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Re: [OM] Purchase of new camera case successful

Subject: Re: [OM] Purchase of new camera case successful
From: "Jim Nichols" <jhnichols@xxxxxxxxxxxxx>
Date: Fri, 26 Feb 2010 17:36:59 -0600
Jon,

I  have reached my limits in this discussion.  I am not sure what takes 
place in the transformer supplying the two hot legs to my house, or, for 
that matter, your 240v supply.  Maybe someone will enlighten us. :-)

Jim Nichols
Tullahoma, TN USA
----- Original Message ----- 
From: "Jon Mitchell" <olympus@xxxxxxxxxxxxxx>
To: "'Olympus Camera Discussion'" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Friday, February 26, 2010 4:05 PM
Subject: Re: [OM] Purchase of new camera case successful


> Thanks Jim, that clarifies a little.
>
> Sounds like you are saying that you have two 120v "legs" from the same
> phase.  That makes sense - mixing phases is not pleasant if you don't know
> what you are doing.
>
> However, it sounds like the two 120v legs are 180 degrees out of phase ?
> That way, measuring between the two "hot" legs would give 240v ?
>
> Over here, we have 240v between what we call "Live" and "Neutral".  If I
> measured between the "Live" legs of two 240v supplies on the same phase, 
> I'd
> get 0v ... right ? (Never tried it, I must admit - most of my EE is at 50v
> or below, and mainly DC).
>
> Just interested, that's all.  I understand what we get over here (at 
> least,
> I thought I did).  Not sure I get what happens "over there".  Think I need
> to go and read some more.  Maybe it's just a case of terminology.
>
> Thanks,
>
> Jon
>
>
> -----Original Message-----
> From: Jim Nichols [mailto:jhnichols@xxxxxxxxxxxxx]
> Sent: 25 February 2010 23:43
> To: Olympus Camera Discussion
> Subject: Re: [OM] Purchase of new camera case successful
>
> Jon,
>
> Though I'm not a EE, I can give you some general concepts of power
> distribution in the US.
>
> I live on a corner lot, alongside a fairly busy throughfare.  There is a
> 3-phase distribution line along that street.  Feeding our homes are a
> connection to a single phase of that line, and the common neutral.  These 
> go
>
> to a distribution transformer which supplies three or four homes.  I have
> little knowledge of what takes place in the transformer, but the output to
> each home is made up of two 120 volt legs and a neutral.  These feed the
> breaker box busses.  120 volt branches are connected between either of the
> two hot legs and the neutral.  240 volt circuits connect between the two 
> hot
>
> legs.  Perhaps someone else can elaborate what happens in the local
> transformer.  I suspect that the transformer drops the voltage down to 120
> volts and feeds two separate secondary windings, which are then fed to the
> house breaker panel, along with the neutral.
>
> Very few homes are served with 3-phase power feeds.
>
> Hope this helps.
>
> Jim Nichols
> Tullahoma, TN USA
> ----- Original Message ----- 
> From: "Jon Mitchell" <olympus@xxxxxxxxxxxxxx>
> To: "'Olympus Camera Discussion'" <olympus@xxxxxxxxxxxxxxxxx>
> Sent: Thursday, February 25, 2010 5:25 PM
> Subject: Re: [OM] Purchase of new camera case successful
>
>
>> Hi,
>>
>> Apologies for answering my own questions.  Not such an "American" trait 
>> in
>> broadcasting any more though - it's spreading fast.  Not that that's an
>> excuse ....
>>
>> Not sure about moving supplier though.  They all get the power from the
>> same
>> place.  I think of it as a wholesale arm of the National Grid selling the
>> power to any of the retailers (they are bound, I believe, to give them 
>> all
>> the same deal).  The retailers then sell it on to you.  That's progress
>> for
>> you !
>>
>> Now on to a more interesting question for other members of the list 
>> (which
>
>> I
>> won't answer myself .... 'cos I can't !).  There's a lot of talk about
>> different power "legs" and "phases" to the same house from our US friends
>> here.  I have little idea how the power supply works in the USA (other
>> than
>> it is 110v 60Hz AC), but is the implication that you have more than 1
>> phase
>> in your homes ?  Over here you can get either a single-phase supply or a
>> 3-phase supply.  Very few (if any ?) homes have a 3-phase supply, as 
>> these
>> are intended for industry.
>>
>> Are your houses wired with some sockets on one phase and some sockets on
>> another ?  Doesn't this pose problems ?  What if you connected 2 devices
>> to
>> 2 separate sockets that were on 2 separate phases - and then connected 
>> the
>> devices together (VCR to TV via a SCART, for example).  At best, nasty
>> interference.  At worst CABOOM, no ?
>>
>> And what about balancing the phases ?  When I've played with 3-phase
>> supplies (lighting rigs, for example) a lot of care is taken to ensure
>> that
>> the phases are fairly evenly balanced (approx same load on each phase).
>> How
>> do you do that within the home, when most home-owners don't understand
>> this
>> stuff ?
>>
>> I'm not questioning whether it is right or wrong, better or worse, but am
>> interested in how it is done elsewhere.
>>
>> Oh, and most scary thing seen whilst working with 3-phase ?  A colleague
>> ran
>> a long run of pre-terminated 3-phase power cable (120Amp, or thereabouts)
>> over the roof of a stadium.  He realised afterwards that he had run it 
>> the
>> wrong way around (male & female connectors at wrong ends for the required
>> usage).  Whilst I agree it would have been a lot of work to de-rig and
>> re-rig the cable, I am sure that it would have been easier (and safer) to
>> chop the ends off and remake them the right way round rather than make 2x
>> 3-phase Gender-Bender cables !  That was one VERY scary cable.
>>
>> Second most scary 3-phase incident ?  The 3-Phase A0 photocopier we had 
>> at
>> work until a couple of years ago.  I still can't comprehend why you'd 
>> need
>> 3-phase power for a photocopier !
>>
>> Anyway, this is all wildly off-topic (though fun).
>>
>> Jon
>>
>>
>> -----Original Message-----
>> From: Chris Barker [mailto:ftog@xxxxxxxxxxxxxx]
>> Sent: 25 February 2010 21:48
>> To: Olympus Camera Discussion
>> Subject: Re: [OM] Purchase of new camera case successful
>>
>> Thanks for that Jon.  But there is something you can do about it: move
>> supplier, complain to your current supplier, to Ofgen etc ...
>>
>> And, don't you start sounding like an American broadcaster, asking your
>> own
>> questions ....
>>
>> ... or Conservative MP :-)
>>
>> Chris
>> On 25 Feb 2010, at 20:26, Jon Mitchell wrote:
>>
>>> FWIW, we looked into this at work recently - problems at some of our
>>> sites
>>> with very low voltage.  UK spec was changed recently to harmonise across
>>> Europe.  I don't have the exact figures to hand, but it used to be
>> something
>>> like 220v in Europe and 240v in UK.  Now it is 230v in UK and the rest 
>>> of
>>> Europe.  How did they get away without changing all of the National 
>>> Grid,
>>> substations, etc. ?  They fudged the error-factor so now UK is something
>>> like 230v +15%/-6% and rest of Europe is something like 230v +6%/-15%.
>>> Phase is much more accurately defined, and has a far smaller margin
>>> before
>>> it becomes "out of spec" - but that was always the same across UK &
>>> Europe
>>> anyway.  In reality, nothing has changed in the power supplied either in
>> UK
>>> or rest of Europe, but now manufacturers have to cope with a wider
>>> voltage
>>> range if they want to sell products across Europe.
>>>
>>> Anyway, back to the point, yes - in theory the power companies are
>> required
>>> to maintain a consistent voltage (within an alarmingly wide margin of
>>> error).  In practise, however, they regularly do not maintain this.
>>> Especially in more rural areas.  But who can do anything about it ?  As
>>> someone else said here - the general attitude of the power companies is
>> "you
>>> get what you're given".
>>>
>>> Does it suck ?  Yes.  Does it bother me ?  A little.  I know a couple of
>>> SERIOUS hi-fi nuts who have taken matters into their own hands and
>> installed
>>> some serious power-conditioning units (basically, AC-DC-AC conversion)
>>> and
>>> run a separate ring-main just for their hi-fi components.  Can I hear a
>>> difference ?  Well, yes - but more to the point is that the cost of the
>>> hi-fi kit in question means it is worth a sizeable investment in power
>>> conditioning to stop it going boom when the power drops (or rises) out 
>>> of
>>> spec.
>>>
>>> Gosh.  2 topics in a week that I can reply to with some experience !
>>> What
>>> is this list coming to ... ;-)
>>
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>
>
> -- 
> _________________________________________________________________
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> Themed Olympus Photo Exhibition: http://www.tope.nl/
>
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> _________________________________________________________________
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> Themed Olympus Photo Exhibition: http://www.tope.nl/
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> 


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