150 Watt SON + Tungsten lamp hybrid control gear

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This unusual lamp control gear from Courtney, Pope Lighting Ltd incorporates a GES (E40) lampholder wired up to a 150 W High Pressure Sodium (SON) lamp circuit.
Alongside this lampholder, however, is a standard two-pin bayonet lampholder designed to run a tungsten filament lamp. Once switched on, and the SON lamp commences its warm-up, the 'Discharge Lighting Sensor' located bottom-right on the gear tray then activates the tungsten lamp, in order to provide immediate illumination. The tungsten lamp extinguishes automatically once the sensor detects that the SON lamp has reached full brightness.
Please note that the filament lamp does not dim during the video; it remains at the same brightness throughout. The much brighter SON lamp caused the camera to adjust the brightness automatically.
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streetlightonli...

[@randacnam7321]

We had something similar on this side of the pond, except the controller for the auxiliary lamp usually used the discharge lamp current as its reference for when to turn on the auxiliary lamp. The auxiliary lamps were usually intermediate dual contact bayonet base halogen lamps. 250W was a common standby lamp size for 250W and 400W metal halide fixtures.
Another fun fact is that many multitap ballasts (due to the range of supply potentials we have, it's common to see discharge lamp ballasts that will run on a number of different supply potentials; the most common type is a 'quad tap' ballast with 120V, 208V, 240V and 277V inputs but there are many others) are often rated to run a standby lamp from their 120V terminal or wire. There are also 480V ballasts with a 120V tap specifically for a standby lamp, but they have warnings on the ballast label about how this is _not_ a supply terminal/wire as the autotransformer it is connected to can't handle the full load current of the ballast.

[@StreetLightOnline]

Fascinating - I didn't think that an auxiliary system would be possible in the US, specifically because of the amount of possible voltages making such a system unfeasible, but your explanation there makes sense. I like the idea of some people mistaking the 120 V lamp supply as a convenient method of running anything that happens to run at that voltage. I expect that the auxiliary lamp supply on the circuit in this video would also be designed for a relatively low current load.

[@randacnam7321]

@@StreetLightOnline Which is why ballasts specify that loads connected to the 120V terminal should be standby lamps only, as the only time the auxiliary lamp is running is when there is no load from the main lamp. The ballast will usually specify the maximum permissible standby lamp as well, especially iffen it is a smaller ballast where the standard 250W standby lamp for 250W/400W fixtures is close to what the main lamp would produce light wise. My 100W mercury ballasts (we use 75W, 100W and 175W mercury lamps in place of the 80W and 125W European mercury lamp ratings; 80W and 125W ballasts do exist over here, but are extremely rare) are usually rated for a 100W maximum standby lamp.

[@FrontSideBus]

Interesting setup. I've seen low bays in use which used r7 halogen aux lamps. I saw one with an EOL discharge lamp and the halogen had taken over.

[@StreetLightOnline]

That's noteworthy, as I've never seen this setup employed for myself. I'd guess that the fittings using a halogen standby lamp might be newer than this one (capacitor dated to 1983) - quite neat that the system recognises a fault with the discharge lamp, and keeps the halogen running instead.

[@thepurdychannel8866]

500w halogen?

[@FinlaysFireSystemsElectrical]

Interesting setup

[@StreetLightOnline]

Thanks!