most of the text.


Daniel

[John Orentas]

Nice wiring Daniel, you haven't served an apprenticeship with a Mr Silcox by any chance. ?

[Sir Nibble]

I'm getting a little confused (especially when the square roots came in to it).

 

I need to try to find a:

CAV AC7 or AC5 ?

or a Butec ?

 

I have found a Butec A100 set up (Leyland National?) on line:

Alternator £220

Charge loom £100

Regulator £30

 

Not knowing much about the cost, is this reasonable? Should I bite his arm off at this price?

 

How difficult would it be to source one via a breaker? I'm not in a massive hurry.

 

Cheers

The A100 is not such a reliable unit and the need to connect via a NATO socket is a pain. On the Leyland National they used to have a habit of the rotor shaft shearing just outboard of the bearing with the result that the belts would grab the pulley and fan assy and shy it across the road!! Look at anyything 70s-80s with a leyland engine, even cummins engines often have butec equipment if fitted to a leyland truck. You will find one I am sure if you can get access to a commercial vehicle breaker. The alternator Dan mentioned like his but shorter is the A13 which is the same but 30A. As a rule, low output units on trucks, high on busses/coaches.

[DHutch]

Nice wiring Daniel, you haven't served an apprenticeship with a Mr Silcox by any chance. ?

Yeah, it was neat origanally with the old alternator.

- All lashed up really neatly with wire by the automotive electritian (who did most of the wiring under my grandads supervision).

- Neat tho it was however i didnt like the way it was digging into insulation of loom, it being a wire in itself. So i cut it all off as i had to adjust it a bit anyway

- Then it just got taped up out of the way so that it cant foul on the fan/belt or whatever. So yeah, fuctional but a little crude. Like the rest of emilyanne!

 

 

 

Daniel

[Proper Job]

This may sound strange, but here goes!

 

I fairly sure (bear with me), my engine rotates anticlockwise (no where in the manual does it state the direction of rotation!), when looking at the flywheel end of the engine to the back of the engine.

 

One of the beasts was fitted with an old alternator (not sure if its 12 or 24v) that I cannot get to work. But the alternator was fitted with a heath robinson bracket that made it face backwards (ie pulley faced the rear of the engine) and jutted out infront of the engine. This was obviously done to make the alternator rotate in an opposite direction to the engine (if you get what I mean).

 

Am I right in thinking that normally rotation is clockwise for most engines. Will I have trouble with alternators?

 

I've put a picci on my album to show it