[pureAC]

Hi all,

Just wondering..

I live in Australia and we have 240v power.

I was thinking about using the isolation transformers used in building sites to acheive some power conditioning?

Would I receive any benefit buy getting two isolation transformers, and wiring the secondaries of both in parallel. Then using the primary of the second to power my components?

I realise this is not a balanced type, so if I had one 240v iso tranny and two 120v isolation transformers, and did the same thing, can I just connect the two primaries on these second transformers to power my components? what abour the center on the two secondaries??

pureac

[Occam]

PureAC,

The use of 'site transformers' is an excellent idea! Actually, its an ideal low cost way of providing balanced power to your components, if they're set up to be powered by 120vac. The transformer from RadioSpares that you referenced in the Richard Gray thread is a balancing transformer, but sadly for you, also a step down. The rational behing these transformers is to allow the use of less expensive powertools. In an effort to provide enhanced safety they ground the center tapped secondary to provide split phase 55vac (totaling 110vac) as a safety measure. In the case of a short, 55vac is about 1/4 as leathal as 110vac. I don't know whether non-step down site transformers, 230vac>230vac, provide that same safety measure of grounding a center tapped secondary. If you do a regular seach on Ebay, you'll often see various site transformers on sale from Australia and GB for bargain prices.

As to using multiple transformers in lieu of dual or center tapped secondaries, yes, that could work. But the efficacy would be dependant on how closely the winding on the separate transformers match. This was discussed here, in the Felicia constructors thread -
http://www.audiocircle.com/index.php?topic=18443&postdays=0&postorder=asc&start=265

Or one could simply take 2 120vac 1:1 isolation transformers, wire both the primaries and secondaries in series, ground the 'center tap' between the connections of the secondaries, and get balanced output, but subject to the matching between the transformer windings. You could also do this with 2 230vac isolation transformers, and in series configuration, although the transformers might 'expect' 460vac, if you feed it 230vac, it will work fine. Just remember, you can feed a transformer winding a lower voltage, but you cannot exceed its current rating.....

The whole idea behind Felicia was to take available low cost surplus transformers and make them useful for powerconditioning. Sadly, there doesn't appear to be much surplus available in Australia, and your retail products seem to be priced substatially higher than in GB (comparing prices between RS Australia and RS Worldwide). If you have to pay 'retail' for your transformers, cascading transformers as in Felicia doesn't make much economic sense. If you're masochistic enough to specify new and/or customized transformers, remember that the secondary should be either shielded from the primary or the primary and secondary should be wound on split bobbins. Either technique will minimize capacitive noise coupling. If possible, the secondary should be wound bi-filar to ensure balance between the antiphase outputs.

Welcome to AudioCircles,
Paul

[pureAC]

Cool,

I am trying to figure out how I can build a felicia, but am finding out that it is very expensive in AU to source suitable components.

I wanted to go for a big, run all your components unit. but might just settle on a small unit for one component to get my fingers wet.

The funny thing is that the large iso trannies, and not that much more expensive that the smaller ones

How woudld the motor run capacitors change if I ran 240v?. It looks like it all matters on the transformer VA rating.

pureac

[Occam]

Motor run caps work quite well. Their big advantage is that the oil filled ones are typically 'protected' (they fail open when an internal metal membrane ruptures under fault conditions). I've used various dry and oil filled motor run, HID, etc... caps. (you can see the journey if you're willing to slog through the 30+ page thread.)
But frankly, for this specific application, IMO, you'd get better results with a 630v rated Solen/SCR/Axon metalized polypropelene axial cap. I realize the ASC and GE motor run caps have mucho audiophile cred, but they simply don't work as well, in this application, as these run of the mill audio caps. In the States, I use Jantzen 400vdc axial polypropolenes for both the main caps and their bypasses, but with your higher voltages, the Solens (rated at 400vac for their 630vdc caps) are a safer bet. Auricaps work very well, but are quite expensive.
I've no technical explanation for my preference, just subjective evaluation. No am I familiar with the regulatory requirements for 'accross the line' AC caps in Australia.