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Author Topic: Genny Voltage Fluctuation Issues  (Read 3096 times)

Zach DeCou

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Genny Voltage Fluctuation Issues
« on: January 27, 2015, 09:21:46 pm »

Hello all
I work for a small company and use three different single phase distros on shows. Last year, my tech called from another show to tell me our powered wedges were winking out and the consoles were rebooting randomly during the show (PRX612's & x32's on a small show). I had him check the power on the small production generator provided by a local lighting company (we usually always use generators from this company). Looked stable and correct. After some frustration and searching for a cause, my other tech checked the power with his personal multi-meter which has a faster refresh rate. They sent me a video of the meter showing rapid and deep voltage drops every time the subs hit. I looked through the distro back at the shop and didn't see anything loose or improper. We chalked it up to a bad voltage regulator in the genny. The lighting company denied it was their genny. We'll say this distro was "A".

Later during another event, I had another distro- this time distro "B". I mixed all the bands during an all day festival until the head liner took the stage. The head liner's FOH guy hit my PA a lot harder than I did. No problem for the PA. I had plenty. But the band's ear rack was winking out and the console (LS9) was rebooting. Their furman was showing large voltage spikes, and the genny voltage meter and my multi meter confirmed this. Back at the shop I looked through "B" and found no fault in the wiring. We decided it was another bad voltage regulator.

Not long after, I had "C" on a show. This time the voltage was dropping, causing various issues for the bands and for us. This time, I had a tech with the lighting company who provided the genny and one of the HL's techs with me trouble shooting this thing. Tech with the lighting company said it was our distro as this seems to be a reoccurring problem, saying the other sound companies who use three phase have had no issues. The HL's tech said the distro was fine and it's a bad genny. Of course, "C" had no faults in the wiring back in the shop, but now I'm pondering the phase issue.

On yet another show, I was seeing huge voltage spikes. This time on the exact same genny as the first instance in this post. My itech's were rebooting, wedges winking in and out, and band gear going hay wire. Had to pull the subs all the way out and bring the PA way back to stabilize the voltage. This time I managed to get a replacement generator. We hooked it in during a set change, fired it up, went into the next band, and the voltage was stable as a slab of granite.  Now I'm conflicted.

There were a couple outdoor events interspersed during this time that had only minor voltage variations (always on sub hits) that were no factor.

Has anyone else seen issues like these? The reoccurring nature of the problem across multiple distros and generators has me puzzled for a common link.
Any insight would be a great help. Thanks!

Zach

[EDIT] We use two hot legs. There are situations where we will set to 3 phase and not use the last leg. Other times we will use the single phase setting on the generator. The first and last instance we used a small generator. During the change out on the last show, the replacement genny was a higher capacity.

I'm sorry I don't have particulars regarding generator capacity or which shows we used single vs 3 phase settings on the generators. It has been a while and since we decided it was the generators, I didn't retain that information. Since I've had some time, I'm no longer satisfied with "it must be the other guy's stuff". And with outdoor season coming around the corner, I may be running into these issues again.
[EDIT 2]
I just talked to my guy who was at the show during the first mishap. He said the drop was only occurring on one of the two legs- presumably the leg the subs were on.
« Last Edit: January 28, 2015, 09:35:31 am by Zach DeCou »
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Ray Aberle

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Re: Genny Voltage Fluctuation Issues
« Reply #1 on: January 27, 2015, 09:41:26 pm »

Hello all

Has anyone else seen issues like these? The reoccurring nature of the problem across multiple distros and generators has me puzzled for a common link.
Any insight would be a great help. Thanks!

Zach

So you've had two instances of using the same generator, but the other times you have had different ones? Are these trailer mounted diesels (WhisperWatt or the like)?

The other companies that use them with no problem, that are on 3 power/distros, are you connecting via cams as well, or using the 50A/1 twist locks?

Are they changing the power setting on the gennie from 3 to 1 before you use it? That shouldn't be a problem, but it's nice to eliminate all possibilities.

Have you tried metering the outputs on the generator while it's running/you're experiencing problems? Voltage drops (or lack thereof) at that point would help to prove or eliminate the distro as the cause.

-Ray
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Mark Cadwallader

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Re: Genny Voltage Fluctuation Issues
« Reply #2 on: January 27, 2015, 09:43:38 pm »

In the absence of other information (like details on the gennie unit involved), it sounds as if the draw on a single phase/leg (and no load on the other two legs) was too much for the gennie to handle. Mark C.
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Zach DeCou

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Re: Genny Voltage Fluctuation Issues
« Reply #3 on: January 27, 2015, 09:59:04 pm »

Sorry for the lack of information. I'm adding to the original post shortly with some additional information...
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Tim McCulloch

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Re: Genny Voltage Fluctuation Issues
« Reply #4 on: January 27, 2015, 09:59:28 pm »

The ITechs will be a source of information.  In the monitoring menu you can find out how many over-voltage and under-voltage instances occurred over X number of hours.  The swings will have to be large, as the PSU can accommodate 100-250v, 50 or 60 Hz.

I suspect you were experiencing a voltage drop when high-demand signals present, like the kick drum.  That's the reason the lights dim and stuff stops working.

Now there are possibilities on the genny side, including a loose neutral that would cause the phase leg with the greatest load to receive the lowest voltage, with the other leg(s) going over-voltage (but can't exceed 240v) or a loose phase leg connection.

As for your distros, absent any loose connections, mis-wiring, or defective outlets I can't immediately think of any problem that could be common amongst them, especially if you don't have problems when using them on shore power or other generator sets.

Quote
On yet another show, I was seeing huge voltage spikes. This time on the exact same genny as the first instance in this post. My itech's were rebooting, wedges winking in and out, and band gear going hay wire. Had to pull the subs all the way out and bring the PA way back to stabilize the voltage. This time I managed to get a replacement generator. We hooked it in during a set change, fired it up, went into the next band, and the voltage was stable as a slab of granite.  Now I'm conflicted.

Was the replacement genset of higher capacity?  That this problem seems to be most associated with the genny from the lighting company, I think it's either got issues of its own or you're simply asking it to do more than it can.
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Ray Aberle

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Re: Genny Voltage Fluctuation Issues
« Reply #5 on: January 27, 2015, 10:15:57 pm »

In the absence of other information (like details on the gennie unit involved), it sounds as if the draw on a single phase/leg (and no load on the other two legs) was too much for the gennie to handle. Mark C.

That's why I was wondering about the 1/3 selection switch. If the gennie is expecting a load on all three legs, and it's only coming in on two, that might freak it out.
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Zach DeCou

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Re: Genny Voltage Fluctuation Issues
« Reply #6 on: January 27, 2015, 10:39:59 pm »

Origiional post edited...
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Stephen Swaffer

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Re: Genny Voltage Fluctuation Issues
« Reply #7 on: January 27, 2015, 10:58:56 pm »

During the instance you were using distro B you indicated that your meter, the furman and the genny voltmeter were showing spikes.  The genny meter would not show a spike caused by the distro.

During the last instance where a replacement genny (larger capacity) fixed the issue it is cut and dried that the issue was the genny-either defective or undersized.

Cheapest, least painful path might be to spec a larger genny and see how it goes since it appears the issue is at the genny for at least two of the cases (and I suspect the replacement genny would have cured the first one as well.)
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Mark Cadwallader

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Re: Genny Voltage Fluctuation Issues
« Reply #8 on: January 27, 2015, 11:38:16 pm »

An insufficiently-sized generator will suffer voltage drops under high demand loads that briefly exceed its capacity.  Spec a bigger generator, and try balance the load on the legs. Using only two legs of three phase on a generator will do bad things too, as Ray pointed out.  It may be time to buy a three phase distro...  Mark C.
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Ray Aberle

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Re: Genny Voltage Fluctuation Issues
« Reply #9 on: January 27, 2015, 11:46:19 pm »

well, if it's set for 1, then you're ok, but if it's set for 3 then it's weird. My 45kW WhisperWatt has a 3-position voltage selection switch, so I can choose what I am working with.

btw, dimmerrack.com has good pricing on basic 3 distros.
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Re: Genny Voltage Fluctuation Issues
« Reply #9 on: January 27, 2015, 11:46:19 pm »


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