Need Recommendation for "Quiet" Inverter

jmb

It is time for me to look into getting a bit larger inverter for our off-grid cabin.

Current configuration:

2.9 KW Panels
2 IOTA 12V 45A chargers in series
MidNite Solar Classic 200SL
800 AH LiFePO4 battery bank
Samlex PST-1500-24 PSW inverter

Everything works well but I need a bit more juice for the air conditioner so I am thinking somewhere in the 2.5 - 3 KW size. My issue with the current inverter, besides being a bit under powered, is the amount of RFI generated on the HF bands.  I run a HF HAM radio rig at the cabin and the noise generated by the Samlex inverter is about +20 on the meter so i have to turn it off whenever i want to operate.  The radio is running off 12V so it's not ingesting any "dirty" power.

I am hoping for a recommendation, based on experience, of an inverter that will meet my needs.

73,

Justin B.
KI5GKD

mike95490

Is your inverter a "heavy" inverter with a big power transformer ?   Those generally run at lower frequencies than transformer-less inverters - which are known for "rich harmonics".
I have nothing but praise for the Schneider XW series, and I know it does not interfere with AM band DX'ing, in my case.

jmb

Really not sure about the Samlex but it is most likely a high frequency switcher of some sort.  I will look t the Schneider.  I operate mostly on 40 Meters and a bit on 20.  

jmb

Just looked at them and really need something a bit smaller. and don't need 240V.

Vic

Hi Justin,

Name-brand inverter/chargers are generally RFI quieter than are MPPT CCs,   because,  if nothing else,   they tend to try to meet  FCC Part 15 Line-Conducted emissions regs.   MPPT CCs,  generally do not need to comply with Line conducted emissions regs,  because they do not "connect" to the Line (which means the AC power Line/s).   And are usually not tested,  and are considered to not need to limit emissions below 30.0 MHz.

An LC AC line filter might be worth a try  --  these are usually Differential Mode filters.

If you have any of the Mix 31 ferrites left,  you might try running the AC cables right at the output of the inverter,  to see if this helps any.

As you know,   generally,  trying to isolate your antennas from the power equipment,  PV array,  and power cables can be a large help.

If your antenna is coax-fed,   try a common mode choke on the coax,  near the radio's antenna jack.

The venerable Xantrex SW+ 5548s (low frequency) inverter/chargers in use here are very quiet.   We run common mode chokes on their AC outputs,  even though the differential filters would be more effective,   there seems to be absolutely NO RFI on the HF bands from then,   so that is moot.

Sounds like you have tamed the RFI from the Classic   ...    73,  Good Luck,    Vic

Photowhit

It might be worth asking over at the Midnite forum as well, several 'hams' there as well. 

jmb

Thanks, Vic, this is about to drive me nuts.  You remember from the MidNite forum (Vic there too?) what I've tried...  Right now I wound my coax through a mix 31 toroid 12 turns right before the radio with no change.  The Classic puts out a helluva squeal efery 25 KHz or so but I can work around that.  The inverter blankets the entire band with "hash" and I have to turn it off to operate.  Does not make wife happy as that kills AC, her freezer, lights in her "she shack," among other perils to my health...

So, since I need to upgrade inverter anyway should I look at low freq inverters?  From what I can tell the RFI from the inverter is radiated as I am running the radio off DC.  I will lengthen the romex between the inverter and breaker panel and wind it through a mix 31 toroid a few turns and see what happens.

mike95490

And try putting a low impedance RF cap at ALL the inverter leads - even rounding the edges of the hash, will reduce the harmonics

softdown

You might find the needed data here: https://www.solar-electric.com/lib/wind-sun/FXR_A_specsheet.pdf

Looks like they have 10% off this week. Makes sense that a higher end inverter would be "quieter". 

What state are you in? I may have an interest in a back up inverter since my Cotek 1500 inverter is powering three freezers. I think Cotek preceded the Samlex name.  Could have swore I bought a case of those inverters but there are none to be found. 

Vic

Hi Justin,

Yep  we have conversed on the MN Forum.   And some additional remedies were mentioned there.

LF inverters are essentially dinosaurs.    Every part of them is much more expensive to build,   than are Hi Frequency inverters.   There is a lot of steel,   and more copper in them than HF units.  This makes them fairly large,   and heavy.   Much  more freight  and material cost incoming to the manufacturing facility,   and larger heavy boxes going into Distribution and to the ultimate customer.   All of this adds a lot to the cost.

The LF inverters here are large,   and heavy (about 130 Lps for each,   and two are required for 240 VAC).   They are solid performers,   but   you should be able to tame your existing HF inverter,  with chokes on the input,  and perhaps a choke on the output (for now,  as an experiment)   An old-fashioned  Pi-type LC filter in a metal can,  would probably be the best,  for filtering the 120 VAC output of the inverter.

One other thing that was mentioned elsewhere,   is that running DC and AC cables in metal conduit (usually EMT is fine).   This can be a large help,  but can be a bit difficult to retrofit.

More later.   WIsh I had more experience with modern-day HF  inverters,  vs RFI.   This is a good Forum for your question,   as it is well-attended by folks with broad experience (IMO).   73   GL.      VIc

petertearai

Outback inverters ,,,, have a transformer in them , are they high frequency ? 

Vic

petertearai said:

Outback inverters ,,,, have a transformer in them , are they high frequency ? 

Hi peter..,

Searched with the term: "   difference between HF and LF power inverters  "

This is the first hit.

https://www.magnum-dimensions.com/knowledge/high-vs-low-frequency-inverters/inversion-methods-explained-high-frequency-vs-low

There are many fine-points in just how each manufacturer chooses to implement the design of each of these general types of inverters.   Am no expert at that.   FWIW,    Vic

jjdh

> Just looked at them and really need something a bit smaller. and don't need 240V.

You probably saw, but Schneider has a smaller line below the XWs as well. Eg. Conext SW 2524. Still almost twice as large as your Samlex: 2500W output; but in case that's helpful.

softdown

Ham radio board perhaps? I know spark plugs used to be available with and without suppression - for radio purposes. Based on that, getting suppression of electrical noise was simple. 

jmb

I think my next step will be to run the cable between inverter and breaker panel in metallic flex conduit.

Dave Angelini

Forgive me if it has been posted. Have you looked at the physical distance between your inverter and you ham station?
Even the Schneider inverters with FCC spec listings need to be a minimum of 5 feet from your transceivers. Use of a pocket AM radio is useful for this.

softdown

Dave Angelini said:

Forgive me if it has been posted. Have you looked at the physical distance between your inverter and you ham station?
Even the Schneider inverters with FCC spec listings need to be a minimum of 5 feet from your transceivers. Use of a pocket AM radio is useful for this.

With Schneifer's gigantic global presence I would imagine they spend  the most on R&D - thus staying staying a step ahead? Perhaps charging for two steps? 

Outback is still a fine name I think. Their core line has not changed much from appearances. They seem to have focused on introducing much larger and more sophisticated equipment. Which their "best/most experienced techs" likely assemble. 

Have any thoughts on changing the inverter output to 125 volts? I feel like maybe it consumes a scosh more power now. Considering trying 118V to see if their is a measurable difference in power consumed. 

The FlexPower really does seem like it consumes ample power to me. I have been pulling out all  the stops in energy conservation and can not see more than 50.4 volts at 6am. Even with the 24V forklift battery system powering the freezers. Even de-commissioned the Samsung Energy Star at 565 kWh.

The savings are hardly worth it for most people - my quest is for my own reasons. 

jmb

Dave - Radio is currently about 10' from inverter.  As I mentioned, next time I head to town I will get some metallic conduit and I will eventually move the inverter into the enclosure I built to house the batteries, bus bars, and other stuffs.  I have thought about lining this enclosure with heavy-duty aluminum foil as well...

I had a back and forth with Samlex Support a couple of years ago and they were not much help and pointed out the FCC Type Acceptance testing does not cover lower frequencies.

BB.

I would suggest that you use metallic conduit, and not the flex/spiral type (I don't think that it makes that good of connection between "coils").

In general, for 30 MHz and above signals (typically to ~ 180 MHz, as I recall--But it is has been decades since I have done RF control on computers), about 10 feet of shield for cabling usually does a good enough job to capacitively shunt the higher frequency signals to ground (metal conduit/shield)... Beyond 10 feet did not really matter.

AC is nice because you can use common mode chokes (as well as differential mode chokes/filtering). The common mode chokes will not saturate.

With DC power lines, you cannot use common mode chokes (one wire through a ferrite bead, for example). The DC current will saturate the ferrite core and kill its usefulness as a common mode choke.

-Bill

Vic

BB. said:

I would suggest that you use metallic conduit, and not the flex/spiral type (I don't think that it makes that good of connection between "coils").

In general, for 30 MHz and above signals (typically to ~ 180 MHz, as I recall--But it is has been decades since I have done RF control on computers), about 10 feet of shield for cabling usually does a good enough job to capacitively shunt the higher frequency signals to ground (metal conduit/shield)... Beyond 10 feet did not really matter.

AC is nice because you can use common mode chokes (as well as differential mode chokes/filtering). The common mode chokes will not saturate.

With DC power lines, you cannot use common mode chokes (one wire through a ferrite bead, for example). The DC current will saturate the ferrite core and kill its usefulness as a common mode choke.

-Bill

Hi Bill,

Completely  agree about EMT (or  IMC/Rigid, for that  matter)  is far   superior to  FMC  (Metal  Flex), as,   the contact between  all of  those  spiral windings is uncertain.  Al Flex is probably the  worse,    in that  regard.

But,    for DC Common Mode  chokes,  seems.  of  the positive AND  negative cables (to an inverter,  CC,  etc)  are wound through a  toroidal core (Bifilar),  that  the currents  flowing  in opposite directions  cancel,   so the  only current  remaining current is   the  noise current,   with  little chance  of core saturation.  Is that not   the case?

Thanks,     Vic

jmb

OK, will use galvanized solid conduit...  This is making me almost want to take down my new multi-band inverted Vee antenna and put the little dinky MFJ 2240 back up!  I still had some RFI but not as much...

BB.

If you can wind/pass both + and - DC power cables through a single core--Yes that is correct, it will not saturate.

If you have a "typical" car type DC AM radio or such... There is a + power lead and the chassis of the radio is the negative power connection. Not really easy to pass + and - power through a single choke/core.

-Bill

jmb

Just about have all of my conduit stuffs rounded up and hope to do this in the next day or so.  I am also looking at bigger inverters and the Outback VFX3524A-01 looks nice.  Although we are strictly off-grid and wouldn't need a hybrid inverter the specs and price on this look good.  Does anybody have experience with this and would RFI be manageable?

softdown

I'm the guy who linked their spec data awhile ago. Don't know about RFI. Keep me in mind should you decide to sell the Samlex. 

Thought I had a case of Cotek 1500 watt inverters. I remember opening the box and selling one in fact. Does anybody know to refine the search function for "case of cotek inverters"? Geez - I get robbed so often I lose count. Like almost every month - somewhere. 

BB.

Softdown,

I am not sure what you are looking for, but you can use the "site:" tag to limit searches (google, duckduckgo, Bing, etc.) to one website:

site:https://forum.solar-electric.com case for cotek inverters

-Bill

jmb

Soft - I will likely keep the Samlex as an emergency spare.  Looking around on Amazon I see that Cotek is still available and I'm thinking about one of their 3KW models...

softdown

jmb said:

Soft - I will likely keep the Samlex as an emergency spare.  Looking around on Amazon I see that Cotek is still available and I'm thinking about one of their 3KW models...

I wonder if the Cotek's are simply older models that have been sitting on shelves. I believe that Cotek and Samlex merger. My Cotek 1500 has a dumb design flaw. There is little room for large wire connective lugs - I had to grind them down severely to fit. Using 2/0 wire as I recall - almost surely larger than I needed. 

jmb

Making progress!  I have finished moving my inverter down into the battery cabinet and have ran the AC wires up to the breaker box in EMT conduit.  I also wrapped both hot and neutral 3 turns through a mix 43 oval core right after the wires exited the conduit in the breaker box.  I didn't have time to do an exhaustive test but it seems the inverter generated RFI has been significantly reduced!  My noise floor dropped to an S9 but I didn't have time to determine if that was natural noise or RFI.  Of course, that did nothing for the CC noise but that is another story...

Vic

Hi Justin,

The Outback inverters  --  Fx and VFXes  -- have been reported as having fairly significant high frequency ripple riding on the AC output waveform.

OB introduced the FXR series several years ago.  Do not know how well suppressed, are their HF emissions.

It would be a good idea to ask on the OB Forum,  and perhaps on the MN Forum.    Ask Hams with interests in HF communications,   for their actual experience with the OB inverters,   or,  really for real hands-on experience with any inverter that you are seriously considering.

I have no personal experience with OB inverters.

But please ask Hams that have been running your target inverter,   as opposed to those,  like me,  who have NO experience trying to listen through possible emissions.  Ask,  also what measures were taken to reduce any emissions,   and how effective this was in reducing them.

Sounds like you are on the right track with your choke.   Mix 31,  should generally do a better job reducing emissions in the 1.8 - 15 Mhz (or so) range.

73,  GL,   Vic   .   .

softdown

Would ya'll speak English? 

BB.

Vic is speaking "Hammish".

MX31 is a type of Ferrite... Different magnetic properties (need to match to the frequencies you are interested in blocking):

https://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-selection

-Bill