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Author Topic: Buck & Boost Transformers  (Read 13966 times)

Mike Sokol

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Buck & Boost Transformers
« on: June 11, 2014, 05:14:53 pm »

I just came back from a church sound consult where the monitor console and its rack was being fed with very low AC voltage, starting at maybe 114 volts max with no load, but dipping down below 108 volts when the HVAC on the roof kicked in all the compressors. It appears that something in the rack (perhaps the console PS itself) ain't happy at 108 volts and begins doing a big buzz reset noise which ends up in all the floor wedges. I proposed adding a Buck-Boost transformer in Boost mode feeding the surge/conditioner that will add at around 6 volts to the incoming power for the rack, so now the voltage would swing between 114 volts and 120 volts rather than 108 to 114 volts.

So here's my question. The electrician doing the wiring thought I was a little nuts describing how to a Buck & Boost Transformer works, and how to hook it up. How many of you know what I'm talking about and have you ever used one to correct chronically high or low voltage powering a sound system or whatever.

BTW: I do know how they work, having installed dozens of them during my IE/EE past life. But I want to know if this is a subject worthy of discussion here. I'm sure that at least of few of you guys know what I'm talking about, but perhaps not a lot.

What your your thoughts on this?   
« Last Edit: June 11, 2014, 05:17:23 pm by Mike Sokol »
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Mike Sokol
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Frank DeWitt

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Re: Buck & Boost Transformers
« Reply #1 on: June 11, 2014, 05:29:37 pm »

Basically a auto transformer.

I have used them more then a few times.  I have one permanently installed it the voltage regulator of a generator of mine that was built for 50 hz.  I have it adjusted for 60 hz but the voltage went high so I fool the feed to the voltage regulator to get it back down.

I also used one to run 5 preamps that ran very hot.  They worked very nicely on 96 volts. 

In both cases I made the transformer from a step down transformer. Make sure the primary winding can handle the current it will see. The coils on the low voltage side are always higher current so as long as the insulation can take the higher voltage, you can series them.  I do wire them so that one side of the output winding is connected to neutral just to be sure.  In the case of the preamps I used a 24 volt transformer with the output winding bucking the input winding. 
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Cailen Waddell

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Re: Buck & Boost Transformers
« Reply #2 on: June 11, 2014, 06:21:44 pm »


I just came back from a church sound consult where the monitor console and its rack was being fed with very low AC voltage, starting at maybe 114 volts max with no load, but dipping down below 108 volts when the HVAC on the roof kicked in all the compressors. It appears that something in the rack (perhaps the console PS itself) ain't happy at 108 volts and begins doing a big buzz reset noise which ends up in all the floor wedges. I proposed adding a Buck-Boost transformer in Boost mode feeding the surge/conditioner that will add at around 6 volts to the incoming power for the rack, so now the voltage would swing between 114 volts and 120 volts rather than 108 to 114 volts.

So here's my question. The electrician doing the wiring thought I was a little nuts describing how to a Buck & Boost Transformer works, and how to hook it up. How many of you know what I'm talking about and have you ever used one to correct chronically high or low voltage powering a sound system or whatever.

BTW: I do know how they work, having installed dozens of them during my IE/EE past life. But I want to know if this is a subject worthy of discussion here. I'm sure that at least of few of you guys know what I'm talking about, but perhaps not a lot.

What your your thoughts on this?

The only application that I have used buck boost is 208v to 240v buck/boost.   I've never thought of them for the application you describe but it is intriguing.   My question would be - are you solving a problem or hiding it?  If the voltage drop is so severe I would think there would be a utility problem or undersized feeder on the building or something else that should be addressed. 


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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #3 on: June 11, 2014, 06:31:13 pm »

The only application that I have used buck boost is 208v to 240v buck/boost.   I've never thought of them for the application you describe but it is intriguing.   My question would be - are you solving a problem or hiding it?  If the voltage drop is so severe I would think there would be a utility problem or undersized feeder on the building or something else that should be addressed. 


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Their plant guys knows the street power transformers are undersized, but PoCo wants a bucket of money to fix it. They claim that 108 volts is fine and won't replace the street transformers on their dime. I'm looking for a $100 fix rather than a $100,000 one.
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Mike Sokol
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Cailen Waddell

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Re: Buck & Boost Transformers
« Reply #4 on: June 11, 2014, 06:34:12 pm »


Their plant guys knows the street power transformers are undersized, but PoCo wants a bucket of money to fix it. They claim that 108 volts is fine and won't replace the street transformers on their dime. I'm looking for a $100 fix rather than a $100,000 one.

Makes sense to me.


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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #5 on: June 11, 2014, 06:38:06 pm »

Makes sense to me.

We'll see if this fixes the buzz problem. I've asked their electrician to take pictures of the B&B installation and report back to me next week. I'll post them here.
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John Roberts {JR}

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Re: Buck & Boost Transformers
« Reply #6 on: June 11, 2014, 06:39:59 pm »

It does not have to be an auto-former but since the secondary is literally connected to the primary there is no benefit from isolating the secondary, so auto-former can be a little more efficient.

I can imagine people getting in trouble from too much no-load high line voltage, and you do not get something for nothing so current draw will increase proportionately.

=====

I've told this story several times, but there is a step-up winding with automatic changing taps at my power sub-station to tweak voltage for changing load. One night I noticed that my lights were too bright and my mains voltage was measuring too high. Turns out the step-up was stuck in bump-up mode. As the neighborhood load started dropping off at night, my lights got brighter and brighter.  ::)  The guy at the power company didn't believe me when I called and told him I had too much voltage, but it was a slow night so he drove out and discovered I was not wrong.  8)

JR
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Steve Kennedy-Williams

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Re: Buck & Boost Transformers
« Reply #7 on: June 11, 2014, 06:57:26 pm »

I just came back from a church sound consult where the monitor console and its rack was being fed with very low AC voltage, starting at maybe 114 volts max with no load, but dipping down below 108 volts when the HVAC on the roof kicked in all the compressors. It appears that something in the rack (perhaps the console PS itself) ain't happy at 108 volts and begins doing a big buzz reset noise which ends up in all the floor wedges. I proposed adding a Buck-Boost transformer in Boost mode feeding the surge/conditioner that will add at around 6 volts to the incoming power for the rack, so now the voltage would swing between 114 volts and 120 volts rather than 108 to 114 volts.

So here's my question. The electrician doing the wiring thought I was a little nuts describing how to a Buck & Boost Transformer works, and how to hook it up. How many of you know what I'm talking about and have you ever used one to correct chronically high or low voltage powering a sound system or whatever.

BTW: I do know how they work, having installed dozens of them during my IE/EE past life. But I want to know if this is a subject worthy of discussion here. I'm sure that at least of few of you guys know what I'm talking about, but perhaps not a lot.

What your your thoughts on this?

We use Buck Boosters for this purpose with projectors, especially when we aren't using our own distro.
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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #8 on: June 11, 2014, 09:09:14 pm »

For those of you who don't already know how these work, here's a basic schematic of one in "boost" hookup. To make it "buck" you just have to flip the polarity of the secondary so it subtracts rather than adds to the incoming voltage.
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Mike Sokol
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Stephen Swaffer

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Re: Buck & Boost Transformers
« Reply #9 on: June 11, 2014, 11:01:57 pm »

Their plant guys knows the street power transformers are undersized, but PoCo wants a bucket of money to fix it. They claim that 108 volts is fine and won't replace the street transformers on their dime. I'm looking for a $100 fix rather than a $100,000 one.

Makes me appreciate the local PoCo.  Last time I even mentioned a voltage problem to a lineman it got fixed quickly at no cost to my customer. 

108 volts might be marginally OK, but the NEC recommends no more than a 5% voltage drop at full load.  The HVAC alone is dropping it 5.25%.  Then again the PoCo will go by the NESC not the NEC and I am not sure what it says about voltage drop.  If you can't approach the right person in the right way and get it fixed that is pretty poor customer service-might even be a candidate for the state utilities board gripe line.

I have used them before in industry.  Voltages from the US, Japan, and Europe are just enough different that some equipment can be pretty touchy, so they are not uncommon.  A lot of Japanese stuff likes 200 volts-and 230-240 is a bit high.  Although it seems the newer stuff is a lot more tolerant on voltages.

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.
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Steve Swaffer

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Re: Buck & Boost Transformers
« Reply #9 on: June 11, 2014, 11:01:57 pm »


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