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Old 10th July 2014, 10:43 PM   #1
greg7 is offline greg7  United States
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Default EI Transformer Question

Apologies if I should have posted this in the power supply forum. I'm building an amplifier and I'd like to use one EI transformer per channel. I realize I should orient the "bells" away from the circuit boards but what about the orientation of the two transformers with each other? Does it matter or is there a minimum distance I should keep between them? They're only 90VA apiece. Should I "stagger them" so their bells aren't pointing right at each other?
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Old 11th July 2014, 03:36 AM   #2
jcx is offline jcx  United States
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mains power transformers should be positioned to minimize mag field leakage coupling to the rest of the amplifier circuit

but mag field leakage coupling between the power xmfrs is not an issue - they both connect to the power line so are already heavily coupled, the mag field leakage coupling between them is orders of magnitude less


audio output xfmrs may have numerically measurable coupling that some may want to minimize but stereo channel crosstalk < -40 dB is not a big deal for listening with speakers
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Old 11th July 2014, 06:43 PM   #3
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Quote:
Originally Posted by jcx View Post
mains power transformers should be positioned to minimize mag field leakage coupling to the rest of the amplifier circuit...

...
Hello jcx,

Does this apply for toroidal transformers as well? Thanks.
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Old 14th July 2014, 12:12 AM   #4
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Toroidal transformer have very low leakage.
2 standard laminated transformer should not be mounted paralell, should have 90 degre angle rotation betwen them.
Same applies to air core inductors in cross over layout.
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Old 14th July 2014, 01:41 AM   #5
jcx is offline jcx  United States
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again - totally depends on what the xfmrs are doing - when connected to the power line there is no reason to be concerned about coupling of leakage mag field between the 2 power line xfmr - their primaries are Wired Together

if anything you would want to see if some orientation of the power transformers could make the sum of their external leakage fields cancel somewhat - that won't be by placing them at 90 degrees to each other
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Old 14th July 2014, 11:25 AM   #6
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External field cancellation is almost impossible .... crosstalk or cross induction can be reduced ... ( in transformer language it is known as coupling factor ).... this is the purpose of 90 degre mounting orientation.
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Old 14th July 2014, 11:43 AM   #7
AndrewT is offline AndrewT  Scotland
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The circuits around the EI transformer can be susceptible to the spray of radiation.
Often rotating the Mains transformer can effect a big change in hum measured on the output of the circuit.
If you have many circuits spread around the floor of a chassis containing an EI transformer, it may be difficult to find an optimum orientation for all the circuits.

Toroids leak much less radiation, but they too can benefit from rotating for least interference.

I would expect Ccore and Rcore and other "exposed core" transformers to be noticeably worse than toroids.

Replacing the solid core tails fitted as standard to many transformers, with stranded wires allow experimentation to minimise interference.
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Old 14th July 2014, 09:39 PM   #8
jcx is offline jcx  United States
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Quote:
Originally Posted by audiofan View Post
External field cancellation is almost impossible .... crosstalk or cross induction can be reduced ... ( in transformer language it is known as coupling factor ).... this is the purpose of 90 degre mounting orientation.
read the 1st post: it appears that the subject is dual Power Line Connected transformers - the 90 degree minimum mutual leakage field coupling condition is irrelevant to this application

minimum mutual coupling is only important for Signal transformers carrying independent signals

the situations are different - the application changes the weighting of which engineering principles are important
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