If you are not familiar with Power Factor Correction (PFC), it is more sophisticated ballast electronics that utilizes a RF Mains Filter to restrict the flow of harmonic currents back onto the supply service. A PFC circuit realigns voltage and current and induces a smoother power waveform at the distribution bus. As a result, the ballast uses power more efficiently with minimized return current and line noise and also reduces heat, thereby increasing their reliability.
For this reason, all major manufacturers include PFC circuitry in large HMIs (12-18kw), and offer PFC circuitry as an option on medium-sized ballasts (2.5-6kw). However, because of the added cost, weight, and complexity of PFC circuitry, manufacturers have not until recently offered PFC circuitry in HMI ballasts smaller than 2.5kw. 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. Ballast manufacturer Power-to- Light, on the other hand, is including PFC circuitry in their ballasts at the same price point as other manufacturer’s non-PFC
There are a number of 240 volt outlets in a typical house, office, or industrial plant in this country that you can also use to power 2.5 – 6kw HMIs. The most common are air conditioner outlets, dryer outlets, range outlets, outlets for large copy machines in offices, and the outlets for motorized equipment in industrial plants. Many of these household and industrial 240V receptacles use a three wire system (no neutral) because they are designed to power single phase motors or heating elements that draw a perfectly balanced load and return no current because the single phase service legs are 180 degrees out of phase and cancel each other out. Where a 4kw HMI with PFC electronic ballast, operating at 240 Volts draws roughly 18.5 Amps on each leg of a single phase 240V circuit, its’ load is well within the capacity of these circuits. Where 4kw ballasts are typically wired with a 120V 60Amp Bates Plug (Stage Pin), you will need a 120V Female Bates to 240V adapter. I keep an assortment of adapters because all these 240V receptacles use a different pin configuration. Where most magnetic 4k ballasts only operate at 120V this method is not an option with magnetic ballasts because they will draw 40Amps.
The only way to power 120V 2.5kw & 4kw HMI magnetic ballasts on wall receptacles (without a tie-in) is from 240V circuits through a 240v-to-120v step down transformer. There is a lighting rental and sales company in Dedham MA by the name of ScreenLight & Grip (www.dvxuser.com) that manufactures a 60A transformer/distro for the Honda EU6500is generators that they modify. Like it does with the enhanced 240V output of their Honda EU6500is Generator, their 60A transformer/distro will convert the 240 volts supplied by these industrial and household 240V receptacles to 120 volts in a single circuit that is the sum of the two single phase legs of 30/50 amps each. In other words, out of a “30A/240v” or a “50A/240v” circuit their transformer/distro makes a 60A/120v circuit that is capable of powering bigger 120V lights, like 2.5kw & 4kw HMIs with magnetic ballasts (even Quartz 5ks, mini brutes (5850W) or Six Light Mole Par (6000W)).
There are even benefits to be gained by powering 2.5kw & 4kw electronic ballasts (PFC or not) on 240V circuits through a 240v-to-120v step down transformer. Most 2.5/4kw electronic ballasts (like the Power Gems (PG) 425CDP, the Power-to-Light (P2L) 425LVI, and Arri 2.5/4 EB w/ALF) typically have an operating range of 90–125 & 180-250 Volts. At 120V they will draw approximately 38 Amps, so you will be able to run additional large lights (like 1.2kws) on the same circuit if, rather than plugging the 4kw PFC electronic ballast directly into the 240 receptacle (operating it at 240V) and monopolizing it, you plug it in through their 60A Full Power Transformer/Distro (operating it at 120 Volts), you will be left with 21 Amps to power additional lights on the same circuit. That’s a lot of additional power to waste by plugging the 4k directly into the 240V receptacle. And, since an electronic ballast “ramps up” gradually during the striking phase, you don’t have to leave head room as you would with a magnetic ballast. By operating the light through the Full Power Transformer/Distro you can more fully utilize the capacity of 240V circuit. For example, since the P2L 4/2.5 LVI ballast at 120V operates a 2.5k HMI luminary at 23 amps, you will still be able to power two additional 1.2kw HMIs (if operated by P2L 575/1200 ballast (11 Amps)), as well as a 800 Joker HMI (if operated by a P2L 800/1200 ballast (8 Amps)), off of the same circuit. That’s a lot of additional light to be gained by not plugging the 2.5 directly into the 240V receptacle.
- Eileen Ryan, Boston Gaffer
Thread: What is HMI Lighting?
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10-24-2009 05:56 PM
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10-24-2009 06:03 PM
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However, it is an all together different situation when plugging HMIs into a conventional portable generator. 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 non-linear loads will to be very high given its small size relative to typical lighting loads, and given the increasing prevalence of non-linear 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 ballast will result in significant waveform distortion of the voltage at the power bus.
For this reason, when your lighting package consists predominantly of non-linear light sources, like HMI and Fluorescent lights, it is important to have power factor correction (PFC) circuitry in the ballasts and operate them on inverter generators. The combination of improved power factor and the nearly pure power waveform of inverter generators makes it possible to power larger lights, or more smaller lights, than has been possible before on a small portable gas generator.
In the past, 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 power waveform below left is typical of what results from the operation of a 2.5kw non Power Factor Corrected HMI load (electronic ballasts) on a conventional portable generator. The adverse effects of the severe harmonic noise exhibited here, can take the form of overheating and failing equipment, efficiency losses, circuit breaker trips, excessive current on the neutral return, and instability of the generator’s voltage and frequency. For these reasons 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. The increasing use of personal computers, hard drives, and microprocessor-controlled recording equipment in production has created an unprecedented demand for clean, reliable power on set.
ScreenLight & Grip (SL&G) has also developed a Gen-set that takes advantage of recent technological advances in HMI ballast design and power generation to create clean stable set power that is capable of operating larger lights (HMIs up to 6kw or Quartz lights up to 6kw), or more smaller lights, off of portable gas generators than has ever been possible before. For example, the power waveform above on the right, is the same 2500W load but with power factor correction operating on SL&G’s modified Honda EU6500is Inverter Generator. As you can see, the difference between the resulting waveforms is startling. Even though the load is the same, the fact that it is power factor corrected and the power is being generated by an inverter generator, results in virtually no power waveform distortion. For this reason, sensitive electronic production equipment will operate reliably and without damage. And, the generator is capable of operating larger, or more smaller, lights than has ever been possible before on a portable gas generator.
Where before you could not operate more than a couple 1200W HMIs with non-PFC ballasts on a conventional generator because of the consequent harmonic distortion, now you can load an inverter generator to capacity. And if the generator is one of ScreenLight & Grip’s modified Honda EU6500is inverter generators, you will be able to run a continuous load of up to 7500W as long as your HMI and Kino ballasts are Power Factor Corrected. For more details on how this is accomplished I suggest you read their very informative newsletter articles on the use of portable generators in motion picture production which where I got these oscilloscope shots. Where the power issues it discusses have been vexing set electricians for years, I highly recommend that anyone responsible for generating power on a set, whether large or small, read this article. The article is available at www.dvxuser.com/html/emailnewsletter_generators.html.
As was the case with 240V wall receptacles, you have several options when it comes to operating your 2.5kw HMI off of a 6500W generator depending on the type of ballast and generator you use. Where electronic HMI ballasts are typically auto-sensing multi-volt ballasts (with an operating range of 90–125 & 180-250 Volts), you can plug it directly into the 240V 4 pin twist-lock receptacle on the generator and it will operate at 240 Volts (where 2.5 kw ballasts are typically wired with a 120V 60Amp Bates Plug (Stage Pin) you will need a 120V 60A Female Bates to 240V 4pin twist-lock adapter to plug a 4kw ballast directly into the generator. Or, if the electronic ballast is power factor corrected (draws 23 Amps) you can plug it into the 30A/120V twist-lock receptacle on the generator’s power panel. If the electronic ballast is not power factor corrected (draws 35 Amps) you will not be able to run it off of the 30A/120V twist-lock receptacle without tripping it’s fuse.
Even though a 2.5 magnetic ballast draws approximately 26 amps you will not be able to run it reliably on the 30A/120V twist-lock receptacle on the generator’s power panel. That is because 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 2.5 magnetic ballast will climb to upward of 30 Amps. To make matters worse magnetic ballasts have a high front end striking load. That is, a magnetic ballast 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 ballast “ramps up”. That is, its’ current draw gradually builds until it “tops off.” For this reason, you must always leave “head room” on the generator for the high front end striking load of magnetic ballasts. And to complicate matters even more, 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, again, suggest you read SL&G’s newsletter article.) 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 SL&G manufactures for their modified Honda EU6500is. SL&G’s 60A Full Power Transformer/Distro will step 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. As was true of 240V wall receptacles, there are benefits to be gained by powering electronic ballasts through their 60A Full Power Transformer/Distro as well.
As was the case with 240V wall receptacles, you can maximize the power you can pull from a generator if, rather then plugging the 2.5kw electronic ballast directly into the 240 receptacle and operate it at 240V, you plug it in through SL&G’s 60A Full Power Transformer/Distro and operate it at 120 Volts. This way the one light does not monopolize the whole circuit. In the case of SL&G’s modified EU6500is you would still have 37 Amps left over to power additional lights through the transformer as well if your 2.5kw ballast has Power Factor Correction. And, as I mentioned previously, if you use only HMI and Kino Flo ballasts with Power Factor Correction you can load the generator more fully.
In the past we had to de-rate portable gas generators because of the inherent short comings of conventional generators with AVR and Frequency governing systems – especially when dealing with non-linear loads. The harmonic distortion created by non-PFC ballasts reacted poorly with the distorted power waveform of conventional AVR generators, and limited the number of HMIs you could reliably power on a portable generator to 65% of their capacity. But now, that the power of inverter generators has virtually no inherent harmonic distortion (less than 2.5%), and power factor correction (PFC) is available in small HMI ballasts, this conventional wisdom regarding portable gas generators no longer holds true. An inverter generator can be loaded to capacity with PFC HMI and Kino Flo ballasts (which in the case of SL&G’s modified Honda EU6500is is 7500 Watts) and safely power sophisticated electronic equipment on the same supply.
The enhanced capacity of their modified Honda EU6500is inverter generator would be wasted if not for their 60A transformer/distro. Without the transformer/distro you could never fully utilize the full power of the generator because the load of a light would have to go on one circuit/leg of the generator or the other. For example, when plugging lights into the factory installed power outlet panel of a Honda EU6500is, you reach a point where you can't power an additional 800W Joker because there is not 8 amps (w/ a P2L PFC ballast) available on either one of the factory installed 20A outlets/leg of the generator. With their Full Power Transformer/Distro you can still add that 800 Joker because the Transformer/Distro not only accesses more power (7500 Watts) through a higher rated circuit (60 Amps), but it also splits the load evenly over the two legs (4A/leg) of the generator on that circuit. The end result is that the generator is capable of handling a larger load more easily because it is a perfectly balanced load.
Another benefit to using their Transformer/Distro is that it splits the load of what ever you plug into it automatically. Which means you no longer have to carefully balance the load over the generator's two 20A/120 circuits/legs as you plug in lights because the Transfomer/Distro does it for you. With their modified Honda EU6500is you simply plug in lights until the load wattage displayed on the generator’s iMonitor reaches 7500 Watts. An overload alarm on the iMonitor display will tell you if you inadvertently overload the Transformer/Distro. Now that you are able to fully utilize the generator's available power, you are able to power larger lights, or more smaller lights, than you could without their transformer/distro. For example, as I mentioned in other forums, I used one of SL&G’s modified Honda EU6500is Generators on a Red shoot to power a lighting package that consisted of PFC 1200, & 800 HMI Pars, a couple of Kino Flo ParaBeam 400s, a couple of ParaBeam 200s, and a Flat Head 80, in addition to a PFC 2.5kw HMI Par. Given the light sensitivity of the Red Camera, this was all the light we needed to light a large night exterior.
- Eileen Ryan, Boston Gaffer
10-24-2009 08:53 PM
Very nice posts Eileen!
You can show up anytime.
10-25-2009 11:17 AM
- Join Date
- Jan 2009
The Honda EU6500is inverter generator to begin with is much quieter than the older movie blimped Honda EX5500. Part of what makes the new Honda EU6500is so quiet is it’s “Eco-Throttle.” The Eco-Throttle’s micro-processor automatically adjusts the generator's engine speed to produce only the power needed for the applied load. It can do this because the Inverter Technology of the Honda EU6500is enables it to run at different RPMs and maintain a constant frequency and voltage. Where conventional generators like the Honda EX5500 and ES6500 have to run full speed at a constant 3600 RPM to produce stable 60 hertz (cycle) electricity, a Honda EU6500is only needs to run as fast as required to meet the load demand. Since their engines do not have to run at full speed, and given the fact that an inverter generator generates 20% more power per revolution of the engine, makes the Honda EU series of inverter generators substantially quieter than conventional models.
To make them even quieter, Honda has designed a new separate triple chamber construction and a new centralized intake/exhaust system. The net result is that the EU6500is is half as loud (ten decibels) as the comparable EM7000is and 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 your typical Crawford 1400 Amp “Movie Blimped” Generator. With sound specs this good all you need is a distro system that will enable you to remove the generator from the set to record sound without picking up generator noise. That is where our 60A Full Power Transformer/Distro comes in.
To record sync sound without picking up any generator noise, all you need to do is add 100' - 150’ of heavy duty 250V twist-lock extension cable between the generator and our Full Power Transformer/Distro which is usually enough cable to place the generator around the corner of a building, or to run it out of a van or truck - which is usually all the additional blimping you need with these generators. The heavy-duty 250V twist-lock cable eliminates multiple cable runs to the generator and the subsequent drop in voltage from line-loss from using standard electrical cords.
For more detailed information about the use of portable gas generators in motion picture production I suggest you read, as Eileen obviously has, an article I wrote on the subject for our company newletter which is available online at www.dvxuser.com/html/emailnewsletter_generators.html.
Guy Holt, Gaffer, ScreenLight & Grip, Boston
10-25-2009 11:33 AM
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- Jan 2009
To respond to Kimberli’s orignal question:
In the interest of full disclosure, I should say at the outset that in addition to being a gaffer, I also own and operate a rental house that rents and sells a lot of the equipment I will recommend in this post. If it sounds like I’m hyping certain product lines it is not because we rent and sell them exclusively. We are dealers and rental agents for all the major brands. The equipment I am about to recommend, I recommend as a professional Gaffer of a lot of historical documentaries for PBS’ American Experience and The History Channel (see my “credit-entials” on Imbd). I recommend this equipment because I think it offers greater production capability for the dollar than anything else out there at this time.
My recommendations are also based upon extensive research I have done on the use of portable gas generators in motion picture production. For this research, 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 light sources available today, including Fluorescent light fixtures.
My tests came up with some rather startling results. They 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 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 that is capable of reliably operating larger, or more smaller lights, off of portable gas generators than has ever been possible before. I have compiled the results of my tests in an article for my company newsletter and it is available on our website at:
Based upon my tests, I have come up with a package of lights that maximize the light output that can be had from a portable generator. The Kino Flo Parabeam 400 made it into this package for the following reasons.
In HD Digital Cinema, the quality of light is more critical than ever. In High Def every detail of on camera talent is rendered clearly on the screen – even the imperfections. Where traditional hard light sources like HMIs can exaggerate textural details, soft light is generally better for lighting talent in High Def productions because it can subdue those same textures and render a more cosmetic appearance. I suggest the Kino Flo Parabeam fixtures, over other fluorescent lights, because they are only fluorescent movie light fixtures that have a punch like an HMI.
What distinguishes the Parabeam fixtures from other fluorescent lights is their throw, power efficiency, and the innovative accessories Kino Flo makes available for the fixtures. Accessories include barndoors, a gel frame, a diffusion panel, and Honeycomb Louvers that act like HMI Par lenses. These features enhance the production capabilities of the Parabeam fixtures and give them the punch to serve as key or backlight sources where conventional fluorescent movie light fixtures are not.
Conventional fluorescent movie lights (Kino Flo’s included) have a very broad soft light output that is hard to control. The light also tends to drop off rapidly which means that to serve as key source, the units need to be positioned close to the subject they are lighting. These characteristics make them best suited to serve as key sources in documentary interview set ups where the keys are typically positioned close to the interview subject. In that capacity they generate a wonderful soft light that wraps around the interview subject without wilting them. But, given these characteristics, conventional fluorescent movie lights have only limited applications as fill sources in dramatic set lighting – that is until the development by Kino Flo of their ParaBeam fixtures.
The ParaBeam fixtures have computer aided designed (CAD) parabolic reflectors that focus the light output where it is needed most for lighting dramatic scenes - at a medium distance – making it an ideal key source for HD Digital Cinema. If you compare the photometric tables of the Parabeam 400 and the Diva 400 (which uses the same four lamps), you will notice that at 16’ the Parabeam 400 puts out almost three times the light level (28FC) than the Diva 400 (10FC) even though they both use the same tubes. In fact a Parabeam 400 generates as much light at 16’ as the 4’ 8-Tube Kino Flathead 80 fixture, yet uses less than a quarter of the power (2 Amps verses 9.2 Amps.) While the seven amp difference is not a major consideration when using house power, it can make a difference when your power is limited (coming from a portable generator) because you can use four Parabeam 400s for the same power as a 4’ – 8 Bank Kino Flathead 80. Kino Flo Parabeam ballasts also include filters to reduce the return of harmonic currents into the power stream and improve their power factor. The Parabeam fixtures have power factor ratings of over .9 making them an especially suitable fluorescent light for use on small portable generators.
Not only are the Parabeam fixtures more efficient, but they are also easily controlled – an essential requirement in a Key source. Parabeam fixtures are controlled by interchanging Kino Flos’ innovative Honeycomb Louvers. Louvers are available in 90, 60 and 45 degrees. Swapping louvers provides beam control similar to that of swapping lenses on an HMI Par. These features enhance the production capabilities of the Parabeam fixtures and make them suitable to serve as a key or backlight source where conventional fluorescent movie light fixtures will spill all over the set. These features make the Parabeam fixtures a good substitution for HMI lights in many situations; and, the power you save by not using tungsten instruments for keys and backlights, enables you to power more lights on the generator than you could otherwise.
Kino Flo Parabeams are not a substitute for HMis in some situations. As long as there is a sun and moon in the sky there will be a place for a large HMIs on interior and exterior sets because Kino-Flos don’t come close to balancing direct sunlight in day light scenes or covering deep background in night scenes. For powerful daylight fill on exterior sets, to create the feel of hard sunlight on interior sets, or to light deep background on night exterior sets, I would recommend that you purchase a dual wattage HMI Par like Mole's new 2.5/4kw Day-Lite Par. Not only will the Par configuration give you more output but it will also be more versatile. When you need a lot of light for fill on day exteriors you can lamp it with a 4k globe. When you don’t need the punch of a 4k Par, like on a night exterior, you can swap the 4kw globe for a 2.5kw globe giving you more power to run additional lights on a small portable generator. The 15 Amps you save by burning the smaller 2500W globe will power quite a few more lights when you consider that a Kino Flo Parabeam 400 uses only 2 Amps.
- Guy Holt, Gaffer, ScreenLight & Grip, Boston