Generator question. . . will any generator do for HMIs and Kinos?

[Stephen Pruitt]

Hi all. . .

I was just about to push the button on a purchase of a Kipor IG6000 inverter generator when I spoke to an engineer friend of mine who wondered why on earth I was buying such a "stable" power source.

I'll be using this generator for electronically-ballasted HMIs (2.5K and 1.2K), Kinos, and, occasionally, halogen lightining.

His point was that since electronically-ballasted HMIs already have their own converting power supplies, they should be almost invariant to deviations from pure sine waves from the supply source. Further, since inverter generators are much more expensive than non-inverter generators, I could either get more power for my money (always good) or buy a cheaper generator of the same wattage (also always good).

Can anyone give me a good reason why I really do need an inverter (or crystal-synched) generator for running movie lights? First-hand experiences are preferred in this case over hearsay.

I mean, if it is just a matter of "it would be better" or "in a perfect world," than real, practical impact, I'd rather save the money. In my case, if I can't see the difference, I sure as heck don't want to pay the difference.

Thanks much.

Stephen

 

[Nick Gardner]

Well, if you are going to buy a generator, then a crystal controlled one is a must. HMI's, computers, anything complicated that you intend to run off the generator will be much happier. Many battery chargers go apeshit when they don't have clean power.

I must say that unless you are shooting more than 30 days or so, it would be way better to rent.

Cheers,

Nick

 

[Jonathan Stevenson]

Crystal synced means that no matter what, the power coming out of the generator remains constant. A standard generator engine will not always output a consistent amount of power, meaning your HMI's could start flickering, dimming, or if there was a sudden spike in power, you could fry your bulbs, chargers, whatever. So basically, crystal synced is just a safer power source for your equipment. Think of it like filling a glass with water from a faucet vs. pouring the water out of a spout by hand. Sure, you can pour with a steady hand, but it wont be totally perfect.

That said, I have shot several night shoots where we used HMI's and regular ole' gennys and we never had a problem. But who knows, I'm sure there's many people here that can attest to NOT using a standard genny.

 

[Rob van Gelder]

I do not know the Kipor generators but expect them to be similar to the Honda 6500 inverter generators that we have at the company. They are for sure a better alternative to regular generators, they are quieter, more economic and lighter. But more expensive, yes.
If you are into buying generators for the electronic equipment that you intent to use, I would go for the electronic version (inverter), if you are doing mainly tungsten or rough machine/motors, normal generators will do fine.
They will do the electronic stuff too, as long as it is decent controlled, but with more inconvenience like noise and weight.

 

[Rob van Gelder]

Oh, make sure they have good sturdy wheels and carrying handles or you will hate yourself for your decision.....

 

[Colin Sheldon]

I'll be using this generator for electronically-ballasted HMIs (2.5K and 1.2K), Kinos, and, occasionally, halogen lightining.

One nice thing about that style of generator is that they tend to be quieter then their non-inverter cousins.

And if the generator isn't running at exactly 60Hz, you run the risk of getting HMI flicker.

 

[Richard Andrewski]

Definitely crystal sync generators all the way for ballast oriented lighting.

 

[Stephen Pruitt]

Okay, so my engineering buddy is nuts? He is positive that ANY generator will work so long as I'm using an electronic ballast. He was equally positive that I'd need an inverter (or crystal-synched) generator on magnetic ballasts.

I'd rather not waste money here. . .

Thanks much.

Stephen

 

[Dominic Jones]

Well, perhaps he simply doesn't understand the optical requirements that lie beyond simply getting light out of a head...

A light "working" can be a slightly subjective term - for an engineer, a light could be said to work if it outputs light, even if that light is not at a precise frequency. For a cinematographer, it would not be said to work if it output light at an odd (or variable) frequency that introduced flicker or colour shift.

So it could just be an issue of semantics.

For the record, I have had some issues with electronic ballast HMIs on regular gennys, although for the most part they do work fine...

 

[Barry Gregg]

Stephen;
I have used a Honda, voltage regulated, generator with a 1.2k HMI with no trouble. This was rented from a standard tool rental shop, not a cine rental house. I was shooting stills so I don't know if flicker would have been a problem, but the lamp fired and worked fine.

Test, test, test.

 

[Stephen Pruitt]

Hey Dominic. . . what issues did you have using electronic ballasts with a standard put-put genny?

I'd really like to buy this generator:

http://cgi.ebay.com/PowerMax-Portab...ryZ46412QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Instead of this one:

http://www.kipor.com/prouducts_detail.asp?info_id=189

Why? Two thousands watts more power. . . and less than 1/2 the price. BUT, I sure as heck don't want to buy something that won't work.

Thanks much.

Stephen

 

[Colin Sheldon]

Or you could go for the cheaper generator, and then get something like this:

http://www.kato-eng.com/voltreg.html

 

[Rob van Gelder]

Okay, so my engineering buddy is nuts? He is positive that ANY generator will work so long as I'm using an electronic ballast. He was equally positive that I'd need an inverter (or crystal-synched) generator on magnetic ballasts.

I'd rather not waste money here. . .

Thanks much.

Stephen

Stephen, as said before, ANY generator with a good AVR and quartz control will do, as long as it has enough power to handle the starts of your HMI lamps without lowering the voltage too much.
But:
The new generation of inverter generators will throttle down when you have only a small load, saving on fuel and reducing noise. Only when you need more than approx. half of their rated load, they will run faster. The electronic inverter will keep the voltage and frequency constant, whatever the rpm of the engine and this is the main difference from the normal generators.
Your buddy is not wrong, but just not really taking everything into account, imho.

 

[Dominic Jones]

As Rob says, it's the constant output (or rather, lack of it) that can cause problems - the issues I've had have been when running gennys closer to max output than is ideal and striking lights - you get a spike in the power load when you strike, and this tends to cause a dip in output on standard gennys, which can cause other lamps already running to cut out. Also, when he power comes back up to full whack again, it's possible to get a hot-strike and bugger a bubble or two...

It's not too much of an issue if you're running your genny under 60% or so load, but over that it can be an problem - I should say, however, it's rare I've had these issues, except on the odd low-budget short when running everything more heavily than one should (which let's face it, happens from time to time).

Hope that helps,
Dom.

 

[Bret Weeks]

Okay, so my engineering buddy is nuts? He is positive that ANY generator will work so long as I'm using an electronic ballast.

He's mostly right, for HMI anyway.... Kino-flo however I'd have to test-

Depending on the electronic ballast, a combination of circuits inside the ballast, as well as power factor corrected electronic ballasts will compensate for nominally Hz challenged generators.

57-63Hz in a 60Hz environment should be within the window of better electronics. Out of that range, however-

We've seen electronic ballasts from Powergems, LTM & Power-to-Light function well in situations where only small Honda generators will work-

We use them for our 1200's up to 4K Pars- anything bigger and we move up to tow plants.

After having owned quite a few small generators, I can tell you that it makes real sense to spend the extra couple of hundred on a readily serviceable brand, not that I'm a Honda commercial, but....

 

[Vince Arvidson]

I can confirm that magnetic ballasts and non-invertor genies will flicker!

No surprise there, but we were in the middle of no where without a budget. It's what we had to work with so that's what we did. Now its up to post to fix the flicker.

Vince

 

[Eileen Ryan]

There is a popular misconception that you should only use electronic ballasts with portable generators. Where that is true with conventional generators without crystal governors, it is not true of inverter generators for the reasons already discussed here.

The biggest reason to spend the extra money for an inverter generator, I think, is that it enables you to use the less expensive to buy or rent magnetic HMI ballasts. Besides the extra bulk and weight of magnetic ballasts, the smaller magnetic ballasts (575-2500W) also offer the distinct advantage of drawing less power (once they have come up to speed) than the commonly available electronic equivalents; and magnetic ballasts are absolutely flicker free operating on an inverter generator. Operating at 120V, a 1.2kw HMI with non-power factor corrected electronic ballast will draw 18-19 amps verses the 13.5 amps of a magnetic ballast. The less power that a light draws, the more lights you will be able to use on a generator. For example, a Kino Flo Parabeam 400 draws only 2 amps, that 4 Amp difference between using a magnetic 1200W ballast and a standard 1200W electronic ballasts, can mean the difference of running two Parabeam 400s on a portable generat or not.

The downside to magnetic ballasts is when you have little head room - i.e. striking an HMI with other lights already running on the generator

As Rob says, it's the constant output (or rather, lack of it) that can cause problems - the issues I've had have been when running gennys closer to max output than is ideal and striking lights - you get a spike in the power load when you strike, and this tends to cause a dip in output on standard gennys, which can cause other lamps already running to cut out. Also, when he power comes back up to full whack again, it's possible to get a hot-strike and bugger a bubble or two...

Dom.

The reason for the nightmare scenario Dom describes is that magnetic ballasts draw more current during the striking phase and then they “settle down” and require less power to maintain the HMI Arc. By contrast, an electronic ballast “ramps up.” That is, its’ current draw gradually builds until it “tops off” - but it “tops off” with a considerably greater draw than a magnetic ballast “settles down” to.

The key to using magnetic ballasts on inverter generators is to use a transformer to power them through the generator’s 240V receptacle.
A step down transformer will give you access to the full power of the generator in a much larger 120V circuit that is capable of powering larger lights. The nearly 60A 120V circuit created by using a transformer on a 6500W generator provides enough head room to accommodate not only the front end striking load of 2500W 120V magnetic ballasts, but also 4000W 120V magnetic ballasts as well. And, by splitting the large front end striking load of 2.5/4kw HMIs evenly over the two legs of the 240V circuit of the generator, the transformer reduces the impact on the generator when you first switch on the light. The same holds true when you switch on large tungsten lights like 6000W Molepar Six Lights or 5ks.

A transformer will enable you to power not only larger lights, but also more smaller lights than you can power off the generator’s 120V receptacles alone. For example, I recently worked on an independent short, shot on the Red, where we used a step down transformer on a Honda EU6500is to power a lighting package that consisted of a 2.5kw, 1200, & 800 HMI Pars, a couple of Kino Flo Parabeam 400s, a couple of Parabeam 200s, and a Flat Head 80. Given the light sensitivity of the Red Camera, this was all the light we needed to light a large night exterior (go to www.screenlightandgrip.com/html/hdfilmstrip4lg.html for details on this production.)

I also don’t want to sound like a Honda commercial, but I would recommend the Honda inverter generators because their "Eco Throttle" feature makes them much quieter than conventional portable generators. The “Eco-Throttle” automatically adjusts the generator's engine speed to produce only the power needed for the application in use. Traditional generators have to run at a constant 3600 RPM to generate the frequency stable power reqiured to shoot with HMI magnetic ballasts without flicker. The Inverter Technology of the Honda Inverter Generators enable them to run at much slower RPMs while maintaining frequency and power for the requested load. Because the engine does not have to run at full speed constantly, the engine is much quieter. Honda's inverter generators are substantially quieter than traditional models.

By utilizing a new separate triple chamber construction, a new centralized intake/exhaust system and the new Eco-Throttle design, the EU6500is achieves a noise reduction of ten decibels and is half as loud as the comparable ES6500 generators typically found at lighting rental houses. Honda's EU Series generators operate at 34 to 44 dBA at 50 ft. - well below what is required for trouble free location recording and quieter than Crawford “Movie Blimped” Generators.


Eileen Ryan, New England Gaffer

 

[Eileen Ryan]

Generator question...will any generator do for HMIs and Kinos

Generator question...will any generator do for HMIs and Kinos

Hi all. . .
Can anyone give me a good reason why I really do need an inverter (or crystal-synched) generator for running movie lights? Thanks much.

Stephen

A gaffer/rental house owner/operator I work with in Boston by the name
of Guy Holt has just compiled what is probably the best argument for
spending the extra money to buy an inverter generator. In a recent
article in his company news letter, he undertakes a comprehensive
survey of the prevalent lighting and portable power generation
equipment. Describes how he systematically tested how well they work
together and has made the results available online.

To paraphrase what he found, harmonic distortion of set power is an
increasing problem in production. It is becoming an issue because
portable generators were not designed for the abundance of non-linear
loads, like the electronic HMI and Fluorescent lighting, that make up
lighting packages today. The problem is being further compounded by
the increasing prevalence on set of sophisticated electronic
production equipment like computers, hard drives and HD monitors which
require clean power, but are themselves sources of harmonic
distortion.

The power waveform below left is from his article and is typical of
what results from the operation of a couple of 1200W HMIs with
non-power factor corrected ballasts on a conventional portable
generator (the very combination Stephen Pruitt is contemplating here).
The adverse effects of the harmonic noise exhibited here, can take
the form of overheating and failing equipment, circuit breaker
trips, excessive current on the neutral wire, and instability of
the generator’s voltage and frequency. It is for these reasons, he
argues, that it has never been possible to reliably operate more than
a couple of 1200W HMIs on a conventional 6500W portable gas
generator. Harmonic noise of this magnitude can also damage HD
digital cinema production equipment, create ground loops, and
possibly create radio frequency (RF) interference.

In the past, attention was given to generator features such as
automatic voltage regulation and speed regulation. But, given the rise
in production problems associated with harmonic noise, an increasingly
more important feature today is the quality of the generated power
waveform and how well it interacts with today's light sources.

For that reason, he did a series of tests which shows that when your
lighting package consists predominantly of non-linear light sources,
like HMI and Fluorescent lights, it is essential to have PFC circuitry
in the ballasts and to operate them on an inverter generator. The
combination of improved power factor and the nearly pure power
waveform of the inverter generator creates clean stable set power
(like that in the power waveform above right of the same 1200 heads
w/PFC ballasts) that is capable of reliably operating larger lights (HMIs
up to 6kw or Quartz lights up to 5kw), or more smaller lights, off
of portable gas generators than has ever been possible before.

For example, as I mentioned in my previous post, I used one of their
modified Honda EU6500is Generators on a Red shoot to power a lighting
package that consisted of a 2.5kw, 1200, & 800 HMI Pars, a couple of
Kino Flo ParaBeam 400s, a couple of ParaBeam 200s, and a Flat Head 80.
Given the light sensitivity of the Red Camera, this was all the light
we needed to light a large night exterior.

I highly recommend that anyone responsible for generating power on a
set read his article. While the lighting package he has developed is
new (introduced Jan 09), the set power issues it addresses have been
vexing electricians for years. The article explains the electrical
engineering principles behind these issues, and how his lighting
package resolves them, in a way I have not seen elsewhere. The
article is posted on their website at:

http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

Eileen Ryan, New England Gaffer​

 

[Greg M]

The cheaper Genny will cause flicker...so while your engineer friend is correct in the sense that the cheaper unit will work, that's with the caveat that you may encounter flicker. If this purchase is primarily for production use then stick with inverter unit.

 

[Eileen Ryan]

The cheaper Genny will cause flicker...so while your engineer friend is correct in the sense that the cheaper unit will work, that's with the caveat that you may encounter flicker.

Where Stephen's HMIs have electronic square wave ballasts, his engineer friend was totally correct that flicker will not be a problem. His point was that since electronically-ballasted HMIs already have their own converting power supplies, they will be invariant to deviations in AC frequency (Hz) from the supply source.

I'll be using this generator for electronically-ballasted HMIs (2.5K and 1.2K), Kinos, and, occasionally, halogen lightining.

The point that I tried to make previosly is that even though flicker will not be a problem, if the ballasts are non power factor corrected (PFC), he will have other problems. The primary factors limiting the use of HMIs on portable generators has been their inefficient use of power and the harmonic noise they throw back into the power stream. The only way to avoid these problems with non-PFC electronic ballasts and conventional generators is to de-rate the generator by a factor of 3 to 1. For instance do not try to run more than a 1200W HMI on a 3500W generator of this type.

While the generator does not need automatic voltage regulation and speed regulation when using electronic square wave HMI ballasts, given the problems associated with the harmonic noise these ballasts generate, a more important feature these days is the quality of the generated power waveform and how well it interacts with your light sources. The improved power factor of the Power to Light 575-1200 ballast, the newer Kino fixtures like the ParaBeams and VistaBeam, and the nearly pure power waveform of a inverter generator creates clean stable set power that is capable of reliably operating larger lights (HMIs up to 6kw or Quartz lights up to 5kw), or more smaller lights, off of portable gas generators than has ever been possible before.

That is, where the harmonic distortion created by non-PFC ballasts reacting poorly with the distorted power waveform of conventional AVR generators, limited the number of HMIs you could use to a third the generators capacity. An inverter generator can be loaded to capacity with PFC HMI and the new Kino Flo ballasts because the near-linear nature of the load and the extremely low harmonic distortion (less than 2.5%) of the original AC power waveform of inverter generators results in virtually no distortion of the power waveform. That is the real reason to spring for an inverter generator.

- Eileen Ryan, New England Gaffer