Issue with Morningstar SureSine 300 inverter

Options
LBergman
LBergman Solar Expert Posts: 42
Hi everyone. It's been a while since I last posted here, but today find myself with an issue which I'm hoping doesn't mean I have a defective inverter.

My current system is two Siemens 75 watt panels and two Siemens 55 watt panels (all 12v and in parallel), a Xantrex C35 charge controller, trimetric 2020 monitor, and three 105AHr 12v agm batteries also in parallel.

Up until last month, I was using a Xantrex 1000w 12v pure sinewave inverter. Although it consumed a lot with self-consumption, the system ran flawlessly with it for four years. Last month I decided to replace it with a Morningstar SureSine 300 inverter (115v) to gain some efficiency. I wired it according to the instructions, and for the last month it worked great. Until today. I flipped on the remote switch, and instantly there was a loud humming from the inverter. My trimetric meter showed 50+ amps being drawn (even with no load connected), and my 100 amp DC breaker tripped about 15 seconds later. My expected load on the inverter should have been around 7-8 amps @12v.

I rechecked the wiring in case something had worked loose, but all connections appeared fine (no shorts). I even disconnected the load wiring just in case, but nothing changed.

Anything that I might be overlooking, or does it seem pretty obvious the inverter has gone south way too early? :cry:
«1

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Sounds like it's time for Warranty Repair (I hope).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • LBergman
    LBergman Solar Expert Posts: 42
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Thanks Bill! That pretty much backs up what I was thinking. Guess I'll be dealing with Morningstar's tech support tomorrow and will find out how nice they are. :D
  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    it sounds like a fault and is definitely blown if so. you will probably need to contact morningstar for instructions to return it. put your other inverter on in the mean time.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Very sorry to hear of your inverter failure. I've had two of them running for over 4 years now and find them to be wonderful high quality inverters. Hopefully you can get your's repaired on warranty. Best of luck.
  • LBergman
    LBergman Solar Expert Posts: 42
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Thanks Guys! Yeah, considering all the positive things I've heard about this inverter, this is a bit surprising. I would switch back over to the old inverter, but I had to cut off the connectors at the ends of the battery cables because the Morningstar inverter needs bare copper, whereas the Xantrex uses flat metal connectors. I'd rather not have to buy new cables for just a short-term (hopefully) problem. On the positive side, I'm sure my batteries won't mind a few weeks at float.
  • LBergman
    LBergman Solar Expert Posts: 42
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Just wanted to update this. I sent Morningstar tech support an email explaining what happened to the inverter. The next day I got a response that they would send a replacement to me, along with return postage for the defective one so they could figure out what went wrong. The replacement arrived today, and is currently working nicely powering my laptop as I'm typing this. I have to give their customer service five out of five stars! :-)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,476 admin
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    If you are in the middle of no-where and/or prep'ing for emergencies... Then you should probably have a backup inverter and cable set anyway.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Nice to hear that Morningstar jumps up to the bar! Mine has been running for woot 4 years now!

    I do keep a cheap MSW inverter at the ready in the event of a failure.

    Tony
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Great news! :D:D
  • LBergman
    LBergman Solar Expert Posts: 42
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Thanks, guys!

    Yeah, having a spare pair of cables probably would be a good idea. Since I'm in suburbia, it's not a critical system, but more for me to learn with and for emergencies. If it came to a real emergency, I could probably rig something up to use the old inverter, but having the "correct" cables on hand would make it easier. (OTOH, since my power is pretty reliable, if there was some event that caused a power outage for more than a day or two, there would probably be bigger things to worry about than electricity... :D )
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    I myself also experienced a Suresine 300 failure . Strange like Mr L Bergman posted.

    I was putting my purchase from 1.5 years ago to trial . Very small solar for just learning , backup , wanted to keep learning .
    Sunsaver controller built by Morningstar 15 amp MPPT controller has been flawless , Have the external battery & the Mobus serial connection etc.

    I followed the installation instructions , and since the Noise & smell,, check it thrice !! ++ just to make sure.
    I was using the Kill-a-watt to see if / what the load draw and what I could output power within reason . LED lighting is nothing , less than 10 watt load , but for playing & learning , one or two LED bulbs won't get the inverter to kick in and stay on, it just flashes the bulb when in sensing mode. If I add an incandescent 40 watt , It's on and stays . I noticed it has a buzz , but that means it's working , right ?? so if this buzz at 40 watt , I want to see if It can get my deep freeze working . Using my Kill-a-watt I measure the shut down small freezer , 180W start , 93-103 running after 3 mins on shore / grid power.

    On the suresine 300 , I get a click and two red lights , then after say 5 seconds a retry start , and the same .. SO I figure Im either way to much starting load or poor 12 volt feed . 4 gauge feeding DC12 volt & i hook up my DVM Fluke in record mode (since the buzz & retry and kick out happens so fast) I get from rest 13.97 to 12.8 on the retry at the suresine lugs. So it not getting cut from under voltage , But maybe the frezzer is overdrawing on startup.
    I then left the deep freeze for a small grain mill , measured with kill-a-watt, start up no load(Grain) 180W , runs 93W , Same bug , A pair of red LEDs on the unit. Open 12v breaker and remove load , incandescent 40 watt with the suresine 300 and the kill-a-watt shows 114.9 V, 59.9 hz, 38w , (amp I can't remember) , SO NOW WHAT ? check my wiring with the manual , neutral leg paired with grounding lug & fuses all seem fine, more than enough 12v power & cables all new and clean .less than 2 days in getting ready to use after sitting for 1.5 year. I had a 3 speed box fan, that has to be a light load , Kill-a-watt on grid power shows 42,58,94 watt , on the sure300 , buzz and it's spinning , second Buzz and it's speeding up , lets see 3rd speed, BUZZ but it moves to its fastest speed , almost like it was on the grid.
    In 10 seconds it BUZZESS and the fan speed is dropping, kill-a-watt is strobeing , Oh Cap , open breaker & pull AC plug ..
    Then It hits , that nose & the thought , Quick get a plastic bag & catch the smoke.


    Reading so many folks here rave about the Morningstar SureSine 300 inverter, plus the post of L Bergman leads me to think I also have a warranty issue.
    My MSW 1000 using the ac & dc lines seems to work well & quietly.

    I'll update my experience with Morningstar Warranty Department also , Looking at Post #7 looks good.
    I'm just going to start buying & building my second alternative power system . Morningstar SureSine 300 inverter is the only one they sell & is it heavy compared to my 1000w MSW cheepy ..
    I did check the internal 3 40 amp fuses , all's fine there but the bag of smoke , I have no idea :D where it needs to go back into ;)..


    VT
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    @ CDN_VT
    Re you're SureSine-300 problems.
    First the good news. To expect it to start a fridge, or freezer that has not had major modifications and the addition of a start capacitor to it's starting circuit, is wrong. Fridges and freezers are notoriously hard to start and even most 600 watt inverters are pushed to their limits, and even then, many can't start them. Not sure where you got the 180 watt freezer start rating, but the start surge is usually several times that, and is too brief for the Kill-A-Watt to properly record. The reaction of your inverter to having the load of a freezer applied, is perfectly normal. It will try 3 times to start the freezer, then shut down for good and sit there with it's two red lights on, until you manually do a restart. That's the normal operation of it's self protection circuits.
    The "small grain mill" is an open question. We don't know what it has for a motor. It could very easily, like the freezer, be demanding far more power to start than you might think.
    Now the possible bad news:
    The BUZZ. It MAY just be a loose lamination in the output transformer. From where I sit, I can only guess at the sound, how loud it is and the exact sound. Usually if there's a fault, or overload, it just shuts down, as it does when presented with the freezer.
    The slowing fan however is a different story. Unless the fan motor has a defect, has tightening bearings, or there are loose connections somewhere, that COULD indeed indicate a warranty issue.
    The fact that you're Kill-A-Watt shows 38 watts when running a 40 watt light bulb however, leads me to believe the inverter is probably OK.
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Thanks Wayne for the reply!

    "The fact that you're Kill-A-Watt shows 38 watts when running a 40 watt light bulb however, leads me to believe the inverter is probably OK."

    That was a measurement before when the SureSine-300 had a fight out with the slowing box fan. Plug the box fan back into the grid power 15a/120v with the kill-a-watt , all the readings are as before plus the fan works again up to speed. SureSine-300 let the smoke out on the fan. As with 180 watt freezer start rating, it probably is too brief for the Kill-A-Watt to properly report the start, On grid power that what is what i caught then it settled down to 108w or close running.

    Like I said I was just in testing to see what the SS-300 could do , I was and still reviewing many ss-300 posts on here , I do like your post on the 1 fridge & 2 freezers on a single SS-300. I got the gist of the circuitry & Caps , but did you use the same compressors / motors and just add caps to the starting circuit ? second question please Sir, your fridge has a output to a relay to cut power to the second & then I assume the second has the same to cut power to the third outside , did i get that correct ?
    Would be nice to see a diagram..

    All Im trying to do right now is the next power outage (longer than 1 day & four + per winter) is have quite power plus. Now my PV's are for keeping the 12 volt system up for the odd led lighting 26w in the 40' x 50' wood shed , that is used when you must be in there because you forgot during the daylight ,have a source to charge Li-lion battery's for flashlight to radios and it's real purpose is to run the dry sump / bilge pump if & when the grid go's down , I don't need to hear the screaming of one of four gen sets here. This bilge pump system with it's spare secondary for backup has been working for 2 years without a power problem (dirt & DuH yes) . Best part is no floods if power is out and were some-where's warm & sunny ;) ..

    My next PV system that will be separate from the 12v bilge / led light, will be for 2 freezers & one fridge . I'd love to have a creek/stream , but I'm on the bump in a rain forest , so this is to maintain them for the up 2 a week power failure. Moving 100% off grid with Mig/Tig/10 HP compressor ,hoists , 50 tonn hyd press plus many other toys in the MAN CAVE is not cost wise for the rude power requirements of that CAVE. ;)

    I truly think the SS-300 had a bug , it's protection systems worked as Wayne posted.

    Waynes fridge & freezer wiring schematic's would help many here , No Pat-tenet on them ?

    VT
  • Dill
    Dill Solar Expert Posts: 170 ✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    definitely seems like a warranty issue to me. I just bought this same inverter for my cabin, and it doesn't make a sound when hooked up with the recommended 6 gauge cable.
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Well that's good to hear or NOT to hear.

    Mine always made the clicking of the searching relays , & the flash of the led bulb (4w type) but as soon as i put any small (incandescent 40 watt bulb) load it had a slight buzz.

    Good luck on your's Dill, I would put a few tests on it just to make sure.Mine also had AWG-6 on the (+-)Power's 8 gauge for the common bonding /ground

    Im really hoping that they(Morningstar) have not succumbed to the trend of built-in-obsoletion/timeusage or part time parts.Having a few defective parts in a batch run is normal sometimes.

    Seeing the new trend of computer controlled cars that have 1000 $ PLUS electronic circuit board gizmo-doohickey made for your household environment but now in the Vehicle of -40 to +160 in the hot sun with windows up.. Winter I hear two type of failures , summer in HI,FL,CA all the toasty zones eat the other heat-Xed part.
    Replacement is the same unit for another 4+ years ,,Very Sad in this "Green" age !!

    I tried too use my Kill-a-watt on the SS-300 to see how it preformed.
    I'll find out Monday Morning when I call Morningstar.

    VT
  • Dill
    Dill Solar Expert Posts: 170 ✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    mine's been running a few weeks in my cabin now, and it works fine even with a single LED (40W replacement) I've run my box fan, computers, chargers etc off of it without a hitch. I would get a replacement and enjoy it, theres bound to be a lemon with anything like that.
  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    For what its worth, I have been using the SureSine 300 for a little over a year. It's on 24/7 powering small loads. After reading this post i decided to put a "heavy" load on my SureSine. With a couple of wall warts pluged in my Kill-a-watt showed a few VA. With a small 4-cup coffee maker plugged in... about 460 VA. I had to get my ear about 3-5 inches from the SureSine to hear a slight hum. Normally i can not hear it al all. The a/c voltage was a little over 104 volts. I don't know what effect temperature may have, but the ambient air temp where the inverter is located is 96F. I have never tried uploading pictures to a post so fogive if they show up wrong.
    Attachment not found.Attachment not found.Attachment not found.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    CDN_VT wrote: »
    I do like your post on the 1 fridge & 2 freezers on a single SS-300. I got the gist of the circuitry & Caps , but did you use the same compressors / motors and just add caps to the starting circuit ? second question please Sir, your fridge has a output to a relay to cut power to the second & then I assume the second has the same to cut power to the third outside , did i get that correct ?
    Would be nice to see a diagram..
    Waynes fridge & freezer wiring schematic's would help many here , No Pat-tenet on them ?
    VT

    Hey VT, unfortunately I have no schematic, did it out of my head and no two are exactly the same. 3 different compressors, 3 different value start caps. The original varistor "starter" is removed from all three compressors and replaced with a timer circuit operated relay that opens the start circuit when the motor gets up to speed. Each timer had to be tweaked to match the requirements of it's compressor, as too short, and the compressor doesn't have time to get up to speed, while too long and the extended time of overload on the inverter triggers it's safety shut down. Likewise, each compressor required a start capacitor of particular value to max out the efficiency of starting. Even with all this, the starting was not reliable, if at all. The surge was just too much, right on the borderline of causing the inverter to shut down. The "cure" was an autotransformer that is only in circuit during the start phase of the compressors. It drops the voltage going to the compressor during start, by roughly 12 to 15 volts, and in doing so, increases the available current, thus allowing reliable starts. In fact, two of them will restart this way on the SureSine 300, even when the compressor was just running and is still under full backpressure. Again, if the voltage is dropped too far, the compressor won't start, while if not enough, the current draw on the inverter is too great and it will shut down. Takes some trial and error for each different compressor. And of course, as soon as the start sequence is completed, a relay takes the autoxformer out of the circuit and connects the now running compressor directly to the inverter output. So you see, it's NOT a simple thing, but it can be done. It also is a huge help if you have a friend running an electric motor repair shop, who will lend you a number of start capacitors to try, to see which value MFD works best. On grid, almost anything from 50 MFD to 150 MFD will do the job on any of the three compressors, but with the limited power from the Morningstar inverter, you've got to narrow it down to the one that really does work best. This is not something to try unless you really do understand what's going on. Any warranty on the freezer will be voided, and if things don't go right, magic smoke will happen. And yes, the first two units have relays that cut the power to the unit(s) downstream. So yes, there are a bunch of relays involved. It would be a whole lot simpler to use a bigger inverter, one that can start the compressors without all the extra circuitry. It would also be a lot more reliable without all those relays, timers etc. Sometimes I just do things because I can. Reminds me of a certain joke about male dogs :blush:
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Thanks Mr Wayne !
    & I think I know that joke ;)

    Once I get a working SS-300 , I'll do some more testing.
    6cf freezer is going to be the test subject. I'll use my pico scope to see whats watt.

    So Do I read your post correct ? 3 compressors on a SS-300 and the ss-300 is set in sensing mode ?
    KEWL.

    VT
  • 65DegN
    65DegN Solar Expert Posts: 109 ✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    LBergman, when a freezer is unplugged while the compressor is running it will leave the system pressurized. Consequently when it is plugged back in within a few minutes the compressor will be trying to start with the system already pressurized and this will draw a lot of current.
    Synchronous motors run very effeciently when allowed to run at their normal speed which is locked to the frequency of the grid or inverter, slow them down and they draw a tremendous amount of current.
    It's best to wait about 20 minutes or so for the system to depressurize.
  • 65DegN
    65DegN Solar Expert Posts: 109 ✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    ...The "cure" was an autotransformer that is only in circuit during the start phase of the compressors. It drops the voltage going to the compressor during start, by roughly 12 to 15 volts, and in doing so, increases the available current...:

    The only way I could see the autoformer providing more current than the inverter can on it's own is if there is a significant impeadance mismatch between the inverter output and the load. For that to be the case it seems that the load would have to be outside the inverters design parameters.
    However I suspect what may be happening is the field around the autoformer windings collapses and provides a surge to the compressor. With a higher power autoformer the voltage would likely not need to be dropped to start it. The larger diameter, lower resistance wire would allow more current to pass at a higher voltage.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    65DegN wrote: »
    The only way I could see the autoformer providing more current than the inverter can on it's own is if there is a significant impeadance mismatch between the inverter output and the load.

    When one uses a transformer to drop voltage but maintain the same VA, the available amperage goes up. In my case, during the start cycle, the transformer drops the voltage by roughly 10%, turning it into roughly 10% more current. The compressor doesn't really need full voltage to get up and running when it has capacitor start, but it does need more current than the 300 watt inverter can directly supply. And yes, it is best to let the compressor back pressure bleed off before attempting a restart, but the fact that with this system, running off the little SureSine inverter WILL instantly restart under full back pressure, indicates how powerful a properly designed starter circuit for conventional fridges and freezers can be. What I'm trying to get across, is that I proved there is no excuse for manufacturers to have such a weak starter system on fridges and freezers. There is no excuse for the all too common buzzing, humming, clicking, and of course the spinning of you're power meter that goes with it, that takes place whenever such a compressor has it's power interrupted while in operation. If I can do it, the manufacturers for sure can do it! Just imagine, you could go to the local Sears store and purchase, off the shelf, a fridge or freezer that would, without any modifications, start and run directly off a little SureSine 300 watt inverter. In production it might cost the manufacturer an extra couple of dollars, but think of the surcharge off-gridders would be willing to pay for such a feature! There is talk of inverter compressors for these appliances, that may do this, but I have yet to see one. Still, I proved there is no need to go that route for small inverter operation.
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    rgk1 wrote: »
    I have never tried uploading pictures to a post so forgive if they show up wrong.

    Well done rkg1 & thanks for you reply !

    VT

    Edit Add: here is a small yid-bit on the inner workings of some motors link.

    Just for the ones who are following & wonder.
  • CDN_VT
    CDN_VT Solar Expert Posts: 492 ✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Made that Phone call to MorningStar !!!
    Reading Mr L Bergmam post on this thread , I wasn't expecting a similar result. Some companys can really make you grovel for warranty anything.

    What a Delightful conversation with a replacement unit on route to me with a return label & in the frozen nut area of Canukland. I did ask the gent at MorningStar why only offer one small 300 Watt inverter in there product line ? , while the gent reminded me that they mostly controllers for the OFF GRID & such , then the news came out about a new larger wattage inverter coming out next year with also grid tie controllers for the higher voltage panels .. Controllers for GT & backup .

    Now if they handle there warranty issues like this with ease, I will always purchase their brand again.
    The SS-MPPT-15L has been flawless , plus after 1.5 years , just a look at the flashing didoes and the time of day / sunshine so far , you can tell the basic condition. I also use the PC Meterbus once a week just to have an in depth look.

    New higher wattage Inverter plus some grid-tie controllers come in 2013 from MorningStar !!!


    VT
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Awesome News on all counts CDN_VT !!!!!!!!!!
    Thanks for sharing! :D
  • LBergman
    LBergman Solar Expert Posts: 42
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    65DegN wrote: »
    LBergman, when a freezer is unplugged while the compressor is running it will leave the system pressurized. Consequently when it is plugged back in within a few minutes the compressor will be trying to start with the system already pressurized and this will draw a lot of current.
    Synchronous motors run very effeciently when allowed to run at their normal speed which is locked to the frequency of the grid or inverter, slow them down and they draw a tremendous amount of current.
    It's best to wait about 20 minutes or so for the system to depressurize.

    Wow, just popped back in - didn't realize this thread was revived.

    All I can say is my replacement SS inverter has been working flawlessly for the last month or so, and I never had any compressors powered by it. ;) As far as I know, the SureSine should be completely silent; when mine started making any noise is when it had gone bad.

    I hope your replacement will work flawlessly too, CDT_VT!
  • 65DegN
    65DegN Solar Expert Posts: 109 ✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    When one uses a transformer to drop voltage but maintain the same VA, the available amperage goes up. In my case, during the start cycle, the transformer drops the voltage by roughly 10%, turning it into roughly 10% more current.
    An autoformer being a single layer coil does have limitations as compared to a two winding transformer. I agree that there is current transformation going on but I'm having a hard time wraping my head around the circuit delivering more current without correcting for an impeadance mismatch. Unless maybe there is one?
    Anyhow, you have come up with a creative solution and yes I agree the startup caps are also a great idea. I could probably use one on my freezer to make it easier to start while running on my Honda 2000i.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter

    Even adding the start cap in series with the starter varistor, with no other modifications, makes a HUGE difference in start surge and greatly shortens the time the motor takes to get up to full speed. Assuming of course you've found the best value MFD for that particular compressor.
    Re the single layer winding on the autoxformer, think of it as two separate windings wired in series, because that's essentially what it is. Just that the series connection is internal rather than external, and has a single lead coming out from it.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    Re the single layer winding on the autoxformer, think of it as two separate windings wired in series, because that's essentially what it is. Just that the series connection is internal rather than external, and has a single lead coming out from it.

    Now for mind bending, think about the variable autotransformer (Variac). That is in effect a center tapped single winding with a moveable center tap. The design of the winding and brush-type center connector is rather elegant.
    SMA SB 3000, old BP panels.
  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    Options
    Re: Issue with Morningstar SureSine 300 inverter
    inetdog wrote: »
    Now for mind bending, think about the variable autotransformer (Variac). That is in effect a center tapped single winding with a moveable center tap. The design of the winding and brush-type center connector is rather elegant.

    Haha Good one "inetdog" :)