Anotherpower.com Forum
Project Journals => User Journals => RossW => Topic started by: rossw on February 07, 2012, 04:54:44 am
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Had one of those "oopsee" moments.
I remember when I was making my solar trackers, thinking "That's funny, I thought I had one more of those to make".
Well, couple of days ago (and it really justifies having a power meter on EACH piece of equipment) I did one of those routine checks on things and thought one of the arrays was waaay down on power. Better go have a look.
This arm *WAS* straight.... it held the linear actuator:
(http://house.albury.net.au/06feb2012/100_5259.JPG)
The steel had fatigued and in the 60-odd kmh gusty wind the day before, had given up the ghost.
(http://house.albury.net.au/06feb2012/100_5263.JPG)
The instant I saw it, I knew what had happened, and remembered the year-earlier event of being surprised that I was one piece ahead of where I thought I was.... I'd counted the template! Worse still, I bolted the template in on the finished piece! It was only ever supposed to be to check my maths, that the geometry worked as I expected!
Here's the template, made of 3mm (1/8") thick angle, against what the other trackers were made of:
(http://house.albury.net.au/06feb2012/100_5266.JPG)
It didn't take very long to cut, clean, shape, mark and drill and re-install the part
(http://house.albury.net.au/06feb2012/100_5269.JPG)
I was dead lucky that I didn't lose one (or more) panels in the process. It wouldn't have taken much more wind for the remaining thin piece to give way entirely.
I can't believe I never *noticed* it was the wrong piece ever since it went up. With nobody to get your back, you have to be super vigilant. Check your work. Better yet, get someone else to check it for you.
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Everybody gets lucky once in a while, guess it was your turn.
That is a classic photo of fatigue.
Makes me feel good that Murphy lost out on this one.
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Good save!
I never thought of putting a power meter on each array until now.
Thanks for posting your mistakes as well as your tracker.
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Good save!
I never thought of putting a power meter on each array until now.
(http://house.albury.net.au/23may2010/100_4452.JPG)
I also have a meter to display the actuator current. Lets me see if anything has stuck or is getting sticky. It's the one on the far right here. The centre-off toggle switch is for manual adjustment of the arrays, if I want to.
(http://house.albury.net.au/23may2010/100_4447.JPG)
Thanks for posting your mistakes as well as your tracker.
One never likes admitting to them, but hell, they DO happen. And if someone else can benefit from your mistakes, why not share?!
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Geez, You do some nice panel work and got to say it's a nice "visual" of your system too!
very nice !
Bill
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One never likes admitting to them, but hell, they DO happen. And if someone else can benefit from your mistakes, why not share?!
I agree.
Are those DC breakers above the 'ammeter box'?
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Are those DC breakers above the 'ammeter box'?
Indeed they are. Specifically rated to 500V *DC*, double-pole breakers.
(http://house.albury.net.au/28jun2011/100_4957.JPG)
Found a better picture, showing the covers on everything. (Still haven't cleaned up all the external wiring :()
(http://house.albury.net.au/16may2010/100_4434.JPG)
Each array comes in on its own cable set, then through its own double-pole breaker, then to the metering box.
(http://house.albury.net.au/23may2010/100_4447.JPG)
I may have already posted this pic? The diodes in the "high side" and the meters in the "low side". The reason for the low-side current metering is that it (should) make the datalogger easier when I make it.
(http://house.albury.net.au/30may2010/100_4478.JPG)
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Ross, I see you're an "analog man" like me. I never could get my head wrapped around flashing digital numbers. But when you see the all the needles layin' up against the peg you know in a single glance that you got power ;D
--
Chris
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Ross, I see you're an "analog man" like me. I never could get my head wrapped around flashing digital numbers. But when you see the all the needles layin' up against the peg you know in a single glance that you got power ;D
I'm a "horses for courses" man. I prefer digital for some things, and analog for others.
This particular application had several main drivers. In no particular order:
* I can use the meters as shunts for my datalogger (later)
* They're isolated (high or low side metering just the same)
* They require zero power to run
* They're easily read even while fluctuating
* They're easier to see a trend
They were cheaper than digital meters by the time I included shunts, and it's easier to mount things in round holes than trying to cut perfect rectangular slots!
(http://house.albury.net.au/10may2010/100_4431.JPG)
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Are those DC breakers above the 'ammeter box'?
Indeed they are. Specifically rated to 500V *DC*, double-pole breakers.
(http://house.albury.net.au/28jun2011/100_4957.JPG)
Found a better picture, showing the covers on everything. (Still haven't cleaned up all the external wiring :()
(http://house.albury.net.au/16may2010/100_4434.JPG)
Each array comes in on its own cable set, then through its own double-pole breaker, then to the metering box.
(http://house.albury.net.au/23may2010/100_4447.JPG)
I may have already posted this pic? The diodes in the "high side" and the meters in the "low side". The reason for the low-side current metering is that it (should) make the datalogger easier when I make it.
(http://house.albury.net.au/30may2010/100_4478.JPG)
Hello Ross, what are the part numbers for the diodes you use to isolate each array from the next. I may have had a problem and hope these type " To220 " style diodes will work with 150v and up to 10amps. Thanks.
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The ones I got are 16A 150V, I think they're MBR16150.
I got them from RS Components because they did free shipping, which made them about $1 each, compared to $7 each from the local ripoff merchant. (And even RS are not considered 'cheap'!)
http://tinyurl.com/6ur9fet
Suggest you do a parametric search, you may find something more suitable.
I think, when I was looking for mine, they had 200V (which in hindsight I should have got!)
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Thanks Ross, I think I will go with these. http://australia.rs-online.com/web/p/rectifier/0463987/?searchTerm=mbr20200&relevancy-data=636F3D3226696E3D4931384E4B6E6F776E41734D504E266C753D656E266D6D3D6D61746368616C6C7061727469616C26706D3D5E5C772B2426706F3D313326736E3D592673743D4D414E5F504152545F4E554D424552267573743D6D627232303230302677633D424F544826
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I think that's a reasonable call.
Dual-diodes, common cathode - means you can only really use them on the hot side, but that's fine.
The other option might have been to get 10A/200V and parallel the two diodes.
Not sure I'd be *THAT* happy running 100% dutycycle (DC) at 10A through EACH diode. Make sure you have plenty of heatsink!
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I think that's a reasonable call.
Dual-diodes, common cathode - means you can only really use them on the hot side, but that's fine.
The other option might have been to get 10A/200V and parallel the two diodes.
Not sure I'd be *THAT* happy running 100% dutycycle (DC) at 10A through EACH diode. Make sure you have plenty of heatsink!
I really only need about 8.5 amps, just thought I'd over build a bit. These will be used in the same capacity as you have used yours. 143.1 volts and 8.41 amps each array. Total of 5 arrays. 4 if I have already ruined a couple of panels.
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Oh hell, I get your point now Ross. Regarding the 100% duty cycle.
What about these instead of a schottky? http://www.ebay.com/itm/MURF1620-Dual-200V-16A-Recitifier-Array-/380109892905?pt=LH_DefaultDomain_0&hash=item588050ad29
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Oh hell, I get your point now Ross. Regarding the 100% duty cycle.
Yes, just pointing out that a great many diodes are rated for their half-wave, sinusoidal current - a totally different animal.
What about these instead of a schottky?
Well, first off - the bulk of the reason I used schottky in the first place was the lower V(f). Double the V(f) and you double the power the device has to dissipate. So the diode with the lowest forward drop that'll do the job, is the best option for the job IMHO.
Second - the device you quoted, claims 16A - however the tech specs say:
"Average Rectified Forward Current Per Diode, (Rated VR), TC = 150C" ..... 8A
In your case, the DC current IS the "Average Rectified Forward Current"
You could use either device - but if you want some safety margin, I think I'd be using both halves of a pack PER ARRAY, whichever device you settle on.
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Thank you Ross. I can stand to shed a few volts at times to keep within the classics voc rating but, I will resort to that if I have to. I think I will just double the number of schottky diodes and use two per array at a 10 amp rating. Thanks again for your time.