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will this gen work?


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#1 john spader

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Posted 15 October 2014 - 09:16 AM

we're in major budget-cutting mode, so we found this gen for like only $300 for the whole week from somebody.

http://www.amazon.co.../ref=pd_sxp_f_i

 

will it comfortably push?:

 

(4) 1000w par cans

(2) 300 Arri fresnel

(2) 600 Arri fresnel

(5) 40w table lamps

(1) Lowell DP 1000W
(2) Lowell Tota 750W

 

 

I know the wattage of the gen is above the wattage of our lights, but I guess I'm asking about the technical side of things

I'm slowly (but surely) learning about amps, line loss, current, etc.

 

I AM OPEN to ALL THOUGHTS about this scenario, the gen, and if you have a better recommendation?

 

 


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#2 Adrian Sierkowski

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Posted 15 October 2014 - 12:34 PM

It should be fine. It will be very very very loud, so you'll need it pretty far away; but you're all tungsten there on your lighting.

My only concern would be flicker but that's only if you're shooting off speed.

The only problem i could see it that it seems to only have 3 20A circuits out in edison (normal household), so you'd need to get some twistlock to edison adapters to tap the full genny output.
 


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#3 john spader

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Posted 15 October 2014 - 12:53 PM

adrian, thanks for your thoughts. would you be able to give me a couple links to which adapters I would need for this gen?

 

Can you describe for me WHY this would flicker? what makes a gen flicker or not flicker?

 

lastly, do you have a better gen recommendation that would be FREE of worrying about flicker?


Edited by john spader, 15 October 2014 - 12:54 PM.

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#4 Adrian Sierkowski

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Posted 15 October 2014 - 01:47 PM

I wouldn't worry about flicker, honestly, I just can't tell if that genny is crystal sync or not. But for 24/25fps @ 180 degrees it really shouldn't be a problem.
You'd need some of these more than likely:

 

http://www.fplogisti...--rpd---482.htm

 

 

Honda makes the best putt putts 'round really; but they tend to cost more.

 

Unless you're shooting 100FPS or something like that, I really wouldn't worry too much. I've used jankier gennys than that without issue.


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#5 john spader

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Posted 15 October 2014 - 02:43 PM

last question--if we go with this unit...by putting it far away so it doesn't affect sound recording, how far can we be running each stinger

before we will start worrying about too much power loss?


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#6 Adrian Sierkowski

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Posted 15 October 2014 - 02:53 PM

The depends on the gauge of cable you run from it and the temperature and the voltage out of the genny.

 

http://www.ehow.com/...-line-loss.html

 

That will give you the proper math. Remember, aside from issues with cables heating up, the primary issue with line loss for tungsten units is they dim-- as though on a dimmer. So, that being the case, for most reasonable runs of power with say 14 or 12 gauge line, you really will only be dealing with a slight color temperature drop.


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#7 Adrian Sierkowski

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Posted 15 October 2014 - 02:55 PM

Or this:

 

http://www.csgnetwor...gedropcalc.html


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#8 Edward Lawrence Conley III

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Posted 15 October 2014 - 03:16 PM

You are really going to be pretty far from that generator.. 74 decibel rating


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#9 john spader

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Posted 15 October 2014 - 03:21 PM

ok.

well, based on our lighting list from first post...whats a better option for a gen that will not only handle it all, but

be at a tolerable db level where we wouldnt have to run as far??

 

thanks for all your thoughts.


Edited by john spader, 15 October 2014 - 03:24 PM.

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#10 john spader

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Posted 15 October 2014 - 04:37 PM

seems like (2) Honda 6500's might be the best way to go. not very loud and by having 2, we can be covered in power.

and they're only $120/day.

 

thoughts?


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#11 Guy Holt

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Posted 15 October 2014 - 05:54 PM



seems like (2) Honda 6500's might be the best way to go. not very loud and by having 2, we can be covered in power.

and they're only $120/day.

 

thoughts?

 

Whether you pick up generator noise or not comes down to how you use the generator as much as which generator you use.  It is possible to record location audio without picking up generator noise if you use them with a transformer. To record sound without picking up generator noise you need a real distro system that will allow you to move the generator  off set (like you would a Crawford),   minimize line loss over a long cable run, and provide plug-in pockets conveniently close to set.  That is where the transformer comes in.

 

 

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.

 

 

To record sync sound without picking up any generator noise, all you need to do is add 200' - 300' of  heavy duty 250V twist-lock extension cable between the generator and a Transformer/Distro. This 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 long cable runs to the generator and minimizes line-loss;  as well as, eliminates the voltage drop you would have using standard electrical cords.

 

 

HD_PP_Demo_Distro.jpg

 60A GPC (Bates) Splitters and Woodhead Box.

 

 

To assure full line level (120V) on set, use a Transformer/Distro designed to compensate for the slight line loss you will have over an extended cable run. Use one designed to slightly boost the voltage on the load side (secondary) so that if you were to  feed the supply side (primary)  of the transformer  240 volts from the generator, 127 volts would come out on the secondary side where you plug in the lights. This slight boost enables you to place the generator further from set where you won't hear it, yet assure that the supply voltage on set does not drop too low. 

 

 

HD_PP_Demo_P2L.jpg

 60A Woodhead Box running Power-to-Light PFC 800W ballast (left) and PFC 1200W ballast (right.)

 

 

Using Honda EU6500s will certainly help. The Honda EU6500is inverter generator to begin with is much quieter than other generators. Part of what makes the new Honda EU6500is so quiet is it's "Eco-Throttle."  The Eco-Throttle's microprocessor 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 EU6500is substantially quieter than conventional generators and it can be modified to generate 7500W.

 

 

12K_Paralleling_Sm.jpg

 Two paralleled Honda EU6500s powering a 12k HMI Par.

 

 

For more details on the use of transformers with the Honda EU6500is for set power,  and even how to parallel two of them for 100A output, I suggest you read the article I wrote for our company newsletter on the use of portable generators in motion picture production. Use this link - www.screenlightandgrip.com/html/emailnewsletter_generators.html for more information about using inverter generators with transformers for motion picture lighting.

 

Guy Holt, Gaffer,

ScreenLight & Grip ,

Lighting Rental & Sales in Boston


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#12 Edward Lawrence Conley III

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Posted 16 October 2014 - 12:00 PM

seems like (2) Honda 6500's might be the best way to go. not very loud and by having 2, we can be covered in power.

and they're only $120/day.

 

thoughts?

Where are you located?


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#13 Guy Holt

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Posted 21 October 2014 - 12:14 PM

 for most reasonable runs of power with say 14 or 12 gauge line, you really will only be dealing with a slight color temperature drop.

 

The effect of line loss on tungsten lights can be more dramatic than a slight color temperature drop because their output falls off exponentially as voltage decreases. For example a 1k lamp operating at 90% rated voltage (108V) produces about 68% of its normal light output - your 1kw lamp is now a 650W lamp. In the case of fluorescents, HMIs, and LEDs, because their power supplies are typically of a “constant power” type, they will draw more current as the line voltage decreases in order to maintain constant power to the lamp. In the case of generator output, voltage loss translates into an exponential loss in power. That is because, if you double the ampere load on the cable, the voltage drop also doubles, but the power loss increases fourfold. What this means is that when a distribution system has a voltage drop, the performance of the generator (its maximum effective load) is reduced. For these reasons it is worthwhile understanding the dynamics of line loss and how to mitigate it. For more detailed information about the effect of line loss and how to correct it, see my white paper on the use of portable generators in motion picture production

 

Guy Holt, Gaffer, ScreenLight & Grip, Lighting Rental & Sales in Boston.


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#14 Guy Holt

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Posted 26 October 2014 - 11:00 AM

http://www.ehow.com/...-line-loss.html That will give you the proper math. 

 

 

While that is true in John’s present circumstances, it would not be true if he were using non-power factor corrected HMIs, Kinos, and LEDs instead of Tungsten lights. These lights will draw harmonic currents that could double the voltage drop. Voltage drop tables and calculators are for the 60Hz primary only and so do not take into account the effect of harmonic frequencies. On top of additional voltage drop,  these lights operating on a conventional AVR generator, like the one John originally proposed, would cause voltage  “flat topping.”

 

Paralleling_Copy_Non-PFC_1.2kHMI_Single_

 

Let’s look at the voltage drop component first. As you can see in the power quality meter reading above of a non-power factor corrected 1200W HMI it  draws a distorted current waveform that is rich in harmonics. The higher harmonic frequencies create what is known as "skin effect" in the cable. Skin effect is a phenomenon where the higher frequencies cause the electrons to flow toward the outer sides of a conductor. Since the flow of the electrons is no longer evenly distributed across the cross sectional diameter of the conductor, more electrons are flowing through less copper and the resistance of the conductor increases. The increase in resistance reduces the ability of the conductor to carry current, resulting in greater voltage drop over shorter distances and overheating of the conductor.

 

skin_effect.jpg

The area of the cross sectional diameter of a conductor used by DC current (left), Low Frequency AC Current (center), High Frequency AC Currents (right).

 

The graphs below illustrates the difference of varying harmonic numbers on both Proximity Effect and Skin Effect for 12 AWG and 4/0 cable (the cable spacing used to obtain the Proximity Effect values is based on National Electric Code (NEC) insulation type THHN.) Comparing the graphs, it is immediately apparent that Skin Effect is more significant in the smaller cable, than the large cable. Within the range of the triplen harmonics alone (i.e. 3rd, 9th, 15th), Skin Effect increases by 60%. 


 

Skin_Effect_12Awg.jpg

 

Which means that the increase in voltage drop due to harmonics is appreciably more significant in the jacketed multi-conductor cables (10/2 or 12/3) commonly used with small portable generators, than with the larger gauge feeder cables (single conductor #2, 2/O, & 4/O) used to distribute power from tow plants. The increase in resistance due to Skin Effect reduces the ability of stingers (12/3 cable) to carry current, resulting in overheating of the conductors and greater voltage drop over shorter distances than with larger feeder cables.

 

Skin_Effect_4Ought.jpg

 

Increased voltage drop from harmonics is not the only problem you face when running non-power factor corrected HMIs, Kinos, & LEDs on conventional AVR generators. The other problem is voltage “Flat Topping” caused by the high impedance of the generator.

 

waveform_com_grid-AVR.jpg

Left: Non-pfc SMPSs powered by grid power. Right: Same Non-pfc SMPSs powered by conventional AVR Generator (Honda EX5500) Note different effect that the same non-linear load harmonics have on grid power and power from conventional AVR generator.

 

The oscilloscope shot above right shows the voltage flat topping caused by a non-pfc 1200W HMI ballast on a conventional AVR generator (a Honda EX5500.) What causes this flat-topped voltage? According to Ohm’s Law current reacts with impedance to cause voltage drop.  Since electronic ballasts consume current only at the peak of the voltage waveform, voltage drop due to system impedance occurs only at the peak of the voltage waveform. The zig-zag saw tooth pattern in the right oscilloscope above suggests the flat topping of the voltage waveform we see here is caused not only by the 60hz fundamental but also by the harmonic currents drawn by the non-pfc SMPSs at higher frequencies that also create voltage drops as they encounter the system impedance  of both the cable and generator. For example, when encountering the high impedance of a conventional AVR generator, a 3rd harmonic current will produce a voltage drop at a 3rd harmonic voltage. Likewise a 5th harmonic current will produce a voltage drop at a 5th harmonic voltage, etc. Each harmonic current drawn by a non-pfc load flows through the system impedance resulting in a voltage drop at that harmonic frequency. In other words, where a distorted current waveform is made up of the fundamental plus one or more harmonic currents, each of these currents flowing into an impedance will according to Ohm’s Law, result in a voltage drop resulting in voltage harmonics appearing at the load bus and distortion of the voltage waveform. This pattern does not appear in the voltage waveform of the grid power on the left in the oscilloscope shots above because of its’ much lower impedance.  The impedance of a generator can be 5 to 100 times (depending on its’ size and design) that of a utility transformer and it will change as the load changes.

 

The first step in mitigating these problems caused by harmonic currents is to eliminate the currents. Using only power factor corrected lights will go a long way in reducing the number of harmonic currents in the power stream.

 

waveform_elec_ballast_AVR-I.jpg

 

Left: Conventional AVR Generator w/  1200W non-pfc HMI. Right: Inverter Generator w/1200W non-pfc HMI

 

A second step in mitigating the problems caused by harmonic currents on small putt-putt generators is to operate them on only inverter generators. For example, the power waveform above on the right, is the same non-pfc 1200W HMI 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 the harmonic currents it draws now encounter the relatively low impedance of an inverter generator, results in considerably less power waveform distortion - making it possible for the generator to operate a larger total load.

 

The extremely low line noise exhibited in the inverter generator power waveform above (right) creates a new math when it comes to calculating the load you can put on a portable generator. Where before you could not operate more than a couple of non-PFC 1200W HMIs on a conventional 6500W putt-putt 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 gear is Power Factor Corrected.

 

These power quality issues have vexed film electricians for years.  If you haven’t already, you might want to read an article I wrote for our company newsletter that explains the electrical engineering principles behind these issues and how to resolve them. http://www.screenlig...generators.html

 

Guy Holt, Gaffer,

ScreenLight & Grip,

www.screenlightandgrip.com


Edited by Guy Holt, 26 October 2014 - 11:02 AM.

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