Have just been perusing the MK Electric on-line catalogue and was checking out their 15Amp 127V Socket Outlets . The data sheet describes them as “American Style” yet they are rated 127V and are not UL or CSA listed. The standard covering their design is given as SSA: 444: 1985. Which standards authority is SSA? It might give me a clue as to the intended market for these devices.
Other interesting difference with the NEMA prototype is the shuttering of the slots. I would also be interested to see how the terminals are labeled. ‘L, N, E’ I suspect from the datasheet though it is not that clear. No mention of brass and silver terminals as I doubt the intended customer uses white as the neutral/grounded conductor. Polarization is the same but I see that outside of America, the earth pin is definitely up!
That socket is intended for the middle eastern market. Saudi Arabian Standards Organization (SASO) issues SSA numbers.
These outlets are used alongside UK style BS1363 which also have an SSA code. MK makes both of them on UK-type plates so they can be installed easily. American plates and boxes would be very problematic.
127V 50Hz is used in quite a few Middle Eastern and caribbean countries. It's an oboselete European standard that was used in a very similar way to 120V in the US.
i.e. circuits were either 127V + 0 or 127+127 giving you a potential difference of around 220V between the two terminals but 127V between either terminal and ground.
However it's survived in places outside the EU but as far as I'm aware is being phased out as it is rather difficult to get 127V 50hz appliences. US appliences designed to be used on 50/60Hz work "ok-ish" on 127V but it's pushing the upper limit a bit particularly if there's any kind of a voltage spike. There are a lot of stories of US appliences plugged into outlets that seemed to be US standard being wiped out.
In most instances you'll find 127V is used almost exclusively for lighting with 220V used for almost everything else. However, most countries that use 50Hz are converging on Cenelec (european) standards and adopting 230V L + 0V N for single phase and 400V for 3-phase.
Interestingly, MK has a very large presence in many places that would have had a lot of contact with the UK / former british colonies. So you'll find MK plugs, sockets, systems and distribution / manufacturing businesses in places like India, HK / China and various Middle Eastern and african countries.
Also, I think MK's version of a NEMA outlet is actually pretty good. Shutters sould be a nice addition!
[This message has been edited by djk (edited 12-28-2003).]
Re: Standard SSA: 444: 1985#139769 12/28/0306:25 PM12/28/0306:25 PM
It's an oboselete European standard that was used in a very similar way to 120V in the US.
So was this same configuration of plug/socket used in Europe on 127V + 0 before obsolescence? I have likewise been trying to establish what plugs were used in the British Isles when the, now long-gone,110-0-110V DC systems were in vogue. Was a 110V supply ever tapped in this system?
Re: Standard SSA: 444: 1985#139770 12/28/0309:18 PM12/28/0309:18 PM
No I don't think that configuration of plug was used in Europe as far as I am aware it was either 2 round pins or light bulb sockets. Although I am not 100% sure as Europe's had endless different standards in the old days. I know 127V remained in exsistance in parts France post WWII but I have never seen a NEMA style outlet even in the oldest French house.
Centre tapped systems with 2 hot terminals supplying 220V between them have remained in service for much longer though. This is partly the reason that connector systems like Schuko etc are not polarised
I guess NEMA sockets would prevent the accidental connection of 127V appliences to 220V sockets though so would make a lot of sense in installations where the system is still in use.
As for the British DC system I think paul UK could give more detail but as far as I know they used BS546 style 3-pin polorised plugs and a 2-pin ungrounded and unpolarised plug which was similar to Europlugs but with shorter fatter pins. (not unlike the current UK shaver plug) The old British system had a LOT of plug configurations all of which were incompatable so most homes were full of adaptors.
I am also not 100% sure when they standardised on 240V 50Hz or what other systems were around.
The Republic of Ireland was very boring and never really used DC systems in domestic/industrial supply in the 20th century. Although various local arrangements exsisted in the late 1800s and into the 1910s and even early 20s. The ESB rapidly standardised on 220V 50hz (with a earth-bonded neutral) and 380V 4-wire 3-phase in 1926 and the independent supply systems were bought up by the ESB under an act of parliament, connected to the fledgling national grid and standardised.
So I have never seen reminants of DC systems other than in UK photos.
Re: Standard SSA: 444: 1985#139771 12/29/0310:42 AM12/29/0310:42 AM
Hutch, the 127V+0 system remained in use at least into the 1970's in parts of Europe. I'm not sure when the system was introduced, but it must have been a long time ago. From another thread we have learnt that the American plug is from the 1920's. I believe the round European plug is older than that, although I have no proof. To this day, shucko plugs carry a DC rating.
Saudi Arabia has been influenced by both American and European practice and use 60 Hz, 127/220V. This makes the choice of an American style socket which fits into a British style box perfectly logical. I know of no other country in the Middle East that uses 60 Hz or 127V.
[This message has been edited by C-H (edited 12-29-2003).]
Re: Standard SSA: 444: 1985#139772 12/29/0301:06 PM12/29/0301:06 PM
I was talking to someone who spent some time working over there and he said
US type plugs, BS1363, Schuko and old BS546 all found in various places and as far as he was aware the system was supplying both voltages and it seemed to depend on who had been involved in the electrification of a particular area. He said you had to be careful what you plugged in as you couldn't guarentee that a European/British outlet meant 220V or that a NEMA outlet meant 127V.. He'd also been warned of 50 and 60hz supplies being used depending on what part of the country you were in so all equipment had to be capable of working on both, just like in Japan.
It's a strange country and it's rather difficult to get any information about anything and censorship etc is taken to extremes. e.g. all internet access is provided through the ministry for communications and is strictly monitored and it's not generally legal to recieve foreign television by satellite.
However, 127V 50Hz is a problematic system as you can't get appliences so in general it's being phased out of use.
Some places, particularly close to North America, simply switched frequency to 60hz and lowered voltage slightly.. which is what I'd expect Saudi Arabia has prob. done, at least officially. Even slightly lowering the voltage without switching frequency would open up a whole range of 110-120V appliences that can function on 50 or 60Hz.
Others are using 127-127 to give compatability with European appliences and gradually moving to 230-0 bit by bit.
Switching frequency is a pretty drastic measure to take though so I would suspect the migration to 230V would be much more common.
[This message has been edited by djk (edited 12-29-2003).]
Re: Standard SSA: 444: 1985#139773 12/29/0302:12 PM12/29/0302:12 PM
the protection mechanism described in the Hubble catalogue is quite different from that used on the European receptacles. The Hubble version is rather sofisticated with two switches that need to be depressed at the same time for the outlet to work. The European shutters are simple mechanical barriers which prevent an object from being inserted.
Re: Standard SSA: 444: 1985#139775 12/30/0312:00 PM12/30/0312:00 PM
As for the British DC system I think paul UK could give more detail but as far as I know they used BS546 style 3-pin polorised plugs and a 2-pin ungrounded and unpolarised plug
The 200/400 to 250/500V DC systems, aw found in the old sections of some British towns were generally used with conventional BS546 plugs. Keep in mind that as far as residential servive was concerned, houses generally took only a 2-wire 200 to 250V service, with half the houses having a positive "live" and half having a negative "live" wire.
I think what Hutch is querying though is what was used in the very early days when some districts had a 110/220V DC supply. I'm not sure how far back our round-pin plug specifications go -- They may have been used on those early 110V systems.
similar to Europlugs but with shorter fatter pins. (not unlike the current UK shaver plug)
Exactly the same dimensions as the current shaver plug in fact, although without the shielded pins which are common on the latter nowadays.
I am also not 100% sure when they standardised on 240V 50Hz or what other systems were around.
I'm not sure when the decision was made to standardize, but the conversion program took many years to complete. Full standardization at 240V was finished only in the early 1970s, and up until that time radio, TV, and other more sensitive equipment was fitted with a voltage range adjustment.
Prior to standardization the declared nominal voltages were anything in the range of 200 to 250V, usually in 10V steps. That's why most old wiring devices were rated for 250V maximum.
[This message has been edited by pauluk (edited 12-30-2003).]
Re: Standard SSA: 444: 1985#139776 12/30/0312:04 PM12/30/0312:04 PM