Hello I am new and need advice

Iya · August 2007

Hello Gentlemen,

I have tried to look for the introduction section but it seems it is not available.

I hope you gusy don't mind if I start here. Thanks in advance.

I am based in Jakarta - Indonesia.

I have a good friend who needs a PV system of approx 2,100 to 2,300 watts for one of his work site. So far he has been getting load calculation and system sizing from a few PV dealers. However, him knowing that I am alot in marine DC charging works, he is asking me to do some real-world checks. I have never fully understood solar technology untill about 3 weeks ago and spend hundreds of hours on the www. It seems it so damn interesting this PV thing and especially the MPPT charger. I love doing this research.

I have been reading Outback Forum for quite a bit since I think by spec, it has the best MPPT charge cotroller at such an attractive price. It is even cheaper than a marine charger rated at 24V 60 amps...amazing....and much smarter too.

Hello Jim/Crewzer,
I been reading a lot of your posts in Outback forum. Thank you for sharing those information.

I am happy today I find this forum because Wind & Sun should be neutral since they carry many brands. I have wanted to ask a few questions in Outback but since one of the questions is about the new Xantrex MPPT charge controller, I rather ask this in neutral forum.

I have a few questions for the expert here. I have tried to search the www for days and could not get a real data. I will ask only questions I fail to source reliably from www. I don't want to waste people time for my own convenience.

I am desperate to know the temperature of the PV panel while in operation. I am very concerned as the project will be located in the equator O* degrees and 114 East. The peak sun hours will be at 4.6 hours as per NASA website but the data is only for 1983 to 1993. I can't get a newer data.

The ambient temperature will be average 30 * celcius all year round.
The location is quite bad because it is not a hill top and there are many tall trees, so a tracker will not be useful. This will be a 100% off grid but I will have a day in a week where I will be able to top up the batteries in case of deficit The charging back up will be 20A x 2 48V volts constant current type charger operated for al least 12 hours a day in desperate situation, powered by a small 3,000 watts diesel generator.

I am planing for a 48 volt system on the battery bank because of the potential voltage loss thru the long wire run.

My questions are :

01. If I have an ambient temp of 30 *Celcsius and located at the equator, how hot can my panel be ? I am so concerned about this because if I based my calculation on 75*C panel temp, I am loosing 4.1 volts on average. That will make a 130 watts panel a 82 watts panel if 16.5V net is what I expect into the MPPT charge controller for possibility of equailizing the batt bank when needed. I am using Kyocera data sheet.

I have read a test graph ( but can't find it now ), in Kobe Japan with ambient temp of 12 *C, in just 50+ minutes the panel temp hits 50*C...WOW...scarry.

I am not worry a bit over cold temp, because it will never get any lower than 25 *C when sunlight is available, even in the rain. This is low altitude work site. Probably less than 200 meters above sea level. I will have to check on this one though.

02. I am leaning towards outback MX60 as it seems the "best" there is today and cheap too. However, I have just read the new Xantrex WX MPPT CC and I am quite impressed, 60 volts DC battery bank capable ( even though quite useless for me since this is off grid and sourcing an inverter at that high voltage input will be so difficult and very expensive ).

I also read in Outback Forum and in the Outback manual that while the MX60 is scanning the MPP, the charging will stop, while the Xantrex doesn't stop. I can't remember how long the MX60 will stop charging while scanning.

Anyone here already use the Xantrex WX ?

03. I have searched very hard for the best panel, in terms of efficiency, weight and size watts per watts and since I am not getting much data from Sunpower, I am now leaning to Sanyo HIT which fortunately Crewzer/Jim mentioned in Outback Forum, has the unique increased amperage at 75*Cel panel temp. Once again thanks Jim, this info is really helpful. I never knew that Sanyo has this kind of PV.

Now I heard Sharp is making something like Sanyo HIT but I can't get any tech sheet yet. Anyone can shed a light here ?

Overall why I am so keen into helping my dear friend on the PV project is because I love the subject. The other reason is because I notice that the suppliers he is dealing with are more of a salesman than an engineer. I don't believe one can selll an effective remote area PV system without learning more of the location of where the PV will be installed and the pro and con of that particular site. Detecting the failure of the suppliers to mention such a loss when PV panel hits 75*C, I am already unhappy with that. I beleive a buyer or a client deserve to know the worst and best scenario for the $$ he will be investing, rather than just hearing the good side of things.

One of my part time job is helping AC & DC system design for simple boats up to 120 feet. I am not an electrical engineer by education but where the vessel in question is not classed, I like getting involved as a second opinion or cross checking what is being offered by other vendors. My job is more to make sure my client gets his money worth and I really enjoy it. I get to play with latest model chargers, inverters and batteries...Yipee !!!!

That's all for today. Thank you very much guys.

Best Regards to All,
Iya

mike95490 · August 2007

Re: Hello I am new and need advice

Yes, heat is your enemy. That lowers voltages, and you have to buy more panels to make up for that loss.

You did not mention what your ultimate load is, a house, a business ?? and what sort of power needs it has) in KWH, and if cloudy weather occurs often? Maybe a moderate sized array, coupled with a diesel backup generator would be the most efficient use of your money, if you can provide fuel and matainance service to the generator. Without twice weekly, full charging of the batteries, they will fail earlier.

Iya · August 2007

Re: Hello I am new and need advice

Hello Mike,

I am still trying to get a user load profile in a very accurate form.
I am trying to use two tables for power consumption.]

Table one is power consumption based on 4.6 hours a day of peak sunlight hours being fed by the PV panel ( via battery & inverter of course ) , while charging of batteries to the required capacity must be maintained.
Some equipments are not operated 24hrs round the clock.

Table two is power consumption based on 18 hours a day of no PV cell power production, or "night" use. Some direct 48 volts DC and some thru inverter.

Recently I modified the calculation because I have decided to use kerosene freezer instead of electric ones. a 350 watts 24 hours freezer will blow a big hole in the PV budget.

Basically my calculation is , total consumption of table 1 + table 2.
The 2 totals are then divided into 4.6 hours and I will add 40% for losses for the charge contoller, inventer, coulometric charging efficiency of the batteries & wiring resitance.

Yes, I have to fine tune again later for cloudy days and so on and I am still stuck at panel temperature. I done search in this forum and one good link lead me to the actual running condition of St Thomas University PV system in Miami where I see the panel temperature is so scarry at 75*C. I am using Miami because it can get hot there like my work site. Good and bad thing is that I never get to worry and unfortunately also no benefit from PV cold temperature voltage charaterisic.

Hoewever reading this forum further on the humidity factor of 95% typical to the work site...

may upset my calculation in the long run.
Then reading further the details of Sanyo HIT warranty problem....geee, I am not worry of claiming the actual warranty, I am worried of failure and the problems it will cause or making a wrong decision of buying them for my kind of ambient temperature.

Looks like I have to spend a few more days searching this forums database & links for better preparation of the load calculation against available charging time and all its associated problems of PV being the power source.

I then have to think of the weather....gee...this is getting more interesting.

I'll get back in a few days with more accurate data so that it won't waste anyone's time who will help me with some calculations.

Thanks very much.

Regards,
Iya

crewzer · August 2007

Re: Hello I am new and need advice

Iya,

Hello to you! I’m very glad to learn that you’ve found my OutBack posts to be useful.

I am desperate to know the temperature of the PV panel while in operation… The ambient temperature will be average 30 * celcius all year round.

PV modules seem to operate at ~25 C to 27 C above ambient when insolation is ~80% (800 mW/m^2) and there’s a light breeze. This is typical in hazy/humid conditions. Check your PV module’s spec sheet for NOCT specs. If you’re location is both hot and dry (low humidity) with a light breeze at sea level, insolation could be ~100% (1,000 mW/m^2) and the PV modules would operate at 30 C to 35 C above ambient. So, at 30 C ambient, you can expect your modules to operate at between 55 C and 65 C at mid-day.

I am leaning towards outback … However, I have just read the new Xantrex WX MPPT CC and I am quite impressed, 60 volts DC battery bank capable…

I also read in Outback Forum and in the Outback manual that while the MX60 is scanning the MPP, the charging will stop, while the Xantrex doesn't stop. I can't remember how long the MX60 will stop charging while scanning.

The MX60 charge controller can also handle a 60 V battery bank. The MX’ charge current output is briefly reduced during mini-sweeps, and it drops to zero A for a few seconds every 1-1/2 hours in Auto Restart Mode 1 or Mode 2. The “lost” energy is real but negligible, in my view. To me, a bigger problem of “lost energy” is the energy left behind when any off-grid charge controller is operating in absorb- or float modes.

I am now leaning to Sanyo HIT which fortunately Crewzer/Jim mentioned in Outback Forum, has the unique increased amperage at 75*Cel panel temp. Once again thanks Jim, this info is really helpful. I never knew that Sanyo has this kind of PV.

The output current of PV modules typically increases a bit with higher cell temperature. Can you remind me of which modules we were discussing?

Regards,
Jim / crewzer

niel · August 2007

Re: Hello I am new and need advice

if you have anything that may be interfered with such as radio equipment, do know that the mx60 is showing some issues. the xw has addressed radio frequency interference or rfi issues. i didn't think the mx60 to be that bad in this area until this thread was started on another forum:
http://www.solar-guppy.com/forum/viewtopic.php?t=568
as to all of the differences between the controllers is one even i am listening up for. solar-guppy can address some of the differences as well as boB for both were instrumental in engineering of both the xw and the mx respectively through 2 differing companies. there will be some similarities between them and even with other controllers such as the appollo and that's to be expected. the differences are a fine line that may or may not matter to some out there, but knowing those differences is important for many in making decisions on what to buy and even for us to give advice on.
we do wish to hear from others out there that get the xw as to the low down on them in their respective systems, be it good or bad.

Iya · August 2007

Re: Hello I am new and need advice

Hello Jim/Crewzer and Neil,

JIm,
You are right, outback can do 60V batt bank. Too much reading at one time have clouded my memory. Thanks for reminding.

I am leaning towards the Sanyo 190 or 195 or 205 watts HIPxxxBA3 panel.
I will check what is coldest temperature the panel can get in the morning.
It is a hard thing to do such detail research in my country because this location is so remote the weather people doesn't really care. I want to maintain 140 volts as maximum incoming voltage for the MPPT. However I am quite certain no way temp will drop below 23*C even in the coldest time of the year.

My plan is to rig the panel 2 in series to get Vpm of 109 volts.
Outback data page 66 shows that at 95 volts input ( why no 110 volts data ??.. ) I can still get average 98% efficiency at 1,500 watts. I am happy to get average 95% efficiency all around and will put in about 10% loss actually.

The target so far, before any more calculation fine tuning is a panel with total of 2,100watts or the maximum power I can push a 60amps MPPT CC all the way to 50 amps based on 48 volts only. I do not have NEC people inspecting the installation, I just want to load the MPPT CC at no higher than approx 85% capacity knowing all electronics are best not to be pushed above that.

Niel,
Yes, the radio frequency interference is a worry on the outback unit. The site will use SSB radio 24 hours a day and VHF 12 hours a day. I may need to re-consider Outback. Thanks for reminding, I have read aout the EMI but been overwhelemed by so much data I need to digest in such a short period of time.

Forum like this is indeed a great help. Thanks to all.

I will write again in a week. Me need to go fishing.....;)

Regards,
Iya

BB. · August 2007

Re: Hello I am new and need advice

By the way, I am kind of wondering how all of these solar charge controllers (and probably the inverters too) can get around selling without FCC compliance... I can see waving hands about getting a real class B certificate (expensive, 10db lower limits, register with FCC). But any electronic device needs class A (self certified) needs class A or runs the risk of getting shut down by the FCC.

Installing these non-compliant devices in repeater locations for emergency services radios seems to be just the think some lawyer would use in a liability lawsuit (...my client would be alive today but for xxxx whose illegal electronic interference prevented my client's spouse from contacting rescue services when their plane went down in the mountains...).

-Bill

Solar Guppy · August 2007

Re: Hello I am new and need advice

I've wondered the same over the years ... My take is basically is this once was a garage built industry that was for offgird/rv/boats where you don't need certification ... look for example at "solar converters" products for example

Apollo, Outback, BlueSky, BZ all are not compliant. I had discussions with some of these folks and they basically shrug their shoulders and say why should we do it if the competition doesn't. FCC Class B be robs a full percentage point in efficeincy, might not sound like allot, but thats 30 watts of heat the controller has to be designed to dissapate.

By the way Class "B" is for residential only, so the manufcatures can say there products are for non residential use ( wink wink )

I know boB is fully awhere of the issues and last back and forth seemed his new units will be compliant, I know it was a MAJOR expense for the WX-MPPT to met Class B and all products that will come from my work will meet ALL regulations.

BB. · August 2007

Re: Hello I am new and need advice

Back in "old'en days"... in the 1980's when I started as a design engineer, we had the FCC making waves by going to trade shows and, if the unit did not have something of "non-compliant demo unit" sign present, the guy would whip out a little RF scanner and write a "ticket" and shut down product shipments.

I have not heard stories like that since... Probably along the lines, if they don't enforce the laws, then folks will take the chance to go around them for personal gain and profit.

Some of the systems back then, we were designing, were pushing the emissions envelope... Our clock frequencies and edges were pushing the harmonics well out beyond 1 GHz--but the regulations did not address those limits back then.

From my point of view--the reasons we were still (a decade ago) spending money and time to really meet the regulations was because a few of our major customers were in Europe--and those customs folks (like Germany) were not beyond opening a shipment and slapping one on an EMI range and testing it... Fortunately, they never bothered to put cables on the systems (which below ~200MHz are where the more difficult signals to kill)--so we never had any issues (that I was aware of).

And for any "new" designs (within the last few decades), basically, anything with frequencies over a few kHz and, literally, used at least the power power than a digital wrist watch, was required to meet the regulations--except for some industrial installations (I don't remember the industrial limitation--probably something like you install and test in place at the factory fence / on complaints)...

-Bill

Solar Guppy · August 2007

Re: Hello I am new and need advice

Thats a good story BB ... I would gather then the real difference is enforcement. Seems the FCC emissions "law" falls into other areas the goverment seems to ingore that there are laws on the books ..

I'm surprised the EU hasn't flagged these products ... maybe for the same reason?

boB · August 2007

Re: Hello I am new and need advice

Guppy Said:
>>FCC Class B be robs a full percentage point in efficeincy, might not sound like allot, but thats 30 watts of heat the controller has to be designed to dissapate.

What ? 30 Watts ??? How come so much ?? Unless the XW had a DC-DC conversion topology downgrade just for EMI reduction... Maybe the filter techniques in there are REALLY lossy at the lower frequencies ??

As far as MX60 EMI goes, you should talk to Dr. Bob at OB, since he is the Ph.D they hired to do FCC compliance modifications on FXs and MXs, among other things.

Marine Channel 16 is sure way up there in frequency. That *should* be a fairly easy one to filter out (SURE ! That's easy for ~ME~ to say ! )

boB

BB. · August 2007

Re: Hello I am new and need advice

It has been many years since I did EMI--But the 30-~200 MHz range is generally from cables. Over ~200 MHz is usually from "gaps" in sheet metal.

For those that have to reduce the 200 MHz and below, adding lossy "Ferrite Beads" and/or about 10' of good shielding grounded back to the source (grounded to the chassis of the source) is usually good enough.

Above 200 MHz, you need to short out the 1/4 wave length frequency of (typically) slot antennas (example, 850 MHz is about 3.5"--ideally, you probably would want that slot cut in half to kill it as a radiator). Using grounding clips or 3M copper metal embossed tape works well (needs to be a clean metallic connection, no paint, glues, or non-conductive adhesive between metal and metal tape).

These solutions are not usually used on production equipment (expensive, awkward to service, looks ugly)--but can be very useful to debug and/or solve a local problem.

-Bill

Windsun · August 2007

Re: Hello I am new and need advice

I am in the process of writing up an article on EMI reduction. Not finished yet - just the bare bones and still a few corrections http://www.windsun.com/General/PV-EMI.htm

Any feedback welcome.

boB · August 2007

Re: Hello I am new and need advice

This is a good start on your EMI page.
Most of the time, it is common mode noise on the 2 wires going from a controller to the PV array or the inverter through the AC output to the loads that radiate RF energy as an antenna -- (the current is IN PHASE on both wires). Try putting the ferrite filter toroid or clamp-on around BOTH wires at the same time (common mode filter ) If there is enough room inside of the ferrite, wrap a couple of turns of those 2 wires through it to increase its inductance (filtering ability). Ultimately, 2 identical capacitors (1 per wire to gnd) on the LOAD side or in the case of the controller, the PV side to ground will complete the lower pass filter, but the ferrite all by itself may help. Ferrite works good in the common mode filter case because it has a high permeability (magnetic conductance) and will not magnetically saturate because it only has to filter the noise which is at a much lower level than the AC load or DC PV current carried differentially.

This all ~may~ help, but it is sorta black magic and can take a lot of tinkering and experimentation to get it good enough. It would be real handy to just have a special pair of glasses that would enable us to just see the dang RF.

The filter should be as close to the electronic noise maker as possible of course.

Remember that FCC class B compliance means that the conducted and radiated EMI will be
below a certain level but it is NOT eliminated and CAN still be problematic in certain cases.

boB

Windsun · August 2007

Re: Hello I am new and need advice

Thanks for the note - I will add more to a section on common mode noise, which is also true for DC lights and a few other things.

BB. · August 2007

Re: Hello I am new and need advice

Looks like a good start--My only two cents (as a start) would be:

One of the major problems with solar and DC power equipment is that almost none of it meets the standards for FCC Section 15, Part B. Nearly all appliances and electronic equipment sold today for consumer use in homes must comply with FCC part B - which regulates the maximum amount of EMI that devices (such as TV's) can radiate. That is why you don't get a lot of noise from your microwave and coffee grinder. But nearly all DC and solar equipment is exempt from Part B. Which means that they can put out a LOT more EMI and still be legal.

Actually, Microwave ovens and other products do put out quite a bit of EMI "noise"... However, there are certain frequency ranges in the regulations where industrial (and home) equipment is allowed to radiate above "normal" limits. Microwave ovens use one of those industrial frequency bands (so do home cordless phones, cheap walkie-talkies, and wifi--that is why some wifi and cordless phones and microwave ovens interfere with each other when attempting to use them at the same time).

Also, it does not matter if equipment is AC or DC, the basic FCC requirement is the "digital" clock frequency... If it is over 9kHz (quote below), then it needs to be tested and conform with FCC Part 15. So, any charge controller that has a "clock" (whether a internal microprocessor for control/LCD display or, probably, even a switch mode DC-DC converter without a microprocessor) with a >9 kHz clock rate--it needs to be FCC Part 15 compliant.

The FCC Rules and Regulations, Title 47, Part 15, Subpart B regulates "unintentional radio-frequency devices". Products regulated include any unintentional radiator (device or system) that generates and uses timing pulses at a rate in excess of 9000 pulses (cycles) per second and uses digital techniques. This includes almost every product that employs a microprocessor including workstations, personal computers, point-of-sale terminals, printers, modems, and many electronic games. It is illegal to sell or advertise for sale any products regulated under Part 15, Subpart B until their radiated and conducted emissions have been measured and found to be in compliance.

Most products regulated by Part 15, Subpart B fall into one of two categories. Class A devices are those that are marketed for use in a commercial, industrial or business environment. Class B devices are those that are marketed for use in the home. Class B limits are more stringent than Class A limits and the Class B certification process is administratively more rigorous than the Class A verification process. The radiated and conducted EMI test procedures are defined in the ANSI Standard C63.4. FCC Rules and Regulations, Part 15, only regulates radio frequency emissions. Currently there are no FCC regulations pertaining to product immunity to electromagnetic fields.

Here is a nice HAM site that discusses FCC part 15 and some of its issues.

In the end for Wind-Sun, unless you are going to make a big deal about FCC Class B compliant equipment at this time--I probably would recommend not discussing the issue on your web site at all the the current time as you (and others) sell lots of, possibly (IMHO), non-conforming equipment at this time.

Later, as new equipment becomes available, it you might highlight that it is quieter than some of the older models out there.

To help people to eliminate interference with their present installations, a section on how to identify noise frequency and sources, and the steps used to isolate and cancel specific frequency ranges (and sources) would be helpful. Ferrite Clamps will not fix a channel 56 TV station interference, or an AM radio station issue--but will work well with FM radio--etc...

If you have specific fixes/issues that you have addressed over the years for Solar/Wind/RE power systems--that would be helpful, and probably would help limit the sometimes overly broad/theoretical discussions that can happen here.

-Bill

Solar Guppy · August 2007

Re: Hello I am new and need advice

boB wrote: »

Guppy Said:
>>FCC Class B be robs a full percentage point in efficeincy, might not sound like allot, but thats 30 watts of heat the controller has to be designed to dissapate.

What ? 30 Watts ??? How come so much ?? Unless the XW had a DC-DC conversion topology downgrade just for EMI reduction... Maybe the filter techniques in there are REALLY lossy at the lower frequencies ??

As far as MX60 EMI goes, you should talk to Dr. Bob at OB, since he is the Ph.D they hired to do FCC compliance modifications on FXs and MXs, among other things.

boB

Well, I had no idea you had a Phd boB :roll:. and if the Phd is fixing the MX/FX that can't help with the classic roll out

The common modes were the real killer. even a few milli-ohms, you talking 4 leads ( hot/return on input-output ) and when running at full current and close Vin/Vout your running the rated current thru all the legs to reduce common mode .. nice little heaters

The SC-60 used the lowest loss common modes available, flat wire torrids that were about 1.5mohm for about 10 watts at 60 amps, but this didn't have enough inductance ... Also SC-60 is single phase unlike the MX60 dual phase so thats harder on the common mode reduction.

The shipping unit has a single torrid with all the wires looping thru it ... haven't measured the losses but they have to be higher just looking at the wire lenghts.

It is a competitive disadvantage if EVERYONE else ships without the power robbing filters and the new product on the block is taking the hit efficiency wise to impelment a compliant unit .. glad to see OB is bellying upto the bar .. my hope is others will follow.

nigtomdaw · August 2007

Re: Hello I am new and need advice

Now that Pandoras box has been opened and the deep affection X and OB have for each other, how long will it take with X having a compliant but yet 2 ship unit! Before a formal complaint reaches the FCC or does that open the really smaller black box inside Pandora,

Love the slapshot keep it up !:p

halfcrazy · August 2007

Re: Hello I am new and need advice

i believe you guys are talking about two different bobs one is boB the other is Bob not related boB no longer works at outback but i believe Bob does confused yet?

niel · August 2007

Re: Hello I am new and need advice

windsun,
i agree that what you've got is a good overview of the problem. solutions can be troublesome and very involved as we all know and i think this time we should leave it up to the ees that designed the stuff to come up with the fixes that you can post.

Windsun · August 2007

Re: Hello I am new and need advice

BB. wrote: »

Looks like a good start--My only two cents (as a start) would be:

Also, it does not matter if equipment is AC or DC, the basic FCC requirement is the "digital" clock frequency... If it is over 9kHz (quote below), then it needs to be tested and conform with FCC Part 15. So, any charge controller that has a "clock" (whether a internal microprocessor for control/LCD display or, probably, even a switch mode DC-DC converter without a microprocessor) with a >9 kHz clock rate--it needs to be FCC Part 15 compliant.

I read that, and it struck me as kind of an odd criteria. The biggest single offender we see is charge controllers, and nearly all of that comes from the PWM, not anything to do with the clock rate.

In the end for Wind-Sun, unless you are going to make a big deal about FCC Class B compliant equipment at this time--I probably would recommend not discussing the issue on your web site at all the the current time as you (and others) sell lots of, possibly (IMHO), non-conforming equipment at this time.

And I mention that - in fact I state that almost NONE of the current crop meets part B. In fact for some things, it is almost impossible to find anything that does.

To help people to eliminate interference with their present installations, a section on how to identify noise frequency and sources, and the steps used to isolate and cancel specific frequency ranges (and sources) would be helpful. Ferrite Clamps will not fix a channel 56 TV station interference, or an AM radio station issue--but will work well with FM radio--etc...

Actually that depends on the source. Ferrites - or anything else - will not do much to fix noise coming from a TV antenna. But the Ferrites that we list so far are type 31 and 43, which cover 1 to 300 mHz, which is where 95% of the problems we get calls on are in. We can get others that go up to 1 gHz, but at this time I see few, if any, complaints about it from solar/dc powered equipment.

If you have specific fixes/issues that you have addressed over the years for Solar/Wind/RE power systems--that would be helpful, and probably would help limit the sometimes overly broad/theoretical discussions that can happen here.

-Bill

Funny you should mention Wind.. Just a couple of hours ago had a call on getting noise from a wind generator on a CB radio.

The problem with any article like that is that if it starts getting TOO long, you lose people, so I might need to condense something a bit.

boB · August 2007

Re: Hello I am new and need advice

halfcrazy wrote: »

i believe you guys are talking about two different bobs one is boB the other is Bob not related boB no longer works at outback but i believe Bob does confused yet?

I spell my name backwards to AVOID confusion ! Sometimes it doesn't work...

30 Watts STILL seems like an awful lot of loss for EMI reduction. There's gotta be another way, somehow.

And channel 56 is in the hundreds of MHz range... Higher than FM broadcast, which is what I assume BB meant. That should be even easier to filter out than FM frequencies ?

AM radio frequencies is pretty tough to beat, but can be helped. It's all those sharp edges. NAWS, you might want to mention the sharp edges as being the big HF/VHF noise maker. If it were sine waves, then it would only be one frequency of noise radiated, like the microwave oven case at around 2.5 gHz.

boB (Not Bob)

Solar Guppy · August 2007

Re: Hello I am new and need advice

Ah, missed the "two" Bob vs boB's as I thought boB was being funny with the Phd thing, now it makes more sense, well the post anyways.

On the 30watts, thats the worst case corner Vin = Vout , Max current so both common modes ... at 60 amps ... It CAN be less, multiphase, higher switching frequencys make a BIG difference to reduce the common mode losses .. stuff I'm into now is totally different than MX/WX switchers

Vic · August 2007

Re: Hello I am new and need advice

My 2 cents ..

For my off-grid Ham Radio installation, have tried to keep all above-ground wiring in pipe, usually EMT with the rain-tite type compression connectors. Metal flex may be better than nothing, but have only about 15 inches of flex between the EMT runs from the PV on the roof to the combiner box. And all runs to/from the MX-60, and all AC, control, instrumentation, BTS etc are in pipe.
. Use a large stack of ferrite donut cores (not clamp type), and #6 wire pairs for the common mode chokes at MX in and out. Need to move them into a separate metal box right at the MX terminals, now they are insied the DC Conduit box.

Have used a common point ground at the exit of the power conduit into the trench which contains the underground PVC pipe buried abt 30-inches below ground. Prefer a trench ground wire vs a ground rod in our rocky "soil". The power room is a steel shipping container which is grounded to the common point.

The AC in/out from the inverters also have large common-mode chokes. May need to use ultra-isolation transformer on the AC out (from the inverters), right at the exit of the AC wires from the power room. For now, the inverter emsissions are very low level, but noticeable on 75/80 Meters.

Could do more, but at this moment, this has contained the RFI to very manageable levels.

Have a second location close by, but too far away to share the current power system. For this new install, plan to revert to 71 VDC Vmpp output for PV wiring instead of the present system's 106 VDC. This will allow dropping back to PWN (TS-60), or even linear MOSFET charge controller if the RFI output is excessive durnig certain times of weak signal work. Have not done much testing of one approach vs the other. Knew that the LARGE switcher represented by the MX-60 could be a problem, so tried to design in those things that seemed rational.

Also realize that if the noise is too much of a problem at a certain time, the PV-IN breaker could be opened and the MX noise will be reduced by 99.99999999 % or so. The MX noise peaks are surprisingly clean -- stable clean carriers with widly varing amplitude. Most problematic on 80 and 75 Meter bands. But that part of the spectrum is seldom used here during the day -- usually used after the MX goes to sleep. With each additional octive of frequency increase, emissions are significantly reduced.

The inverter noise is much broader-banded, and unstable. They drift through the bands slowly, perhaps driven mostly by battery voltage changes.

And stating the obvious, the greater the separation between the PV/power system and the antenna(s) the lower the received emission. Lower frequencies, where the system emissions are higher, and antennas have longer elements, separation is often more difficult. For directional radio systems, it is good practice to try locate the antenna system such that the primary direction of interest is looking away from the primary noise-generating parts of the power system.

The power system as currently configured presents no real problems regarding RFI, but we always seem to look to improve things. Vic K6IC

Windsun · August 2007

Re: Hello I am new and need advice

Most of the calls we get on noise are from RV/Marine people, and from people running remote cell phone or radio repeater type sites.

The biggest problem with the cell phone sites seems to be common mode noise getting into everything. A lot of those places are on top of rocky hilltops, which makes it very hard to get a good ground. And a lot of them are pretty old, with only the equipment being upgraded and none of the wiring or other components.

BB. · August 2007

Re: Hello I am new and need advice

Yes, as boB said--I was indicating that different frequencies are frequently radiated by different types of sources... Cables tend to radiate lower frequencies, slot antennas (gaps in sheetmetal) tend to radiate higher frequencies.

Placing a choke/bead on an antenna input for a TV will rarely help anything and my just succeed in reducing overall signal input (and making reception worse). There are various notch filters used to filter out specific frequencies (HAM and CB) that you can use if your TV is near a HAM/CB transmitter--but those would not usually apply to general EMI noise problems.

Last night, I did not initially find the actual FCC regulations... And I was trying to figure out how the FCC would regulate a device with fundamental frequencies of less than 9 kHz (sharp edge rates and poorly designed LC circuits--like switching FETs in power supplies--even at low frequencies like a simple PWM controller) that can still create problems that the FCC would/should regulate... Here is a set of links to the various FCC regs themselves.

What I found in reading the regs--was an exception big enough to possibly drive a solar charge controller through:

Section 15.103 Exempted Devices:

The following devices are subject only to the general conditions of operation in Secs. 15.5 and 15.29 and are exempt from the specific technical standards and other requirements contained in this part. The operator of the exempted device shall be required to stop operating the device upon a finding by the Commission or its representative that the device is causing harmful interference. Operation shall not resume until the condition causing the harmful interference has been corrected. Although not mandatory, it is strongly recommended that the manufacturer of an exempted device endeavor to have the device meet the specific technical standards in this part.

(a) A digital device utilized exclusively in any transportation
vehicle including motor vehicles and aircraft.
(b) ...(n/a)...
(c) ...(n/a)...
(d) A digital device utilized exclusively in an appliance, e.g.,
microwaveoven, dishwasher, clothes dryer, air conditioner (central or
window), etc.
(e) ...(n/a)...
(f) Digital devices that have a power consumption not exceeding 6
nW.
(g) Joystick controllers or similar devices, such as a mouse, used
with digital devices but which contain only non-digital circuitry or a
simple circuit to convert the signal to the format required (e.g., an
integrated circuit for analog to digital conversion) are viewed as
passive add-on devices, not themselves directly subject to the technical
standards or the equipment authorization requirements.
(h) Digital devices in which both the highest frequency generated
and the highest frequency used are less than 1.705 MHz and which do not
operate from the AC power lines or contain provisions for operation
while connected to the AC power lines. Digital devices that include, or
make provision for the use of, battery eliminators, AC adaptors or
battery chargers which permit operation while charging or that connect
to the AC power lines indirectly, obtaining their power through another
device which is connected to the AC power lines, do not fall under this
exemption.
(i) Responsible parties should note that equipment containing more
than one device is not exempt from the technical standards in this part
unless all of the devices in the equipment meet the criteria for
exemption. If only one of the included devices qualifies for exemption,
the remainder of the equipment must comply with any applicable
regulations. If a device performs more than one function and all of
those functions do not meet the criteria for exemption, the device does
not qualify for inclusion under the exemptions.

I can see several methods for completely avoiding FCC regulations for
Solar Controllers--if I read the above correctly.

-Bill

BB. · August 2007

Re: Hello I am new and need advice

I forgot to add that FM was (IIRC) intended originally to improve radio reception quality since it was much better at rejecting typical noise sources (in the days of analog only equipment).

And, I can say it works--drive around in San Francisco (especially decades ago--I seem to remember the old buses generating more clicks and wines) in the areas that have electric "trackless trolley" buses that pickup power from overhead lines. FM was virtually static free whereas AM was full of interesting sounds.

The newer electric bus equipment seems to be much quieter now-a-days.

But, of course, it is hard to do an A/B comparison here since the commercial AM band is so much lower in frequency vs the commercial FM band--it ends up with very different physics in wave propagation and EMI control (basically, I never have had to worry about AM band noise radiated through the air--we only tested for conducted current in power cords).

And the US TV band covers a very wide range of frequencies (from 55 MHz to about 800 MHz). So problem sources and solutions vary--depending on source and frequency of interferences...

-Bill

Hello I am new and need advice

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