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How to add an Isolation Transformer to AV system.Thanks Bob!
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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Sun Dec 04, 2011 4:17 am    Post subject: Reply with quote


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Don't let the end balanced Xfmer part of my goal get confusing... it is much further downstream than the initial IsoT I'm working on now. You are 100% correct, I can do the same thing you did with 1 or more smaller 2-3kVA IsoT to separate the digital (noisy) components from the AMPs etc or however I need to divide it up. How that plays out depends on me finding either IsoT or BP Xfers on eBay etc.. a reasonable costs. I also have seen balanced power xfmers with multiple taps at lower amps if I'm patient enough. Those are next steps. First I have to get the IsoT and subpanel installed - correctly.

I thought showing my final goal would be helpful in the overall solution.

I'm still not sure I have the setup correct based on page 21 in the doc link I posted which is labeled "best" for AV setups but they omit a few details which would make it 100% clear.

From page 21 picture, the identification of X2 & X4 as N1 and N2 and then bonding both to Grnd in the IsoT is confusing.

Thanks.


Last edited by gattaca on Sun Dec 04, 2011 5:51 pm; edited 1 time in total
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Boilermaker



Joined: 21 May 2006
Posts: 527



PostLink    Posted: Sun Dec 04, 2011 9:31 am    Post subject: Reply with quote

Quote:
a) Input on Topaz. This cable / breaker is @ 60A, in case I want to move to a 7.5kVA unit. (125%) 30A would do for 5kVA at 125% technically.
7500 / 120


While you can certainly use a 60 amp service, it is not necessary. Since you really need to use the 240 volt primary configuration, it is 7500/240, not 7500/120.

Also, while it would still work, I would not configure the subpanel feed as is shown in the Middle Atlantic schematic on page 21.
Unless you have some particular reason not to, I would parallel the two secondary windings and have this feed the two sides of your subpanel. Easiest way is to connect the top of both secondary windings to one wire and have the other end feed both legs of your subpanel by looping from one to the other.

This way you get the full 5KVA of the transformer. If you separate them, you effectively have two separate 2.5 KVA transformers.

Make sure you isolate both the neutral and the ground bars in your subpanel with isolators as shown in the schematic.

It is not necesary to use the orange "isolation receptacles" a shown as in your case there is no functional difference.

I didn't read your last post on some balanced configuration, but you should know that there will be 0 volts from one leg of your secondary to the other leg on your subpanel - not 240 volts. If, however you decide to wire the two legs separately as shown on page 21, you might end up with a few volts difference between the two legs depending on the relative difference in size of the loads.

Also, if you do separate the feeds, remember the the new neutral now carries the sum of the two legs current so size appropriately.

Hope this helps.


Bob
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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Sun Dec 04, 2011 6:09 pm    Post subject: Reply with quote

Boilermaker wrote:

This way you get the full 5KVA of the transformer. If you separate them, you effectively have two separate 2.5 KVA transformers.

It is not necessary to use the orange "isolation receptacles" a shown as in your case there is no functional difference.


Hi Bob, Thanks for the correction - updated.

No ISO outlets planned or needed

I believe you nailed the advantage of output option c vs. option d which is it provides two secondaries which may be desirable to provide isolation for two circuits where one has noisy components which should be isolated from less noisy ones.

While output option b is similar to the Torus option B linked reference.

Thanks.
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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Sat Jan 07, 2012 1:32 am    Post subject: Sizing an isolation transformer for AV Reply with quote

Hi Athansios and BoB:

I finally got my Topaz IsoT installed today. Worked out well. It ended up in the garage and we took the two 12/2 feeds for the main AV setup from the main panels and rerouted them to the breakers in the sub-panel on the output side of the IsoT. I wired it per page 21 as I discussed. It does get warm but not hot under about a 20A load. The expected noise is contained in the garage!

I have a question about the output voltages.

Since these feed into a pair of UPS, I'm able to monitor the input voltages of the UPSes and they went into alarm mode with an over-voltage condition. Checking the logs it shows the voltages jumped from a steady 122.2 / 123.5 to 131.9 / 132.6.

Should I have expected this? Is this normal?

What is the danger of this nearly 10V increase on the downstream electronics?

I do have over-voltage protections in place but this is getting awfully close to the cut off?

THanks!
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Nashou66



Joined: 12 Jan 2007
Posts: 16167
Location: West Seneca NY


PostLink    Posted: Sat Jan 07, 2012 3:47 am    Post subject: Reply with quote

Mine never went up in voltage. Something is not right i would think. The whole reason for the Iso is to stabilize the voltage as well.
I use to have an issue when my AC would kick on id get a brown out then a spike when measure with a scope at my main theater
outlets. After installing the Iso it stayed right at about 119vac during the AC turn on.

So you hooked it us you stated per that link? Can you hook it up as in this thread and bring the UPS into the garage and test it there before going to the panel box? Just use a an end of an extension cord for testing. thats what I did before I went to the panel box
and how I tested the AC problem I mentioned earlier.

Athanasios

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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Sat Jan 07, 2012 2:53 pm    Post subject: Reply with quote

Athanasios,

I am sorry, my post was a not clear. The voltages are not hopping from 122.2 / 123.5 to 131.9 / 132.6 with the IsoT installed.

The 122.2 -> 123.5 is the utility MAX input voltage consistently recorded by the UPS for weeks before the IsoT was installed yesterday.

The 131.9 -> 132.6 is the MAX range of of input voltages being reported by the UPS now after the IsoT was installed inline. The voltage is darn consistent in that range.

I measured the input voltage on H1, H4 at the IsoT is ~ 242/243VAC.

So I expected to see ~ 121/122 on the output side (X1, N and X3, N) not 132/133V.

I'm guessing this IsoT windings may not be in perfect symmetry, so I'm seeing some "step up"?

I'm running the IsoT as option C from my earlier posting, per the Mid-Atlantic doc reference.

a) Input on a 7.5kVA Topaz. 7500VA/240V * 125% = Dual 40A
a1) H3 <----> H2 jumper
a2) H1 <----- dual breaker <- 240V main panels.
a3) H4 <----- dual breaker <- 240V main panels.
a4) GND <--- Existing Main Panel GND

c) Output (120V 120V 0V 0V)
b1) X1 -----> L1 in new subpanel (120V @ ~ 20A)
b2) X3 -----> L2 in new subpanel (120V @ ~ 20A)
b3) X2 -----> GND BAR inside IsoT -> Isolated Neutral in new subpanel
b4) X4 -----> GND BAR inside IsoT -> Isolated Neutral in new subpanel
b5) GND -> GND BAR inside IsoT -> Equipment GND in new subpanel.

Thanks, Vincent
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Nashou66



Joined: 12 Jan 2007
Posts: 16167
Location: West Seneca NY


PostLink    Posted: Sat Jan 07, 2012 3:27 pm    Post subject: Reply with quote

so your running two separate outputs from the iso.... bridge it for only one out put at 120 and measure that. It could be the dual set up is off.

I do not have my GND bar connect to any neutral in the sub, only to the subs ground which is isolated from the neutral I believe .

I can touch the hot and ground and not get shocked.

Put a multimeter on the hot and ground in the sub panel, it should not have any voltage, try using an analog as a digital might give you erroneous voltage.

EDIT: Make sure the green screw that bonds neutral to ground in sub panel is removed, you want to keep ground isolated from neutral.

Athanasios

_________________
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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Sun Jan 08, 2012 4:17 pm    Post subject: Reply with quote

Athanasios,

My IsoT is connected is per page 21 in the MidAtlantic Manual for "best AV" setup, see below:

a) a reference from Middle Atlantic, specifically, page 21 / 22 -> http://www.middleatlantic.com/pdf/PowerPaper.pdf

In this "Best AV Connection" option, I have ~131V between P1 and N1 and ~131V between P2 and N2 with a 242/243V input on IsoT Supply side. I think this not being 121/122V is due to the imprecise windings providing a little step up but I cannot be 100% sure unless I connect it differently by bonding the P1/P2 or try another IsoT. Wink

Now per page 21, N1, N2 and the Secondary electrostatic shields and GND are all connected together to the IsoT inside the output side of the IsoT. Per Bob's earlier suggestions, I basically installed a small bar inside the output side and bonded it to the IsoT's case and used it for all the connections as there was no way to do this otherwise.

For reference, there is also 131V between P1 or P2 and the GND Bar inside the sub-panel (b/c these are actually connected AT the IsoT) What I was not able to do exactly per page 21 was locate an Isolated Ground Bar for the panel. The electrician was already hesitant so he installed the GND Bar connected to the case for now. The subpanel's Neutral Bar is isolated at the panel and is not connected to subpanel's case or GND in the subpanel.

Also, there is 0V (0.12) between P1 and P2, which when I thought about it based on how it is connected, P1 and P2 are both in the same phase (H1/H3) so 0V is expected which is what my electrician was guessing and is what was posted earlier. Until now, he had never seen or connected one of these before.

I may try to find an Isolated Ground Bar for the sub-panel (or use another Isolated Neutral Bar) and swap out the GND bar but I still have to GND the panel's case.. so its another cable back to the same GND at the IsoT either way.

I understand that some recommendations are not bond the secondary N1, N2 and GND on the output side which is why you have 0V between P1/P2 and GND on your setup. This creates a "floating system" where the Neutrals are not bonded to GND. However, from other postings, and the MiddleAtlantic paper, I have the impression that the layout on Page 21 is required to meet US NEC code.

The N1 to GND bonding has to do with the safety / failure of the transformer, it shorting to the case / GND and then there being no GND return. Also, if any GCFI devices are downstream of the IsoT, for them to function, Neutral and GND must be connected at some point, I read. This may differ in other countries and it may differ when using IsoT in boating / marine setups - which are not the same as the application here.

For my application, wiring to US NEC and human safety is paramount over noise, knowing that with age, we will never be able to hear it in a few years anyway.. Wink

Does this help? For why I did it this way?

My only explanations for 131/132 V are:
1) that the secondary windings are slightly not perfect
2) this IsoT is defective in some way. (It was purchased as University surplus.)

Other thoughts? Thanks, Vincent.


Last edited by gattaca on Sun Jan 08, 2012 7:21 pm; edited 2 times in total
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macgyver655



Joined: 22 Aug 2007
Posts: 8508



PostLink    Posted: Sun Jan 08, 2012 6:02 pm    Post subject: Reply with quote

Your output is probably high because your input is high. Transformers are not smart so they can't put out precise voltages with varying inputs. Unless they have some sort of built in regulation.

And again would not be a volt for volt difference. 2v in difference could yield 6v out/ or more.

With that said there is not much you can do with your power coming in other then contact the local power co.

In thinking about your 130v+ output, I can't see this causing a problem with your equipment anyways. Your equipment merely takes the A/C input and converts it to D/C and then regulates it to what it requires.
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Nashou66



Joined: 12 Jan 2007
Posts: 16167
Location: West Seneca NY


PostLink    Posted: Sun Jan 08, 2012 6:34 pm    Post subject: Reply with quote

Never thought of that Mac!! Makes perfect sense.

My 240 line was spot on measured on the input side.

I doubt the Electric Company would do anything for that small a variance.

Nashou

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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Sun Jan 08, 2012 7:28 pm    Post subject: Reply with quote

Mac and Athanasios,

Thanks for the reply!

I too did not think 243V vs 240V would shift the secondary output up that much but it makes sense now that you said it.

The secondary output has been pretty consistent at 130, 131, 132 V.

I lowered the UPS sensitivity thereshold not be as sensitive and to transfer at 138V. This will hopefully be the compromise needed to:

1) keep the UPS out of alarm mode (unless the voltage > 138V
2) Stop the UPS from "trimming" the power back down to 115V.

I have no idea how it does #2, but the manual said it could operate that way indefinably and that is not switching to battery to do the trim. I'd prefer the UPS only be active when really needed.

Photos -> https://picasaweb.google.com/103727542964700646227/20120108IsoTProject?authuser=0&authkey=Gv1sRgCIXKiIXL2PWavgE&feat=directlink

Later, Vincent
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Boilermaker



Joined: 21 May 2006
Posts: 527



PostLink    Posted: Tue Jan 10, 2012 10:07 am    Post subject: Reply with quote

Sorry, but I just noticed these last posts!

Your overvoltage is most likely caused by the fact that your iso transformer is a 208 volt transformer. Most of them are, as 208 volts is the phase to phase on many three phase distribution systems. The easy, proper, and inexpensive solution is what I recommended earlier - simply install a buck-boost transformer in the primary side. It only needs to be sized for the percentage increase or decrease in the voltage ratio, so about 15% of the iso transformer rating.

Also, unless I misread your post, why are you feeding a ups system from your iso transformer? It is redundant.


Bob
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Boilermaker



Joined: 21 May 2006
Posts: 527



PostLink    Posted: Tue Jan 10, 2012 10:42 am    Post subject: Reply with quote

Just ran downstairs to get the nameplate data on the buck-boost I use. It is a Square D cat. no. 500SV46F and rated at 0.5 KVA. It is about 7"X7"X7" and barely gets warm. It has been on for over 25 years.

Bob
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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Wed Jan 11, 2012 4:10 am    Post subject: Reply with quote

Hi Bob. Thanks for the suggestions! I checked and my Topaz has 120/240 Input, not 208. See the photos posted.

As in prior posts, my "240V" varies between 240V - 243/244V.

The reason for the UPS downstream (which is measuring the voltages constantly) is because I have DLP hardware in my AV setup. The UPS protects the UHP bulbs as they do not like to loose cooling... It also keeps my DVR alive during power blinks etc.. Been running like this for more than 10 years.

Our earlier discussion centered on my higher than 240 V... with the other guys noting it will shift the output more then a few volts. Presently, readouts are 125V - 128V, so I guess my utility is allowing the voltages to fluctuate.

Thanks, Vincent
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Nashou66



Joined: 12 Jan 2007
Posts: 16167
Location: West Seneca NY


PostLink    Posted: Wed Jan 11, 2012 4:18 am    Post subject: Reply with quote

So the Big Question is...HOW does your system look and sound now with super clean power?!?!

Very Happy

Nashou

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Boilermaker



Joined: 21 May 2006
Posts: 527



PostLink    Posted: Wed Jan 11, 2012 4:42 pm    Post subject: Reply with quote

Quote:
Mine never went up in voltage. Something is not right i would think.


I agree - Something is wrong. As Mac said, these transformers are very simple and dumb devices. Using the schematics you supplied, there is an exact 1:1 ratio of turns on the primary to secondary windings when used with a series secondary configuration. Each of the two secondary windings has 1/2 the number of windings that the primary does. i.e., you could supply 120 volts to one of the secondary windings and get 240 on the primary. Being dumb, transformers work backwords just as well as forwards.

Please do this:
1 - remove all the secondary loads.
2 - measure the primary voltage which should be approximately 240.
3 - measure each of the secondary cvoltages - they should be virtually identical to each other and 1/2 of the primary voltage you measured. If not, there is something wrong!

Since your connected load is nowhere near the load rating of the transformer, the IR drop would be insignificant.
Assuming that the nameplate is correct, if the no load voltages are not inline with the 1:1 turns ratio, I believe you might have a winding to winding fault. This fault(short) would change the effective turns ratio as no current would flow in that one winding. The transformer would still work, but at the incorrect voltage as its true turns ratio changed.

Please let us know what you find.



Bob
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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Thu Jan 12, 2012 5:50 am    Post subject: Reply with quote

Boilermaker wrote:
Quote:
Mine never went up in voltage. Something is not right i would think.


Please do this:
1 - remove all the secondary loads.
2 - measure the primary voltage which should be approximately 240.
3 - measure each of the secondary cvoltages - they should be virtually identical to each other and 1/2 of the primary voltage you measured. If not, there is something wrong!

Bob


Athanasios, Thanks for asking. It is SO quiet that I can only tell the AV setup is on by looking at the power LEDs. Now I'm going to have to work on quieting those cabinet cooling fans! (next project)..

Hi Bob, Here's the info, measured AT the transformer terminals:

Loaded:
Input ~ 244.3
Output: 132.2 V P1 / 132.3 V P2

Unloaded
Input ~ 244.7V
Output 125.65 / 125.6

Someone borrowed my clamp-on meter and has not returned it so I cannot measure the AMPs presently. My guess, will be 6-10A for P1 and 6-10A A for P2. I'll try to locate my meter, (it will be next week) and get a better AMP measurement so we know the load.

Does this help tell you guys anything?

Thanks, Vincent
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Boilermaker



Joined: 21 May 2006
Posts: 527



PostLink    Posted: Thu Jan 12, 2012 9:39 am    Post subject: Reply with quote

Quote:
Does this help tell you guys anything?


If you look at the unload voltages, they appear to be within normal tolerances at about 2:1. Also the secondaries are very close to each other which would allow you to parallel them with no wasted current caused by any unbalance.

Also, if you look at the unloaded primary vs the loaded primary there is a slight drop as you would expect through normal IR loss.

What doesn't make any sense is that the secondary voltage increases with load! If anything, I would have expected a slight drop. It seems backwards to me, so I am bumfuzzled!


Bob
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Boilermaker



Joined: 21 May 2006
Posts: 527



PostLink    Posted: Fri Jan 13, 2012 6:29 pm    Post subject: Reply with quote

Sorry, but I just can't leave this one alone!

Please try this:

1 - Unload both of the secondaries and take voltage readings.
2 - Load one of the two secondaries and take readings on both secondaries.
3 - Increase the load even more on the loaded secondary and read again.

I want to see what happens to the loaded and unloaded secondaries and surely the primary won't change.


Thanks,
Bob
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gattaca



Joined: 28 Nov 2011
Posts: 20



PostLink    Posted: Sat Jan 14, 2012 2:26 pm    Post subject: Reply with quote

Good Morning Bob,

It will be mid to late next week before I can take those readings. All the up/downs are disruptive and my better 1/2 will not be happy with visiting relatives.

I am also curious so I will bond / connect both secondaries and measure the voltages unloaded / loaded on the primary and secondary while I'm measuring.

OK, thinking about this more, could what I have downstream be altering the expected outcome under load? I KNOW the downstream loads are at least 7-18A w/ the Furmans on and also the SmartUPSes have some large transformers inside them as well. I need to get my clamp on meter before I can provide AMP readings now.

When I first installed the Furmans, I collected measurements and they were consistent with the higher VA readings I expected from the Torids via my little Kill-o-watt for a few minutes. The post here by Matthew J Hammett (30 Jul 2011) confirmed - a high VA reading from the Furmans so I concluded that is expected and fortunately, we in the US are billed by KWH. --> http://www.hometheaterhifi.com/power-conditioners/611-furman-it-reference-20i.html?start=2

Here's the layout again:

Stage 1 is contained within about 15' of each other in the garage:

240-244V / 40A Brkr Panel -> Topaz IsoT -> 2 x 20A Panel Breaker -> 2 x 20A SurgeX ->

Stage 2 includes ~ 75' dedicated home runs of 12/2 Romex:

-> 75' of 2 x 12/2 Home Run Romex to AV closet -> 2 x 20A APC Smart UPS3000VA -->20' 12/2 Romex ->

Stage 3 is actually inside the AV cabinets:

2 x Furman Reference IT Balanced Power PDU --> AV Setups

I know my Furmans may not be necessary now, but I'm keeping them b/c they are providing:

1. The outlets are the main power distribution units for the AV endpoints
2. They contain Furman's "Power Factor Technology" which is capable of supplying 80A at high peaks for handling the power AMPs.
See --> http://www.furmansound.com/page.php?div=01&id=FAQ_PowerFactorCE
See --> http://www.furmansound.com/video.php?id=11
There is a large cylinder is installed inside my units and that contains this reactive circuit which I believe is some sort of a capacitor bank, but exactly what's inside the tube is proprietary and you would have to destroy / open it to know for sure. It looks like a large section of PVC tubing with wires entering one end and exiting the other.
3. They are quieting noise the UPS may be inserting.
4. They are, with each pair of outlets on the rear (other than the AMP outlets), isolating each component and noise from the other components as the Torid is a multi-tap design.
5. They are providing additional linear noise filtering for both normal and common-mode noise.[/list]

Does this help explain what we are seeing? Does it muddy the waters?

Later, Vincent
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