Originally Posted by dpalomaki
Lightning strikes are fast events. A standard test waveform reaches its peak in 10 microseconds and decays in another 30 microseconds. Protection has to act fast to beat that.
Power surges are much slower events, often caused by the sudden drop of a major load and driven by overall power system design and the distribution of connected loads.
Power line switching event's speeds are measured in cycles (e.g., 16.7 ms/cycle for 60 Hz).
Power factor correction for home appliances such as desktop PCs is a relatively new concern driven by the "green" movement. Unity power factor is more efficient use of power infrastructure and has lower transmission and other losses. Power factor correction has always been important for large load centers such as industrial plants and more recently major data centers.
Standard practice for power supplies has evolved over the years. Designs today are difference from the 1980s. In the early days slight power interruptions caused crashes, literally destroying storage and data. Today's drives are far more "crash proof" but nothing is perfect. In any case unsaved date loss is still a fact with random shutdowns, and mechanical shocks may effect system components and tapes if motors sputter and stutter.
I had a camcorder perhaps 20 years ago. When using the A/C adapter to power it I had to be careful of routing the DC cord that ran from the power supply to the camcorder. If located to one side it would induce noise in the recorded video/audio. Part of knowing your gear and how it best functions. All wall wart power adapters are not the same.
The degree of protection to add is an individual, personal decision based on one's carefully evaluated (or not) tolerance for the risks involved. And the risks are driven by the gear, the environment, and power system specific to the individual user.
I entirely agree.
Pf is getting into the weeds here, it was just thrown into the mix, but for the routine domestic user it has an astonishingly small impact. I was cautious about Pf being drawn into this as a metric for determining fault tolerance if you understand what I mean. It's a totally different concept, as I know you're aware.
I *think* (but do not know) that most decent PSUs made over the last decade or so have some element of Pf correction, whether that's just a capacitor/inductor in passive topologies, moving into active I'm out-dragged in knowledge, it's not an area I've been more than tangentially involved in, beyond selectable L/C reactive components and a rough idea of how they work.
SMPS noise is a ballache
(I'm a 'ham
') which is why I'm all too aware of UPSs issues with RF intrusion, and SMPSs in general. Like you've said, they're more than able to create interference in baseband AV signals if no consideration is given.
We run about our most sensitive equipment in DC-DC using some lovely, but very old heavy linear regs' I had from my instrumentation days, it's a weird setup and it's woefully inefficient, but when we're down to trying to squeeze the absolute best out of a tape it's a step we've taken. We have climate monitoring in the suites as specified by some customers, it gets toasty warm with that lot running at full tilt, I can assure you. Extra credit for having 'hand-wound' transformers as it was Mrs RR(1) who wound them.
A lot of this stuff is more robust than is made out, it's the insistence that a device is automatically 'trashed' should it ever be plugged directly into the mains I can't fathom. It's a low-risk exercise in the case of this device, ultimately if the devices have survived until this point, they're fairly robust.
Your stuff about transient testing is interesting, I might model that circuit using those specifications for analysis.