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Messages - BruceM

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1
Everything else / Re: Easy PV water heating
« on: May 22, 2022, 08:14:47 PM »
With those 4 panels in series, you could have as much as 1000W with perfect conditions cool and clear, ideal alignment, at roughly 122V.  Alas at around that voltage, about 300W.   (You can calculate the resistiance of the element and then it's wattage at some other voltage using Ohms law, which I did for your case.)  So yes, you can do it, you just won't get as much bang for your buck without switching to a better suited element at 120V. There are solid state relays for up to 250VDC which are well suited, since your open circuit PV voltage would be only 37.8x4= 151.2V.  Midnite Solar makes DC rated circuit breakers you could use for manual disconnect.

The practical way to drive the element at it's rated power is to use a 220VAC inverter; there are some all in one, off grid inverters that will operate without batteries.  In that case the panels will have to be configured to a voltage that suits the inverter. 

I would rather go the straight DC route myself, and just get a 120VAC rated element, which should be cheap enough.  It's a perfect match for your 4 panels, and should be quite efficient at a range of sun inputs with no other electronics than the 200V DC SSR  (solid state relay) connected through a thermostat to 3-12VDC.   An adjustable snap disk type thermostat that can be glued or attached to the water tank, that has contacts rated for low voltage DC is best for long term reliability.
 
https://www.amazon.com/SSR-25DD-3-32VDC-Output-5-240VDC-Plastic/dp/B08GNSPCND/ref=sr_1_4?crid=3B2GYWD419TQS&keywords=dc+solid+state+relay&qid=1653246620&sprefix=dc+solid+state+relay%2Caps%2C256&sr=8-4

Don't be shy if you need more info.
Bruce


2
Listeroid Engines / Re: My fix for Listeroid light flicker
« on: May 15, 2022, 03:52:45 PM »
Yes, it's cheaper to buy your own cells, cheaper yet if you get seconds or derated used cells.
https://www.youtube.com/watch?v=E4pN4DVPOcY

The price I gave is an estimate  for a good priced, prebuilt 100AH 12V battery. 

Will Prouse keeps reviewing cells, BMS units, prebuilt batteries, rack mount setups.
https://www.youtube.com/c/WillProwse

While a young enthusiast, and thus optimistic on new technology reliability and longevity, his reviews and material are technically competent.
 



3
Listeroid Engines / Re: My fix for Listeroid light flicker
« on: May 15, 2022, 01:27:38 AM »
Yes, and you may be able to use the 100AH, since you can use them to near full capacity.
The situation is likely to improve by the time your existing one's are done.

4
Yep, designed and build my own hyperbaric chamber and tried that 20 years ago. It  gave me a nasty MS flare up that lasted a few months.  About 10% with MS react very badly to hyperbaric oxygen, according to some UK research. Most find it helpful to some degree.

It was made from a 90 psi horizontal water pressure tank with an extra end cap. It had 8  1 inch by 4 inch light openings on top,  with 1/2 polycarbonate "windows" fitted inside, and dual outside or inside controls for operation.  I could sit and turn around in it.   It had an oval door which sealed via gasket with even the slightest pressure.  It was made from an extra stamped end piece I bought with the tank from an in-state manufacturer.

I sold the chamber to an MD in Texas who wanted to try it for her husband.  She was pretty thrilled to get a chamber tested to 4 atmospheres for (then) under $3.




5
Listeroid Engines / Re: My fix for Listeroid light flicker
« on: May 14, 2022, 04:13:47 PM »

Regarding you specific question, Veggie, as long as the alternator is set to charge at a normal wet lead battery voltage, you should be able to use LFP batteries without any change.  The BMS will disconnect charging once the cells are full, and will disconnect the load when the cells get too low.  A BMS failure has resulted in battery destruction. 

DIYsolarforum is a good place to watch for the best deals/reviews on lithium batteries.  I think the waiting game is a winner. There have been plenty of issues with premature failures of lithium cells, and both price and performance keep improving each year.  About $500 for a 12V. 100AH battery, twice that for 24V, 100AH.


6
Thanks for the kind thoughts.
Alas, I have memory and cognitive impairment from MS and epilepsy, so technical writing is just plain misery.  Can't remember the previous paragraph so can't hold onto context, etc.  Same issue (worse) with software.  Makes technical projects very hard and stressful.

So I'm doing a whole lot less, plus seeing quacks and doctors,  trying new treatments without any success, which is hard on morale and the wallet.


7
You're most welcome, Veggie. 
Putting a 0.1 uF capacitor parallel to diodes is what's called a "snubber".  It reduces the bust of high frequency EMI that occurs when diodes start and stop conduction.  Sometimes a resistor and the value are specifically tuned to the circuit, but for many low frequency applications like this one, just 0.1uF works quite well. 

In the case of the stock (no AVR) ST-3, these 4 capacitors (about $1.20) will reduce the high frequency EMI as much or more than a $70 dual common mode choke filter unit.  A demonstration of the cost effectiveness of correcting an EMI problem at it's source (or even better by design) vs a downstream filter.

The fast switching of an AVR can also add high frequency EMI to the AC.  A snubber capacitor across the excitation in/out switch may help with this, but it is best solved by design.  In my own AVR, I intentionally slowed down the switching speed to limit the emissions. This works using either Mosfets or Darlington Bipolar power transistors, but requires the use of a bigger transistor that can handle the slower transistion, and often, an upgrade in heat sinking as well.  In practice, you can often get huge reduction in emissions with very little or no loss of efficiency. 

Most devices will tolerate this EMI on top of the AC without difficulty, but some may have problems.

8
If you're changing the bridge rectifier pre-emptively (a wise suggestion, 38ac), then consider cleaning up your the high frequency EMI by adding 4 capacitors to the bridge. The use of the piggyback spade connectors works well, or you can solder them to the base of each connector.  One on each side. 

This is the type of capacitor you want, with the part number on Digikey:

CMPPAC310V104K10S5

It's a thin film 310VAC rated capacitor, 0.1 uF.  About $0.30 US.  Similar spec parts should be available around the world.

I can't get the page to load or I'd give you link.  Digikey seems to be overloaded this afternoon.

This is highly effective in reducing radio frequency noise from the ST line output.  Check it with an AM radio (old regenerative tuner type with static sound between stations) before and after and you'll agree.




9
That may be OK, it looks like a modern one.  A picture from the other side would help.
I'd order a new one to have on hand, in case it's crap.  When your output voltage suddenly goes way low, that's the usual culpret (with Chinesium bridge diode).

Here's an example of what you want:
https://www.ebay.com/itm/224811975854?epid=25016784898&_trkparms=ispr%3D1&hash=item3457d684ae:g:LP0AAOSw07hh9D9b&amdata=enc%3AAQAGAAAA4DnkmsOqUD5Je7CXIp1vp20AWgEgoojiNCXA37jPM8BMpvjM1U4Yfupo7yaDHQ%2FWrT%2Fcg4npkrGOlp5z50wf8GCQFT68xqa89gdinHLtlG0vPIZUGluNz0ey9Ioc0pK3Egc8qiRPkpJjqCOqHKNYkftz9cvug0K4JLVudSv8c1EZzaWdRRSb8BoT9diH5euXC1Ihu0SFZuxvdHAKjrf9cCk4jDaSsDU2C8qjhiastbesKQfUKpD7COBS946hkpx6XRc%2FpBP24L9PhzmcE15wZsOrD8Tkccxa%2BJxCaq%2FUaYPc%7Ctkp%3ABFBMssOY95Vg

A bridge rectifier is just four diodes potted in a metal or plastic box.  Two AC inputs, usually opposite corners, and two DC outputs, usually marked + (plus)  and - (minus).  It turns AC (from the harmonic winding on the stator, which is very spikey and non-sine, and turns it into pulsed (spikey) DC for the rotor.  The rotor windings have a huge inductance, so they smooth the input current to create a more constant magnetic field at the 4 rotor poles. 

For this application, the metal body is better for heat sinking to some aluminum. A die cast aluminum case to replace the doghouse comes to mind. Use some thermal paste or a dab of silicone caulk It should be as thin as it can be, to just increase the surface contact area.






10
Yes, you won't know what you've got until you check it out and also take a look at the waveform, and see if you have issues with your various intended loads. (Check your AC voltage using a true RMS voltage mulitmeter at a range of loads.)  Many ST's are being sold that are wildly high voltage, and thus will likely require an AVR or a large dropping resistor in the harmonic to bridge rectifier circuit.   If you intend on using it for non-electronically regulated lighting, you will have less Listerflicker by using an AVR using the AC ouput as excitation instead of the harmonic , and this will also help with "harmonic hump" distortions if present. 

Some LED lights are electronically regulated with a small AC to DC switch mode power supply. They will get rid of the Listerflicker unless it's extremely bad.  The stock harmonic regulation amplifies Listerflicker, and during compression stroke, the harmonic output will drop so low that the AVR won't help, since it only limits the excitation and can't amplify it.


11
Ha, thanks Butch, my experience with the ST's is just one of practical necessity.   It was an educational "opportunity". 

MikeNash, good point on the need for removing the doghouse, I forgot to mention that abomination.  Adequate heat sinking of a modern, metal cased bridge rectifier is also essential. 

It really is a shame that the ST's aren't made in a more reliable and consistent manner with decent QC.  The best ones have acceptable waveform and voltage regulation by the stock harmonic system, though I expect THD is still about 15%.
For a smooth sine, you really need skewed rotor windings, it seems.








12
My neighbor has one on his ST-3.  His is using the harmonic for excitation, regulated by the AVR, as the stock unit voltage so high that there is no choice but to use it, which is common with some of the CGG units.  He gets about 2-3 years per unit, with heavy use.   

FYI- these do NOT regulate to RMS voltage so won't work well with a nasty PF load like a cheap high current , switch mode batttery charger.  Output voltage will be too low for a very bad PF load.

One of the issues regarding longevity is that even in the ST-3 with a normal harmonic, the voltage peak is over 400V, while RMS voltage is much lower. 

The standard harmonic system of the ST3 sorta regulates output voltage by sensing load current via the harmonic winding, so for a big load spike, like starting a motor, it really works well.  I have a dual mode setup, my own design AVR for normal running, but I can switch to harmonic only for running a small switch mode type MIG welder.  I have an adjustable resistor to limit harmonic current to get the desired voltage. 

For cleaning up the output waveform several methods have been reported depending on what the problem is.  The cheapest digital o-scope or usb scope will let you see what needs to be done.  The common methods are- adding motor run capacitors on the line output (for some ratcheting and spike distortions),  running an AVR on the line voltage instead of the harmonic (if you have "harmonic hump" distortion.  Some found adding capacitance after the bridge diodes helped with harmonic hump distortion.  If the ratcheting and spikes are really bad, I'd add two 200-400 uH chokes plus capacttance on the line output.  A surplus line reactor plus motor run capacitor will also help but is pretty spendy. Putting massive amounts of capacitance (> 60uF) of motor run capacitors starts to affect your peak motor starting capability and starts to show a little in fuel consumption. 

For the high frequency EMI on the AC line,  I found that adding 0.1 uF snubber capacitors parallel to each diode in the bridge (4 total) made a world  of difference.  With these small caps (240VAC rated) the EMI went from detectable across much of the AM band from 8 feet away from AC wiring to 8 inches in just a few spots.  A standard dual common mode choke filter will also be helpful but I found the snubbers got it good enough for me and only cost me a few bucks.

That's my pitch on ST heads-  I envy the guys with Stamford clones who just belt them and forget about it!  The variation  in different ST heads is huge, in terms of waveform quality.  At one point I had 3 different ST-3 rotors and stators on my bench- and none were physicially identical to the others.  I"ve seen lots of waveform screen shots from ST-5's also, and they also vary dramatically.  The best thing I can say about ST heads is they are cheap, and simple. If you get copper windings and put in good bearings, and a modern bridge rectifier, they are reliable in creating a high THD waveform for thousands of hours.  My custom low EMI inverter with a 5 step sine has lower measured THD (measured THD of 12%) than my ST-3 (measured THD of 15%), even when running on mains excitation instead of harmonic.  Either runs everything I need just fine, but the timer motor on my washer makes some noise on the generator.




13
Engines / Re: Oil filtration
« on: April 16, 2022, 10:39:16 PM »
I thought that even toilet paper roll filters couldn't remove suspended carbon in diesel engine oil, certainly not to clear oil levels.

That's why Mike is asking...  me too.

14
General Discussion / Re: Welding from a Listeroid/ST generator rig
« on: April 14, 2022, 04:02:23 PM »
olNick,
Bravo on that repair. 
I expect a 90's design with IGBT's would not be power factor correcting, so it would need a much higher rating on the generator head to cope.

Inverter-welders have always been at the cutting edge of power designs.  I can't imagine a more difficult power design application; high current arcing and shorts are normal. 

 



15
General Discussion / Re: Welding from a Listeroid/ST generator rig
« on: April 13, 2022, 03:48:40 PM »
Oldnick, I think your assessment of the failure is interesting and quite possibly spot on.  Adding  large electrolytic capacitors on the 12V might be the simple solution.  But it is a very poor inverter-welder design that doesn't protect it's critical IGBT or Mosfet gate control from voltage sag.  Even if it did work admirably with a stronger AC supply.  All power electronics designers are not created equal; it's like any other professional, a brilliant minority and the rest barely getting by. 

I'm in the latter group.  I popped a couple MOSFETs in my own home-hobby inverter design last week when I accidentally applied a hard short to the 120V (transformer stepped down) while testing a current/voltage/power smart sensor for a water chiller project. The 230V AC breaker didn't pop in time, and the DC fast blow fuse for that H-bridge blew but not quite fast enough, apparently.  This is the first failure ever of my inverter.  I never tested it for an overload/ short on the 120V side, only 230V.  Luckily it's all my own design so the repair was $8. in parts and a lost day.

I'm adding a fuse on the 120V side to protect me from future senior moments.  If it was a commercial design,  I'd add a microcontroller and circuitry watching the real time current to shut down the waveform generator in real time, safely as soon as a peak load exceeded the safe limit for peak current and/or time at peak.  Fuses are too crude. 




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