Power Factor when Designing Circuits

[Spark123]

And halogen down lights

 

[SimonH2]

Question. Not really sure if it is connected to original question. I can understand the power factor related to electric motors, and CFLs have been mentioned - which is not as clear to me-, but what other equipment? Induction cookers can be quite large machines - is it relevant here? Mostly I use this site as a learning resource (as if you hadn't guessed).

Any load other than a simple passive resistive one (like a heating element) is likely to have a PF less than 1.0. As well as obvious inductive loads such as motors and things with inductive ballasts (like traditional fluorescent lights), I think one of the greatest type of culprits are switched-mode power supplies (SMPSUs), which are becoming increasingly prevalent in this world. 'PF-corrected' SWPSUs exist, but I don't know how common they are, and I have a feeling that there are some problems associated with them. I would suspect that, as you say, an induction hob would probably have a low PF.

Actually, SMPSs were a serious problem a decade or two ago - leading (I believe) to burned out neutrals in some commercial buildings when lots of computers got installed on what were by that time "undersized"* electrical installations.
* Ie, when the building was built, the assumptions on load were effectively "lights plus the cleaner's vacuum" - but then the place has been filled with power hungry computers.

But for (IIRC) a decade or two, there have been quite strict limits on harmonics, so pretty well any SMPS that complies with standards will have a reasonably decent PF and crest factor. Of course, I suspect we all possess some cheap PSU where the board has vacant holes that only had components fitted in the samples sent for testing

For an induction cooker, I actually wonder if they don't have an inverter drive for the induction coils these days. Given the way power electronics has progressed, I suspect it wouldn't add much cost/complexity and allow for the fine grained control I assume is "standard" - at least the one my mate's just had installed seems to be "all bells and whistles" including a function to limit maximum power drawn from the supply.