Powering Studio Strobes Using An Inverter

To take this the other way. Why wouldn't a light designed to be plugged into a wall outlet draw all the power it could expect to find there? 15 amps shouldn't be a problem on normal North American outlets if I understand right. The more power it draws the faster it's ready for the next firing. No?

 

I know Speedotron claims my monolight has an average draw of 8 amps with a peak of 13amp. That's a full recharge.

 

Why would a bigger WS power pack draw less?

Without getting too technical, capacitors have what is called ramp time. It is the rate they charge and discharge.

 

If you attempt to charge one too fast it will explode.

 

Best advice is still to have someone who knows electricity to put an amp meter on the power cord and find out the draw at standby and recharge.

 

And use a pure sinewave inverter. Things will work better.

I am glad that some scientific explanation was given.

 

SHIVER uses the equations, yet comes up with "the RULES OF THUMB or conventional wisdom"? - that conventional wisdom seems taking over the scientific equations? or are the equations not applicable?

 

So the scientist comes with suggestion of: "it is safe to provide a headroom of 60A for when it recharges". Yes, that will certainly work OK, safely.

The question I asked (specificly) was what it would take to power a P2000D or P2000XT (I have both packs). So the answer from Norman is a specific answer to the original question. If you think you're smarter than the manufacturer so be it. Perhaps you'll grace us with your own line of pack lighting in the near future.

My apoligies for the formating, the forum won't let me use the <pre> tag

 

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From: "Scott Osada" <Scott.Osada@photo-control.com>

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HI Jim

 

Most inverter do not have enough current for the packs. The packs can work on a modified wave but will work better on a true sine wave. The inverter will have to be able to put out more than 20 amps.

 

Scott

 

 

-----Original Message-----

 

From: jim feldman

Sent: Wednesday, April 05, 2006 3:37 PM

To: PCC-Info

Subject: dc power inverter for Norman Packs

 

I've got some Norman packs (P800D, P2000D, P2020) that I may occasionally want to run off of DC power by way of a power inverter. Do the packs (and heads) need pure sine wave output or can they handle modified sine wave?

 

thanks

jim feldman

Jim, You had asked question to Norman, and received your answer,

that certainly did not satisfy you?, since seems you keep asking again.

 

If I am smarter than Norman's tech? - nobody really can tell, but chances are that perhaps I am, since I can answer your questions, so you will stop searching for anwsers.

 

I only know the Norman P2000D, and do not know the other models, but perhaps it is the most powerfull of them ?

 

And the answer is: there are many many power inverters that will provide sufficient power, just do not go to Radio Shack for them.

 

Some inverters from Power Master Technology will work OK with Norman P2000D.

 

If you turn Off 7 all modelling lamps, inverter PM-650L will work for you. It only provides 650 Watts continuos, and nearly 2000 Watts short duration peak (surge that will sustain HUGE capacitor loading time of 1 to 2 seconds). E.g. I think this inverter could handle 2 modelling lamps (at 150 Watts each), in addition and any number (up to 7) of the strobe heads ( 5 of them without modelling lamops).

 

If you want to power continuosly all your 7 x 150 Watts modelling lamps, then you may need a bigger inverter, and that would be model PM-1200L with continuous power of 1200 Watts (1000 for 7 modelling lamps, plus spare power for the 7 strobe heads). This unit has 3600 watts surge power, and will be more than you need for the P2000D Norman Strobe.

 

I really did use successfully a 500 Watts inverter with single 1800 WattSeconds monolight and single modelling light of 150 Watts. Recommendations to provide an inverter supplying 60 Amps of current (at the output level 110 Volts) are simply expression of ignorance.

Show me how I have been ignorant, Frank, with physics, not bullshit opinion?

 

If you can't, you are the ignorant one.

I think the guy from Norman is smokin' something. His statement of <i>The inverter will have to be able to put out more than 20 amps.</i> means that it cannot be used in any normal household outlet without blowing the breaker.<p>

 

Do yourself a favor and just spend the 5 minutes to get it tested.

Shiver,

Take it easy, you are not ignorant, we all do fantasize, sometimes...

 

You presented 2 equasions:

1. - Energy = 1/2 x Capacitance x Square (Voltage); Power = Current X Voltage.

2. - [2 x Energy x Square (Current)]/Capacitance = Square Power.

 

yet you could not figure what to do with them ?

 

and found them totally useless in providing usable advice,

 

then you resorted to a "RULE of THUMB" and "common wisdom", and came up with a 60 Amps, why not 100 Amps ?

Thank you, Frank. I know that given enough rope you will soon hang yourself.

 

So, you cannot prove that I am ignorant and think that by muddying the waters, you can get away with it. Not only cannot you not prove that I am ignorant, you also prove that even with equations biting you in the ass, you still cannot figure it all out. In short, it is you who don't know what you are looking at and what to do with the equations.

 

The equations relate Power to Energy which in your assertion are qualities which are not related. I proved your ignorance beyond belief. I dragged out the equations to prove that you do not know what you are talking about.

 

And if your reading comprehension is up to scratch, I have said in my posting UNLESS YOU KNOW THE CHARACTERISTICS OF THE CAPACITORS AND DESIGN OF THE PACK, these equations do NOT describe the RECHARGING behaviour of a flash pack which is another kettle of fish.

 

Rules of Thumb are guidelines which have been tested and known to work SAFELY out in the field by those who practise their trade everyday. If you do not have the requisite knowledge of the equipment at hand, you fall back on Rules of Thumb. Engineers do it all the time as do scientists and professionals. It is conventional wisdom and common sense guidelines which are tried, tested and work SAFELY.

 

The 3X times Rule of Thumb came about because manufacturers of these packs know that capacitors from different capacitor makers come in a wide range of tolerance with different charging characteristics.

 

The ignorant are the ones who would tell you to do it because it worked for the ignorant and thus it should work for you.

 

So, tell me, Frank, where is your scientific proof that I am ignorant. You talk a good game but where is your proof?

 

As expected, you have NO PROOF. You are not only not as smart as you believe, you are actually a pretty dim bulb. So stop pretending that you know better than those manufacturers who design the equipment and dispensing advice. You, more intelligent than that Norman tech? Don't make your children blush.

 

In lieu of a scientific proof that I am ignorant, you are proof positive that you are just a dim wit blowhard.

I had to type that hastily as I had to meet a client. Upon re-reading it, I found that I had stooped to ad hominem attacks against Frank Skomial which were unnecessary and regrettable.

 

Frank asked why 60amps and not 100amps? That is because in studying the characteristics of most capacitors used in the construction of flash packs or generators (as they're commonly called in Europe), if the flash is rated for a 20amp continuous or RMS draw, 60amps i.e. would provide sufficient headroom for the recharging surge or ramp characteristic of the caps. You can provide 100amps and all the power to you for providing headroom in excess of what is required. Nobody is saying you cannot do that but it is more than necessary.

 

There is another factor which I had neglected to mention and that is Power Factor. In a purely reistive load, 1W = 1VA. However, in a reactive load like a flash pack where there are capacitors and resistors and possibly inductors, phase shift occurs. And where there is phase shift, there is a change in power factor. For example, 1W = 0.7 VA or 1W = 0.259VA, depending on the reactive load of the flash pack. That is where the Rule of Thumb comes in (and I was not smart enough to invent this rule of thumb): use a 3X VA rating of your pack if you do not know its design characteristics. Thus, if it draws 3 amps RMS, use a power supply that can swing 9amps.

 

Vince, an inverter is of really quite a different creature from the mains power supply. I don't think you should imply that the Norman tech was on some hallucinogenic substance until you find out more about the difference between inverters and the mains. An inverter converts DC to AC. For example, for a 600W continuous rating inverter (with a 1200W surge rating) running off a 12V battery supply, the iverter makes 60amps draw at 12V DC, and 120amps draw at peak surge power of 1200w at 12V DC. And we have not even gone into the gauge of wire required to handle this draw.

 

I apologise to Tom Hanser who asked this question; I think he is even more confused now. I have not helped him any but I had hoped to steer him away from erroneous though well-meaning advice put out by a few. Internet discussions have a tendency to degenerate and I have contributed to it, regrettably.

 

All this is more involved than I would want to get into. As I said from the beginning, we are photographers, not flash engineers, and I defer to the knowledge of the people who designed these things. For the here and now, The Rule of Thumb is conventional wisdom which works SAFELY.

Listen Guys, i'm glad to see everyone discussing such a valuable topic. I appreciate that you all have an opinion- and that all the information is based on a hint of knowledge and experience.

 

The only thing you all lack is a common agreement on a single effective solution. Until now.

 

Monday morning I read all the posts in the hope I could become enlightened.

 

Today I will share my solution with you all - as I spent yesterday building a mighty black suitcase with the power of the gods and the bite of a hungry lion.

 

It's a power supply from hell - with firepower to eclipse those field battery operated strobe kits you pay through the nose for.

 

Enter Jaycar electronics.

 

With the help of JayCar in Sydney - I took along my most power-hungry BronColor strobes and proceeded to churn through box after box of "high" powered inverter, testing each one on the store bench.

 

I found the following in my quest:

 

1: A PURE SINE wave inverter is much more equipment friendly than anything else and wont blow up your strobe

.

2: A 1500Watt inverter with 3000Watt surge abilty - thats what you'll need.

 

3: The JayCar model is a BEAST. 24 Volts is produced by a 'in-series' joining of two 12Volt GEL batteries of about 60 Amp hour rating.

 

These provide 24 Volts to the Inverter, whilst being able to disconnect and re-connect in parallel for recharging by car or normal 12v power supply.

 

When fully charged, this unit (which fits into a large black and silver hard-case, has passed my load test > Hairdryer+ 3 bron color studio strobes + bar fridge all at once on full load startup cycle.

 

It didn't miss a tick and the recycle time for full-burst is under one second even with all appliances on.

 

Now thats a real life fact without the bickering over watts and amps etc.

 

My complete kit including the giant batteries, cables and inverter, oh and the case to hold everything in, came to AUD $700.00

 

And it will last forever and power a small village if ever required.

 

Hope it helps ;)

 

If anyone wants specs or pics of the beast please email me.

 

raffael

The inverter that I used is only to charge camera, not studio. If you are going to power a studio with inverter, you can choose a high watt inverter, like 1000w. 300w power inverter is enough to meet my requirement. The cheapest inverter that I have bought is bestek power inverter, you can get it on bestekmall.

Did you notice the original posting date of this thread? Or is this just an ad for an online shop?

 

And - sheesh! Did nobody contributing to this thread think to look at what current the fuse in the Norman pack was rated at? That would be the obvious way to find the maximum power needed, surely.

Edited April 19, 2017 by rodeo_joe|1

Ellis, I like the caller from farm country that called Dr. Laura to comment on how people learn. He said some guys can learn from others, some from books and some, well, they just have to pee on that

electric fence themselves.

The flash unit should have a label which cites the voltage and amperage needed for its power supply. The inverter would have to meet that requirement at a minimum. Sometimes there is a specification for the peak or surge requirement, which would have to be compatible with the source. Most line service is rated at 120-240 VAC and 15 or 20 A.

 

Industrial service usually runs between 20 and 50 amps, requiring larger wires and special receptacles. Heavy equipment runs at 450 to 600 volts, and must be hard wired to the device with a disconnect. I've never seen a flash unit like that.

 

The power emitted by the flash unit is measured in joules (watt-seconds), and is expended in a fraction of a second, typically about 1/1000 for a studio flash. That energy is spread over a much longer time to recharge the capacitors, typically a second or two up to about 10 seconds. The flash unit can't draw any more power than the lines or inverter can produce. As long as the inverter can supply the sustained power, it can probably handle the peak demand, simply extending the amount of time to recharge the flash.

 

There is an inverter inside every flash subject to the same limitations. This inverter converts the line voltage to 600 VDC. The flash is triggered by an impulse which generates about 10,000 volts to initiate the arc in the flash tube. The energy required for the trigger is relatively low.

There is an inverter inside every flash....

"There is an inverter inside every flash"

- Not quite true.

 

All battery operated flashes, such as speedlights, need to use an inverter to boost their battery voltage to the 330 volts or so necessary to drive a flashtube.

However, a flash driven by 240 volt ac mains only needs a rectifier circuit since the peak voltage of a 240 v ac sinewave is 336 volts.

 

110 or 120 volt ac mains power can be boosted using a circuit called a "Cockcroft multiplier" or a simple transformer, and again needs no complicated and inefficient inverter circuitry.

 

Almost no modern flash uses a voltage as high as 600 on its storage capacitor(s). Only 330 volts or so is necessary to make efficient use of a Xenon discharge tube. It's difficult and expensive to make a compact electrolytic capacitor with a thick enough dielectric to withstand much more than 400 volts. Therefore keeping the voltage below this level makes sense in both economic and safety terms.