Balanced Mains - first impressions very favourable

[worrasf]

Do you have a DVM Steve...I would be interested to see the difference in voltage between the inpuit and output......

Hi Ray,
I do have a DVM but I installed the BMS using an analogue VM. I did not detect any difference between the input voltage from the mains going into the transformer and the output voltage at the wall sockets measured live - neutral, live- earth (50%) and neutral - earth (50%). The BMS transformer is in the loft - next time I have cause to go up I'll put a DVM across the input terminals and then at the wall sockets and let you know but going by the AVM readings if there is a difference it will be negligible.

Steve

[Ali Tait]

It will drop a little depending on the load.

[jantheman]

It will drop a little depending on the load.

The opposite is true in my case...V/OUT is 4.7% higher than V/IN.....measured with no load.

[Glen B]

With balanced power, difference between input and output tells you nothing. At no load, the voltage at the secondary will always be slightly higher than the primary. Exactly how much will vary some from one transformer to the next.

What matters with balanced power is that the voltage between the center tap and ends of the secondary winding be as identical as possible. This is achieved by the transformer manufacturer getting the center tap as close as possible to the center of the secondary winding. The smaller the difference in voltage between the two halves, the better the common-mode noise rejection value, and vice versa.

[jantheman]

Accumulation of tolerances.............

[Ali Tait]

The opposite is true in my case...V/OUT is 4.7% higher than V/IN.....measured with no load.

Aye, but put some load on it and watch V/out be less than with no load.

[jantheman]

Aye, but put some load on it and watch V/out be less than with no load.

I agree...but....look at it from this point of view......
Measuring the O/P of the balanced transformer........
With no load I get a reading of 259V...outside the accepted tolerance for mains in the UK. The spec for UK voltage is now 230V +10v -6v. Fudged to harmonise with the rest of Europe. Just a note..my mains tends to run quite high, as I write its at 247V.
Looking at this then the max 'in tolerance' voltage should be 253V. So..I'm +6V on this.
For every 100W I plug in I get *about* a 1V reduction in the voltage out.
So, I'm going to have to have a *constant* power draw of some 5/600W in order just to stay within the current accepted tolerance.
There are 1 or 2 items of my hifi gear that I dont switch off but they dont even add up to 100W so they would be running well outside of the tolerance limit for UK voltage.
Is this voltage damaging to said kit, no one will say, least of all the designers...........

[Reid Malenfant]

What's the VA rating of the balanced transformer Ray?

I have a cunning plan

[jantheman]

What's the VA rating of the balanced transformer Ray?

I have a cunning plan

1500VA....and dont say a Variac..cos I already have one........

[Reid Malenfant]

1500VA....and dont say a Variac..cos I already have one........

No, you just need a 50VA 6V transformer me old fruit!

I made this diagram to show how i think the VPhase unit works, in your case you'd need a 50VA 6V transformer to step the mains voltage down slightly for safetys sake

VPhase.jpg