Whether you can reliably operate a 4k HMI on a portable gas generator is a complicated question because it really depends on the type of 4k ballast you are using and whether the generator is a conventional generator with crystal governor or an inverter generator. Broadly speaking, HMI ballasts now come in two varieties. They are magnetic ballasts and electronic square wave ballasts, also called flicker free ballasts. Electronic square wave ballasts also come in two varieties - those with and those without Power Factor Correction (PFC) (Arri calls it ALF for Active Line Filter

There is a popular misconception that you should not use magnetic ballasts with portable generators. Where that is true with conventional generators without crystal governors, it is not true of inverter generators like our modified Honda EU6500is mentioned above. 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 EU6500 generator is quite often better than what you get out of the wall outlet. By using an extremely fast microprocessor to switch IGBTs according to a Pulse Width Modulation (PWM) control logic, 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. Our modified Honda EU6500is generator provides true sine wave power with low enough distortion, and frequency stability, to power 4k HMIs with magnetic or non-PFC electronic ballasts without problems.

But, since most 4k magnetic ballast operate at 120V and draw 40 Amps, you will not be able to run a 4k magnetic ballast off of the 30A/120V twist-lock receptacle on the generator without tripping it's fuse. The only way to power a 120V 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 to provide access to the enhanced 7500W output of our modified Honda EU6500is. Our 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 a 4kw magnetic ballast operating at 120V.

You will not be able to run a 4k non-PFC electronic ballast reliably on a conventional (non-inverter) 6500W generator even though it draws only 26 amps/leg at 240V. 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 non-PFC 4k electronic ballast will climb even higher. To make matters worse non-PFC electronic ballasts kick a lot of harmonic currents back into the power stream that can cause severe voltage waveform distortion in conventional generators. This harmonic distortion 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 an article I wrote for our company newsletter on the use of portable generators in motion picture production which is going to be cited in the upcoming 4th edition of "The Set Technician's Handbook" - the article is available at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html

In my experience the load of a 4kw non-PFC HMI ballast is too near the operating threshold of 6500W generator for it to operate reliably on conventional (non-inverter) models. That is because the harmonic noise that non-PFC ballasts kick back into the power stream has an adverse effect on the power waveform of conventional generators where it does not on Inverter Generators. Normally, when you plug an HMI light into a wall outlet you need not be concerned about current harmonic distortion 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 placed upon it will not affect the voltage at the load bus.

However, it is an all together different situation when plugging non PFC ballasts ( HMI or Kino) 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 by a non-PFC electronic ballast will result in a large amount of distortion in its' voltage. 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 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 reliably power larger lights, like 4ks, on a small portable gas generator.

In the past, the primary factors limiting the use of HMIs on conventional portable generators has been their inefficient use of power and the harmonic noise they throw back into the power stream. The power waveform above left is typical of what results from the operation of a 2.5kw non-PFC 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.

Left: Conventional generator power w/ 2500W load of non-PFC Elec. HMI & Kino Flo Ballasts. Right: Inverter generator power w/ 2500W load of PFC Elec. HMI & Kino Flo Ballasts
Our HD Plug-n-Play Gen-set that is designed to take advantage of recent introduction of Power Factor Correction to HMIs smaller than 6kw and Honda's introduction of the inverter EU6500is 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. What we do is tap the Honda EU6500is inverter generator as it is designed for 240V markets like the UK, EU, Australia, & India (to name just a few.) By doing so, we gain access to the full 7650 Watt power capacity designed into the generator for 240V markets, but not available in generators manufactured for 120V Markets like North America. We then use our proprietary step-down transformer/distro to convert the full 240V power into a single 60A/120V circuit (7500Watts) capable of power large lights.

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 powered by a modified Honda EU6500is
Finally, where inverter generators generate a nearly pure power waveform, our modified Honda EU6500is is capable of reliably powering even large HMI lights, like 4ks. For example, the power waveform above on the right, is the same 2500W load but with a Power Factor corrected ballast operating on our 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.

The PFC 2.5 & 1.2 HMI Pars, PFC 800w Joker HMI, Kino Flo Flat Head 80, 2 ParaBeam 400s, and a ParaBeam 200 of our HD P&P Pkg. powered by our modified Honda EU6500is through our 60A Full Power Transformer/Distro
The substantial reduction in line noise that results from using PFC ballasts on the nearly pure power waveform of an inverter generator creates a new math when it comes to calculating the load you can put on a portable gas generator. In the past we had to de-rate portable generators because of the inherent short comings of conventional generators when dealing with non-PFC electronic ballasts. The harmonic distortion created by non-PFC ballasts reacting poorly with the distorted power waveform of conventional generators limited the number of HMIs you could power on a portable generator to 60% of their rated capacity (4200Watts on a 6500W Generator). But now, where inverter generators have virtually no inherent harmonic distortion or sub-transient impedance and power factor correction (PFC) is available in small HMI ballasts , this conventional wisdom regarding portable gas generators no longer holds true. 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 our 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. According to the new math of low line noise, you can load an inverter generator to 100% capacity.

A 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
According to this new math, when you add up the incremental savings in power to be gained by using only PFC HMI ballasts, add to it energy efficient sources like the Kino Flo Parabeam & Tegra fixtures, and combine it with the pure waveform of inverter generators, you can run more HMI lights on a portable gas generator than has been possible before. For example, the 7500W capacity of our modified Honda EU6500is Inverter Generator can power a lighting package that consists of a PFC 2.5kw HMI Par, PFC 1200, & 800 HMI Pars, a couple of Kino Flo ParaBeam 400s, a couple of ParaBeam 200s, and a couple of Tegra 400s. Given the light sensitivity of HD cameras, this is pretty much all the light you will need to light both the foreground and deep background of night exteriors. For more details on how this is accomplished I suggest you read the article I wrote for our company newsletter (mentioned above) on the use of portable generators in motion picture production.

For this reason, I would recommend you use a 6500W Inverter Generator, like the Honda EU6500is, and a multi-volt electronic ballast with Power Factor Correction (PFC) like the Power-2-Light 4k PFC 425LVI Electronic Ballast in our HD Plug-n-Play Pkg. This combination will be the most reliable and will give you the most options. If you are not familiar with Power Factor Correction (PFC), 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. A multi-volt 4kw electronic ballast with PFC (like the the Power-2-Light (P2L) 425LV) will typically draw 38 Amps on a 120V power supply, so they are well within the operating capacity of a 6500W generator with our Full Power Transformer/Distros.

Don't forget that our 60A Full Power Transformer/Distro offers the same benefits when accessing more power on location from common 240v household outlets (use this linik for details.) Adapters are available that will enable you to plug our Transformer/Distro into common 240V sources found on interior locations - including Range Plugs, Dryer Plugs, and special receptacles installed for Window Air Conditioners. By giving you access to more "house power" through common 240V household outlets, our 60A Full Power Transformer/Distro can eliminate the need for dangerous tie-ins or expensive tow generators.

Left: Arri AS18 1800W Par powered from Transformer/Distro.
Right: 4Kw and 1800W HMI ballasts powered from Transformer/Distro.
To maximize the number of lights that you can operate on our new Gen-set or a Dryer/Range plug, contact us for competitive pricing on the latest motion picture lighting equipment by Arri, Mole-Richardson, & Kino Flo that make up our HD Plug & Play Pkg. If you let us know what additional equipment you want, we will work up a more detailed quote. Financing is available for orders of more than $5000.00. Please inquire for details.

We are confident that you will be more than satisfied with the performance of our HD Plug & Play Pkg.. Harry Box, author of the authoritative trade handbook "Set Lighting Technician's Handbook" has endorsed our HD Plug & Play Gen-set in the just released 4th Edition of the handbook. In addition, he has established a link from the companion website for the 4th Edition of the Handbook, called "Box Book Extras" , to our company news letter article on "Portable Generators in Motion Picture Production" (I have attached a copy of the link.) Of the article he exclaims:

"Great work!... this is the kind of thing I think very few technician's ever get to see,
and as a result many people have absolutely no idea why things stop working."

"Following the prescriptions contained in this article enables the operation of bigger lights, or more smaller lights,
on portable generators than has ever been possible before."

What earned Harry's endorsement is that our HD Plug & Play Gen-set is the first portable "movie blimped" generator/distro system to offer 7500W of power in a Single 120V circuit capable of, as Harry puts it, "powering bigger lights, or more small lights, on a portable generator than has ever been possible before." For example, our modified Honda EU6500is inverter generator with 60A Full Power Transformer/Distro is capable of simultaneously powering a 4kw & 1200w Pars of our HD P&P Pkg. - which is sufficient to get good production values on bright day exteriors.

Our modified Honda EU6500is with our Transformer/Distro can power
the PFC 2.5 & 1.8 HMI Pars, PFC 400w Lighthouse HMI,
2 ParaBeam 400, 2 ParaBeam 200s, and 2 Tegra 400s of our HD P&P Pkg.
If you were to swap out the 4k globe for a 2.5K globe our gen-set is capable of powering the 2.5kw, 1800w, 400w Pars of our HD P&P Pkg., plus a couple of Kino Flo Parabeam 400s, Parabeam 200s, and Tegra 400s. Given the light sensitivity of HD Cameras, this constitutes a complete interior daylight or exterior night location lighting package for HD Digital Cinema productions.

Please let me know if you need any further information.

Guy Holt
ScreenLight & Grip
rentals@screenlightandgrip.com
Office: 781-326-5088
Cell: 617-224-8534