charlieharper wrote in post #12036751
Dunno...but "Everyone" says that for electronic (digitally controlled) gear you should use pure-sine-wave electrickery, whereas for analogue stuff like bar heaters and incandescent light-globes it doesn't really matter.
PCB was talking about a not-unrelated topic, and he said that for strobes their high initial recharging current is past the maximum capacity of most cheaper (but still sine-wave) inverters, and when the current draw is too high they shut-down, whereas his inverters are current-limited, so as the current draw goes up, so then the voltage drops to compensate as the strobes capacitors suck the initial recharge.
He said that the (115v) output) can drop to as low as 35v during the initial surge, and his (digital) Einsteins were designed to accept this whereas many other digital strobes would "crash" if their input voltage fell from 115v to 35v.
Dunno if this
helps, or is even
relevant 
!!!
Austen.
Both! It helps clarify the situation. See below,
SkipD wrote in post #12036774As I mentioned above, the design of the electronic circuitry (whether it's digital or analog actually makes little difference) is what really dictates what the AC power requirements are.
This is another type of AC power requirement, but it is as important as what I was referring to above.
Flash units draw a very high current for a short time. While the average power consumption may be well within the specs of a given generator, the peak power consumption by things like studio flash units may not be.
Okay, the problem is surge - more commonly known as - Inrush Current.
Inrush current is the instantaneous current drown by a capacitor on being connected to the supply. Bear with me, I'll try to make this as clear as possible.
When you connect a flat capacitor to a supply, it, for an instant, appears as a a short-circuit across that supply. As the voltage across that capacitor increases the load current decreases logarithmically with time. You know the sound your flash makes as it recharges between flashes? that's the switchmode charger in action. The lower the pitch, the harder that it is working.
Now for a say, 350w flashgun, this instantaneous load could be equivalent to somewhere between 3500-7000 watts. This is the inrush current I mentioned.
The second aspect is voltage. Our (aussie) power supply is 240 volts RMS. RMS means Root Mean Squared. For now I'll leave you to google it, but accept that this means that 240 volts RMS equals 375 volts peak to peak (for our US friends, this mean 110 and 170 volts, roughly)
375 freakin' VOLTS I hear you ask? That's fine, the capacitors are specced to handle peak voltages. Due to the averaging effect of these capacitors, you get 240 volts (give or take) DC for the flash tube.
I'm going to ignore the pure vs stepped sine wave arguments for now and hope next to explain why.
Choppers, that is inverters, provide power by rapidly switching high-power transistors on and off to produce a desired waveform (pure, square, modified-stepped, whatever) and this is the problem. This produces switching noise which may be transmitted to your flash. A properly designed flash should have no problem with this as it filters the mains supply to remove such annoyances.
But this filtering is limited. When connected to the mains, the inertia of the power grid means that such spikes should be few and minor. On the occasion that something serious makes its way through you won't be the only one in your neighbourhood screaming at the moon.
Inverter-based generators could given the right circumstances create exactly these conditions. Pure sine units are still modified-step but with better filtering. The possibility exists, unless you purchaes something with 5 to 10 times your requirements (inertia, remember?)
If you want a smooth sine-wave unit, I'd advocate a good old-fashioned 240/110v alternator. No switching spikes, On high-current load, its output voltage will sag, meaning that your cycle times on high power shots may be slightly longer, but your flash won't mind. Yeah, push-rod technology it might be, but when you put (as I have) 360 300w choppers on the back of a 135 kva genset, and nothing breaks, I like it that way (BTW said genset had a nasty habit of going over-voltage on high load (crap regulator) but apart from flickering flouros, no major drama.
Sorry for the long-winded reply.
Open for Q&A,
C:\>
