AC Transformer failure Trace SW4024

stmar · July 2018

I have had two AC transformers fail over the last 15 years in my Trace/Xantrex SW4024 and I would like some opinions or theories as to why this happened. I realize things don't last forever but want to see if anything we do is contributing to the issue. First time grid was down for 3 days, we used power for heat and refrigeration sparingly. When the grid came up everything looked fine, inverter went to bulk to charge batteries. Then after a few minutes the fans came on and a fire erupted from the transformer, luckily I was there and shut it down quickly. Second time, just last week, grid was down for for several hours but the wife did not realize it and did her normal morning routine, hair dryer and curling iron, so used quite a bit of power. When we found the grid down we cut power usage and battery bank came back up to about 25 volts. After about a 12 hour outage the grid came back up, inverter went into bulk charge as normal then after a few minutes the fans came on and the coil smoked. I got to it before it burst into flames and shut everything down. Anybody have any ideas as to why this would happen? We have had grid outages in the several hours range many times and everything came back up normally. Could the excessive use of power been a factor? Hair dryer, curling iron, etc. this time and heat and refrigeration for days in the first scenario.

mcgivor · July 2018

Hair dryer, curling iron are resistive loads, no power factor involved, anything with an indication motor or microwave is a different story, imbalance could be the cause on a split phase, hard to determine over cyber space, but the more I think of it, split phase results in more problems than it solves. Others may differ.

mike95490 · July 2018

My guess is a software glitch having to do with power restoration. Internal limits are supposed to prevent that, but sometimes a "race condition" causes issues. The SW line is mature enough, I'd expect these issues to be solved, unless your 2nd unit was a 15 year old spare with old software in it.

My guess is the transformers were fine till some software glitch cooked them. Mr Dave Angelini ought to be able to chime in with his view

Estragon · July 2018

I have a heat gun that seems to use some sort of rapid pulsing to adjust temp. At some mid-range heat levels, the thing makes lights go all disco on me. My inverters seem to be okay with it so far...

I wonder if in your case when the power came back on it might not have been quite kosher for a spell. For example if lots of folks "upsteam" between you and the grid were running loads after the outage, and you're also drawing a lot for battery charging, the AC may have been browning out some. Browning out can be hard on loads and may have contributed to the failures?

Dave Angelini · July 2018

mike95490 said:

My guess is a software glitch having to do with power restoration. Internal limits are supposed to prevent that, but sometimes a "race condition" causes issues. The SW line is mature enough, I'd expect these issues to be solved, unless your 2nd unit was a 15 year old spare with old software in it.
My guess is the transformers were fine till some software glitch cooked them. Mr Dave Angelini ought to be able to chime in with his view

At Mr. status, I am honored! Could be software but I doubt it. Most of many people using the old SW's this very day are not connected in any way to the grid. The grid is the source of surges and also grid owners doing dumb things under battery charging/loads. No SPD's

Offgrid it is the use of gensets and again dumb things under load. Arc welding etc. In either case SPD's not being used.

An offgrid home with no genset and minimal lightning, has a power system and appliances that seem to last forever, in my opinion.

stmar · July 2018

I would go along with grid quality in both cases, long widespread outages. When we do have an outage I minimize power consumption while the inverter is charging in bulk mode. That is not to say that the freezer and refrigerator don't run during that time. With the new SW I have a Xfer switch for grid and inverter so I will have more control if we do have an extended outage, I can wait a reasonable amount of time for the grid to stabilize then let the batteries charge with no load or I can even let the batteries charge from solar array with no load on the inverter.

I am afraid to ask but what does SPD stand for?

Estragon · July 2018

In context, SPD = Surge Protection Device.

westbranch · July 2018

like these, there are DC and AC versions and different voltage limits too

http://www.midnitesolar.com/productPhoto.php?product_ID=283&productCatName=Surge Protection Devices&productCat_ID=23&sortOrder=1&act=pc

stmar · July 2018

I have two older Sq D SDSA1175 surge suppressors. Is there any way to test these to see if they are good? These do not have an indicator light. If not I will buy a new one.

Went ahead and ordered a new surge suppressor just to make sure. Is there any place/application where I can use the old SDSA1175's? Do you have to use a breaker with them? If so I really don't know any place in my system where they would work.

BB. · July 2018

Here is the Schneider website for these devices:

https://www.schneider-electric.us/en/product/SDSA1175/load-center-1ph-secondary-surge-arrestor/?range=61965-type-sdsa1175&node=209917816-sds

They say there should be a green LED on them. LED=On is protected. LED=Off is no protection.

Looking around, they are fused MOV devices (metal oxide varistor), and they should be installed close to the output/branch circuit side of the fuse (surge=>MOV clamps voltage=>causes high current through breaker=>trips breaker == As I understand the function). So, yes, you need a breaker (Rated for the branch circuit wiring).

No breaker (such as AC Mains from transformer), and more than likely the excess current will simply blow the fuses (and possibly the MOV themselves) and not effectively protect downstream equipment.

If the output (AC power supplying device) has limited output current (smaller genset, smaller AC inverter), then you would not need to add any additional breakers/fuses to the system (In my humble opinion).

-Bill

stmar · July 2018

"They say there should be a green LED on them. LED=On is protected. LED=Off is no protection."

Not on these, they are probably 20 years old, before LEDs. No indicators of any kind that I could find, I was wondering if there was a way to test with a meter? To be safe I went ahead and ordered a new unit.

BB. · July 2018

You could test (possibly) with a capacitance meter.... If there were blown fuses or other MOV problems, the capacitance would probably read lower (do a resistance check too--Look for higher than normal leakage current).

If a MOV is damaged--They can be blown apart (normal operation during a surge event):

Image: https://us.v-cdn.net/6024911/uploads/attachments/512/2840.jpg

Here is a thread where MOVs and lightning suppression was discussed:

http://forum.solar-electric.com/discussion/12968/metal-oxide-varistors-mounted-in-pv-junction-box

-Bill

westbranch · July 2018

you might want to watch the SPD comparison video and read the second link on LIGHTNING..

http://www.midnitesolar.com/video/videoPlay.php?video_ID=9&videoCat_ID=8

How Lightning works

&productCat_ID=23&sortOrder=1&act=http://www.midnitesolar.com/pages/frontPage/robinsCorner/howLightningWorks/howLightningWorks.php

AC Transformer failure Trace SW4024

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