The Lamp Room

So I've made a bit of a discovery. I've said before that the Philips CPO-TW lamps for 45 and 60W look identical, same size arc tube. Well I've gotten hold of an energy monitor and these are the results for the 45 and 60W lamps:

CPO 60W on 60W ballast = 66W (60W + 6 ballast loss)
CPO 45W on 45W ballast = 66W (60W + 6 ballast loss) Exactly the same!
CPO 45W on 45W ballast with permanent dim to 55% = 51W (45W + 6 ballast loss)

I used three of each ballast and took an average but they were all within 1 or 2 watts anyway. Two of the three runs had a brand new lamp, the third had a used lamp (~3 years nightly service), the used lamp didn't affect the power.
Also visually, the 60 and 45 at full power seemed to be pretty much identical in terms of brightness. The 45W on the permanent dim ballast was noticeably dimmer.
So it seems like the 45 and 60W CPO lamps are literally identical, and the 45 is just a 60 with a different etch. To get 45W out of a 45 you need to run it with a permanent dim ballast.

Did you record the lamp voltage and currents?

No I didn't, I only have a basic in-line energy monitor for the incoming side. I've never really gone into the technical aspects of lamps

This is my 45W CPO

I do not have a 60W CPO lamp, I only have a 140W ans^d 45W example in my collection. That beeing that the only ballast for these things I have is 60W.

What I find interesting is that the 45W Lamp draws on a 45W Ballast 66W which i think is accesive. The ballast generally have an efficiency of around 85-90%. I also doubt that there is any problem regarding the waveform that could confuse the power meter as these ballast have a power factor of about .95.

Electrically all three CPO lamps are standardised in IEC 61167:
Page 96
Lamp power: 45W
Lamp Voltage: 90V+25V-10V
Lamp current: 500mA

page 132
Lamp power: 60W
Lamp Voltage: 90V+25V-10V
Lamp current: 670mA

maybe this can help you when you measure your lamp voltage/current. However if you wish to do so make sure sure to use a true RMS multimeter as a standard multimeter can only measure sinusoidal signals accurately.

Is it possible the 45W ballast used could be defective or even mislabelled? Will have to see what the power draw is for my own 45W lantern.

I'll run some tests this weekend.

Kev - Interesting yours runs fine. You are at 20V less than my tests, but I can't imagine how that would make a difference on electronic gear with a wide operating voltage.

Alex - Interesting information there. I don't have any test equipment for measuring on the lamp side, it's something I've never went into. Maybe I should find some equipment for this kind of thing.

Beta 5 - It is possible for a mislabelled ballast, or a mislabelled lamp. We must have had a batch of them though, as all the ones I've tested are like that and came out of lanterns installed at pretty much the same time. I'll see if I have any more ballasts knocking around to compare.

FSB - Cheers, let us know what you find

Yes, seems unlikely though could be a bad batch if they are all identical? Were they original Philips ballasts or one of the others like Harvard or Venture?

Agent - are you on street lighting in your area? I’m after some 140W lamps if you have any knocking around