Author Topic: can you do something for me ?  (Read 10209 times)

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Offline Zero999

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Re: can you do something for me ?
« Reply #25 on: June 20, 2011, 08:45:43 am »
But that is only true in the UK because of post-war copper-saving, where pairs of 15A radial circuits were allowed to be joined together to form 30A rings.  In most of Europe, sockets are wired on 16A circuits, which actually provides better protection against flex fires than a BS1363 plug with 13A fuse.  (Because a 16A MCB breaks faster for small overloads than a 13A BS1362 fuse, and because the breaker is for the whole circuit, not just the faulty device.)
That maybe so but then there's the disadvantage of not being able to connect two large appliances to neighbouring sockets so if the toaster and kettle were connected to the same circuit, the breaker would blow when they're both turned on. The 13A system is also more convenient because it's obvious where the fault lies, the house breaker tripping would be a pain because you'd have to unplug each device until the faulty one is located.

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A BS1363 plug with a 3A fuse theoretically provides much better protection for the flex.  But the user might not fit one.  In any case, harmonized European regulations do not permit appliances to be sold with thin flexes that could not carry a 16A fault current for a short time.
I wouldn't agree that 0.5mm2 cable or even 0.752mm cable is sufficient for a 16A circuit.

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Class III is SELV.  All appliances, even if polarized, should treat the live and neutral as equally hazardous, since the neutral becomes live if it is accidentally severed upstream.  Having two fuses would be pointless since you do not know which will blow first.  Unless you are thinking of a fault to earth in a Class I device, in which case any fusing does not matter as long as the earth conductor is adequate.
Yes, I meant class 1.

Although the live and neutral are both hazardous, fusing the neutral, rather than the live is a bad idea because when the fuse blows, the appliance is certainly live. If the live only were fused, the appliance will probably be safe when the fuse blows, although, as you say, there's the remote possibility the neutral has also been broken. This is why the fuse is always fitted in on the live conductor and having a non-polarised plug is bad because it defeats this.

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The shutters on UK sockets are a nice feature, though arguably only necessary because of the huge pin sizes.  But the system has bad points too.  The risk of foot injury.  The fact that if the plug is smashed or comes unscrewed then live parts are exposed and it is very difficult to remove safely.  (Rewireable plugs with rear cable entry tend to screw together sideways instead.)
You're right, it's not perfect and I've stood on plugs in the dark before ouch!

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The fact that chained extensions include multiple redundant fuses, which makes the system unusable in industries such as stage lighting.
I'm not sure how this is any worse than not being able to identify which appliance is faulty when all the sockets in a room go dead because of one faulty appliance.

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Regarding UK wall-warts, what annoys me far more than cable routing is the crappy plastic earth pins that many of them have.  I cannot understand why these are allowed.  I have actually witnessed one snap off and stay in the socket when the plug was removed, thereby leaving the socket disabled and with its shutters open.
I've had that problem too.

Actually, I think if we're to harmonise, a totally new plug should be designed combining the advantages of both the European and UK systems. I'd definitely want to keep the fuse, polarisation and safety shutter but the maximum current could be increased to 16A, the connections made from the rear of the plug to reduce the risk of foot injury and the plug should unscrew from the side, not the bottom.
 

Offline vk6zgo

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Re: can you do something for me ?
« Reply #26 on: June 20, 2011, 10:56:28 am »
Although I recognise the advantages of the UK style plug,it just seems too "clunky".
The fuse in the plug does die with age, & domestic appliances  are unnecessarily replaced at extra expense,when it is just an "aged" fuse.

Although it does have issues,I prefer the Australian standard plug.
It is light, convenient,fulfils all the requirements of a 240v plug,except the standard orientation is reversed
to what would be logical--earth  pin is at the bottom instead of the top.
The standard cable outlet on an Australian plug is at the rear of the plug (in line with the pins).
The standard material is heavy duty flexible PVC.

It is just as easy to hurt bare feet with an Aussie plug as with a UK one, though,in fact the pins are sharper!!

Have you ever had a play with a US 240v 20A plug?
They are incredibly over-engineered!

In the USA,the 240v supply is from a centre-tapped pole transformer with both sides  being "hot" w.r.t neutral
(& earth),hence ,you find equipment with fuses in both sides.I think this is actually illegal in Australia,but equipment wired this way is common among USA & Canadian sourced equipment.

I bought a shortwave radio many years ago, which was equipped with a 2 wire power cord.
This was a 240 volt device, but was designed for the US system.

It had an RF filter circuit on the AC mains input,with capacitors from both legs to the chassis,which in the USA
would be a "virtual earth".
In Australia,the chassis was tapped halfway down a capacitive voltage divider,so when ,in my eagerness,I attached an aerial & earth,the earth lead went "zap"!
Not enough current to do any harm to a person,but if I had attached any other equipment,it might not have
survived its first introduction to the new radio! ;D

Needless to say, the first "mod" was a three core power cable!

VK6ZGO
 

Offline Lance

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Re: can you do something for me ?
« Reply #27 on: June 20, 2011, 12:54:58 pm »
Simon I'm having a hard time visualizing what you're saying up in the OP. Can you post a picture or two?
#include "main.h"
#include <pic.h>
//#include <killallhumans.h>
 

Offline Simon

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Re: can you do something for me ?
« Reply #28 on: June 20, 2011, 03:47:59 pm »
Simon I'm having a hard time visualizing what you're saying up in the OP. Can you post a picture or two?



now imagine having half your plus with a wire out of one side and half with it out of the other (opposite). Now think of wall warts made so, not fun eh ? either way a standard should be maintained.
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Offline firewalker

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Re: can you do something for me ?
« Reply #29 on: June 20, 2011, 09:55:41 pm »
Take a look at this!!!



A friend of mine told that one wall plug wasn't working normally. I bought a new one and tried to replace the old...

Alexander.
Become a realist, stay a dreamer.

 

Offline Lance

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Re: can you do something for me ?
« Reply #30 on: June 21, 2011, 01:57:58 am »
Simon I'm having a hard time visualizing what you're saying up in the OP. Can you post a picture or two?



now imagine having half your plus with a wire out of one side and half with it out of the other (opposite). Now think of wall warts made so, not fun eh ? either way a standard should be maintained.
Oh, I see. I agree! It would make everything fit together better. In canada everything either comes out of the back, or the bottom. Some of the slimmer adapters (like my cell phone charger) actually have the prongs mounted sideways so it doesn't cover up any other outlets.


Take a look at this!!!



A friend of mine told that one wall plug wasn't working normally. I bought a new one and tried to replace the old...

Alexander.
Eww.
« Last Edit: June 21, 2011, 01:59:54 am by Lance »
#include "main.h"
#include <pic.h>
//#include <killallhumans.h>
 

Offline Zero999

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Re: can you do something for me ?
« Reply #31 on: June 21, 2011, 03:40:28 am »
Although I recognise the advantages of the UK style plug,it just seems too "clunky".
The fuse in the plug does die with age, & domestic appliances  are unnecessarily replaced at extra expense,when it is just an "aged" fuse.
I've never seen that happen before.

Fuses are rated for a minimum of 1000 hours at full load and most mains appliances draw much less current than the fuse rating. A TV may have a power rating of  70VA, drawing 0.3A but will be fitted with a 3A fuse which will never blow, unless there's a fault. Only larger appliances have a power rating nearer to the plug fuse but they tend to not be left on continuously so it is still not an issue.

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I bought a shortwave radio many years ago, which was equipped with a 2 wire power cord.
This was a 240 volt device, but was designed for the US system.
Are you sure?

It seems odd that such a small device would be designed for 240V in the US. As far as I'm aware, in the US 240V is reserved for larger appliances such as washing machines, cookers and air conditioning units.

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It had an RF filter circuit on the AC mains input,with capacitors from both legs to the chassis,which in the USA
would be a "virtual earth".
In Australia,the chassis was tapped halfway down a capacitive voltage divider,so when ,in my eagerness,I attached an aerial & earth,the earth lead went "zap"!
Not enough current to do any harm to a person,but if I had attached any other equipment,it might not have
survived its first introduction to the new radio! ;D

Needless to say, the first "mod" was a three core power cable!
The capacitors should be Y1 rated, otherwise it doesn't meet any safety legislation. That kind of configuration is actually quite common here in Europe. The capacitors are connected between both live and neutral to the case because some countries have a non-polarised plug. If they connected an X capacitor from live to neutral and a Y2 capacitor from the case to neutral, the cause might float at 230V, if it were connected to a dodgy non-polarised EU plug.

I don't like this kind of configuration, not only does it pose an ESD risk, it's also a serious shock risk (not just a tingle) if the chassis of many appliances are connected together because the leakage currents add.
 

Offline vk6zgo

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Re: can you do something for me ?
« Reply #32 on: June 21, 2011, 04:14:45 pm »
Although I recognise the advantages of the UK style plug,it just seems too "clunky".
The fuse in the plug does die with age, & domestic appliances  are unnecessarily replaced at extra expense,when it is just an "aged" fuse.
I've never seen that happen before.

Fuses are rated for a minimum of 1000 hours at full load and most mains appliances draw much less current than the fuse rating. A TV may have a power rating of  70VA, drawing 0.3A but will be fitted with a 3A fuse which will never blow, unless there's a fault. Only larger appliances have a power rating nearer to the plug fuse but they tend to not be left on continuously so it is still not an issue.

You are probably correct,as I wasn't in the UK long enough to have a fuse die on me!
I have,however,read quite a few comments from UK based TV service people,who maintain this does happen,&
I have personally experienced fuse failure due to aging in other situations.


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I bought a shortwave radio many years ago, which was equipped with a 2 wire power cord.
This was a 240 volt device, but was designed for the US system.
Are you sure?

It seems odd that such a small device would be designed for 240V in the US. As far as I'm aware, in the US 240V is reserved for larger appliances such as washing machines, cookers and air conditioning units.
Yes,I am sure.
Working in TV Studios & TV & Broadcast Transmitters,I have come across this kind of circuitry a number of times in 240volt US & Canadian sourced equipment.
My guess is that  240volt outlets are fairly common in TV studios in the USA,so that equipment for that voltage is made to the US standard.
Also US "Hams" commonly run linear amplifiers from 240volt as 120volt sockets usually are inadequate to supply enough current to run these devices at max legal power,so an HF receiver powered by 240volts is a possibility in that country.


Quote
It had an RF filter circuit on the AC mains input,with capacitors from both legs to the chassis,which in the USA
would be a "virtual earth".
In Australia,the chassis was tapped halfway down a capacitive voltage divider,so when ,in my eagerness,I attached an aerial & earth,the earth lead went "zap"!
Not enough current to do any harm to a person,but if I had attached any other equipment,it might not have
survived its first introduction to the new radio! ;D

Needless to say, the first "mod" was a three core power cable!

The capacitors should be Y1 rated, otherwise it doesn't meet any safety legislation. That kind of configuration is actually quite common here in Europe. The capacitors are connected between both live and neutral to the case because some countries have a non-polarised plug. If they connected an X capacitor from live to neutral and a Y2 capacitor from the case to neutral, the cause might float at 230V, if it were connected to a dodgy non-polarised EU plug.

In this case,the caps were only between both legs of the mains supply,so the maximum voltage present on the chassis w.r.t. neutral/earth if the caps don't fail is 120volts

I don't like this kind of configuration, not only does it pose an ESD risk, it's also a serious shock risk (not just a tingle) if the chassis of many appliances are connected together because the leakage currents add.

I definitely agree.When 2 wire cords were used back in the day,AC filters were not commonly used,so there
was less of  a problem.


VK6ZGO
« Last Edit: June 21, 2011, 06:51:59 pm by vk6zgo »
 


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