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#201774 06/23/11 07:45 AM
Joined: Jul 2002
Posts: 8,407
Likes: 2
Trumpy Offline OP
I'm back wiring dairy sheds and a 2nd hand alternator turned up here last week.
It has a large diesel engine on the front of it, but when I spyed the name plate on it, it turns out it came from the US.
Single phase voltage is between 120 and 208VAC
Three phase voltage is between 277 and 380VAC. crazy
I'm not sure what to make of this machine, I never even bothered to have a decent gander at the actual machine itself.
All the farmer said was "Pretty Grunty, Eh!!" bash
Apparently it came out of a hospital, I have no idea which hospital it was.
Will get some pics and move this over to the Pics Submitted Area.

My understanding is, this was bought on the cheap and although the farmer has never heard it run, I think the diesel motor might be had it.

Your thoughts on the voltage though, over here we need a single phase voltage of 230VAC and a 3 phase voltage of at least 400VAC.
Sure this might only be a back-up, but I have a problem with wiring this at all.
Oh BTW, the alternator is 50Hz, just to make it more "fun".

Joined: Mar 2004
Posts: 947
twh Offline
50 Hz isn't from North America. It might have come from the US, but probably wasn't used there. 50 Hz makes the clocks run slow.

Joined: Apr 2002
Posts: 7,282
Likes: 3
120/208 single phase/neutral is normal from 120/208 3 phase. 'Y' setup here. The 380 volt, 3 phase is 'odd' to say the least. Our other common voltage is 277/480 'Y'.

And the 50 Hz is not our 'common, as THW said.

Sounds like it was 'made' to run some custom type equipment.

Greg (Gfretwell) is the 'local' maven on the 'odd' voltages here IMHO; he helped me out last week on something I was unfamiliar with.

Good luck, & stay safe!

Joined: Jul 2004
Posts: 783

how many output leads are there? Hopefully 12.

Can you verify it is 277/ 480 not 380.

Also verify the frequency. The stated voltages sound like standard 60 Hz values.

Joined: Mar 2005
Posts: 1,803
You can adjust the hz [50 - 60] at the engine governor. [3000 - 3600 RPM] with the aid of a tacho and a 16oz hammer laugh.
Assuming this isn't a set cobbled together by an amateur, the governor should be able to hold revs within a few % of set speed throughout the power band - and the voltage controller should be capable of maintaining the output with minimal sag within the generator max. output amps. If it's an unmodified vehicle engine nailed to an alternator, it will have an automotive governor designed to run 15% or more sag on demand - it is virtually impossible to drive a diesel-powered vehicle with a generator type governor, [unless you're a kangaroo! crazy] which would make for some interesting phenomena in use.

I did this back in the eighties, coupling a close-governed fire-pump engine to a huge ancient 36" cylinder-type bowling-green mower. As I lurched up the lawn at ever increasing velocity perched on the roller-seat, the clutch failed to disengage and the governor ignored the throttle. The choice was now between driving into the kitchen [and incurring the wrath of Her Indoors] and a rockery. I chose the latter. The engine finally stalled with me halfway up a larch tree.

Last edited by Alan Belson; 06/24/11 09:41 AM.

Wood work but can't!
Joined: Jul 2004
Posts: 783
You can adjust the hz [50 - 60] at the engine governor. [3000 - 3600 RPM] with the aid of a tacho and a 16oz hammer.

If the prime mover is a diesel engine, the engine speed is probably 1/2 to a 1/4 of that. Typical diesel engine speeds for 60 Hz are 900, 1200, and 1800 RPM. Corresponding 50 Hz speeds would be 1500, 1000, and 750 RPM.

If you have access to all 12 output leads (dual voltage) or all six leads (single voltage), you should be able to wire it for single phase dog leg (derated) or three phase output. Tweaking the voltage regulator for a non factory output voltage may require some precision surgery.

Joined: Mar 2005
Posts: 1,803
Larry, pardon, I assumed pro-rata on the revs, whether that be by pole # numbers or gearing up a 2 pole alternator. The plate says 120-208v. NZ 2010 REGS = 230v6% 1, 400v6% 3 poco supply as Mike says, so some volts tweaking will be necessary for ideal service. Most stuff would still run at 208/380 and 60hz as a temporary emergency supply, induction motors a bit fast, lights a bit dim[?], Amps a bit higher... breakers replaced with knitting needles! mad - only joking! A dairy shed may well need 3 for the vac-pumps etc..

The biggest hurdle will prob'ly be that oiler lump. If the external condition is reflected inside, no amount of tweaking will help. Only one way to find out, clean filters, clean oil, fuel-up and turn her over.... aspirin

Wood work but can't!
Joined: Mar 2005
Posts: 1,803
I just read the destructions [Rule #1 - only to be read once you have wrecked the unit!] on my 6kw 3 415v 2 pole Italian built alternator. The mnfr. recommends setting the Voltage Control 3 or 4% over-voltage to allow for sag when drawing power using a gas-engine drive. The adjuster appears to be a simple setscrew in the pic. [I never touched it from new, the only mod was to ground the centre-tap on delta as recommended on ECN for anti volts-drift.] I use a pair of single-phase duplex-drive 2 pole induction motors [ = 50 hz supply in theory] , pulley-veebelts @ 1:1 to the alternator: this must give me about 4% sag on hz as the motors slip at full chat, but the machinery I run just goes a bit slower, with no probs after 6 years of daily use.

Wood work but can't!
Joined: Feb 2003
Posts: 939

This what you have to do with this primemover { engine } readjust the speed down to 50 HZ so the primemover it have to be 1000 or 1500 T/min { most common depending on which engine } but 1500 T/min is the universal speed for most genney on 50 HZ supply with 4 pole alternator for 6 pole alternator it will be 1000 T/min while 8 pole verison will be at 750 T/min

Once you get the primemover on the correct speed as I listed above then adjust the voltage the 12 lead alterantor will be same as 60 HZ verison beside 120/240 volts 1 will not be avabile on that on 50 HZ.

If you can get a photo of that unit one of the guys will indentify it quick ditto with the primemover we can able tell you quick.


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Joined: Jul 2002
Posts: 8,407
Likes: 2
Trumpy Offline OP
Thanks Guys for your ideas.
I intend to get some pics of this unit tomorrow and will post them up tomorrow night.
Oddly enough, this unit must have come from the US, because there is an OSHA sign on it about minimum clearance, referencing the NEC.
It also has a Westinghouse disconnect on the side of it, as far as people over here are concerned, Westinghouse only make refrigerators. grin

Pretty much, the only things in a dairy shed over here that run on single phase is the flourescent lighting, the power supplies for the pulsator and electronic cup-removers and maybe a few refrigeration controls, the rest of it is all 400V delta connected.

Will keep you posted.

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