4k arri hmi fresnel on 5kva generator

Alex Wuijts · November 12, 2006

Hey all,

Is it generally possible to start a 4k hmi fresnel on a 5kVa generator? I'm about to assist on a shoot, and ofcourse we're going to test this rather restricting package, but i'm curious about the relation between generator and the startup power you can draw from it.

Thank you very much for your time.

Bobby Shore · November 12, 2006

Hey all,
Is it generally possible to start a 4k hmi fresnel on a 5kVa generator? I'm about to assist on a shoot, and ofcourse we're going to test this rather restricting package, but i'm curious about the relation between generator and the startup power you can draw from it.

Thank you very much for your time.

yeah man, a 4K HMI will draw roughly 40 amps of power (8.3 amps per 1000 watts), so you should be fine with a 5000 watt generator (I'm assuming that's what you meant by a 5kVa generator)...

you'll definitely want to be careful about your voltage though... check it very carefully as HMI's tend to flicker or pulse when hooked up to smaller generators (whose voltage tends to fluctuate).

Hope this helps. Good Luck.

Bobby Shore

Director of Photography

Los Angeles / Montreal

Alex Wuijts · November 13, 2006

great, thank you!

Kevin Zanit · November 13, 2006

It?s more about the Hz rate of the generator. The smaller "put-puts" have a hard time keeping at a solid 60Hz (in the US), and thus they tend to flicker.

With a flicker free ballast, you can be in better shape. But I frankly would not recommend running a 4k on a put-put. Plus the 5k generator can barley handle the 4k (on paper it is fine, but in practicality it is a stretch), a 5.5k has a chance, but that is still hard for the generator to handle.

If you are shooting video, you can sometimes play with the "ECS" to get rid of the HMI flicker that you almost certainly will have, but even then it is very inconsistent.

Kevin Zanit

Brian Drysdale · November 13, 2006

You get a bit of a surge on start up with HMI and I heard you should allow around 50% excess capacity to allow for this. I'd tend towards at least a 6k or even bigger generator and use a flicker free ballast on the light. I recently used a 4k on a 10k geny and it was very comfortable with the load.

On another shoot, a spark recommended that we only use a 1.2K HMI in combination with a 4k with a similar rated generator (as against using a 2.5K as the second light).

Alex Wuijts · November 13, 2006

Thanks, this is all very helpful. We're probably gonna use a 2500W instead, because even with an electronic ballast we'd still be pushing the limits of the generator. Even when it starts, there's probably no way to make sure it doesn't turn itself off because it gets too hot.

Too bad we can't get a bigger power source.

Alex Wuijts · November 20, 2006

Everytime we struck the 4k it blew the main fuse of the Honda 5500 generator we were using after three minutes or so, so we went with an 2500 Par, which was a very reasonable alternative for our purpose - to give a little bit more contrast to the actors faces on a cloudy day.