----- Original Message -----
From: "Randy Little" <randyslittle@xxxxxxxxx>
To: "List for Photo/Imaging Educators - Professionals - Students"
<photoforum@xxxxxxxxxxxxxxxxxx>
Sent: Friday, June 14, 2013 11:15 PM
Subject: generator math help
I'm trying to calculate how big a generator I need to do some location
work. I need to power 4x2400 w/s packs and a 2000 w/s pack with over
head
to charge 2 ranger batteries at a time and 2 Leaf batter packs at a time.
that later items are only 3v. So I can just rent huge but Im trying to
rent as physically small and quite as possible.
easy way, it doesn't matter how small a generator you get - just put a
lightbulb in series with the flash units .. do not exceeded the output
wattage of the generator. That way say you have a teeny 0.5 amp generator,
110V - that's 55Watts it can produce. If you put a 40W bulb in the line
you limit the current flow out to the flash pach to 110V at 40W, that means
you'll only draw 0.36 Amps from the generator. the flashes will take a time
to charge up, but it'll do them no harm and the lower drain will smooth the
power supply and reduce the risk of damaging it. Initially when you turn
the unit on, the bulb will glow bright then dim as the power accumulates in
the flash packs capacitors until th caps are saturated and the bulb will
appear to go out - you've drawn all you can, fire your flash!
if you run modelling lights, swap them down to a lower wattage or shut them
off - their constant draw is a load you probably don't need.
Conversely if you just plugged in 1000W of lights to the generator it's
stall immediately or burn out as the flashpack sinked a massive load ..
so that's :
110V Gen ------------lightbulb-------
|----- socket
plug ------
flash pack
|----- socket
plug-------
110V Gen-------------------------------
the cool thing is you can use really cheap light globes to act as current
limiters, swapping them up or down based on your needs
if you want to go at it like you were operating froma wall plug, i'd expect
you need at least 21 amps continuous (+ modelling lights).
