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HMI and Generators


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#1 Corydon Anderson

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Posted 25 October 2012 - 11:22 PM

Has anyone had any experience with running HMIs from generators? I'm only looking to use a 575 but i'd like to know if anyone could point me in the direction of some good resources on the subject.
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#2 Guy Holt

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Posted 26 October 2012 - 05:21 PM

Has anyone had any experience with running HMIs from generators? I'm only looking to use a 575 but i'd like to know if anyone could point me in the direction of some good resources on the subject.


I recommend the just released 4th Edition of Harry Box’s “Set Lighting Technician’s Handbook.” Not a cheap book, but Harry Box has put together a free companion website called "Box Book Extras." The website includes the source material used for the handbook, articles by Harry Box published in other periodicals, related websites, a list of production oriented i-phone apps, as well as more in depth discussion of topics touched upon in the handbook.You can log onto the site at http://booksite.foca...ox/setlighting/ with the pass-code "setlighting."

- Guy Holt, Gaffer, ScreenLight & Grip, Lighting and Grip Rental in Boston
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#3 Eric Jaspers

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Posted 31 October 2012 - 05:56 PM

Has anyone had any experience with running HMIs from generators? I'm only looking to use a 575 but i'd like to know if anyone could point me in the direction of some good resources on the subject.


One of the best resources I have seen that explains in detail how to run HMIs on portable generators is Guy’s own article on the “Use of Portable Generators in Motion Picture Production” available at http://www.screenlig...generators.html. As he says in the intro “given the increasing prevalence of harmonic currents and the problems they cause, an increasingly more important feature (in generators) today is the quality of the generated power waveform and how well it interacts with today's light sources. As production gets more electronically sophisticated, a thorough understanding of the demands placed on portable generators by (non-linear) production equipment is necessary in order to generate power that is clean and reliable.” A bit challenging, the article has everything you need to know about using portable generators, including Honda’s new 10kw Digital AVR EB10000. It is well worth reading in full.

Eric Jaspers

Edited by Eric Jaspers, 31 October 2012 - 05:57 PM.

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#4 Guy Holt

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Posted 11 November 2012 - 03:40 PM

... article on the “Use of Portable Generators in Motion Picture Production” available at http://www.screenlig...generators.html. … A bit challenging, the article has everything you need to know about using portable generators, including Honda’s new 10kw Digital AVR EB10000.???


It gets a bit complicated with HMIs because it not only matters what type of HMI ballast you use, but also what type of generator you use. If the OP were using incandescent lights, he could use a home-depot type of AVR generator (AVR stands for Automatic Voltage Regulator.) However, the harmonic noise that the non-PFC electronic ballasts (both HMI & Kino) kick back into the power stream can have a severe adverse effect on the power waveform of conventional AVR generators like those available from Home Depot. The harmonic noise these light sources generate will not have nearly as bad an effect on the power supplied by an inverter generator like the Honda EU6500is.

As the middle oscilloscope shot below indicates, when you power a standard non-PFC HMI Electronic ballast from a conventional portable generator, the harmonic noise they kick back into the power stream can have a severe adverse effect on the power waveform. 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.

Posted Image
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.


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. Harmonic noise of this magnitude can also damage HD digital cinema production equipment, create ground loops, and possibly create radio frequency (RF) interference.

When your lighting package consists predominantly of non-linear light sources, like HMI, Fluorescent, & LED lights, it is essential to have Power Factor Correction circuitry (PFC) in the ballasts and to operate them on an inverter generator. The combination of improved power factor and the nearly pure power waveform (1-2 %THD) of the inverter generator creates clean stable set power (like that in the power waveform below right).

Posted Image
Left: Grid Power w/ 1.2Kw P-2-L PFC Elec. Ballast. Center: Conventional AVR Power w/ 1.2Kw P-2-L PFC Elec. Ballast. Right: Inverter Power w/ 1.2Kw P-2-L PFC Elec. Ballast.


Corydon’s best bet would be to use a 575 with PFC ballast and use an inverter generator like the Honda EU2000is. The Honda EU2000is will also generate less than half the noise of Home Depot type generators – making it easier to record clean audio tracks.

Guy Holt, Gaffer, ScreenLight & Grip, Lightng & Grip Rental and Sales in Boston
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