DAB radios in the UK

[Fanie]

Always better to remove the cause of a problem than try to treat the symptoms.  While you still can !

[Stephen Moss]

I rembemer that about 30 years ago we had cause to look at the mains at work and on all three phase were a little flat on the top, but the Red phase was particularly bad dropping about 20 volts off its peek. There was talk of building a power factor meter but it was more of a side project that was never built although I did look at try to use the feedback signal of a power factor correction chip to calculate the power factor but how much correction it had to make.

Power factor correction only applies above a certain power level, and I think it's above 1.5Kw but I'm not sure.

At work we have a lot or large milling machines and lathes that probably accounted for much of that, but I also remember reading something (probably 20-25 years ago) back when PC's were becoming more heavily used in the workplace that their power supplies were starting to have a significant affect the power factor and so to compensate for and prevent additional loading that there was going to be a requirement for all new electrical/electronic equipment of 50W or higher to have power factor correction built in, although over the years the Wattage requirement may have changed (lowered?) to cover the millions of mobile phone chargers that are in use now.

[charliecoutas]

I'm pretty sure that most low-end stuff (up to several hundred watts) doesn't have power factor correction. I can say this because when I worked at Telonic Instruments Ltd I had to repair a lot of power supply equipment and much of it had no PFC. It was usually a hefty diode bridge followed by a hefty capacitor or more. Then the switch mode stuff followed that.

The "regulations" seem to indicate that PFC should, perhaps be "considered" for several KVA upwards. I have fixed quite a few TV switched mode psu's and never come across PFC. The only PFC of 1 that I saw on my gear at home was on the little plug-in scent gadgets that Lynda likes to litter our 13A sockets with. They work (I guess) by heating a resistor to evaporate the smelly liquid, and a resistor (non-wirewound) will cause a power factor of one.

But I'm guessing that a low power factor will be penalised by the power companies because some of the power (the reactive bit) is wasted.

I'm still looking for that rogue 300 watts.....

Charlie

[John Lawton]

Try finding a free copy of IEC 61000-3-2:2018 Electromagnetic compatibility (EMC) - Part 3-2: Limits - Limits for harmonic current emissions (equipment input current ≤16 A per phase).

It's available here European Standards for only Euro 270.

So unfortunately I can't afford to back up my statements on mains harmonics for low power equipment but I believe that it's in these regulations.

John

[John Lawton]

I'm still looking for that rogue 300 watts

What sort of power meter are you using? I have one using a clip-on current transformer on the house meter tail. I think that it uses quasi-peak detection rather than true RMS as it over-reads badly on low power factor loads such as much electronic equipment, though it's accurate for resistive loads. So your 300W may not be entirely 'real' power.

John

[charliecoutas]

It's a Kikusui KPM1000 power meter, calibrated last year. Yes, I agree that the 300W may be reactive but the meter on the wall shows a cost of either 6.8p or 8.6p for that load, so it's costing regardless.

Charlie

https://global.kikusui.co.jp/w2-2/measurement-instrument-en/kpm1000-en/kpm1000/

[John Lawton]

Depending on how distributed the 300W consumption may be, another approach might be to use an Infra-red camera to detect the heat generated. I have one and it is fun and sometimes instructive to use.

John