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HMI light sources and TIPS.

Hello all, i am new to the forums. My Name is Fernando Weberich and i am from Brazil (living in TEXAS).

In Brazil we don't find information about HMI lights and portable power sources, so i came here to ask you folks, about how to build a HMI lighting set for Photography and video, with 4 light sources (or more), all the cables, bulbs, ballasts and other accessories, as well as portable power source (generator or others).
(The less expensive, the better).

For Internal shooting and even some external, we have 110-127v (60hz) and 220-240v (60hz), but on some locations we have no power source, so the Generator would do the job.

I would like to understand more about HMI light sources and how to use it properly, and would definetelly like to participate in a COURSE or WORKSHOP in United States or Canada, or even a particular COURSE (if someone is interested). The purpose is to learn about how to use HMI lights and acessories to achieve the results desired for still and video, indoors and outdoors. We'll be using SLR cameras and other HD cameras for this.

Thank you all, and have a great year!
 
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.. i came here to ask you folks, about how to build a HMI lighting set for Photography and video, with 4 light sources (or more), all the cables, bulbs, ballasts and other accessories, as well as portable power source (generator or others)...I would like to understand more about HMI light sources and how to use it properly....The purpose is to learn about how to use HMI lights and acessories to achieve the results desired for still and video, indoors and outdoors.

I am a gaffer and rental house owner/operator. For my company news letter I have written an article on the use of portable gas generators in motion picture production. As part of my research for the article, I ran a series of tests in order to analyze the interaction of conventional AVR generators (a Honda EX5500 with Crystal Governor), as well as inverter generators (a Honda EU6500is), with the prevalent HMI and Kino light sources available today. The results of my tests are going to be cited in the upcoming 4th edition of the “Set Lighting Technician’s Handbook.” My article is available online at:
http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

To quickly summarize what I discovered, distortion of set power by the harmonic currents that fluorescent and HMI electronic ballasts dump back into the power stream is an increasing problem in HD production. It is increasingly an issue because portable generators were not designed for the abundance of non-linear loads, like 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.

Normally, when you plug a fluorescent or HMI light into a wall outlet you need not be concerned about the current harmonics generated producing voltage distortions. The impedance of the electrical path from the power plant is so low, the distortion of the original voltage waveform so small (1-3%), and the plant capacity so large, that inherently noisy loads like HMI and fluorescent ballasts placed upon it will not affect the voltage at the load bus.

waveform_pkg_comp_AVR_In.jpg

Left: Conventional generator power w/ pkg. of non-PFC Elec. HMI Ballasts & Kino Flo Wall-o-Lite. Right: Inverter generator power w/ Pkg. of PFC Elec. Ballasts & Kino Flo Parabeam 400.

However, my research has shown that it is an all together different situation when plugging HMIs into conventional portable generators. Given the large sub-transient impedance of conventional portable generators, even a small degree of harmonic noise being fed back into the power stream will result in a large amount of distortion in its’ voltage. Add to that, the likely hood that the percentage of the generator’s capacity taken up by electronic HMI & Kino ballasts will to be very high given its small size relative to typical lighting packages, and given the increasing prevalence of these types of light sources in production. Finally, add that the original supply voltage waveform of a conventional generator is appreciably distorted to begin with, and you have a situation where the return of any harmonic currents by an HMI or fluorescent ballast will result in significant waveform distortion of the voltage at the power bus.

HD_PP_DemoCU.jpg

Two Shot of Night exterior scene

The power waveform above left is from my article and is typical of what results from the operation of a couple of Kino Flo 4x4s and a couple of 1200W HMIs with non-power factor corrected ballasts on a conventional portable generator. 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, it has never been possible to reliably operate more than a couple of 1200W HMIs with electronic ballasts on a conventional 6500W portable gas generator.

HD_PP_DemoWS.jpg

Wide Shot of Night exterior scene lit with a pkg. consisting of PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 .

In the past, when portable generators were used in motion picture lighting, attention was paid to such features as automatic voltage regulation and crystal 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 the lighting units predominantly used today.

HD_PP_Demo_SetUp_Night.jpg

PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 powered by a modified Honda EU6500is through a 60A Full Power Transformer/Distro

My tests also show that when your lighting package consists predominantly of non-linear light sources, like HMI and Fluorescent lights, it is essential to have Power Factor Correction (PFC) circuitry in your fluorescent and HMI ballasts and to operate them on an inverter generator. As the power waveform above right of the same HMI and Kino Flo lights but with PFC ballasts indicates, the combination of improved power factor and the nearly pure power waveform of the 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. For example, on a recent Red shoot (the production stills attached) we used the 7500W continuous load capacity of our modified Honda EU6500is Generator to power a lighting package that consisted of a 2.5kw, 1200, & 800 HMI Pars (w/PFC ballasts), 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.

HD_PP_Demo_Transformer-Distro.jpg

A Distro System consisting of a 60A Full Power Transformer/Distro, 2-60A GPC (Bates) Splitters, 2-60A Woodhead Box distributes power from a modified Honda EU6500is. Even though the generator is 100' away to reduce noise, plug-in points remain conveniently close to set.

I highly recommend that anyone responsible for the generation of power on a set read this article. While the lighting package I have developed as a result of my tests, maximizes the number of instruments that can be run on a portable gas generator, is new; the set power issues caused by non-PFC fluorescent and HMI ballasts have been vexing electricians for years. The article explains the electrical engineering principles behind these issues, and how my lighting package (detailed elsewhere in this forum at http://www.indietalk.com/showthread.php?t=20218 ) resolves them.

Guy Holt, Gaffer, Boston
 
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In Brazil we don't find information about HMI lights and portable power sources, so i came here to ask you folks, about how to build a HMI lighting set for Photography and video, with 4 light sources (or more), all the cables, bulbs, ballasts and other accessories, as well as portable power source (generator or others).(The less expensive, the better).

Fernando Weberich said:
We're thinking about what HMI's we will need. We were planning to get 2-2500watts and 2-1200 watts…. What do you think? Used HMIs… would be awesome.

In order to maximize the number of lights you can run on the generator it is important to use an inverter generator and HMI ballasts with Power Factor Correction. As for what HMI fixtures to get, check out my post at http://www.indietalk.com/showthread.php?t=20218. I would suggest you get at least one combination 4/2.5kw HMI Par so that you have a bigger light, that you can still run off the generator, for daylight fill.

It is going to be very hard to find Power Factor Correction in used HMIs. While it is true that all major manufacturers include PFC circuitry in HMI ballasts in the 6-18kw range - they do so by necessity. Because of the added cost, weight, and complexity of PFC circuitry, ballast manufacturers in the US have offered PFC circuitry only as an option in medium-sized 2.5-4kw ballasts. And, until very recently manufacturers did not offer PFC circuitry in HMI ballasts smaller than 2.5kw in the US (in the EU PFC circuitry in mandatory in all HMI ballasts sold.) Except for one notable exception, when manufacturers do offer PFC circuitry in smaller ballasts it is at a premium, adding as much as a $1000 to the cost of a 1200W ballast for instance. The new ballast manufacturer Power-2-Light, on the other hand, is including PFC circuitry in their ballasts at the same price point as other manufacturer’s non-PFC ballasts. But where Power-2- Light is still very new to the market, it is still the case that almost every 575 - 1200 W electronic ballast that you will find in North America will be a non-PFC.

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 like the Honda EU series. Magnetic ballasts will operate reliably on the Honda EU series generators because Honda's sine-wave inverter technology provides much higher quality power than conventional (non-inverter) generators. With a waveform distortion factor of less than 2.5%, the power generated by Honda’s EU series of generators is quite often better than what you get out of the wall outlet. The power these machines generate is rock solid with a frequency variance of only hundredths of a cycle - which eliminates the need for costly crystal governors. The Honda EU series generators provide true sine wave power with low enough distortion, and frequency stability, to power HMI's with magnetic ballasts without problems. As long as you shoot at one of the many safe frame rates, magnetic ballasts are also “flicker free” (where the topic of safe frame rates for magnetic ballasts is discussed extensively elsewhere in this forum I won’t get into it here.) Besides the extra bulk and weight of magnetic ballasts, the smaller magnetic ballasts (575-2500W) offer the distinct advantage of being less expensive and drawing less power (once they have come up to speed) than the commonly available non-PFC electronic equivalents. So if you don’t have access to the newest PFC electronic ballasts, you are better served by using the older magnetic ballasts on an inverter generator like the Honda EU 6500is over non-PFC electronic ballasts. I know this is contrary to the conventional wisdom, so I will quickly summarize why.

When electronic square wave HMI ballasts came on the market, they were at first thought to be the solution to all the problems inherent in running HMI lights on small portable generators. By eliminating the flicker problem associated with magnetic ballasts, they also eliminated the need for the expensive and ultimately unreliable AC governors required for flicker free filming with magnetic HMI ballasts and portable gas generators. Electronic square wave ballasts eliminate the potential for flicker by squaring off the curves of the AC sine wave supplying the globe. Squared off, the changeover period between cycles is so brief that the light no longer pulsates but is virtually continuous. Even if the AC Frequency of the power were to vary, a frame of film or video scan, would receive the same exposure because the light intensity is now not pulsating but nearly constant. Electronic square wave HMI ballasts allow you to film at any frame rate and even at a changing frame rate.

Since they are not frequency dependent, it was thought at first that electronic square wave ballasts would operate HMI more reliably on small portable generators – even those without frequency governors. For this reason, as soon as electronic square wave ballasts appeared on the market, many lighting rental houses replaced the more expensive crystal governed portable generators with less expensive non-synchronous portable generators. The theory was that an electronic square wave ballast would operate reliably on a non governed generator and allow filming at any frame rate, where as a magnetic HMI ballast operating on an unreliably AC governed generator allowed filming only at permitted frame rates.

In practice, electronic square wave ballasts turned out to be a mixed blessing. Part of the problem with operating electronic HMI ballasts on portable gas generators in the past has to do with the purity of the power waveform they generate. With an applied voltage waveform distortion of upwards of 19.5%, conventional generators do not interact well with the leading power factor (current leads voltage) of the capacitive reactance created by electronic square wave HMI ballasts. The net result is harmonic currents are thrown back into the power stream, which results in a further degradation of the voltage waveform and ultimately to equipment failure or damage.

The oscilloscope shots of the power waveforms below is from an article I wrote for our company newsletter and is typical of what results from the operation of a 1200W HMI with non-power factor corrected ballast on grid power (left), on a conventional generator (middle), and inverter generator (right.) The adverse effects of the harmonic noise generated by non-PFC electronic ballasts and exhibited here in the middle shot, 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. Harmonic noise of this magnitude can also damage HD digital cinema production equipment, create ground loops, and possibly create radio frequency (RF) interference.

wwaveform_elec_ballast.jpg

Left: Grid Power w/ 1.2Kw Arri non-PFC Elec. Ballast. Center: Conventional AVR Power w/ 1.2Kw Arri non-PFC Elec. Ballast. Right: Inverter Power w/ 1.2Kw Arri non-PFC Elec. Ballast.

As is evident in the oscilloscope shots below of a 1200W magnetic HMI ballasts on grid power, on power generated by a conventional Generator (Honda EX5500), and power generated by an inverter generator (Honda EU6500is), the lagging power factor caused by the inductive reactance of magnetic ballasts has by comparison only a moderately adverse effect on the power waveform. Outside of causing a voltage spike in the inverter power, magnetic ballasts actually show a positive effect on the already distorted power waveform of the Honda EX5500 conventional generator.

wwaveform_mag_ballast.jpg

Left: Grid Power w/ 1.2Kw Arri Magnetic Ballast. Center: Conventional AVR Power w/ 1.2Kw Arri Magnetic Ballast. Right: Inverter Power w/ 1.2Kw Arri Magnetic Ballast.

These oscilloscope shots confirm that if you don’t have access to the newest PFC electronic ballasts, the older magnetic ballasts are in fact cleaner running on portable gas generators than non-PFC electronic ballasts. And, where inverter generators like the Honda EU6500is do not require crystal governors to run at precisely 60Hz, you can operate magnetic HMI ballasts reliably on them. In addition, the smaller magnetic ballasts (575-2500W) offer the distinct advantage of being less expensive and draw less power (once they have come up to speed) than the commonly available non-PFC electronic equivalents (13.5A versus 19A for a 1.2kw.)

Of course there are downsides to using magnetic ballasts. One down side is that you are restricted to using only the safe frame rates and shutter angles. But when you consider that every film made before the early 1990s was made this way, you realize it is not such a limitation. Another downside to magnetic ballasts is that you can’t load the generator to full capacity because you must leave “head room” for their higher front end striking load. When choosing HMIs to run off portable generators, bear in mind that a magnetic ballasts draws more current during the striking phase and then they “settle down” and require less power to maintain the HMI Arc. By contrast, an electronic ballasts “ramps up”. That is, its’ current draw gradually builds until it “tops off.”

For example, even though a 2.5kw magnetic ballast draws approximately 26 amps you will not be able to run it reliably on the 30A/120V twist-lock receptacle on a 6500W generator’s power panel. As mentioned above, magnetic ballasts have a high front end striking load. For this reason, you must always leave “head room” on the generator for the strike. But, even though the twist-lock receptacle is rated for 30 Amps conventional 6500W generators are only capable of sustaining a peak load of 27.5 Amps per leg for a short period of time. Their continuous load capacity (more than 30 minutes) is 23 Amps per leg. And if there is any line loss from a long cable run the draw of a 2.5kw magnetic ballast will climb to upward of 30 Amps. To make matters worse, the lagging power factor caused by the inductive reactance of the magnetic ballast kicking harmonic currents back into the power stream causes spikes in the supply voltage that can cause erratic tripping of the breakers on the generator or ballast. For a more detailed explanation of why that is I suggest you read my newsletter article. The article is available at www.screenlightandgrip.com/html/emailnewsletter_generators.html. In my experience the load of a 2.5kw magnetic ballast is too near the operating threshold of a 6500W generator for it to operate reliably.

The only sure way to power a 120V 2.5kw (or even a 4kw) HMI magnetic ballast on a portable gas generator is from its 240V circuit through a 240v-to-120v step down transformer like the one we manufacture for our modified Honda EU6500is. Our 60A Full Power Transformer/Distro steps down the 240V output of the generator to a single 60A 120V circuit that is capable of accommodating the high front end striking load, and even the voltage spikes, of either a 2.5kw or 4kw magnetic ballast at 120V. 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. And since, magnetic HMI ballasts will operate flicker free at all standard frame rates on an inverter generator (without the need for a crystal governor), our 60A Full Power Transformer/Distro gives new production life to older 2.5kw & 4kw HMIs with 120V magnetic ballasts. It provides an affordable way of powering more affordable HMIs.

Guy Holt, Gaffer, Boston
 
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