dickq
Specifier/Regulator
- Feb 8, 2002
- 2
I'm based in the UK and intending to install display lighting to a long narrow exhibition space app 80ft. x 18 ft.
To minimise cost I want to use standard Quartz Halogen 12 V spot reflector bulbs suspended from pairs of catenary stretched-wire conductors by a simple system of my own devising, using brass double-screw connectors of various sizes (cut out of the ordinary polythene connector blocks that you can buy in strips anywhere)- the first pair of these are the largest size available, and clamp L-shaped brass rods (3mm brazing rod)to the stretched conductors; the next pair connect short, flexible - but thick - copper wire links to the ends of the brass rods; and the third pair connect the copper wires to the pins of the spot-bulbs.
This way I can manually twist the spots to point in any direction I choose - and they'll stay there - without the expense of a fancy shop-bought connection system - with 4 different spotlight spread angles available this gives me a very versatile system.
The conductors will be either high strength braided brass picture-hanging wire - the stuff they use in public art galleries to hang big pictures -or if that turns out not to be strong enough, or too stretchy if it heats up with the current, stainless steel rigging-wire - the high-conductivity stuff that they use to double for radio aerials on yachts.
There will be perhaps 100 of these spots at up to 50 Watts each,in perhaps 2 - 4 switched groups - or possibly ALL fed off one 12v supply if it's feasible, so I need a transformer from 240 v mains, capable of carrying up to perhaps 400 amps load in the 12 v secondary (ouch - sounds a lot! well- maybe 200 amps, or 100 amps for 4 groups of 25 lamps)The transformers that are specifically designed for use with 12v lighting typically can only cope with 3 or 4 lamps at most, so I need something industrial:
Questions (I'm not an electrical engineer!):
1) Is this a sensible proposition at all?
2) Where can I source such a transformer in the UK?
3) Am I right in thinking that, for transformers, bigger=more efficient?
4)Air-cooled? Oil-cooled??
5) Is there a welding transformer with as low as 12V output that might do the trick at lower cost?
6) Does anyone know of a source of high-conductivity + high tensile strengh catenary cable designed for this application?
7) will the catenary wire melt with these currents? I could always run solid copper bus-bars parallel with the catenaries and cross link at intervals - but now it's getting silly!!
- Those are my practical questions - now for some theoretical ones that have occurred to me as a result of puzzling over this:
8)With alternating current, the voltage, hence current, drops to zero every half-cycle(?) 100times? 50times? per second; so the temperature/luminosity of the filament of an incandescent bulb is constantly going up and down - the bulb is 'out' for part of each cycle. (Hence 50 Hz stroboscopic effects).
Would, therefore, direct current at the same 240 voltage produce more perceived light? Would the filaments, spared the presumed stress of constantly heating-up and cooling down, last longer?
(None of my electrical engineer acquaintances has been able to answer this one - but they're all high-voltage distribution-grid specialists.)
9) Supposing direct current WOULD result in greater efficiency in converting electrical energy into light, and/or a longer life for the bulb filaments, would the losses involved in having a large power rectifier in the circuit negate any advantages? (not to mention the capital cost of the rectifier!)?
9) If NOT, and there WOULD be significant advantages to DC, where can I get such a rectifier, to match the transformer?
Any advice and comments gratefully received - any rebukes for naive stupidity humbly borne.
Dick Q
To minimise cost I want to use standard Quartz Halogen 12 V spot reflector bulbs suspended from pairs of catenary stretched-wire conductors by a simple system of my own devising, using brass double-screw connectors of various sizes (cut out of the ordinary polythene connector blocks that you can buy in strips anywhere)- the first pair of these are the largest size available, and clamp L-shaped brass rods (3mm brazing rod)to the stretched conductors; the next pair connect short, flexible - but thick - copper wire links to the ends of the brass rods; and the third pair connect the copper wires to the pins of the spot-bulbs.
This way I can manually twist the spots to point in any direction I choose - and they'll stay there - without the expense of a fancy shop-bought connection system - with 4 different spotlight spread angles available this gives me a very versatile system.
The conductors will be either high strength braided brass picture-hanging wire - the stuff they use in public art galleries to hang big pictures -or if that turns out not to be strong enough, or too stretchy if it heats up with the current, stainless steel rigging-wire - the high-conductivity stuff that they use to double for radio aerials on yachts.
There will be perhaps 100 of these spots at up to 50 Watts each,in perhaps 2 - 4 switched groups - or possibly ALL fed off one 12v supply if it's feasible, so I need a transformer from 240 v mains, capable of carrying up to perhaps 400 amps load in the 12 v secondary (ouch - sounds a lot! well- maybe 200 amps, or 100 amps for 4 groups of 25 lamps)The transformers that are specifically designed for use with 12v lighting typically can only cope with 3 or 4 lamps at most, so I need something industrial:
Questions (I'm not an electrical engineer!):
1) Is this a sensible proposition at all?
2) Where can I source such a transformer in the UK?
3) Am I right in thinking that, for transformers, bigger=more efficient?
4)Air-cooled? Oil-cooled??
5) Is there a welding transformer with as low as 12V output that might do the trick at lower cost?
6) Does anyone know of a source of high-conductivity + high tensile strengh catenary cable designed for this application?
7) will the catenary wire melt with these currents? I could always run solid copper bus-bars parallel with the catenaries and cross link at intervals - but now it's getting silly!!
- Those are my practical questions - now for some theoretical ones that have occurred to me as a result of puzzling over this:
8)With alternating current, the voltage, hence current, drops to zero every half-cycle(?) 100times? 50times? per second; so the temperature/luminosity of the filament of an incandescent bulb is constantly going up and down - the bulb is 'out' for part of each cycle. (Hence 50 Hz stroboscopic effects).
Would, therefore, direct current at the same 240 voltage produce more perceived light? Would the filaments, spared the presumed stress of constantly heating-up and cooling down, last longer?
(None of my electrical engineer acquaintances has been able to answer this one - but they're all high-voltage distribution-grid specialists.)
9) Supposing direct current WOULD result in greater efficiency in converting electrical energy into light, and/or a longer life for the bulb filaments, would the losses involved in having a large power rectifier in the circuit negate any advantages? (not to mention the capital cost of the rectifier!)?
9) If NOT, and there WOULD be significant advantages to DC, where can I get such a rectifier, to match the transformer?
Any advice and comments gratefully received - any rebukes for naive stupidity humbly borne.
Dick Q
and you couldn't use bare wires. 