As I said, different use case because cost of failure greatly outweighs the cost of the entire product if it shuts something down.Most just buy a new supply some send the whole thing back, a small % open a warranty claim although we've got live pros answering the phone empowered to take car of them.
When you say oversize - what do you oversize?
The power over the products baseline consumption?
The MTBF of the entire unit at 100% power?
Oversize by how much ?
Does it make sense to sell a 100K hour power supply with a product carrying a 5 year (50K hour) warranty?
Curious how you do it.
For basic instrumentation and controls - which I think would be closest to what your asking about, we tend to size the supply at roughly 150 - 200% more than the calculated load because power supplies tend to operate most efficiently at half load and hence produce the least amount of heat at that point - ie longer life.
Most of our devices are 24VDC +/- 20% so voltage isn't much of a concern but not enough current can cause a lot of problems. So if I need one Amp I am wanting a 1.5 or 2.0A of supply. We try to get our stuff on its own supply but sometime not possible - panel space can be a real premium.
Power quality on the AC side generally isn't an issue for whatever reason. I guess a simple analog supply with a not all that sensitive device on the other side doesn't cause many issues?
MTBF, or B10 if the manufacturer will give it tend to be >100,000 hours anyways - which is way longer than any of us care. Unless its going to be somewhere in a panel that is really hot - but they make supplies with higher temp ratings for much higher $ and we try to use those when we need to.
So back to your wall wart - is there a lot of quality variability with wall wart suppliers? Can you even get a quality wall wart now - or do they all come from somewhere in China at the cheapest possible price?
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