Please help! Isolation/balanced power question.

[jborum]

I'm brand new here, as of today, so Hello!

I run a recording studio and have recently decided to revamp the power in the studio and control room. My goal is better grounding and balanced power, and I will be replacing all the wiring in the walls. I was recently given a Topaz Ultra Isolation Transformer 91001-11 (1kVA, 50/60 Hz, 240/120, .005pF). It is my understanding that I can use this both for isolation and to create balanced power.

Will somebody be so kind as to tell me precisely how to wire this up? I found this post http://www.audioasylum.com/audio/tweaks/messages/58208.html but it only addresses where to put the ground wire and I sadly don't know what to do with the other two.

I have both 240 and 120 available to me, and my goal is 120 balanced. I will attach my schematic, or you can see it here: http://www.jeremyborum.com/TopazSchematic.jpg

Thanks in advance from a less knowledgable music guy.

- Jezza
jb@jeremyborum.com

PS: Out of curiosity, do transformers continue to consume energy when the load is turned off? They always hum, so does this mean they always consume some small amount of power?

 

[Speedskater]

You might be able to wire it balanced 120 Volt input and 120 Volt output, but you will be limited to 500VA (same current in the primary windings but only one half the voltage)

 

[paulb]

PS: Out of curiosity, do transformers continue to consume energy when the load is turned off? They always hum, so does this mean they always consume some small amount of power?

Yes.

 

[cyclotronguy]

power

Yes, they consume "charging current"..... mostly as VAR or wattless power and for what it's worth, so do utility company transmission lines, especially underground ones. Having said, for most users; it's a minimal energy expense.

Cyclotronguy

 

[jnb]

Re: power

A transformer primary has a considerable inductance which presents a high impedance when it isn't being shorted via the secondary load.

mostly as VAR or wattless power

This is true, a pure inductance doesn't draw power like a resistor does. WRT the buzzing, this is producing heat and sound energy so that consumption is real (but small). Just a thought, can the bolts be tightened?

 

[jcx]

It might be worth reading Bill Whitlock's stuff, seeing if a seminar is close by and calling him up at Jenson for recommendations

http://www.jensentransformers.com/apps_wp.html

Bill's seminar notes covers some of the AC line side causes of the problems as well as the signal level balanced/transformer solutions Jenson supplies


also you will need to meet electrical safety code and have the local inspector approve the installation

 

[jborum]

I have already spoken with two different electricians regarding the rewiring of my studio. They're both quite skilled and know all the code, but neither had heard of balanced power and didn't know what I was talking about. I may need to find an electrician who specializes in studio and theatre wiring.

 

[Conrad Hoffman]

I can't imagine how balanced power is even permitted under code unless they allow it with different plugs to prevent common items with polarized two prong plugs from being accidentally connected to it.

 

[jnb]

http://www.diyaudio.com/forums/showthread.php?s=&threadid=21802&highlight=

http://www.diyaudio.com/forums/showthread.php?s=&threadid=82520&highlight=

 

[jcx]

Google is your friend, the above threads gave enough leads to get to this NEC commentary:

ART. 647 — SENSITIVE ELECTRONIC EQUIPMENT
An Article covering the wiring requirements for “Technical Power” or “Balanced Power Systems” was added to the 2002 NEC. Technical power is a separately derived, 120V line-to-line, single-phase, 3-wire system with 60V to ground from each ungrounded conductor. Technical power systems reduce objectionable noise in sensitive electronic equipment locations. They are restricted to commercial and industrial occupancies under close supervision by qualified personnel [647.3]. You cannot install them in dwelling units.

Intent: Technical power has been permitted in the NEC since 1996. However, it was located in Art. 530 — Motion Picture and Television Studios and Similar Locations, so its use was limited to these applications. By locating the requirements in a separate Article, its use can be greatly expanded.

equitech has some articles, explanations pushing the idea

http://www.equitech.com/articles/articles.html

 

[Conrad Hoffman]

Cool- didn't know about the NEC provision.

 

[AndrewT]

Hi,
Re post1 transformer schematic:
that electrostatic screen (S1 & S2) is connected to H4 and X4.
The input side could remain connected to the neutral but it is much more usual to connect the screen to the safety earth.

The output connection between X4 and S2 must be broken if you want balanced power. Otherwise your screen is going to be connected to 55Vac.

In the UK all our industrial power portables MUST be powered by split phase 55Vac, commonly called 110Vac, to ensure that accidents never expose anyone to more than 55Vac. Our electricians know how to wire them up.

 

[jborum]

After much internet searching, and thanks to the links above, here is how I've wired the transformer:

The primary and secondary are both in series.

Input:
Neutral (white) to H1
Hot (black) to H4
Ground to chassis

Output:
Hot 1 (white) to X1
Hot 2 (black) to X4
X2/X3 center tap connected to chassis ground and outlet ground.

It's very simple, as I knew it would be, and it works fine with single amps. I'm still nervous about plugging in my computers and my whole rack full of stuff though...

 

[AndrewT]

and where are the screens connected?

The s1 screen is normally connected to safety earth but can go to neutral.
The s2 screen is normally connected to safety earth, but must not go to neutral and certainly not to antiphase pole (hot2). It may comply by taking S2 to audio ground.
Any safety expert out there with a view.

Before you plug it in, wire a mains light bulb in series from mains hot to primary hot.

 

[jborum]

Andrew,

Thanks for the reply. Balanced power is a novelty here in the states, and most electricians never have to think about it. As I said earlier, I've asked two different electricians about it and gotten blank stares.

I will attempt to open the metal chassis and see if I can locate the contacts for the shield (S2) to disconnect them. I'm afraid I don't understand why it needs to be disconnected though. Don't I want voltage on both X1 and X4?

Forgive my novice questions - I'm a musician who dabbles in technical stuff out of necessity.

- Jezza

 

[jborum]

PS: I do not have readily accessible contact points for the screens. They're connected internally.