Re: Toroid vs. Conventional Transformers

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Posted by Andy Peters on January 17, 2001 at 13:16:19:

In Reply to: Toroid vs. Conventional Transformers posted by Arthur J. Dock on January 16, 2001 at 18:13:42:

Arthur

1. What are some advantages of a toroidal transformer

The big one: EMI (electromagnetic interference). The geometry ensures that the magnetic field is contained within the donut. Among other things, this means that the transformer won't "talk" (couple magnetically) nearly as much as a square transformer to other transformers that are nearby. An example of that coupling would be: put a cheap passive DI (with an un-mumetal-shielded transformer) on top of an SVT. Hummmmmmmm city. That's magnetic coupling.

2. How much extra does it cost for a manufacturer to use one?

Well, they're more difficult to build. More importantly, the transformer companies don't sell as many so they cost more. How much more depends on the deal the OEM can get with the vendor!

3. How do they compare to switched power supply designs?

In terms of weight and heat, they're the same as with standard linear (non-toroidal) transformer-based power supplies.

Switch-mode power-supplies can generate more radiated electric-field interference (the switching frequency can be in the AM radio band), but with careful design and shielding can mitigate those problems.

The main advantage of the switch-mode power supply is that you can use a much-smaller transformer.

-a

: - Arthur

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Comments:
: Arthur

: <i>1. What are some advantages of a toroidal transformer</i>

: The big one: EMI (electromagnetic interference).  The geometry ensures that the magnetic field is contained within the donut.  Among other things, this means that the transformer won't "talk" (couple magnetically) nearly as much as a square transformer to other transformers that are nearby.  An example of that coupling would be: put a cheap passive DI (with an un-mumetal-shielded transformer) on top of an SVT.  Hummmmmmmm city.  That's magnetic coupling.

: <i>2. How much extra does it cost for a manufacturer to use one?</i>

: Well, they're more difficult to build.  More importantly, the transformer companies don't sell as many so they cost more.  How much more depends on the deal the OEM can get with the vendor!

: <i>3. How do they compare to switched power supply designs?</i>

: In terms of weight and heat, they're the same as with standard linear (non-toroidal) transformer-based power supplies.

: Switch-mode power-supplies can generate more radiated electric-field interference (the switching frequency can be in the AM radio band), but with careful design and shielding can mitigate those problems.

: The main advantage of the switch-mode power supply is that you can use a much-smaller transformer.

: -a

: : - Arthur




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