ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1] 2 3 4   Go Down

Author Topic: What do you want in a genny?  (Read 7792 times)

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2268
What do you want in a genny?
« on: October 01, 2014, 06:23:06 pm »

quote author=Nick Enright link=topic=151677.msg1391202#msg1391202 date=1412197264]
I know that the Lincoln model Ranger 305 and Red D Arc GX300 produce a pseudo sine wave output, and that the voltage varies as the load on the welder, and that frequency varies as load on the welder.....

Modern welding is as technical as modern audio, however these welders are designed to weld, and the 120v AC outlets are only designed for construction grade equipment, and NOT for audio equipment. The engineer I spoke with could not guarantee anything when used for audio amplifiers, and definitely not digital gear,.......

[/quote]

The first point only makes sense-any genny (excepting inverters) will do so when hit with a load near its capacity-the assumption would be that it would be unlikely you would be welding during a gig?

On the second point, no offense intended, but even if a welding engineer would guarantee something regarding audio equipment, I am not convinced it would mean a great deal-does he know what they need?

I have no doubt that a Honda inverter would be preferable.  From my POV, there is no way to know if the Lincoln is better than a non-inverter Honda, or any other genny out there because no one publishes meaningful specs-likely because they are not mandated by law, nor are they requested by customers.  No doubt, other genny manufacturers will soon be on the inverter bandwagon-and lower quality ones will become more common.  How do you compare the power quality between two gennys?  If I were designing a genny for audio, what features/benefits would the industry be willing to pay for?

SMPS rectify the input anyway-they should actually work just fine if fed the correct DC voltage,  they would seem to be the least frequency sensitive power supply?
Logged
Steve Swaffer

jasonfinnigan

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 329
Re: What do you want in a genny?
« Reply #1 on: October 01, 2014, 06:33:51 pm »

As far as I know there is no inverter generators over 10kw. I think the inverter generators are generally more of toy generators - around 1kw-2kw or less. Good for running somethings like TVs and such but no serious festival or concert could run on that. not to mention festivals need long runtimes offered by bigger generators.

I do know some of the ones we rent monitor the output voltage and "adjust" itself accordingly as the load goes up to keep in within range. I don't think the other gennys do that. No idea about inverter ones as I've never used them.
Logged

Tommy Peel

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1454
  • Longview, Texas
    • Facebook Profile
Re: What do you want in a genny?
« Reply #2 on: October 01, 2014, 07:28:59 pm »



As far as I know there is no inverter generators over 10kw. I think the inverter generators are generally more of toy generators - around 1kw-2kw or less.
Looks like the biggest Honda inverter generator is 7kw. I imagine you could run a reasonably powerful, but efficient, PA off of that.



Sent from my Moto X (XT1053) using Tapatalk

Logged

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Offline Offline
  • Posts: 3418
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: What do you want in a genny?
« Reply #3 on: October 01, 2014, 08:12:29 pm »

As with everything in life.... it depends. Haha.

I ran a 3-over-2 VRX932LAP/918SP rig this past summer on an EU3000is, mains and FOH, and two amps for monitors. I think we ended up later in the day putting stage power on a separate EU2000i (not ground-connected, tho, please don't hit me) when one group was a bit more intense then the others, but beyond that, we made it through. This was for a park event, mild music (not EDM or heavy rock) and no more then 3-400 people at the stage at any one time. VRX was flown in truss (Global Truss ST180s).

-Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

jasonfinnigan

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 329
Re: What do you want in a genny?
« Reply #4 on: October 01, 2014, 08:26:11 pm »

We're lucky to have an event where someone wants under 8 individual monitor mixes. So we tend to use a lot of power. Yeah I think the local/regional bands around here may have gotten spoiled diva with their monitors somehow. I remember back when 4 monitors was considered plenty.
Logged

Ray Aberle

  • Classic LAB
  • Hero Member
  • *
  • Offline Offline
  • Posts: 3418
  • Located in Vancouver, WA (and serves OR-WA-ID-BC)
    • Kelcema Audio
Re: What do you want in a genny?
« Reply #5 on: October 01, 2014, 09:25:30 pm »

We're lucky to have an event where someone wants under 8 individual monitor mixes. So we tend to use a lot of power. Yeah I think the local/regional bands around here may have gotten spoiled diva with their monitors somehow. I remember back when 4 monitors was considered plenty.

Oh, I totally agree. But Tommy mentioned running a powerful and efficient PA off of a Honda-- and I wanted to cite an example where I did just that.

For larger shows, yep, 6-10 mixes and the amps to go along with it. I always brag about having a 45kW WhisperWatt- yeah, I have to maintain it, worry about getting it to events, don't have a backup in case of major failure-- but at the same time, it is a nice feeling that it's a known factor. I know it's condition, that it provides good clean power, that the internal batter is getting old and needs to be jump-started at times (really! Annoying.) -- it's good to know what to expect, when you are responsible for maintenance yourself.

... and I've been able to bail out other companies with it on short notice. :)

-Ray
Logged
Kelcema Audio
Regional - Serving Pacific Northwest (OR, WA, ID, BC)

Tommy Peel

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1454
  • Longview, Texas
    • Facebook Profile
Re: What do you want in a genny?
« Reply #6 on: October 01, 2014, 10:01:10 pm »

I did a gig a while back with an eu2000i with a powered Mackie rig(2 tops, 2 subs, and 3 monitors), FOH, and backline. We had enough SPL for the gig but couldn't get anywhere near FTB. Never tripped the breaker, but I saw the overload light blinking with the music at one point and had to turn down a bit.

Sent from my Moto X (XT1053) using Tapatalk

Logged

Guy Holt

  • Full Member
  • ***
  • Offline Offline
  • Posts: 125
Re: What do you want in a genny?
« Reply #7 on: October 02, 2014, 07:13:56 am »

How do you compare the power quality between two gennys?  If I were designing a genny for audio, what features/benefits would the industry be willing to pay for?

SMPS rectify the input anyway-they should actually work just fine if fed the correct DC voltage,  they would seem to be the least frequency sensitive power supply?

SMPSs are impervious to frequency but very susceptible to the voltage distortion created by the very harmonic currents they draw when powered by conventional generators. Because the capacitors in SMPSs draw current only at the peak of the voltage waveform, SMPSs cause a voltage drop at the peak of the waveform, which leads to “flat topping” of the voltage similar to that in the oscilloscope shot below center.



Left: A non-linear Load powered by Grid Power. Center: A non-linear Load powered by Conventional AVR Power. Right: A non-linear Load powered by Inverter Power.


And since, according to Ohm’s Law, harmonic currents react with impedance to cause voltage drop, the magnitude of this voltage waveform distortion caused by SMPSs is a function of the source impedance. In the case of generators, source impedance is not an easily defined value as generator reactance varies with time following a load change. However, what is certain is that the generator with the lowest internal reactance to an instantaneous current change at a given load will typically have the lowest value of total harmonic distortion under nonlinear load conditions. This is one of the great benefits to using inverter generators over conventional generators: inverter generators have much lower internal reactance and so they are less prone to voltage waveform distortion caused by the harmonic currents drawn by SMPSs. Most generator manufacturers don’t give specifications for internal reactance,  but will give specifications for THD of voltage.

Inverter generators are less prone to voltage waveform distortion because the inverters completely processes the raw power generated by its alternator (converting it to DC before converting it back to AC) –making the AC power it generates completely independent of the engine. In fact, its’ microprocessor controller can vary the engine speed without affecting the voltage or frequency of the power the inverter module puts out. Now that the internal reactance of the engine is separated from the power output, harmonic currents encounter very little impedance; and, as is evident in the oscilloscope shot above right, there is considerably less voltage distortion at the load bus of inverter generators than there are conventional generators. The net benefit is that non-linear loads, like the SMPSs of most electronic equipment, do not adversely affect the power of inverter generators as they do the power of conventional generators. Which means that electronic equipment powered by SMPSs will operate more reliably on inverter generators.

Where there is appreciable voltage waveform distortion created by operating non-linear loads on a conventional generator, other electrical devices operating on the same power are unable to use the distorted waveform effectively. For instance, the SMPSs of electronic equipment depend on the peak value of the voltage waveform to operate effectively. They therefore work sporadically, if at all, on the squared off voltage waveform caused by the harmonic currents they draw encountering the high impedance of power generated by conventional generators. In fact, operating the pseudo square wave of distorted voltage, they will be starved of power.



Effect of DC Bus Voltage with Flat Topping

Special precautions must be taken with computers and hard drives in particular. The majority of computer based equipment derives its’ internal DC power from AC power switched by a SMPS, or similar power supply, and so it is often here where harmonic problems first arise. As is evident in the illustration above, voltage flat topping from harmonic currents reduces the operating DC bus voltage these power supplies will generate. As a result, the load will be starved of power even though you may read full line voltage with an RMS meter and the power indicator lights light. 
Symptoms to look for are hard drives locking up, internal fuses blowing, and inexplicable malfunctions.

For a more detailed explanation of the electrical engineering principles behind these issues and how to resolve them use this link for a newsletter article on  the use of portable generators in motion picture production.

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

Stephen Swaffer

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2268
Re: What do you want in a genny?
« Reply #8 on: October 02, 2014, 08:13:32 am »


For larger shows, yep, 6-10 mixes and the amps to go along with it. I always brag about having a 45kW WhisperWatt- yeah, I have to maintain it, worry about getting it to events, don't have a backup in case of major failure-- but at the same time, it is a nice feeling that it's a known factor. I know it's condition, that it provides good clean power, that the internal batter is getting old and needs to be jump-started at times (really! Annoying.) -- it's good to know what to expect, when you are responsible for maintenance yourself.


The only things on the Whisper Watt spec sheet that would relate to power quality are frequency reg, voltage and power factor.  I have no doubt the whisper watt is a very good unit-but what is acceptable?  Does the power facto spec adequately address waveform concerns?

The post I mentioned in my OP made the point that welders need consistent performance - ie output.  The interesting thing is that a function block diagram of the ranger has a rectifier creating a DC bus with an output controlled by a microprocessor firing thyristors-in other words it is a large SMPS with a specialized precisely controlled output-but it doesn't seem to mind the voltage/freq variations caused by rpm fluctuations.

I think it was Dick that mentioned watching gear go up in smoke after time.  This makes perfect sense to me with "big iron" gear.  Transformers are frequency dependent and waveform distortion causes heating in transformers and motors.  So a transformer designed to handle "x" watts being pushed to its limits while being fed a distorted waveform can be expected to let the smoke out soon enough.

Perhaps I am being too technical-it just doesn't seem to make sense that a power supply happy with 90-240 vac would be overly sensitive to a gennys output voltage (provided it is not pushing the low end) and waveform?

Maybe I am being over optimistic, but I there seems to be a lot of frustration over getting a proper genny for audio.  Inverters are good-but limited in size.  Then there is always the g-n bond issue.  But nobody is going to spend money to design something unless the have a target customer that knows what they want.
Logged
Steve Swaffer

frank kayser

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1433
  • Maryland suburbs of Washington DC
Re: What do you want in a genny?
« Reply #9 on: October 02, 2014, 10:10:50 am »

<snip>

Perhaps I am being too technical-it just doesn't seem to make sense that a power supply happy with 90-240 vac would be overly sensitive to a gennys output voltage (provided it is not pushing the low end) and waveform?
<snip>
Stephen,
Through my inexperience and general electrical ignorance, I arrived at the exactly same question as your too-technical reading.
Great minds run in the same circles ;D   It would be great to understand this apparent inconsistency.
I have been in situations of very overloaded line power where SPMS power supplies were shutting down, but my "big iron" supply was still marching on.
Obviously there's so much more to this than meets the eye...
frank
Logged

ProSoundWeb Community

Re: What do you want in a genny?
« Reply #9 on: October 02, 2014, 10:10:50 am »


Pages: [1] 2 3 4   Go Up
 



Page created in 0.049 seconds with 22 queries.