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Hi Guys,
I'm about to start a Balanced Power project but I need some guidance.
Background Data
===============
I've sourced a 2.4kVA isolation toroid from Plitron, schematic: http://www.plitron.com/shopping/specs/877001.pdf
I plan on using this enclosure from diyenclosures:
http://www.diyenclosures.com/products/chassis/diy1013/
I already own a Zero Surge 2R15W (120v/15A) all-in-on surge suppressor and EMI filter (see: http://www.zerosurge.com/HTML/standaloneres.html)
I plan on having two output receptacles. The first outlet will be used by all my digital equipment with the Zero Surge unit connected in-between to provide EMI filtering (and possibly surge suppression?)
In the second outlet I plan on plugging in the my ht receiver. I read somewhere that EMI filters can affect sound dynamics (can't remember where I saw this)
Questions
=========
(1) Is my choice of toroid sufficient
(2) Is it was to put a surge suppressor on the output side of the transformer
(3) Do EMI filters really affect dyanmics? If not, I will put the Zero Surge unit between the wall receptacle and input to the transformer.
(4) Did I miss anything (e.g. tweaks?)
Thanks!
George
Follow Ups:
OK...where to begin???1. The transformer size is fine, but I would look into a bifillar transformer. Sometimes BPT will sell bulk NBT transformers. Email Chris and ask....worst case you can mention my name. The NBT will offer superior internal noise filtering.
2. It is wise to put a surge protector on the input side of the transformers, the output is stupid. The noise filtering the surge unit is going to provide is garbage at best, better to keep it on the primary and allow the transformer to filter out the harmonics created by the surge unit.
3. Filters on the primary and secondary will greatly effect the dynamics of the transformer. It is better to use parallel designs for both applications. Look at the Hammond 193L and M tweak. The Hammond can be used with any kind of multi cap value parallel filter to extend the bandwidth.
4. Yes...you are only taking into account the noise filtering aspects. you need to understand other things will also effect the harmonics. The chassis, if metal, will ring. The ringing will inject noise into everything attached to the chassis. The noise filters will be unable to filter properly because the added ringing will alter the filters ringing character. It is best to float the components. I suggest two products...1. 1/4" microsorb and 2. EAR C-1002 1/4". Place the Microsorb over the entire bottom of the case. Place the EAR C-1002 on top of the Microsorb. Microsorb is self stick so no need for glues. Use brass hardware to mount everything. Next...when mounting the outlets, use a .015" thickness of EAR C-1002 between the face and yoke of the outlet and the chassis. The reason why many people upgrade outlets is because of ringing character of each model. The C-1002 will help control and reduce some of the upper high frequency harmonics tat the chassis is creating. Other materials can be used too pending the filtering design of the case. For example, if you decided to use ERS for added noise filtering, install the ERS under the bottom Microsorb layer. Cover all sides in ERS including the outlet side of the case. This will offer good passive filtering....make sure to add a single layer around the transformer as well...no need to cover the top and bottom of the transformer if the chassis is covered...don't want to cause overlap in harmonics by adding too much product...if that happens you wind up putting a lot of other sh*t in series to compensate for the screw up.
If you need additional help just drop me an email.
Alan
Sounds a little more complicated than I originally thought :-)
I'd like to ask a more fundamental question.
Is there a significant difference in noise reduction between using a medical power isolation unit (see link below) and a balanced power unit?
http://www.plitron.com/shopping/shopdisplayproducts.asp?id=106&cat=North+American
The reason I ask this is because I've calculated the balanced power project costs and they are around $900-1000.
Using a parallel filter or line-to-ground surge suppressor on the input is NOT a good thing, especially if a technical ground is not used. A parallel filter or line-to-ground surge suppressor on the input will inject filtered garbage into the ground line, exactly what you DON'T want. A series filter like the Zerosurge would be better on the primary. It doesn't dump into ground line. Commercial EMI filters are usually balanced. If they dump into the ground, then they should be used only on the balanced side or secondary of the transformer.
As to the "ringing", you are unclear as to whether you are speaking of electrical ringing or mechanical ringing. If it is mechanical ringing, I'd like to know how this "ringing" affects the quality of the electrical power, and why it would not be easily filtered out by load transformer/rectifier/capacitor filters down the line. Just how high in frequency can this ringing possibly be that any possible effect in the power is harmful?? Balancing is about keeping the ground line clean.
Maybe a y-cap on the primary but not a parallel across the load. Any filter running to earth on a balanced set up, primary or secondary, is a no no.
I was speaking about mechanical ringing. Why would you want to filter it down the line when you could attack the source? I have built PLC's with and without damping material. The shock mount method has always resulted in better overall performance from the unit.
Alan
<>
Don't know how you distinguish a Y-cap from a parallel, but a Y-cap is a line-to-ground cap and will dump high frequency noise on the ground line. If this safety ground on the primary is tied to the neutral/ground of the secondary center tap, you've essentially shot the balance transformer in the foot. This is because the primary is not balanced, and dumps all the noice current into the ground line. If you use y-caps, they should be from each hot to ground on the balanced secondary, where the noise will ideally cancel in the ground line. That's what balanced is about!
On the other hand, you could run a separate safety ground and a technical ground. These should not connect anywhere except at the service entrance. The technical ground is connected to the midpoint of the secondary. The safety ground can then be used to carry filtered noise without conductive coupling with the clean technical ground.
<>
What do you think the power supply caps do?
< >
Ringing is usually a term for electrical oscillation. Vibration is a clearer term for mechanical vibration. I can appreciate that if you damp mechanical vibrations to prevent sound emmissions from the enclosure, but what mechanism can possibly make an electrical difference in the load?
oops (2) should read
(2) Is it wise to put a surge suppressor on the output side of the transformer?
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