[pure-silver] Re: Enlarger Lamp Life

The following page gives some infos of the nominal voltages in various 
countries:
http://kropla.com/electric2.htm

Aside of this, depending of your position on the line (close to the power plant 
or very far) and the electrical consumption on your line (a high consumption 
lowers the available voltage and vice-versa) very variable throughout the day, 
the available voltage varies quite a lot.
A friend of mine, who lives close to the power plant, has a very high bulbs 
consumption ...

Regarding your question on transformers, classic transformers, say those made 
of an iron core and copper primary/secondary windings have a transformation 
ratio defined by the number of turns between the primary and secondary.
If your transformer is meant to give 12V out of a 220V primary, then the ratio 
is 12/220, if you apply 230V, then you'll obtain 12.55V (+4.5%), if you have 
240V, then it becomes 13.1V (+9%).

This impacts not only the life of the bulb but also its brightness (high impact 
in B/W) and color temperature (low to no impact at all in B/W) which varies in 
the same manner during the day giving inconsistent exposures unless you have 
closed-loop analyzer/timer.

Claudio Bonavolta
http://www.bonavolta.ch

----- Message d'origine -----
De: Eugene Barrington <eandpbarrington@xxxxxxxxxx>
Date: Wed, 29 Oct 2008 17:32:23 +0000
Sujet: [pure-silver] Re: Enlarger Lamp Life
À: pure-silver@xxxxxxxxxxxxx

>Here, in Ireland, and, I suppose the rest of W. Europe the voltage is  
>220v.
>
>Would'nt the transfomer's o/p still be 12v even if the input varied a  
>bit? BTW Ole what brand of lamp do you use? I've been using Philips  
>Focusline 6834 FO.
>
>Eugene Barrington
>
>On 29 Oct 2008, at 17:08, Richard Knoppow wrote:
>
>>
>> ----- Original Message ----- From: "Ole Tjugen" <ole@xxxxxxxxxxxx>
>> To: <pure-silver@xxxxxxxxxxxxx>
>> Sent: Wednesday, October 29, 2008 7:41 AM
>> Subject: [pure-silver] Re: Enlarger Lamp Life
>>
>>
>>> That's strange, as I haven't had a lamp blow in my Meopta enlarger  
>>> with  colour head - ever. And I do just the same with a metronome  
>>> and the power  switch.
>>>
>>> The transformer on mine delivers about 13V too, many colour head  
>>> lamps are  deliberately overvolted.
>>>
>>> Also: The voltage supplied by the electricity companies hasn't  
>>> increased  over the years. But as lines are replaced, transformers  
>>> upgraded et  cetera, the assumed voltage delivered to the customer  
>>> has increased  through a reduction in transmission losses.
>>>
>>> Ole Tjugen
>>
>>
>>    Certainly not in Los Angeles and other places in the US. Standard  
>> voltage here was 115 and occasionally 117 volts for many years,  
>> these are the rated voltages on equipment of many sorts. Now,  
>> measured line voltage is closer to 120 to 125 volts, enough higher  
>> to cause problems with some older electronic equipment. Lines and  
>> distribution transformers get replaced routinely so the overall  
>> "age" of the syetem tends to be constant except for new  
>> developments. I am in a very old part of LA with old distribution  
>> equipment and still have high line voltage. OTOH, line voltage  
>> varies during the day and varies with general demand. Power in the  
>> City of Los Angeles comes from the municipally owned Depart of Water  
>> and Power but outlying areas get power from the Sothern California  
>> Edison Co. I don't know, but can find out SCE practice vis line  
>> voltages. There are also some independant municiply owned power  
>> suppliers here such as the Burbank and Pasadena departments.
>>
>> --
>> Richard Knoppow
>> Los Angeles, CA, USA
>> dickburk@xxxxxxxxxxxxx
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