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Author Topic: Voltage drop under load  (Read 1971 times)

EdDee

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Re: Voltage drop under load
« Reply #45 on: October 10, 2018, 02:58:06 PM »
Hey JD...

Fire it up, isolated from supplying any load, and give us the following readings:

All AC:

Live to Neutral
Neutral to Earth
Earth to Live
Neutral to a clean, exposed piece of the metalwork of the genhead itself
Live to a clean, exposed piece of the metalwork of the genhead itself
Earth to a clean, exposed piece of the metalwork of the genhead itself

I know I am coming in on the ass end here....but humour me if you would....

Regds
Ed
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Johndoh

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Re: Voltage drop under load
« Reply #46 on: October 10, 2018, 04:52:19 PM »
Hey JD...

Fire it up, isolated from supplying any load, and give us the following readings:

All AC:

Live to Neutral
Neutral to Earth
Earth to Live
Neutral to a clean, exposed piece of the metalwork of the genhead itself
Live to a clean, exposed piece of the metalwork of the genhead itself
Earth to a clean, exposed piece of the metalwork of the genhead itself

I know I am coming in on the ass end here....but humour me if you would....

Regds
Ed

Hi Ed
The results are....

Live to Neutral - 234
Neutral to Earth - 282
Earth to Live - 391
Neutral to a clean, exposed piece of the metalwork of the genhead itself - 282
Live to a clean, exposed piece of the metalwork of the genhead itself - 104
Earth to a clean, exposed piece of the metalwork of the genhead itself - 0

I did these by using the positive lead on the multimeter to the 1st part and the negative to the second eg red to earth and black to the exposed metal, was this correct?

|thanks
Paul
It is better to light a candle than to curse the darkness

glort

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Re: Voltage drop under load
« Reply #47 on: October 10, 2018, 11:02:32 PM »

You did it right mate. Wouldn't matter which way you did it though with AC.

Unfortunately, You have problems.

Johndoh

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Re: Voltage drop under load
« Reply #48 on: October 11, 2018, 12:44:52 AM »

You did it right mate. Wouldn't matter which way you did it though with AC.

Unfortunately, You have problems.

Could you enlighten me please?
It is better to light a candle than to curse the darkness

glort

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Re: Voltage drop under load
« Reply #49 on: October 11, 2018, 05:18:20 AM »

You did it right mate. Wouldn't matter which way you did it though with AC.

Unfortunately, You have problems.

Could you enlighten me please?

Proabably not.
A bit over my head and  I don't know if your system is the same as what we have here or something different.
Either way, I'm pretty sure you should not have the results you are seeing. The more informed will probably educate us both.
To the best of my knowledge you should only get a couple of volts at most going neutral to earth.  The fact you are getting more neutral to earth than live to earth and the same back to the head I think  indicates something is wired backwards somewhere.  Could also be I think the Neutral is bridged to earth which is also not good.

If I were you, once the problems have been rectified I'd be putting a separate Ground on the gen frame so if anything does ever go hot, you are protected.

 I'm pretty sure corrections are needed by an expert.  last thing you want is to let the magic smoke out of yourself.

Johndoh

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Re: Voltage drop under load
« Reply #50 on: October 11, 2018, 08:15:55 AM »
Bugger I was afraid you were going to say something like that. The problem for me now is that I know nothing about wires and wiring. The machine was very cheap but anyone around here that knows how to fix it would be very expensive! I'll see what the people on here say about it if it's unsafe I cant use it nor would I sell it to someone else if unsafe.
It is better to light a candle than to curse the darkness

glort

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Re: Voltage drop under load
« Reply #51 on: October 11, 2018, 08:24:35 AM »

It's most likley to be wires in the wrong position.  Easy to fix if you have an idea and are in front of the machine.  Bit more difficult when you are not.
I would think a competent electrician should be able to fix it, especially one whom has had experience with industrial applications.
Motor and gennys can be wired  often in 2 ways, Wye and Delta.  It could just be the genny you have has the output leads hooked together in the wrong pattern as it were. Still not sure that explains the variations but..... again i'm not in front of the thing to see how many wires are coming out of it or how they are hooked up.

Seems Ed was onto and suspected something straight off so will no doubt be able to shed some of his normally insightful light onto things.

Don't panic yet! Could be something real simple, easy and cheap to fix.

EdDee

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Re: Voltage drop under load
« Reply #52 on: October 11, 2018, 08:46:58 AM »
Hi Paul...

Going from this:
Live to Neutral - 234
Neutral to Earth - 282
Earth to Live - 391
Neutral to a clean, exposed piece of the metalwork of the genhead itself - 282
Live to a clean, exposed piece of the metalwork of the genhead itself - 104
Earth to a clean, exposed piece of the metalwork of the genhead itself - 0

I would say there is a possibility that the unit has been wired with the actual Neutral bonded to the Earth of the machine, not an uncommon practice and still done today in lightning prone areas.

So, if we assume that neutral and earth are the same here -
1) Your existing "Live" you measured would be a 240V output, it's a little high, 20% high, but there might be an adjustment to lower it.

2)The "Neutral" you measured would actually be a 110V output, a little low, but usable

3)Going by what I have seen in the past with "adjustments" being made, probably this unit was used in a 110V role... the output was a bit low, an adjustment was made, nothing changed(on that 110V output anyway) and the adjustment wasn't returned to previous position/setting...hence the 280v output on the 240V line...It wasn't used at the time, so why bother...

Right - Where to now? - Look for someone who can confirm this and poke around inside the thing... It's not advisable to push 280V to a 240V system - things could get a tad toasty.... or, take a chance and load the 280V line a bit (Neutral and Earth would be the Chassis of the unit, the Live would be what you had measured as a "Neutral" previously... See if the voltage stabilizes at around the 220-240 mark.... If your meter has a frequency measurement, see what the actual frequency of the output is, sometimes running the genhead a little too fast causes problems in interesting ways...(particularly with RMS voltage measurement on cheaper voltmeters)...

Long and the short of it is that its not safely saleable as is, not safely usable as is, its stuffed, if the smoke escapes while paying school fees, nothing lost! If it works to spec when you are finished - it a WIN!

Cheers
Ed

Edit: A bit of an afterthought.... Simple and easy... Put a good old 60W incandescent light bulb between your existing Earth/Neutral and fire it up with nothing else connected... If the bulb lights up, problem, measure the voltage... if not, measure from earth to neutral anyway with it connected... come back to us with your reading....
« Last Edit: October 11, 2018, 09:07:07 AM by EdDee »
12/1 750RPM/9HP Roid 5kVA- WMO Disposal/Electricity & Hot Water Gen
12/1 650RPM/8HP Roid 4.5kVa - Demon Dino
Chinese Yanmar - Silent Runner with AutoStart
Classic Komatsu 1963 Dozer/Fergusson 35 Gold Belly ...
Bikes,Cars,Gunsmithing & Paintball...Oh yes, a 5Ha open air Workshop to play in!

Johndoh

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Re: Voltage drop under load
« Reply #53 on: October 11, 2018, 09:30:05 AM »
Thanks Ed I will go get a bulb this morning we use low energy bulbs now so I have to get one from the shops.

Anyone that would do house calls to look at a generator would want more than it cost. It's a heavy thing to be moving and to be honest when you leave in in with someone you either pay or let them keep it.  I thought getting 230 odd volts ac was all it had to do. When I got this generator my original idea was to junk the alternator and get a new capacitor alternator however the AVR was very appealing. There are 4 wires coming to the control panel from the alternator but I have no clue which is which.
It is better to light a candle than to curse the darkness

ajaffa1

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Re: Voltage drop under load
« Reply #54 on: October 11, 2018, 11:19:02 AM »
Hey Johndoh, looks like this unit may have been tampered with to customize it for some unknown application. Do you have any history which could help with diagnosis? For example is it ex-military, was it used for agriculture or telecom/hospital back up.

Some photos of the insides would be very helpful.

Bob

glort

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Re: Voltage drop under load
« Reply #55 on: October 11, 2018, 12:08:44 PM »

Anyone that would do house calls to look at a generator would want more than it cost.

Might pay to ring around and see. Sometimes things can be cheaper than you think.
  If they could put it in order, it's probably a lot cheaper than getting another head and mucking around with that.

Clearly the thing works, most likley the wiring just needs sorting.  Gen heads can have 12 wires coming out of them. They need to be set up right. If they are not you get problems like this.  Undo them, put them in the right positions and all is fine and good with the world.
Should not take a knowledgeable person long especially if you can find a schematic of the thing and have that for them to refer to.

I would be cautious about touching the thing when it was running and try to bond it to it's own earth to the frame just in case.

Johndoh

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Re: Voltage drop under load
« Reply #56 on: October 11, 2018, 12:27:07 PM »

Anyone that would do house calls to look at a generator would want more than it cost.

Might pay to ring around and see. Sometimes things can be cheaper than you think.
  If they could put it in order, it's probably a lot cheaper than getting another head and mucking around with that.

Clearly the thing works, most likley the wiring just needs sorting.  Gen heads can have 12 wires coming out of them. They need to be set up right. If they are not you get problems like this.  Undo them, put them in the right positions and all is fine and good with the world.
Should not take a knowledgeable person long especially if you can find a schematic of the thing and have that for them to refer to.

I would be cautious about touching the thing when it was running and try to bond it to it's own earth to the frame just in case.

I paid 50 for it Glort nearly  all the stuff I bought were related to the engine eg starter new exhaust kill switch etc. It's no longer safe and we have a storm coming well fcuk all that! The nearest guy that repairs generators is about 9 miles away next that I know of is in Dublin which is 40 miles away neither would commit to coming out to view it.

The generator was just in a shed for backup ajaffa nothing too exciting was done with it. I did read somewhere that a generator has a "floating" earth and that neutral and earth should be connected but thats not helping with the neutral having power.

Bob I got a bulb forgot to get a bulb holder I'll have to dismantle one of the bedside lights in the spare room and do it quietly!
It is better to light a candle than to curse the darkness

Johndoh

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Re: Voltage drop under load
« Reply #57 on: October 11, 2018, 12:49:12 PM »
Hi Paul...

Going from this:
Live to Neutral - 234
Neutral to Earth - 282
Earth to Live - 391
Neutral to a clean, exposed piece of the metalwork of the genhead itself - 282
Live to a clean, exposed piece of the metalwork of the genhead itself - 104
Earth to a clean, exposed piece of the metalwork of the genhead itself - 0

I would say there is a possibility that the unit has been wired with the actual Neutral bonded to the Earth of the machine, not an uncommon practice and still done today in lightning prone areas.

So, if we assume that neutral and earth are the same here -
1) Your existing "Live" you measured would be a 240V output, it's a little high, 20% high, but there might be an adjustment to lower it.

2)The "Neutral" you measured would actually be a 110V output, a little low, but usable

3)Going by what I have seen in the past with "adjustments" being made, probably this unit was used in a 110V role... the output was a bit low, an adjustment was made, nothing changed(on that 110V output anyway) and the adjustment wasn't returned to previous position/setting...hence the 280v output on the 240V line...It wasn't used at the time, so why bother...

Right - Where to now? - Look for someone who can confirm this and poke around inside the thing... It's not advisable to push 280V to a 240V system - things could get a tad toasty.... or, take a chance and load the 280V line a bit (Neutral and Earth would be the Chassis of the unit, the Live would be what you had measured as a "Neutral" previously... See if the voltage stabilizes at around the 220-240 mark.... If your meter has a frequency measurement, see what the actual frequency of the output is, sometimes running the genhead a little too fast causes problems in interesting ways...(particularly with RMS voltage measurement on cheaper voltmeters)...

Long and the short of it is that its not safely saleable as is, not safely usable as is, its stuffed, if the smoke escapes while paying school fees, nothing lost! If it works to spec when you are finished - it a WIN!

Cheers
Ed

Edit: A bit of an afterthought.... Simple and easy... Put a good old 60W incandescent light bulb between your existing Earth/Neutral and fire it up with nothing else connected... If the bulb lights up, problem, measure the voltage... if not, measure from earth to neutral anyway with it connected... come back to us with your reading....

Hi Ed

Connected a small lamp to neutral and earth, bulb didn't light but voltage became very unsteady going between 50 and 300 volts. This was also showing as fluctuating on the analogue dial on the generator. I ran the generator a few weeks ago during a power cut and everything seemed to work ok apart from the well pump but that was traced to 40 feet of coiled wire.
Paul
« Last Edit: October 11, 2018, 12:50:44 PM by Johndoh »
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EdDee

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Re: Voltage drop under load
« Reply #58 on: October 11, 2018, 02:09:34 PM »
Hi JD...

I think I know what is wrong....

If its a Yanmar close coupled to a chinesium genhead (a la the pic that you referred to via this link:
( https://www.ebay.com/itm/Yanmar-6KW-Diesel-Generator/183384598167?hash=item2ab292e697:g:pBIAAOSw-mdbdzYO )

Pull the AVR off the back of the genhead and take a look to make sure that the heatsink on the back of the AVR isn't touching earth.... The chinesium replacements I got for my genhead had the heatsinks a little to proud and not insulated from the bits inside the epoxy either... Caused a "ground loop" when I connected the gennie to the house, power cycled, regulation went for a ball of sh!t, weird readings on chassis/earth pin, live and neutral.... If it ran stand-alone, it was fine...regulation perfect, all smiles...

Problems only showed up when I connected it to the house, which has a bonded E/N at the db board....

I put a spacer in to lift the AVR away from the genhead, all problems sorted!

Ed

Edit: <Quote:>Connected a small lamp to neutral and earth, bulb didn't light but voltage became very unsteady going between 50 and 300 volts. This was also showing as fluctuating on the analogue dial on the generator. I ran the generator a few weeks ago during a power cut and everything seemed to work ok apart from the well pump but that was traced to 40 feet of coiled wire.<Unquote> -

If its the heatsink shorting, the coil of wire caused enough "transformer effect" to feed back onto the Earth line of the lead, entering the regulator via the heatsink, stuffing up the regulation on the AVR... Once you have checked that spacing on the AVR and if you found it looped to ground, plug in your 3000' coiled lead and all should be well....
« Last Edit: October 11, 2018, 02:24:52 PM by EdDee »
12/1 750RPM/9HP Roid 5kVA- WMO Disposal/Electricity & Hot Water Gen
12/1 650RPM/8HP Roid 4.5kVa - Demon Dino
Chinese Yanmar - Silent Runner with AutoStart
Classic Komatsu 1963 Dozer/Fergusson 35 Gold Belly ...
Bikes,Cars,Gunsmithing & Paintball...Oh yes, a 5Ha open air Workshop to play in!

Johndoh

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Re: Voltage drop under load
« Reply #59 on: October 11, 2018, 07:03:56 PM »
Hi Ed

This was originally a silent enclosed generator the avr is mounted on the frame of the generator not on the head its self. I have a spare avr chinese made I will try it tomorrow. I suppose it could be that its race is run!
It is better to light a candle than to curse the darkness