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Identifying components within an inverter
Question
Good afternoon everyone,

In my recent spare time i have been stripping down a solar PV inverter to better understand how it operates and performs. So far i have identified most of the components and what they do, however i have discovered some quite large components that i believe could be a type of choke. They are not mounted on the PCB`s.
Can anyone offer me any advice on what these components do within the inverters and are they a perishable part. They look very robust.
The inverter I have been looking at is a small single phase domestic unit of 3.6kW.

Many thanks
Barry
5 Replies
mapj1
2444 Posts
If you can upload a photo - the forum will let you do this- it is the icon that looks rather like a patients temperature chart next to the grining face on the left, and then on the window that opens, you need the second tab 'upload' - I am very happy to talk you through whatever it is  if I can . - I have been designing electronics since the last century, so can probably advise ;-)

There will be inductors, both for EMC, and as part of the inverter proper.
 
Thanks Mapj,

Photos added - I hope.
These are situated in the very top part of the inverter.

mapj1
2444 Posts
The lower two are "reactors" basically a fancy name for an inductor, on what are probably tape wound cores of some low magentic hysteresis steel. a bit like these.  The tape core gives a lower loss for higher frequencies than traditional laminations, making them more suited to the non-sinusoidal inverter waveforms but are harder to wind than a simple bobbin. Sometimes the tape core is wound, then cut, then a normally wound bobbin is threaded on and the core clamped shut. Magnetically this is not as good as a closed core, but the economy of manufacture may outwiegh the disadvantage.

Without seeing how they were wired in there are  a number of places in an inverter design that such reactors may be used, but commonly for un-gapped cores they will be in series with the AC output, to take the edges off what would otherwise be a very square switching waveform, and make it a bit more sinusoidal before it joins the outbound mains.
The highly simplified circuit here  so simplified it has none of the electronics that creates the switching waveform, may illustrate this.


The upper two appear to be split bobbin construction, and may be transformers or chokesor if in series with the output, then they may be current monitoring as well as chokes. - how many wires go to  each one?




The ferrite ring (well more of a tube to be honest ) at the top is an EMC feature, and as a number of wires share the core, it is presumably acting to raise the common-mode inductance.

Do come back if this is at the wrong level and makes no sense, or if you would like more information - happy to help.
best regards
Mike
 
Good afternoon Mike,

That is really helpful thank you.

The top have 2 wires each coming from them.

Kind regards
Barry
mapj1
2444 Posts
Simple reactors then, despite the split bobbin construction. May be a standard part  that can be used as a current transformer as well, but is not in this version.

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