It has that in common with 95% of what the EU is blamed for in the popular imagination, and much of the remaining 5% was a British initiative anyway. And the channelisation of LW must have been someone's fault, I liked the nice round number.
You mean we were running the EU? Gosh - who knew? They certainly kept
*that* quiet.
The frequency changes were under the auspices of a UN agency - not an EU one.
But capacitors dont have losses.
The renewable obligation which costs this country far more than its net payments to the EU, is entirely an EU initiative.
We could not scrap it if we wanted to.
sssh. don't confuse with facts
Some may be, but not the ones I bought from TLC around 7 years ago. The output was a bipolar square wave at around 25kHz 100% modulated by 50 Hz.
John
We changed frpm c/s tp Hz years before we joined what was then the EEC.
He quoted it in his original post.
Parasitic ones with random stuff as dielectric certainly do. In any case, the problem with parasitic capacitance is having to have more wire to achieve the same L:C ratio which is needed for other reasons. This is a bit off-topic, but excessive parasitic capacitance is definitely a bad thing.
And the UK government was one of the prime movers in it becoming EU policy. Not the only one, obviously.
Roger Hayter a écrit :
+1 Many coils on toroid cores use parallel wires. Also horizontal deflecting coils for CRT.
FR4 capacitance tempco is about 800ppm/C.
NT
Life's too short guys
Bill
It started out in aus.cars and this Paul Saccani often chimes in with highly technical and sometimes wrong but often right stuff that is not always needed in simple conversations.
This is paul's latest contribution which started out as a simple question, The question, I want to run a 12v 20 watt LED light. For arguments sake, it's approx a
20 metres away from a 12v battery bank that consists of 4 x 12v truck batteries, which are fed by a 200w solar panel.I was going to buy a roll of this: 4mm
Or should I go for 6mm
What it doesn't say is 4mm^2, but if that is what it is, then it should *not* be used to deliver 22 amps over 20m at 12V. The voltage drop is 3.74V, a whopping 31% loss used to heat the wire, 82 W worth of wasted power.
Believe it or not, what you would want for 22 A, 12V over 20m is a
65mm^2 cable. Distance matters. You get the same voltage drop if you use 24V, but you have much less waste heat.That same cable could transmit 60A over 200 km with less than 3% losses, at 220 kV.....
Usually the first question is, is it an aerial, is it in conduit, is it on a surface with clips, is it under insulation? But this load is so trivial. Forget about setting things on fire with anything over
1mm^2.If you go with 1mm^2, voltage drop is 1.16V, therefore the wire generates less than 2 W of heat. Sure, you've wasted about 10% of your power, but it isn't catching fire any time soon.
Normal practice is to limit voltage drop to 3%, so a maximum of 0.36 V is acceptable at 12V. Therefore, by calculation you want a conductor of 3.2mm^2 or more, which if your first option is 4mm^2 and not "4mm Industry", is ample for.
Having said that, I don't think 2.5 mm^2 TPS 2C&E is out of the question if you have it lying around, but you'll be wasting 3.8% of the power you deliver.
However, there is an issue as to the nature of the LED. Good ones have a current limiting circuit and tolerate a wide range of voltages, typically 10-30 V AC/DC. Many cheap ones just have a volt drop resistor, designed to prevent excess current at 14.5-15 VDC - sometimes these will stop working at 11.5 V or thereabouts. So dependant on what kind of LED you are using, the voltage drop could be quite critical as to whether or not and for how long (battery state of charge) the light would work.
You could use diodes to provide a modest supply at 24V from the existing battery configuration and use easily available (or convertible) 24 V LED fittings.
For under $10, you could get a buck converter with a 250W rating to take the "12V" up to 28V (nominal 24V) with a current limiting fitting. This will also make sure your lighting works the same over a much wider state of charge of the batteries. You save on copper and get a better end result. You could also use a buck converter to 60V and another at the other end to take it down to 12V. Whether this is worthwhile depends on the cost of the wire.
With 1mm^2 at 28V, you then get a voltage drop of 0.49V, 1.75% for a
20W light. 0.35W wasted instead of 2W.Personally, I use 48V lighting to make life easy on the lighting front, but 28V (nominally 24V) makes a huge difference and is much easier to source lighting for..
I can't remember if I stressed this before, but with regard to your inverter, it is unlikely to be an isolated type. If you allow "neutral" to be earthed, the case become live at 110-120 V WRT earth. Also be aware that conventional switching is only on the active, so if you poke around in equipment connected to such an inverter, it is still might be live if the equipment switch is off. It is OK to earth the case.
As the output is not referenced to earth, this is safer in some ways compared with normal domestic power.
6 mm is good for about 63 A, too generous for sure.
Perhaps you should school him in power = voltage x current, and therefore 20 / 12 <> 22
big snip
2x12v leds in series on 24v certainly makes life easier, if the batteries aren't already set up as 12v for some other purpose.And don't forget T&E has 3 conductors, 2 of which can be parallelled to reduce V drop a little. Or if you have 1mm^2 lying around you could use 2 lengths of that, all 3 conductors parallelled. Etc.
NT
None are rectified - the loss in a rectifier at 50kHz would just be a pointless waste and well exceed all the existing losses in an electronic transformer. The transformer secondary is connected directly to the output terminals with no other circuitry on the secondary side.
It's modulated at 100Hz (not 50Hz) because there's no mains input smoothing capacitor, so it works on a mains phase angle dimmer.
(LED transformers are rectified.)
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