Toroidal transformers

[Jcris]

Purchased a Antek AS 4218 transformer and see that it’s not round. The outer wrapping is not damaged but the donut, if you will, is clearly not round. I suspect this is not an issue but had to ask. The picture doesn’t really show it very well but I wonder if this is because of the rather large gauge secondary wires?
I haven’t used a toroidal before so this seems like a total rookie question

 

[H713]

Not a problem, they're all like that. It's got to do with the shielding they use and the input / output connections. Ends up with a couple bumps.

I would not worry.

 

[rayma]

The core is perfectly round, and then wires etc are added around and on it.

The most popular rookie mistake is to connect both ends of the mounting bolt
galvanically to the metal chassis. That would cause a magnetic short circuit.
Only one connection is allowed.

 

[Mr_Zenith]

Absolutely not an issue, as the others have stated. Mount it well, hook it up, and enjoy!

 

[Jcris]

Excellent, thanks!

 

[abraxalito]

Do to the deviation from being perfectly circular, the magnetic fields around the trafo aren't equally uniform. Its best to orient the trafo so that the lead-outs are furthest from the sensitive circuits (input stage of your amp for example).

 

[Jcris]

I wondered that, so much to learn and remember.
Old guy issues ��
Thanks Abraxalito

 

[H713]

Do to the deviation from being perfectly circular, the magnetic fields around the trafo aren't equally uniform. Its best to orient the trafo so that the lead-outs are furthest from the sensitive circuits (input stage of your amp for example).

I'm not sure that's quite right. As Rayma mentioned, the core itself IS perfectly circular (or very close to it). The tape-wound cores they use are reasonably decent and the radius should be very consistent.

There will be some stray magnetic fields caused by the lead-in / lead-out wires themselves (twisting them helps those fields cancel).

 

[abraxalito]

As Rayma mentioned, the core itself IS perfectly circular (or very close to it). The tape-wound cores they use are reasonably decent and the radius should be very consistent.

Yes, no disagreement there.

There will be some stray magnetic fields caused by the lead-in / lead-out wires themselves (twisting them helps those fields cancel).

Yes, twisting them helps with the fields created by the current flow in the lead-out wires. But there's still more flux leakage from the core (even when zero current drawn from secondaries) where the lead-out wires are as uniformity of flux requires geometric uniformity of windings around the core too.

When I wrote 'deviation from being perfectly circular', I wasn't referring to the core, rather the lead-outs of the windings are the irregularity.

 

[NareshBrd]

Much better in this regard than E-I cores.
Don't worry too much.
Can you connect the mounting bolt to Earth directly?

 

[Jcris]

Hadn’t considered that but seems worthwhile.
And easy enough to do
Thanks