I had used those bulbs for my workbench. I had an 150W and an 250W above the work area and the lighting was very good. I am not sure if they wre made by Philips or what brand they were, but the light was nice, the filament continued to glow even after the mercury tube ignited and its warm light complemented very well the cold light gave by the mercury tube. It was plaesant to my eyes and even with bright 250W light I did not felt uncomfortable. I understand that the filament acted as ballast, limiting the discharge current in the tube, being so able to use it in any fixture (E27 socket), many people using them for exterior illumination.
Nice lamp, actually the safety feature is if the outer envelope is broken, the arc tube will extinguish. Since the lamp is normally under vacuum the filament stays intact and once it's exposed to air if the outer envelope is damaged, the filament will burn up and extinguish the arc tube
A common application for these lamps would include gymnasium high bay lighting because in gymnasiums, balls would have a tendency to sometimes destroy the outer envelopes of mercury vapor lamps because of the ball hitting the lamp whenever it is thrown. The reason that these lamps were so beneficial to gymnasium lighting was because whenever a mercury vapor lamp has a damaged outer envelope, its arc tube would release copious amounts of UV radiation that could potentially cause spectators and athletes to receive sunburns. In fact, I have read that these lamps have been manufactured specifically due to a lawsuit involving athletes and spectators receiving sunburns from broken mercury vapor lamps emitting UV radiation. Additionally, I am also aware that even some probe start metal halide lamps have this specific safety feature as well because they have also been commonly used in gymnasiums as well.
I am a retired Broadcast engineer. I worked with several older transmitters that used mercury vapor rectifiers. We had to preheat them on the workbench before installing them. If there was liquid mercury they could malfunction and arc over. I suspect the incandescent filament is a preheater to avoid that procedure and still allow the bulb to work with untrained installers. The procedure was more complicated that what I described. Once heated the tubes had to kept in the correct orientation or the tube would need to be reheated. Using these old transmitters really needed well trained operators.
Not for these bulbs, the filament was used as a safety feature that would cause the lamp to go out if the outer glass was broken. The inner arc tube puts out shortwave ultraviolet radiation. They were designed to be used in areas with people.
That "filament" is actually a fuse, if I'm not mistaken simply a strip or wire of carbon connected in series with the arc tube. The reason for this is because a common application for these lamps is in school gymnasiums, and sometimes the outer glass shell of the lamp is struck and broken from a soccer ball or other similar objects and the inner quartz arc tube continues to light. When this happens intense levels of UV are emited, which depending on the conditions (distance between the damaged lamp and spectators, reflectors, type of finish on ceiling and walls, etc. ) can be comparable to a welding or carbon arc. When the internal fuse is exposed to oxygen upon cracking or breaking the outer envelope it burns out and removes power from the arc tube. Metal halide also suffers from this problem and are (or were) still available with the safety fuse in select wattages. These lamps are known as self extinguishing lamps and sometimes referred to as the type T lamp vs type R. For example, a GE MVT400 would be a 400 watt self extinguishing metal halide. Not to be confused with the more common protected metal halide, which are not self extinguishing but rather is constructed with a ballistic quartz shield encircling the arc tube, to prevent red hot quartz from breaching the outer envelope and showering the area below in case of an explosive lamp failure.
No, the filament is a ballast replacemet, limiting the current for the mercury tube. This type of bulbs is meant to be used dirrectly to mains, replacing old incandescence high power bulbs (for exterior or large spaces); I saw it commonly used in rural areas or for large home garage. I used them to illuminate my workbench with one 150W and one 250W in a ceramic normal (E27) socket, replacing the 100W and 150W incandescent bulbs that I had used before. The carbon stripe I found in the bulbs that were meant to be used with external ballast.
In the gymnasiums are remember occasionally when a ball would accidentally hit a fixture I think I remember that one of the evolves theater break once but most of the time if the ball hit it and Justin bounce off and nothing happened with the fixture other than a bit of swaying. Oftentimes the bulb would extinguish and once it cools come back on. And also I've seen and heard about when somebody raps on A Street Lamp Post hard enough or gives it a really hard knock of some sort or a really hard kick in some manner something can happen when it goes off extinguishers the ark somehow. I've heard a couple theories on this as well how it could happen. Probably be worse than one show me in on this that would have some info as to why it interrupts the ark just for confirmation would love to hear it too . I remember once is in the outdoor field somebody hit a liner right to one the fixtures at this time they were all off and the fixture came on when the ball hit and also another time a ball got wedged in with the fixtures unfortunately that ended the game no extra balls left. However that one that came on and started up and stayed on. Apparently there was security lighting that was not made aware of for many years it was just kind of left there probably most of the lamps for probably out. They have to take a walk eventually and sure enough there was a separate group of lamps that was just on normally and apparently the controls have been bypassed to just have them on constantly for some reason. Eventually got that fixed up to operate normally but if I remember correctly there was some bad part in the system possibly the controller or timer or photocell or something cannot remember all the details of the system And also the system there was old enough that had the I called ancient Transformers not the typical round canned ones on the Utility side but even some of the old rectangular that would almost look like an indoor Drive Transformer except has the high attention bushings of course you're talking about way back in the day. And yes more than likely of course all those Transformers have pcbs in them! In that town there's a lot of old electric gear in Silver locations if you knew where to look you'd see it. For example the park where the fair was held there are a few places that probably had the original distribution. There is one place in that area I think I even saw an old birdhouse cut out in the woods somewhere we would love to have that thing! Isn't back of a property that someone I knew had owned however that area was just too overgrown and just completely abandoned the really access anything but they said if the pole ever was able to be accessed I could have it. Along with some really nice old insulators as well
I think I know why there's a filament in them, considering that these are (Safety) Philips Lifeguard lamps, they might be the ones that once the arc tube is done, the filament acts as a safety prevention, it blows out, and disconnects the arc tube from power.
So the filament limits the current through the arc tube and acts as a self ballast? Seems plausible, as many technicians use filament bulbs (DIM bulb tester) to limit current to electronic items under test.
I used to work in a place that had self-ballasted mercury vapour lamps in a garage / storage area. They were run direct from the 240V mains supply (this is in Australia), no ballast involved. They were remarkably durable. On roughly 10 hours a day Monday - Friday and they lasted many years.
Thr filament acts as a fuse. What happens is if the lamp loses its vacuum, the filament will burn out and extinguish the lamp. So if a lamp is broken, prevents harm from the UV radiation.
This is a so-called self ballast lamp It is a mixed light bulb In the Netherlands not in 100W but 160W you no longer need a ballast The filament is for the red light part and the arc tube is for the green and bluish part of the spectrum Together this gives a warm white light
