One of the most common complaints I get from our customers is that they go through a lot of bulbs in their properties.
When I get these complaints, I install voltage recorders and if the supply voltage exceeds oour limits (216 to 253V) then I can alter the local transformer to bring it into line.
If the customer lives close to a distribution transformer, they can experience a high average voltage (240V+) but not exceed the threshold.
As all bulbs are manufactured for European 230V systems they tend to get a bit upset when subjected to 240V+ for long periods of time.
Has anyone got any thoughts on how people could get around this problem? One customer told me that he had sourced light bulbs manufactured for 250V systems and they lasted a long time, but I can't find any suppliers who would be able to supply them.
Any thoughts or cost-effective solutions would be appreciated.
My first thought was a bucking transformer, one with a 12v output would work for to drop 240v to 228, thus bringing it into line with 230v bulbs.
Normal low voltage lighting transformers may or may not have the required primary to secondary voltage withstand and insulation resistance figures, but it would be worth looking at.
A simpler solution (more DIY than professional however) would be a dimmer switch inline with the normal switch, somewhere inaccessible, set to drop the voltage to 230v rms or even 220, thus increasing the life of the lamps.
Other possible solutions that crossed my tiny mind were back to back zener diodes, and resistors, both of which would require protection, and plenty of heatsinking, even with a 40w bulb as the load. (dropping say 20v at the current required by a 40w lamp still comes close to 4 watts, which in an enclosed area requires plenty of heatsinking).
Other 'sideways' solutions would involve CFL or LED lamps thus bypassing the problem of filament lamps altogether, and increasing lamp life and reducing the power bills as an addition.
I expect this problem to become more common now equipment is being produced for 230v, although our brethren on the European mainland are probably experiencing longer lamp life due to the same causes.
I suspect that the 'super long life rugged' lightbulbs available a few years ago were in fact merely designed for 250-260v, thus providing enormous life on 230-240v supplies, I suspect the 60w version was in fact a 75watt 250v lamp being underrun. I haven't seen these for a few years now but they may also be a solution.
Ian, If it has become that much of a problem, fit a DIN Rail mount Surge Diverter to the incoming Mains. These clamp voltages in excess of 253VAC. What you should be looking to get rid of is voltage spikes. Incandescent lamps do not like shocks to the filament and will blow a lamp as quick as. Before you address the lamp issue, address the voltage spike issue. That is not to say that lamps made these days are nothing short of rubbish.
I've been hearing many reports on thes side of the pond about bulbs quickly burning out.
Many times, this seems to be because the "cheap" bulbs- especially the ones that come with the appliances- are not rated for the actual voltage applied. (Our new areas often have 127v (measured) vs. the 110v (rated) bulbs supplied. The problem is usually solved by using 130v rated bulbs. But....
There are enough remaining complaints that I wonder if something else is happening. Sure, we have several types of "rough service" bulbs, and those address problems caused by vibration and thermal/ mechanical shock.
Still, I would not be the least bit surprised if the manufacture of bulbs has advanced to where the glass is thinner, the filaments finer, than they once were. My lighting suppliers assert that the big discount stores get 'factory seconds' bulbs. And many of our bulbs are made in China- which has a rather abstract concept of "quality control." (Summed up in the phrae 'close enough-doesn't matter (silly gweilo)')
Dodging the issue, I have developed a preference for compact fluorescent bulbs. Ordinary lights just seem so....yellow. These bulbs seem to come in two varieties- the ones that quickly fail, and the ones that run forever. There's that QC issue again. The ballasts in them ought to eliminate any surge or harmonic related problems, though.
Which may be why the ordinary bulbs are failing. These days, we have all sorts of household electronics, everything from the TV to the microwave. These may be 'dirtying' up our supply, and contributing to bulb failure. I just don't know.
Could it be anything to do with the inrush currents? Filament bulbs have a very low resistance cold, I measured 65 ohms for a 60W 240v bulb, which would be 960 ohms at full brightness. Lower impedance supply wiring would reduce the life of the bulb.
260V bulbs used to be easy to get here...they were made for use in Western Australia which until the 1980's ran on 250V (in reality up to 265V in some areas) Here on the east coast using those bulbs on 240V would give an exceptionally long life...so long in fact that the glass would have become blackened by filament evaporation before it actually burnt out. I'd get several years out of a bulb that was used every day. I was surprised to find 260V bulbs again after about 15 years in the local Bunnings. I do know that Crompton still make 250V bulbs. I've gone off CFL's for my own use...they can't handle mains spikes and the RFI is annoying. The first generation of Philips CFL's with iron cored chokes were great though. It's been about 10 years since the "240-250V" rating was printed on our light bulbs (were they really 245V I wonder?). Now they're all simply "240V".
In my garage is a 300W GES based light bulb. To prolong its life I have a 40 ohm resistor in series with it to absorb the initial inrush current. After a few seconds the resistor is shorted out by means of a time delay relay (ie. a 555 timer IC driving a 12V relay). It seems to work very effectively as the bulb comes up from a gentle glow as the filament heats up and the current drops before the full voltage is applied.
The idea of using a transformer to reduce voltage is a good one; you can use a halogen light transformer with the 12v secondary connected out of phase in series with the load. I had to do a similar thing with my fridge which would trip the thermal cutout in hot weather... yet another appliance fitted with a 220V 60 cycle induction motor foisted on the Australian public.
[This message has been edited by aussie240 (edited 09-17-2005).]
This is a well known problem in Scandinavia too. There used to be two sorts of bulbs: 220-230V and 230-240V. Now they have 230V bulbs. However, as a special item, there are 240V bulbs for buildings with "elevated mains voltage", i.e. close to the transformer. Aren't such available in the UK?
Osrams catalogue lists both 230V and 240V bulbs: http://www.osram.se/Bilder/PDF/Allm%c3%a4nbelysning/Glodlampor.pdf