Author Topic: Voltage drop under load  (Read 18199 times)

EdDee

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Re: Voltage drop under load
« Reply #45 on: October 11, 2018, 08:55:49 PM »
Hey Jd,

Check for that little heatsink on the back of the avr sorting to frame ground... Unbolt the avr and let it hang loose if you need to, then do the lightbulb between n-e test again...

I don't think the avr is buggered....not yet anyways....

Ed
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guest23837

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Re: Voltage drop under load
« Reply #46 on: October 11, 2018, 09:01:32 PM »
Hey Jd,

Check for that little heatsink on the back of the avr sorting to frame ground... Unbolt the avr and let it hang loose if you need to, then do the lightbulb between n-e test again...

I don't think the avr is buggered....not yet anyways....

Ed

Avr isnt touching anything its on a little piece of sprung steel. It was probably made in china too so it could be dodgy?

ajaffa1

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Re: Voltage drop under load
« Reply #47 on: October 12, 2018, 09:46:53 AM »
Hi JD. just to emphasis the issue, here is a photo of a standard Chinese AVR, please note the warning on the hearsink, It`s live when running!  :o

Do you know if your generator was originally built with an AVR or was it fitted later? If it was retro fitted, you can probably remove it all together and see how it goes just running with the original rectifier. Won`t be anywhere near as smooth an output but it should identify if the problem lies with the AVR.

Bob


EdDee

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Re: Voltage drop under load
« Reply #49 on: October 12, 2018, 01:06:25 PM »
Hi Bob,

Those little genheads wont put out any real power without the AVR, the 6 wire units have 2 inputs for supply, 2 inputs for sensing and 2 outputs to the slip rings - You can cobble a small dc supply together and feed the slip rings thereby getting output, but a right PITA to regulate under a varying load....been there!!

Cheers
Ed

(PS - Also "been there" regarding the heatsink shorted to earth....kept me running around looking at just about everything else before I tracked my induced fault down!!)
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Re: Voltage drop under load
« Reply #50 on: October 12, 2018, 01:44:31 PM »
I Noticed, there's a couple of guys selling cheap generators that have been used for electro fishing. I have no idea what this is but the ads all say the generators could be modified for normal use. I got to thinking, is this what I have???

EdDee

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Re: Voltage drop under load
« Reply #51 on: October 12, 2018, 02:04:17 PM »
No, I don't think it is what you have....possible, but unlikely....I still think you have a genhead of similar nature to mine with a fault that came about after someone, at some stage, replaced the AVR....Have you unbolted the AVR and checked yet?
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guest23837

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Re: Voltage drop under load
« Reply #52 on: October 15, 2018, 11:02:40 PM »
At last my new voltmeter has arrived! I plugged it into the house it showed 50.7 HZ I then plugged it into the generator and it's showing 57 HZ @ 3000 rpm, what should I do next??

EdDee

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Re: Voltage drop under load
« Reply #53 on: October 15, 2018, 11:10:21 PM »
Frequency measurement at the generator outlet is a bit hit and miss... there are quite a few stray magnetic fields and some minor harmonics on the lines up close... trust the frequency reading only when you have a bit of a load on it and you measure it 'at a distance' ...

Have you pulled the AVR off it's mounting plate yet to check for that suspected short?

Cheers
Ed
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guest23837

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Re: Voltage drop under load
« Reply #54 on: October 15, 2018, 11:15:19 PM »
Frequency measurement at the generator outlet is a bit hit and miss... there are quite a few stray magnetic fields and some minor harmonics on the lines up close... trust the frequency reading only when you have a bit of a load on it and you measure it 'at a distance' ...

Have you pulled the AVR off it's mounting plate yet to check for that suspected short?

Cheers
Ed

Hi Ed
I didn't do anything to it since. I will take a look tomorrow when I load it up to check frequency. Should I run an earth lead from the alternator to my earth stakes?

Paul

EdDee

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Re: Voltage drop under load
« Reply #55 on: October 15, 2018, 11:38:40 PM »
Hi Paul,

Take care when working on it while it is running... Personally, I wouldn't earth it, for fear of a feedback loop and blowing the AVR, but that does present the possibility of 'shock hazard' if you touch ground and gen frame at the same time.

In this case, I would use utmost care, de-mount the AVR, install the small globe between N-E, then start it up... if the power fluctuates as before, shut it down immediately... Without touching metal on the gen if at all possible.. Dry leather glove or a good rubber glove recommended... The chances of killing yourself are slim, but hey, why take a chance if you are not familiar with the angry pixies...they might try and bite you!

If the power fluctuates with the AVR unbolted from the plate, I think you will need a pro to come take a gander... If the voltage is stable, we have found the problem....

Also, when you unmount the AVR for the test, stick it in a plastic container or something to insulate it and prevent it from touching other metalwork and  shorting out on something else...

Further, if this solves the problem, don't expect the 'AVR in a plastic box trick' to be a solution long term... it will need proper mounting without being enclosed for cooling...

Cheers
Ed
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Re: Voltage drop under load
« Reply #56 on: October 16, 2018, 01:32:35 PM »
Ok guys here's an update report. I had a spare AVR the black one in the link, unused from the land of "please be understanding" it wouldn't adjust, started at 280 volts ended 280 volts thats crap. I only just got the votmeter so I connected up the old AVR and played with it for a while. Turns out the frequency is better than the house by .5%. I did the other tests again and they are a little interesting in that they power is one way so red probe to neutral and black to earth shows voltage reversed they dont same with live to earth. live and neutral shows voltage and minus voltage. I touched it when it was running and lived!

Here is a link to the photographs https://www.dropbox.com/sh/h0ety3ppwht4wsm/AAAokl9kwbM1USKcSwwl2LvIa?dl=0

FG Wilson on generator earthing http://www.fgwilson.ie/files/generator-set-neutral-earthing.pdf

EdDee

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Re: Voltage drop under load
« Reply #57 on: October 16, 2018, 01:56:02 PM »
And with the AVR unbolted from the frame, in an electrically insulated position, with the light globe between N-E?

...

..

.

?

Edit: Incidentally, on some of the older Yanmar gens I have worked on, the older metal cased AVR's had to be insulated from ground - They were originally mounted on two insulated posts on the rear of the genhead. (Hence the crescent shape.) The "modern" chinesium replacements are "potted" with only the little heatsink tab on the back needing to be insulated from electrical contact to ground, but its a crap shoot as to whether you get one with the wiring done correctly. The new ones often have the 2 Blue and 2 Yellow wires (Sense and Supply) in the 4 contact block switched around. They are not polarity/phase sensitive from what I can make out....
« Last Edit: October 16, 2018, 02:12:37 PM by EdDee »
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guest23837

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Re: Voltage drop under load
« Reply #58 on: October 16, 2018, 02:33:35 PM »
The AVR is in a small plastic tub. The bulb doesnt light connected neutral to earth

EdDee

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Re: Voltage drop under load
« Reply #59 on: October 16, 2018, 02:43:14 PM »
Is the output steady and not varying?

What is the N-E voltage now?

Ed
12/1 750RPM/9HP Roid 5kVA- WMO Disposal/Electricity & Hot Water Gen
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