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Using a couple of 240V mains step down transformers, undecided whether to use E/I laminated or toroidal, one 22VA the other 7VA. How to mount them in the case, so that they're not affected by each others magnetic fields?

This is unless I can find one ready made with separate secondaries of 22-0-22 and 7-0-7.

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2 Answers 2

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Toroids have very little magnetic leakage, so if you can find two of those, that would be ideal. There are many toroidal transformers for sale on eBay, give that a try. E-I laminants are pretty good also. Is this for a high-end audio amplifier? Magnetic flux dissipates inverse-square with distance, so even a few inches is good enough for most applications. If you can put them on opposite sides, even better. :)

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Try putting in a piece of steel sheet (contains iron) in between the transformers, never tried it myself but it should provide a low reluctance path for the magnetic flux, so the flux should concentrate inside the steel sheet and provide isolation between the two. But you'll get eddy currents induced in the steel sheet which will create their own magnetic field..that may not be a problem though. But as rdtsc says, physical separation will help. Magnetic fields don't reach so far in air.

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