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PA off electric Generator, Inverter Required?

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Will standard generators destroy expensive PA gear leaving only pure sine wave inverter generators safe to use, OR is it ok to use a large 3,600 rpm generator?

 

There are times when I need to run PA off generators for a DJ setup. Some older and experienced djs mentioned that the only type of generator to use is a "pure sine wave inverter generator" and say that other generators will destroy equipment if used long enough. Other djs with long experience do not seem to be worried about that issue. I read that power conditioners simply do not address this power issue. I look through the net and find conflicting information. Some things seem to indicate that if the engine speed is 3,600 rpm the power should be fine, while others say that an inductive load (which requires more power at times and less at others, typical of dynamic music) really needs a good inverter generator to maintain sine wave power. It seems that with normal generators voltage and frequency can change and this can damage capacitors (and perhaps other components). Some things say that motors will vary in speed and any variance affects the electricity generated. Does anyone here have experience or knowledge in this field. Pure sine wave inverter generators are much, much more expensive than regular generators. What are your thoughts?

Thanks!

 

http://www.solarlink.de/PDF-Files/Sterling/generatorbenzin.pdf

 

http://www.hondapowerequipment.com/products/generators/content.aspx?asset=gg_inverteradvantage

 

http://bellsouthpwp.net/j/o/johngd/files/rv/inverter_generator.pdf

 

http://en.allexperts.com/q/Electronics-3923/2009/1/Inverter-vs-non-inverter.htm

 

http://www.arrl.org/files/qst-binaries/QS0608Kleinschmidt.pdf

 

http://www.angelfire.com/planet/als_space/ham/Generators.pdf

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I also saw the following statements around:

"All models of two bearing generators MUST operate at 3600 R.P.M. If the generator speed os less than 3600 R.P.M., the voltage and frequency (hertz) will be lower than required and if the generator operates above 3600 R.P.M., the voltage and frequency (hertz) will be higher than required. Either condition will cause damage to the items being operated by the generator and also to the generator. Generator shaft speed below 3400 R.P.M. and above 3800 R.P.M. will cause damage to items and the generator. "

 

[this is +/- 5% flux and I see some generators spec at 5%]

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Generators

In many countries without fully developed electrical power distribution systems, the use of generators is common. Generator supplies can be very good, however, in many places they are not, and can cause damage to sensitive equipment if it is connected. The voltage, frequency, and waveform shape (it should be a smooth sine-wave) can vary. In some places, people modify generators to run faster. This gives more voltage and power but increases the frequency too. The part of a generator that keeps it running at a constant speed is called the governor. If this is tampered with, the output voltage could rise sufficiently to cause damage. The best advice is not to connect valuable equipment to the supply, or at the very least disconnect it as soon as it is finished with.

 

If you are unsure about the quality of generator in use, there are a few simple rules. If it runs from petrol/gasoline it is bad - anyone serious about using generator power uses a diesel oil powered system. A good quality generator will have a low engine speed. 1500RPM for 50Hz or 1800RPM for 60Hz. If the engine speed is 3000RPM+, it is not a good machine.

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What a bunch of cock and bull information.

 

1. the RPM is a function of the number of poles on the generator. 2 pole is 3600 RMP, 4 pole is 1800 RPM, 8 pole is 900 RPM etc.

 

2. All generators are "pure sine wave". That's how a generator works. Period.

 

3. Inverter generators (generally, though marketingspeak can alter the real meanings of words) refers to the exciter supply and how the voltage regulation is handled.

 

4. There are good gasoline/petrol generators, They are not going to be "cheap".

 

5. There are bad diesel generators (not all that many though).

 

6. All generators should be operated with a ghost or dummy load of around 2% of their rated load or 200 watts, whichever is greater. This improves the voltage regulation under light inductive loads.

 

7. For large dynamic loads (audio and stahge lighting can fall into this catagory), it's common to derate the generator's capacity by 50%. This improves dynamic performance of the generator system.

 

8. Proper maintenance is essential with all generators.

 

Inverters (DC-AC) do come in sine wave, modified sine wave or square wave flavors. Sine wave inverters are PWM type, and are the best to use for audio provided they are of sufficient quality and you have sufficient battery capacity. Most are not.

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Thank you. The information I was finding was very confusing to me. What I probably need to get then is a standard generator of about double the wattage of the amps/electronics I will use on it.

 

Do you think a regulator such as the Furman AR1215 AC Line Voltage Regulator is necessary http://www.zzounds.com/item--FURAR1215 ? I normally run a Furman with the led voltmeter and the meter has proved useful, but I don't know if a regulator for each amp would be necessary.

 

Thanks again.

 

OK, I read one of your posts about not using amps on a regulator, so I guess that answers that question. : )

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Thank you. The information I was finding was very confusing to me. What I probably need to get then is a standard generator of about double the wattage of the amps/electronics I will use on it.


Do you think a regulator such as the Furman AR1215 AC Line Voltage Regulator is necessary
http://www.zzounds.com/item--FURAR1215
? I normally run a Furman with the led voltmeter and the meter has proved useful, but I don't know if a regulator for each amp would be necessary.


Thanks again.

 

I wouldn't recommend this. First and foremost, you shouldn't need one. If the venue power is that bad, don't play.

 

A *good* regulator will cost a lot more than the Furhman you show as an example. It should be noted that regulators will correct voltage but at the expense (nothing's free) of current. Power (watts) is a constant. In the case of a regulator that can use a typical 15a wall plug, if supply voltage drops to 95 volts, the available current is less than 12 amps. In other words, you always need more current capacity in order to compensate for lower voltage. If the venue service is crappy, this becomes a cascading problem...as voltage drops a regulator draws more current to compensate, and this larger load reduces voltage further.

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I had been thinking of using the regulator to cover voltage changes when using a generator outdoors, but using a generator that would supply twice the watts of the amps and equipment used, so there should be extra power to compensate.

 

The Furman I normally use at venues is an inexpensive conditioner that basically serves as a group of plugs with a led voltmeter and lights for the rack. I use a probe tester of the outlet before plugging anything in and if a lot of power is needed, I will plug into a separate circuit (have a tester for this too to be sure it is a separate circuit) for the sub amp. I also bring a box with four plugs on each side with each side on with separate 15A breakers and the outlet goes to a 20A connector which also has a 15A adapter.

 

Haven't bought a regulator or generator yet and am looking through as much info as I can find to try to understand how they work so I don't burn anything upallgone and I can understand how to address any problems or failures. Even in the middle of Dallas/Fort Worth, we sometimes have to use generators because the venue ties all their electricity up with festival bs. We are mobile PA/DJ.

 

To take the horseman out of context, I read in a current "power conditioner" thread:

"Power amps should never be on a voltage regulator unless there is a very specific and well defined fault and correcting for it won't cause a much bigger fault.

 

I will never use a voltage regulating device without understanding exactly how it works so that I can analyze the entire system under dynamic conditions for possible failure modes (soft white underbelly)."

 

Looking at the manual specs for the amps, I see no listed tolerance for flucuations in voltage or frequency on the power supply...

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A voltage regulator could cause the generator to hunt. Bad end result.

 

Amplifiers will not have this spec, it's a function of many variables and you need to understand control system stability concepts to analyze this. The electrical load varies with the dynamics of the music and so does the inlet power voltage. As the current increases the voltage decreases due to line impedance. Now as the voltage decreases the regulator increases the voltage which increases the current which increases the voltage drop and there exists the potential for positive feedback and oscillation. A fatal happening.

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From a strictly empirical standpoint (I dont' have Aged's EE background), I run Everything from a Pioneer CDJ-1000 to QSC amps off of a Somewhat standard 6500w Honda Genny. It's not one of the inverter types. Gear works fine. I've removed all my AVR gear from my Amp racks, and only use it work more delicate stuff.

 

Todd A.

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A voltage regulator could cause the generator to hunt. Bad end result.


Amplifiers will not have this spec, it's a function of many variables and you need to understand control system stability concepts to analyze this. The electrical load varies with the dynamics of the music and so does the inlet power voltage. As the current increases the voltage decreases due to line impedance. Now as the voltage decreases the regulator increases the voltage which increases the current which increases the voltage drop and there exists the potential for positive feedback and oscillation. A fatal happening.

 

I had a flashback to a time when I asked Edward Teller a question about nuclear physics. BUT, I think I get the idea on why and it really makes good sense.

 

Some of that hip hop bass really pulls down the voltage in the middle of a song and I could see how something like this could happen.

 

Thank you very much for your time and information. We haven't gone with a generator because we wanted to understand more first as to whether we could use a regular generator or HAD TO HAVE one of those inverter types.

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Some of that hip hop bass really pulls down the voltage in the middle of a song and I could see how something like this could happen.

 

Absolutely.

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Interesting thread! We are playing a small outdoor event on Tuesday and we have a 5500 watt generator. Do you think we will have any issues using it with our gear? We are not using any lighting either.

 

Amps:

Peavey CS4000

Peavey CS2000

Peavey PV2600

Peavey PV1500

Peavey PV1500

 

Thanks!

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Interesting thread! We are playing a small outdoor event on Tuesday and we have a 5500 watt generator. Do you think we will have any issues using it with our gear? We are not using any lighting either.


Amps:

Peavey CS4000

Peavey CS2000

Peavey PV2600

Peavey PV1500

Peavey PV1500


Thanks!

 

Yes... you have too much dynamic load for the genny. Time to step up to a more commercial unit. I assume there will be some back line too?

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We also have a Honda 12000 watt generator. Could we run the backline on the 5500 watt genny and the FOH gear on the 12000 watt honda genny?

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Maybe that would work, but be sure you have a dummmy load (say 200 watts of lights) on the gennys all the time, and turn off the econo-functions.

 

Also, you should electrically connect the two generator frames together and insure that the ground-frame bonds are properly connected on each generator. Then connect the frame(s) to a properly driven ground rod.

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Maybe that would work, but be sure you have a dummmy load (say 200 watts of lights) on the gennys all the time, and turn off the econo-functions.


Also, you should electrically connect the two generator frames together and insure that the ground-frame bonds are properly connected on each generator. Then connect the frame(s) to a properly driven ground rod.

 

 

HOLY CRAP!

OK, you guys always come up with a new thread that throws me for a loop, but I had no idea about the Generator do's and don'ts.

I have an event in October, and I have been running the sound from a Towable 20KW diesel Generator for years now.

I don't have any "regulators", but I do have Furman Line conditioners.

Also, I had no idea about the Dummy load. I can make sure I have lights plugged in.

 

As far as the ground frame bonds....alright now my head is swimming.

I don't get this part at all.

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You don't need external regulators, the generator has this built in via the field winding compensation current. In fact, external regulators and dynamic loads can cause additional problems.

 

The "line conditioners" aren't much if any help either, but they are a convenient power strip.

 

The genny frame should be bonded to the "neutral" on your genny already, a driven ground rod connected to the genny frame is for safety. It can also reduce noise (hum, buzz and RFI) with some equipment.

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You don't need external regulators, the generator has this built in via the field winding compensation current. In fact, external regulators and dynamic loads can cause additional problems.


The "line conditioners" aren't much if any help either, but they are a convenient power strip.


The genny frame should be bonded to the "neutral" on your genny already, a driven ground rod connected to the genny frame is for safety. It can also reduce noise (hum, buzz and RFI) with some equipment.

 

WHew!

Thanks.

That helps a lot.

Now I can't believe I used to run the whole show with a 6000 Watt

Honda Generator, with no problems....well one problem.

We ran out of gas during a set.

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When using the larger "towable" gen sets with a user adjustable voltage knob, be sure so set the voltage from about 118 to 121 VAC before connecting a load. When these units are used on construction sites, many times the voltage knob is cranked up (too far). Cranking the voltage too high can result in a severe over voltage situation if the load drops off suddenly. Having the dummy load helps voltage stability issues.

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There are some advantages for a DJ to run a PA system off of a DC battery bank: no genset needed, therefore no noxious fumes, flamable fuels, loud engines, long power cable runs, or genset failures. Also no worries about bad power burning up gear if you use good sinewave inverters or straight DC powered gear (with DC-DC converters). If you do remote gigs on a regular basis, then it may be worthwhile to invest in such a rig.

 

I have built my own remote PA system using a car amplifier with PA speakers, and DC/battery power for my rig. My system isn't big enough to do a large outdoor venue, but it's good enough for me as a solo artist who wants to jam in the middle of nowhere with good sound and volume as long as I want. I have a range of deep cycle batteries that I can use to make up a 12V bank of various capacities. Sine wave inverters large enough to run high power audio amps are expensive, so that's one reason why I use a car amp instead. Also, going from DC-AC-DC-AC for batteries to inverter to power amp rails to power amp output seems is rather power inefficient. A car amp goes from DC-AC to do only a single conversion instead of three. You do have to run some pretty heavy batteries for long running off of inverters. The music style and number of subwoofers will have a huge affect on the power demand, so that is something to think about before attempting a battery rig. For my music I can run very good volumes with relatively low current draws. My standby draw is under 1amp, while my program level is 6-30amps. That's running a pair of PR10 with a PR15 as a 2.1 setup, with a 4 channel car amp having 2 channels bridged mono for the PR15.

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In the power range these systems are looking at, an inverter is not a practical solution unless they want to rent deep cycle batteries and at 6kW, you are looking at 48 volt input inverters due to DC bus current.

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In the power range these systems are looking at, an inverter is not a practical solution unless they want to rent deep cycle batteries and at 6kW, you are looking at 48 volt input inverters due to DC bus current.

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In the power range these systems are looking at, an inverter is not a practical solution unless they want to rent deep cycle batteries and at 6kW, you are looking at 48 volt input inverters due to DC bus current.

 

What....don't wanna run 250kcmil cable????;)

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That is only if you assume that they actually need 6KW of audio power. There's a good chance they are using at least 6dB just to overcome the sound of loud generators, if not more. One of the great things about remote locations is that you generally don't have to overcome ambient noise unless you generate it with GenSets. A scaled back system using a respectable car audio amp might work, might not, depending on the circumstances. I can tell you that the sound of GenSets blaring full blast isn't music to my ears.

 

There is no need to rent deep cycle batteries when you can buy them for under $80 a pop at Sam's Club, which has the Energizer GC2 for $71.28 and the GC8 for $77.82, at least in my area. Some audio equipment may be able to run fine on the cheaper 1500-3000W MSW inverters, but that's a bit tricky to test, as you probably know. I wouldn't run audio amplifiers or other high current draw devices that will be sensitive to the shape of the power wave. That's why I use a car amplifier to avoid that situation. I know this configuration will work for many remote gigs for DJs, but not for a big venue rave or anything with that scale. Running a 48V inverter could also be worthwhile if the gigs are a regular thing, but the Xantrex and Outback 48V inverters aren't cheap either.

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After the power went out last year due to a hurricane, we did a block party off my small generator. I brought bare equipment and it went OK. I knew I was running too much power through it though.

 

About 1 month later, my good guitar amp crapped out on me. When the manufacturer was fixing it, they said they've never seen the power transformer die like that. Sometimes you don't see the damage you do until later. This thread has got great info I will remember.

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For the op's system, that's a lot of energy storage and I doubt 6dB is needed to overcome a (good) generator. Figure 6kW x 25% = 2kw/h x 6 hours and that's 12kWh. How many deep cycle batteries would you need to provide this... there's about 800Wh available in a good 12v deep cycle battery, so you are looking at 15-16 batteries to get you through the gig? Not practical IMO, at this point it's time to look at a forklift battery.

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