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Old 30th December 2012, 10:13 PM   #1
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Default Isolation transformer

I would like to use a set of isolation transformers in my studio. I would likely use 5 in total they would be 120V and unlikely that either would ever see more than 5 amp current.
How do I calculate the rating? What would the physical size be and where is the best source for these?
Thanks
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Old 30th December 2012, 10:22 PM   #2
AJT is offline AJT  Philippines
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make a list or all equipment in your studio, tabulate power consumption of each, then get total, divide the total by 0.7 to get the va capacity you need...
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Old 31st December 2012, 03:00 PM   #3
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There are premade devices that you require... See Sola-Hevi Duty
Sola/Hevi-Duty Products | Sola MCR Hardwired Series Power Conditioners

The traditional isolation XFMR will do what it states, isolate you from the grid. There are advantages to this, but no other features to help correct issues. If grid sags, the output sags...

Sola offers many products that help correct problems as well as isolate. No I am not a paid person. There are many other companies that offer similar products, Sola is THE brand in industrial applications in the USA. For your size requirements, you might fall into a commercial/industrial solution. Not sure if price is cheaper than DIY, I would assume so.
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Old 31st December 2012, 10:37 PM   #4
CZ101 is offline CZ101  United States
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Quote:
Originally Posted by argonrepublic View Post
I would like to use a set of isolation transformers in my studio. I would likely use 5 in total they would be 120V and unlikely that either would ever see more than 5 amp current.
How do I calculate the rating? What would the physical size be and where is the best source for these?
Thanks
Hey I have often wondered if using multiple isolation transformers for separate but connected pieces of gear could potentially introduce grounding problems?

Would anyone care to comment?
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Old 1st January 2013, 05:21 PM   #5
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Well the more transformers, the more chances of wiring them up wrong!
The current best thinking is to put everything on one circuit. (with the exception of real big power amps) To reduce the length of AC power cables between components.

Before doing anything read this paper, starting at page 19.

http://www.middleatlantic.com/pdf/PowerPaper.pdf
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Old 4th January 2013, 04:37 PM   #6
GoatGuy is offline GoatGuy  United States
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Dunno... but in my experience, a good SINGLE, high-power isolation transformer is helpful - in eliminating floating ground problems, mis-wired power wall sockets, stupid shortcomings of the abode power system, and the influence of back-current and DC current from other sources.

The single transformer though should be selected/wired though to step UP the voltage a bit, on the average. Measure line voltage. Say it is 113 volts. Choose a set of winding combinations that produces an output less than 130 volts, but close to it! Any further sags in power should now fall within the tolerances of your equipment. Even if you go significantly over-voltage (toward 140 VAC), there are precious few pieces of equipment that will even so much as burp with the higher drive voltage. Best though is to be close to 130 V. The same argument goes for european 220/240 volt circuits.

Then, on the output (secondary) of the isolation transformer, add the usual combination of inductors and A/C capacitors to make a rudimentary high-frequency interference squelch circuit. All your devices will be happy! You could even then include (on the primary) both filtering LC devices as well as overvoltage clamps and high-energy transient suppressors.

Happy filtering!

GoatGuy
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