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Author Topic: Buck & Boost Transformers  (Read 2058 times)

Barry Singleton

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Re: Buck & Boost Transformers
« Reply #10 on: June 12, 2014, 12:50:52 am »

Perhaps the biggest thing to consider in this situation is that likely no one will remember the boost transformer when the PoCO does fix the problem-after the transformer lets the smoke out or whatever-so you don't want it to boost high enough to create a problem at that time.

  That would be my worry. How much current are you talking about? Could you use a real computer grade AVR?  We have some in our server rack that are 6000 watt and they surely do make smaller ones.
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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #11 on: June 12, 2014, 07:00:38 am »

  That would be my worry. How much current are you talking about? Could you use a real computer grade AVR?  We have some in our server rack that are 6000 watt and they surely do make smaller ones.
That doesn't worry me in this particular situation. They've got a Monster power conditioner as the distro in the rack, and it's got a BIG voltage display they watch all the time. But even if somehow the incoming voltage goes up to 120, then my 6 volt boost would only take it 126 which should be perfectly safe for everything. Hey, the line voltage at my school is 130, which made me a little worried the first time we measured it in sound practicum class, but the school plant guys insists it's been like that for a decade. What is it with these plant guys?  >:(

Right now, the church sound tech manually cycles the HVAC units off when the voltage gets below 110 and the preacher is doing his message. Then they'll turn the HVAC compressors back on when the choir and band is singing and let the voltage drop below 110 since the congregation can't hear the buzz from the monitors. Now these are BIG compressors since the room seats at least 2,000, but they have a wall mounted control next to the monitor console so at least he doesn't have to run into an equipment closest to tweak the HVAC. 

If this cheap fix works, then I've suggested they use it as a pitch to PoCo to fix the incoming voltage sag, but their plant guy insists the PoCo says they're not responsible for fixing the street transformers since the church is in an industrial park. Don't know what that has to do with it, but sounds to me like PoCo is just knitting A$$hole covers. 

Keith Broughton

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Re: Buck & Boost Transformers
« Reply #12 on: June 12, 2014, 08:00:36 am »

Mike, you could use a varac to power the console (HVAC off) and drop the voltage to see if it's actually a low AC supply that is causing the hum.
It may be something else rather than low AC.
However, if I had to bet, I would say it is the low supply voltage. :)
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TJ (Tom) Cornish

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Re: Buck & Boost Transformers
« Reply #13 on: June 12, 2014, 08:05:23 am »


If this cheap fix works, then I've suggested they use it as a pitch to PoCo to fix the incoming voltage sag, but their plant guy insists the PoCo says they're not responsible for fixing the street transformers since the church is in an industrial park. Don't know what that has to do with it, but sounds to me like PoCo is just knitting A$$hole covers.
I think a device like this has a place, however on the continuum of cheap/low function -> expensive/high function, this is on the bottom end, as I assume it's a hardwired device.  A more end-user friendly version would be an automatic voltage regulator like this: http://www.sweetwater.com/store/detail/AR1215/, albeit at a higher cost.  The next step up the curve is a double-conversion UPS: http://www.tripplite.com/sku/SU1500RTXLCD2U.



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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #14 on: June 12, 2014, 09:55:25 am »

A more end-user friendly version would be an automatic voltage regulator like this: http://www.sweetwater.com/store/detail/AR1215/, albeit at a higher cost. 

That's a good idea. I'm sending it up the food chain.

Kevin Graf

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Re: Buck & Boost Transformers
« Reply #15 on: June 12, 2014, 10:15:20 am »

The Rod Elliott page on buck/boost transformers.

'Bucking Transformers'
Rod Elliott (ESP)
Contents
    Introduction
    1   Step Down Transformer
    2   Autotransformer
    3   Bucking Transformer
    4   Boosting Transformer
    Conclusion
    References

http://sound.westhost.com/articles/buck-xfmr.htm
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Barry Singleton

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Re: Buck & Boost Transformers
« Reply #16 on: June 12, 2014, 11:07:39 am »

The Tripp Lite unit is exactly what I was referring to.

Our building has terrible power quality, so much so that the UPS's placed at PC work stations cycle so often that the batteries are exhausted by mid day and they shut off. After monitoring /data logging the voltage for eight days it was decided that retapping the transformers in the building would create an also unacceptable high voltage condition at night and weekends. Like you, our issue is inadequate supply on the PoCo side compounded by severely noisy, power unfriendly machinery on our floor.

  A fairly large AVR up stream of the offices was a complete fix. The UPS's in the server rack which are logged are not activated even once a month now, only on real power outages.

Our church seats 250 and likely has a similarly scaled budget, and while I would accept a small hand made / modified boost transformer in line to a peice of our equient as a proof test for a permanent fix, I would not allow it to be left in.  Why would you want that liability anyway?

  This is not a rebuke so please don't take it as such.

  All the best,
                     Barry.
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Frank DeWitt

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Re: Buck & Boost Transformers
« Reply #17 on: June 12, 2014, 11:52:45 am »

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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #18 on: June 12, 2014, 12:37:25 pm »


Our church seats 250 and likely has a similarly scaled budget, and while I would accept a small hand made / modified boost transformer in line to a piece of our equipment as a proof test for a permanent fix, I would not allow it to be left in.  Why would you want that liability anyway?

Actually, Buck-Boost transformers are not hand made. They're standard in industrial power and have both Code on UL approval. When the PoCo adjusts the power coming into your building, that's essentially what they're doing, adjusting taps on a buck-boost transformer. We're just doing it on a small mixer rack that seems to be overly sensitive to low voltage (below 110 volts) instead of adjusting the entire building which is cost prohibitive. Plus I really can't be sure the noise is coming from this one rack due to voltage below 110. I only heard it once for a few seconds, and the rest of my troubleshooting matrix is from hearsay evidence provided by the sound team. So I'm looking for simple and cheap first, then more expensive and permanent later.

If the noise goes away by keeping this rack voltage between 114 and 120 volts, then I'm going to recommend a more permanent automatic solution like you mention. But right now this is basic troubleshooting 101 and figuring out intermittent noises is one of the hardest things to do. If I had a large Variac transformer for testing with at least 10 amps output, I would put it on the rack and keep reducing voltage until something made noise. But all my variable AC supplies are low power, maxing out at 3 amps which is too low to power the rack. Still, I think this is a reasonable try which would pass a code inspection.

I only brought this subject up because it's something unusual in commercial power, but used all the time in industrial power. I'll report back here in a week or so to see if my guess was correct.

Josh Millward

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Re: Buck & Boost Transformers
« Reply #19 on: June 12, 2014, 12:41:51 pm »

That's a good idea. I'm sending it up the food chain.

I agree completely with TJ on using the Furman AR-1215.

It is essentially an automated buck/boost transformer that is already set up for you. You just need to plug it in, turn it on, and you are ready to go. They offer a surprisingly wide range of correction. That way, when/if the PoCo does correct their problem, it doesn't create a bigger problem in your facility.

RE: PoCo knitting asshole covers...
I'm going to have to remember that one, I like it.
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Josh Millward
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