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[Maidson Pierre Louis]

I would like to know if a 25kw Diesel Generator is power enough for a 65kw sound system:
8 x jbl vt4888
6 x Jbl vt4880
3 x crown itech 1200hd
6 x crown itech 9000hd
2 x crown itech 5000hd

Plus monitors, 2 digital consoles and accessories.

[Chris Hindle]

I would like to know if a 25kw Diesel Generator is power enough for a 65kw sound system:
8 x jbl vt4888
6 x Jbl vt4880
3 x crown itech 1200hd
6 x crown itech 9000hd
2 x crown itech 5000hd

Plus monitors, 2 digital consoles and accessories.

Full Tilt Boogie, those iTechs are going to draw pretty close to 20 KW. Add in a half dozen steam powered wedges and side fills, and you're pretty close to 25K. I like to have my Genny at around twice my expected load. In other words, get a 50K or 75K, and make sure the lampey's get their own !

[Maidson Pierre Louis]

Thx you chris for you your answer.

[Jamin Lynch]

I would like to know if a 25kw Diesel Generator is power enough for a 65kw sound system:
8 x jbl vt4888
6 x Jbl vt4880
3 x crown itech 1200hd
6 x crown itech 9000hd
2 x crown itech 5000hd

Plus monitors, 2 digital consoles and accessories.

http://www.crownaudio.com/media/wysiwyg/ITHD2/ITHD2_Power_Draw_Thermal_Dissipation.pdf

[Chris Hindle]

http://www.crownaudio.com/media/wysiwyg/ITHD2/ITHD2_Power_Draw_Thermal_Dissipation.pdf

Taking numbers from this excellent info Jamin found, the main PA is going to want around 16K at F-T-B. Add in the rest of audio world, and you're still going to be pushing that to over 20K.
Get a 50K whisperWatt, and have a trouble-free show !
20K out of a 25K Genny will work. Just not very well. You'll find that out the first time someone thumps the kick 3 or 4 times in a row. Gee. How would I know that ??

[Ray Aberle]

Also keeping in mind that a 25kW WhisperWatt is running through a 60A main breaker; the 45kW through a 110A breaker. So, you don't have that full 25kW available from a 25kW generator. (The manual goes into this in depth.) 1Ø/120-240 is available either through the lugs or the twist locks; 3Ø is available only through the lugs. So if you're spider boxing it (hopefully not!) you might encounter issues.

For that rig, run the 45kW-50kW model and be done with it. And what Chris said about lighting and video...

[RYAN LOUDMUSIC JENKINS]

A 25kVa MQ Power generator is really only a 20KW Generator.  The 45kVa is a 36KW generator.

[Guy Holt]

20K out of a 25K Genny will work. Just not very well. You'll find that out the first time someone thumps the kick 3 or 4 times in a row.

Curious why that is the case.  What is the rationale?

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com

[TJ (Tom) Cornish]

Curious why that is the case.  What is the rationale?

Guy Holt, Gaffer
ScreenLight & Grip
www.screenlightandgrip.com

I believe Chris is referring to the dynamic nature of power amp loads where in a given situation the average load would be less than the generator's capacity, however the instantaneous load could be significantly more.  There is some rotational inertia in the generator that can provide some burst capacity for the first kick drum hit or two, but that can be depleted with repeated hits , causing loss of voltage or frequency, or possibly stalling the generator.

[Robert Piascik]

And the difference in cost between renting a 25kW vs  45KW is so small there is no reason not to get the larger capacity. I would get even larger 70kW(?) myself.

[Guy Holt]

I believe Chris is referring to the dynamic nature of power amp loads where in a given situation the average load would be less than the generator's capacity, however the instantaneous load could be significantly more.  There is some rotational inertia in the generator that can provide some burst capacity for the first kick drum hit or two, but that can be depleted with repeated hits , causing loss of voltage or frequency, or possibly stalling the generator.

Thanks for the clarification.  I was wondering if it wasn’t for the same reason film electrics de-rate generators by 50% when supplying non-linear lighting loads like some HMIs, Fluorescent, and LED Fixtures. Where it appears that you guys use a lot of gear operating on Switch Mode Power Supplies (SMPSs), you might be interested in the graph below  from a Caterpillar Technical Service bulletin on sizing gen-sets. It is a  “Limit Characteristic” graph that illustrates the effects that non-linear loads have on generators. The fluctuations in the Engine Stability line in the illustration below represent the generator’s operating limits depending on whether its load has a leading or lagging Power Factor. As you can see by the right quadrant the effect of harmonics on a generator is a significant limiting factor.

A Limit Characteristic graph for a generator illustrates the effect of leading
or lagging Power Factor on the generator's output.

What the Limit Characteristic graph above tells us is that, operating a capacitive load (the leading power factor quadrant right of the Unity Power Factor center line), an AVR generator like the Mulitquips first reach a thermal limit as a consequence of heat generation in the generator's rotor from harmonic currents. And, since increasing harmonic content leads to a tendency toward erroneous self-excitation (SE), the generator output is inevitably affected by instability of the Excitation circuit from higher leading power factor loads. Finally, since there comes a point as the Power Factor of the load decreases, when harmonics inhibit the successful operation of the generator’s Automatic Voltage Regulator all together, and hence the generator’s capacity to generate any power at all, the kW output eventually drops to zero. This Limit Characteristic graph also tells us that operating an inductive load with lagging Power Factor (the left quadrant of the Limit Characteristic graph) the generator’s output is more stable; but will eventually be limited by both the rotor (field) and stator (armature) heating (many times the field temperature limit is lower than the armature limit, especially at low power factor values.)

These same power quality issues have vexed film electricians for years, which is why most movie gaffers still oversize their generators by 100%.  For more details see an article I wrote for our company newsletter that explains the electrical engineering principles behind these issues and how to resolve them. The newsletter article is available at http://www.screenlightandgrip.com/html/emailnewsletter_generators.html.

Guy Holt, Gaffer,
ScreenLight & Grip,
www.screenlightandgrip.com

[Lyle Williams]

Add metering to your rig that captures peak and average power draw.  Then you will know, rather than guess.

[ProSoundWeb Community]