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Author Topic: Alternator test  (Read 8709 times)

dieselspanner

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Alternator test
« on: January 01, 2017, 12:00:56 PM »
Hi All

I've fitted the 8kva Stamford Newage alternator with a frequency meter - 50 Hz and 100v, at 620 rpm it's showing 51 hz, with no load. its driving through a polyvee belt off the flywheel rim.

Plugging an electric kettle in to any of the three phases, each one has its own socket, drops the revs 15 rpm or so for 5/6 seconds then they build up to 617 and hold steady, with 50Hz, 9 amps on the meter and 218v.

Is it possible, advisable, worthwhile or sensible to tinker with the AVR to up the voltage to 220v or do I leave well alone?

As the alternator will produce more than the Lister, nominally a 6/1, how much load should I try as a max power test with out endangering the AVR etc as the revs drop?

All advice welcome, usual caveats apply!

Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

millman56

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Re: Alternator test
« Reply #1 on: January 01, 2017, 08:35:12 PM »
Hi Stef, 

Is the 100V 50Hz @ 620 RPM in your first sentence a typo?                                                                                                                                                                            In my limited experience an  ideal unloaded voltage would be 237 and depending on the alternator and AVRs repspnse to load, this would probably drop 10 volts or so on full load with the engine speed remaining fairly constant after the initial dip caused by applying the load.     If the AVR is a modern type it will probably have UFRO function  (under frequency roll off ) ,  this reduces the excitation voltage proportionally, below  a preset frequency which then reduces the alternator  output voltage which reduces the load which in turn allows the engine to regain speed, in theory of course.                                                                                                                                                                                                                                                                                                                                                                                                                                               
                                                                                                                                                                                                                                                             If the   AVR is an older type without UFRO then certain underspeed conditions can lead to the magic smoke, however if as is common  either type of AVR is powered by the main stator output then gross overload/underspeed  will cause a collapse of the output anyway.     
                                                                                                                                                                                                                                                            Your 8 KVA 3 phase alternator should be good for 2.5 Kw 1 phase to neutral, this is the nominal output of a 6-1  Start-O-matic set.

Hope this helps,
Mark.   

dieselgman

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Re: Alternator test
« Reply #2 on: January 01, 2017, 09:29:06 PM »
If your Stamford is using the SX460 regulator, then no worries about under-frequency stresses on the regulator. It has a limit below which it will simply cut out and drop the load. This happens after the UFRO function range is exceeded that is designed to stabilize the output under varying (and especially heavy) loading conditions.

You should be able to adjust your output voltage to a higher value without concern. The 6/1 horsepower will top out around 3.5kW, (or slightly less), well under the capacity of your generator head. If you excessively overload the engine, then it will slow below electrical tolerances, probably blow black exhaust and drop the load.

dieselgman
« Last Edit: January 01, 2017, 09:33:10 PM by dieselgman »
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dieselspanner

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Re: Alternator test
« Reply #3 on: January 01, 2017, 10:45:47 PM »
Hi Both,

Thanks for the replies.

Mark,

it's not a typo, just my inability to express myself concisely!
I have a frequency meter, rated at 100v between 1 phase and neutral, this is where my readings come from, the ammeter only works on one of the phases, as does the volt meter. The rev counter is a home made device which picks up on 4 magnets on the camshaft retaining collar, via a Hall effect switch, powered by a 9v battery. A mate made it for me, electronics are pretty much beyond me!

Gary,

Yes, it's an SX 460 AVR, well that's what the label says...
There was a sticker inside the control box which I took the precaution of photographing before disturbing it to relocate the gauges. I've laminated it so it can carry on providing a permanent record on the machine.

It's nice to know that if I over load things in a fit of exuberance that it'll all shut down before the magic smoke escapes, it's a shame more things in my past haven't been so well protected!
 
I intend to fit a rotary switch in order that the ammeter serves all three phases, to help with (future) load balancing between the 3 phases, however am I correct in assuming that given the size of the gen head that if it all ends up on one phase I won't damage anything?

Thanks again,

Stef


Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

dieselgman

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Re: Alternator test
« Reply #4 on: January 01, 2017, 11:53:05 PM »
Some of the Stamfords are 12-lead and can be re-wired to single phase. Some are NOT. Look for a winding spec 311 on your data plate and if so, it should be able to reconfigure a bunch of different ways. If you want the highest possible reliability for single-phase balanced loading, then re-wire to single-phase if the head will support that.

If keeping the head in 3-phase configuration, you will not want to overload any single set of windings. If it is rated at 8kW 3-phase, then it should be de-rated to two-thirds (5.3kW) of that value, for the single-phase configurations. You will still be dealing with two pairs of windings at the lower rating and should expect about an equal split of 2.6 kW per each side in a 120/240 single-phase configuration. It IS possible to overload/overheat the Stamford if you put an entire 120v single-phase loading all on one single winding. If you are using the 240 volt wiring configuration, then should not ever overload with only 6 horsepower input. Like you suggested, read the individual currents being drawn per leg, and try not to exceed the maximum rating for any single one. Ideal would be equally balanced.

Much more precision is available on loading specs and wiring options if you have your Stamford data plate information.

dieselgman
« Last Edit: January 02, 2017, 12:02:49 AM by dieselgman »
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dieselspanner

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Re: Alternator test
« Reply #5 on: January 02, 2017, 10:02:58 AM »
Hi Gary,

Here, I hope! is a photo of the spec plate, as well as electronics, generators and painting houses, internet type stuff is almost beyond me as well!




Cheers Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

dieselgman

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Re: Alternator test
« Reply #6 on: January 02, 2017, 04:27:21 PM »
Stef,

That appears to be a 311 winding spec (although hard to read in your image)... all good! Stamford BC164 specs and all wiring/installation/maintenance instructions are easy to get from NewAge, if you have any trouble finding it let me know and I can zap a copy over to you.

dieselgman
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dieselgman

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Re: Alternator test
« Reply #7 on: January 02, 2017, 05:08:21 PM »
Note that your 3-phase load specification on that Stamford is 21.3 amps (per leg), 3-phase, at the (lower) voltage 127vac... this is where the 8.1 kVA is derived - and/or vice-versa.

If you use the head wired per data-plate, you should easily remain within insulation temperature specs as long as no single leg exceeds 21.3 amps continuous. Short-term spikes, (within reason) will not matter much.  Very nice to be running an oversized head indeed!

dieselgman

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millman56

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Re: Alternator test
« Reply #8 on: January 03, 2017, 07:38:16 PM »
Hi Stef,
The photo makes all the difference, it`s now as clear as mud !!     220 V line to line voltage not 415 V as per my assumption.     

Mark. 

dieselspanner

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Re: Alternator test
« Reply #9 on: January 03, 2017, 09:45:14 PM »
Hi All

Thanks for all that, sorry I'm not as switched on as I should be, mind you I'd not be asking questions and cluttering up the site if I knew what I was on about in the first place!

Sadly I doubt you've heard the last of me!

I'm thinking I'll leave it as a 3 phase unit, then if I ever get my hands on any 3 phase workshop equipment I'll have power to hand.

I've got the Lister running as well I envisaged, there's one or two little jobs to tackle - at the least a dipstick, Butch! and the rad I begged out of an LDV van to fit and plumb, then I'd like to fit a starter (all suggestions welcome!) and get my electronically gifted mate to knock me up a 'Startomatic' type set up.

Some time over the next few months I'll try for another video on Youtube, just to secure the bragging rights!

Cheers Stef




Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.