Same question, different lamp: Philips CPO-TW. The lamp voltage again roughly corresponds with that of a SOX lamp. And again, Philips has a specific driver for it.

In this case, drivers are still available. But the 45w driver costs over 90 euro. The drivers for higher powered lamps are significantly cheaper (17,50), but those are much too bright to operate in my house.

Does anyone know what the difference is between the Philips HID-DV PROG Xt 45 CPO (for the CPW-TW lamp) and the Primavision SON/CDO 50 i already have?

You can google lamp data (voltage/current) for both lamps and compare.

I often search for these specifics using the lamp’s part number followed by filetype:pdf to get the best results.

You can google lamp data (voltage/current) for both lamps and compare.

Oh i know, but for instance for the SDW drivers there should be some difference in the drivers, despite it (for now) working fine on a SON ballast.

@Laurens
According to this site:
https://www.docs.lighting.philips.com/en_gb/oem/download/cosmopolis/MASTER-CosmoWhite-datasheet.pdf
Your 45W lamp has a voltage of 91V and a current of 484mA. This is very different from the characteristics of 50W SON, which has a voltage of 85V and a current of 760mA.

Unfortunately, this ballast combination is probably going to overdrive the lamp pretty severely (assuming my specs are correct).

Here is a user that runs a Philips Cosmowhite CPO-TT 90W Extra on a 100W HPS gear: https://www.youtube.com/watch?v=7lWFXWC63pQ

So what is the point? Pretty anyone can run a lamp on a wrong ballast and flush this to youtube...


My guess is if CPO lamp is run on a standard electronic MH ballast of close wattage (50/100W) it will be overdriven by about 10-20%.

Specs are somewhat entangled for them. While for CPO lamp 91V*0.484A = 44W is almost exactly lamp design power, for 50W HPS/MH lamp 0.76A*85V=65W which is way higher. I guess this is because CPO is specced to work exclusively on squarewave e-ballast and power factor is close to one, regular HPS/MH lamps are originally specified to run on 50Hz choke at sinewave, so lamp power factor has to be accounted. 

That last bit makes the most sense. Thanks.
I had no clue that *that* is what made them so different from common HID lamps.

My goal is to have a color 628 HID lamp. I happened to find the CPO at a dutch web shop. I'll continue and see if i can find any similar lamps with low CRI but warm white color, but designed for the drivers i already have.
While 90something euro for a brand new Philips driver is a good price, it's just a bit too much for something i am unlikely to put in regular use.

And no, i'm not planning on overdriving it.

Shall I send you some CPO drivers. I got a bunch of used ones as well some nos. Only 45 and 60W

That sounds nice! Send me a message with the cost including shipping to the Netherlands. Mainly interested in the 45w one.

Is their a reason you want the lower CRI? Eles there is a high CRI warm white lamp, the Philips CDM Warm in 925. https://www.lichtunie.nl/philips-mastercolour-cdm-tc-warm-70w-925-g8-5/
If you want lower colour rendering the only try e CDM lamp i can think of would be the CDM Fresh in 645

CDM fresh is not about low color rendering, it is about artificially oversaturating R-G-B colors to make merchandise look more appealing!

I wonder how it will look in a living room. The effect is probably like /840 rare-earth fluorescents do, but these tend to turn deep reds into crappy red-orange, while CDM Fresh is really deep-red rich like SDW sodiums.

Old style tin based Osram HQI-T /NDL have some of these properties, I kinda like how they emphasize blues without looking cold.

Is their a reason you want the lower CRI? Eles there is a high CRI warm white lamp, the Philips CDM Warm in 925. https://www.lichtunie.nl/philips-mastercolour-cdm-tc-warm-70w-925-g8-5/
If you want lower colour rendering the only try e CDM lamp i can think of would be the CDM Fresh in 645

I like seeing the variety in colors and color rendering that the different technologies have to offer. I have all types of sodium vapor now - LPS, HPS, HPS Comfort (so still very yellow but with a 60-something CRI) and White SON/SDW (which is absolutely gorgeous and one of my favorite types of light).
Once every so often i switch around what lights i actually use. With modern 94 cri LED lamps i have lighting that is as perfect as it gets, but where's the fun in that.
Much in the same way i have a collection of old radios, while also having a very good hifi system.

In the same way i'd like to have some low CRI MH lamps.

Aside from the difference in power factor, extremely important is also the current crest factor which determines the required size of the electrodes.

Magnetically ballasted lamps suffer a high CCF which causes considerable electrode heating cycling variation during the 50/60Hz sinus, and the electrodes must be made large enough to accommodate that.  These significant heat losses reduce lamp efficacy and shorten the life.

At higher frequencies above about 400Hz, or on squarewave operation, the current peaks are drastically reduced.  The electrode size can be reduced drastically - just look how small are the CPO electrodes vs the equivalent SON types.  Even if you can set up a magnetic ballast that operates the lamp at the same power as electronic (ignoring voltage and current differences which will always be significant due to the different waveform), it will quickly destroy the electrodes by severely overheating them at the peak of each current cycle and causing higher continuous temperature operation.  For this reason, electronically ballasted lamps of almost any type should not be run on magnetic gear if there is a desire to achieve anywhere close to the rated life.  In some extreme cases life may be reduced to only a few hundreds of hours.

My 50w and 70w SON/CDM/CDO drivers are both electronic.
My LPS ballasts are inductive, as are my 150w HPS, 100w SDW-T and 50/80w MV ballasts. I tend to call those ballast, and an actual switching/oscillator circuit a driver because it's an active thing rather than something just being a impedance in series with sometimes an ignitor that only serves to start the discharge.

But interesting to know how those things work and what makes them different.