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SMA SI6048US-10 transformer rating
I opened the back of one of my (ex-DC Solar) 6000 watt inverters, just for grins, and found this:

[Image: bqsnlRb.jpg]

A little research revealed that dtw Magnetics in Poland partnered with SMA in the early 2000's, and was bought out by them in 2011. My inverters were built in 2017, but apparently the new company SMA Magnetics was happy to keep using dtw labels on their products. What caught my eye were two things:

1. The label clearly states "SI 5048 - 60Hz". That was, of course, the previous model, and the "new" 6048 when it came out was advertised as producing an impressive 20% more power. I'm wondering whether that means a) the transformer was way overrated for the 5048, or b) they designed improved cooling to get more power under warranty than before, with the same transformer.

2. This transformer is also labelled 3300VA, which is not particularly reassuring!

OTOH, from what I've seen online, the SMA off-grid inverters are considered extremely robust, and are very heavy for their power ratings. This unit weighs about 140 lbs, and is rated for 5750W continuous at 25C or 4700W continuous at 40C. The 3-second peak allowable at 25C is 11 KW.

I was also surprised, considering the reputation of German engineering, to see the orientation of the diamond pin seen in the following photo:
[Image: 8BP8zBR.jpg]

It may be a little hard to make out in this photo, but the pin on the left, the diamond-shaped pin, has its larger axis horizontal, rather than vertical in this photo.
These are two cast pins, or protrusions, rising from the floor of the casting, that serve to locate the transformer case when installing it (it's really really heavy!). The principal of a diamond pin is for locating a part using two holes. If you had two round pins entering two round holes, any tolerance on the spacing between holes or between pins would prevent the part from fitting. So one typical solution is to make one hole oblong, with its long axis pointing towards the other (round) hole. Another typical solution, often used in machining fixturing, is to have two round holes but one round pin and one diamond pin (McMaster, for example, sells sets of round + diamond pins that press into reamed holes). The diamond should be oriented, of course, so its shorter width points towards the opposite pin. But here, and this looks like it was cast this way, so the error was made in the tooling (the casting pattern!), the longer width is pointing towards the opposite pin. A simple goof!

In spite of all this, I'm sure they are very nice inverters and will serve me well for many many years. Definitely not bashing them! Just found these discoveries interesting!

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