HMI 575W/GS ballast- magnetic or electronic?


Newly Enlightened
Jan 8, 2018
Hi there
I'm in the UK, and many years ago I did nightclub lighting.
I managed to get a ballast, igniter and new HMI 575 lamp
from a fitting, and kept them for years to maybe do a big searchlight/ pencil beacon project.
I've run the set of bits, and it works. I have an old 15 inch military airfield searchlight that it will fit in.
The /GS lamp is a universal orientation lamp, so that's handy, and I guess I'll have to do a fan cooling system.

Two questions- the old searchlight is glass fronted, but I've no idea whether this is enough on its own to block UV.
I can get UV blocking perspex to put on as well, I suppose...

Also, the magnetic ballast presumably has a power factor of way less than 1 ( no capacitor in the original lamp),
and the lamp current in the specs is 7A, so running this in the future off an inverter so I can use batteries may be a bit tricky...
Would an electronic ballast ( if one is available anywhere) make the drawn current when on 230V or the inverter a bit smaller
and easier for the inverter to handle, and drop the battery current?

( I still have a Philips lamp that's a 400w ( tin halide?) and it had a power factor of .39, and,
unsurprisingly, had a 4mm cable! My mate plugged two into a single 13A extension lead at a gig, and after a while I noticed
that the cable was hot and like jello......he couldn't get his head round it, since he 'obviously' only had a load of 800w! )




Nov 17, 2013
Ordinary glass will give you full protection from the most dangerous UVC, and almost all of the UVB. (the stuff that produces vitamin D) It does let UVA through, but we get plenty of that from the sun, so you could probably get a tan from the light if you really wanted too, but you won't be blind or get instant cancer. If I wanted to use the light indoors for a long period of time, I would use better UV protection, not only for people, but also paint and fabric that could fade. But as a spotlight outdoors, glass is perfectly fine.

Regarding magnetic or electronic ballast running on an Inverter, I really don't know. But an electronic ballast has other benefits regardless of that, mainly less weight and is generally better for the lamp.
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