p.80 of “Electrical Safety for Live Events” by Marco van Beek has an interesting case study. Given the book is UK based so it’s of limited use for terms and technology used in the Us, but it does have some good information to supplement better US based texts. In the case of PAR 64 lamps, even if 230v power supplies, often they will use 120v lamps and 28v ACL lamps just as we do here. In their case, they are using both lamps in series as opposed to here we would just be doing the ACL lamps in series. Four 28v ACL lamps in series equals 112v at 1,000 watts when supplied by a 110-125v service. This as opposed to eight of them in the UK or two 120v lamps for 230v based systems. So in the study it was found that for some reason when a 28v/250w ACL was stuck in series with a 120v/1,000w lamp on a 230v system, the 120v/1Kw lamp would blow first. Why is this? No cheating.

Ok, think of it in another way. Given even I in a normal electrical lowest voltage blows first type of way will have initially assumed in it being wrong that the 28v lamp will have blown first, consider other than or in addition to the voltage effects on the lamp. The 28v lamp by the above report is a give it won't blow first. Why is this? Otherwise should you have a "in series" on four lamps, three at 28v, and one at 120v? (Will it even?) Or say in series nine 12v lamps, but for some reason a 24v lamp in the chain? (will that than?) Otherwise in a six pack of 24v lamps, and given a 12v lamp thrown into the mix, why might or might not it blow first verses the other lamps? Why would assuming something will blow up, why will the higher voltage lamp as stated blow first? This taken as a given the higher voltage lamp blows first in the chain of lamps. After all the lower the vlotage below the rated voltage, the shorter by a factor of 12 that lamp's life will be. How than can a lamp in series of higher voltage blow first given this statement of fact for line voltage? Ah' that's all Euro lighting and ACL bars, I'll never have to deal with them. We have ETC Dimmer Duplexing and installing by mistake a 120v lamp into the system has no potential effect other than being dim. - Why or why not?

In reality the range is as follows: HPL 550/64 Osram #54813 (UCF) CL, Quartz 550w/64v T-6 4-C8 LCL 60.3mm G9.5*HS (Ultra Plus) Any Burn Pos. 3,265°K 16,340 Lum 300 HPL550T6/64v Osram/Sylvania #54813 (Disc.) CL, Quartz 550w/64v T-6 LCL 60.3mm G9.5*HS Any Burn Pos. 3,265°K 14,600 Lum 300 HPL550/77 Osram/Sylvania #54623 (UCF) CL, Quartz 550w/77v T-6 4-C8 LCL 60.3mm G9.5*HS (Ultra Plus) Any Burn Pos. 3,265°K 16,170 Lum 300 HPL-550/77v+ Ushio #1000668 CL, Quartz(JS 77v-550w C) Low Seal Temp. 550w/77v T-18.35mm 4-C8 LCL 60.3mm G9.5*HS (*HS = Heat Sink Lamp Base) 3,250°K 16,170 Lum 300 HPL 550/77/X Osram #54604 (UCF) CL, Quartz 550w/77v T-6 4-C8 LCL 60.3mm G9.5*HS (Ultra Plus) Any Burn Pos. 3,065°K 12,160 Lum 2,000 HPL 550T6/77/X Osram/Sylvania #54604 (Disc.) CL, Quartz X-Life 550w/77v T-6 LCL 60.3mm G9.5*HS Any Burn Pos. 3,265°K 12,160 Lum 2,000 HPL-550/77X+ Ushio #1000669 CL, Quartz(JS 77v550w X) Low Seal Temp. 550w/77v T-18.35mm 4-C8 LCL 60.3mm G9.5*HS (*HS = Heat Sink Lamp Base) 3,050°K 12,160 Lum 2,000 HPL 550/77X Halco CL, Qaurtz 550w/77v T-6 G9.5*HS Universal Burn 3,000°K 12,160 Lum 2,000 HPL575T6/95v Osram/Sylvania #54822 (Disc.) CL, Quartz 575w/95v T-6 LCL 60.5mm G9.5*HS Any Burn Pos. 3,265°K 16,600 Lum 300 HPL 575/100 Osram #54822 (UCF) CL, Quartz 575w/100v T-6 4-C8 LCL 60.3mm G9.5*HS (Ultra Plus) Any Burn Pos. 3,265°K 16,730 Lum 300 #6989P/S Philips #924541930900 CL, Quartz (GLC type w. Remov. Heat Sink) 575w/100v T-20mm 13x8.5mm LCL 60.5mm G9.5+HS “Compact Source” (Shock Res.) 3,200°K 15,500 Lum 400 HPL750/77 Osram/Sylvania #54825 (UCF) CL, Quartz 750w/77v T-6 4-C8 LCL 60.3mm G9.5*HS (Ultra Plus) Any Burn Pos. 3,265°K 22,950 Lum 300 HPL 750 / 77v Ushio #1000676 CL, Quartz(JS 77v750w C) Low Seal Temp. 750w/77v T-18.35mm 4-C8 LCL 60.3mm G9.5*HS (*HS = Heat Sink Lamp Base) 3,250°K 22,950 Lum 300 Now, as mentioned, what would the following lamp have on such a system? HPL575/LL/C (120v) G.E. #92435 CL, Quartz Long Life (HRG) 575w/120v T-6 10.5x6.9 LCL 60.2mm G9.5*HS Universal Burn 3,050°K 12,360 Lum 2,000

OK – here are my thoughts on this question: Both lamps are significantly lower than the supply voltage (230v) so you would expect both to blow. Why does the higher voltage and higher wattage lamp blow first? Well I thought that the resistance may be sufficiently different to account for this. P=EI and we know P (watts) and we E (volts) so to find I (amps) we need to divide P into E. Therefore: I = 250/28 which gives us 8.93A for the 28V 250W lamp and I= 1000/110 which us 9.10A for the 110V 1000W lamp Now, to work out the resistance of each – The formula here is E=RI, where R is resistance. As we now know E and I it is a simple case of rearranging the formula, such that we have R=E/I So: R= 28/8.93 which equals 3.14 ohms for the 28V 250W lamp; and R= 110/9.10 which equals 12.1 ohms for the 110V 1000W lamp So, given that the 110V 1000W lamp has about four times as much resistance, my guess is that it more quickly and therefore blows before the 28V 250W lamp. Seem feasible?