What can I do with these? Blog

[AcousticBruce]

It turns out that I might be getting lots of interesting old electronic equipment at work. Well, first thing I have this old stereo that Im am going to part out. I see tons of interesting transistors and some pretty good caps. There is also some inductors and a really really BIG inductor. This came from a 15 million dollar Yacht, so this audio was pretty high end at its time.


1) This inductor has lots of wires, can this be something I can learn from using function gens and oscilloscope?
2) Why such a big inductor?
3) Any ideas on experiments?

 

[tvtech]

Hi Bruce

That very big Inductor looks like a Toroidal Transformer to me. Most probably the PSU Transformer for the amp it is pictured with.

Quoted from Wikipedia:

Toroidal cores

**broken link removed**
Small toroidal core transformer
"Toroidal transformers are built around a ring-shaped core, which, depending on operating frequency, is made from a long strip of silicon steel or permalloy wound into a coil, powdered iron, or ferrite.[53] A strip construction ensures that the grain boundaries are optimally aligned, improving the transformer's efficiency by reducing the core's reluctance. The closed ring shape eliminates air gaps inherent in the construction of an E-I core.[21] The cross-section of the ring is usually square or rectangular, but more expensive cores with circular cross-sections are also available. The primary and secondary coils are often wound concentrically to cover the entire surface of the core. This minimizes the length of wire needed, and also provides screening to minimize the core's magnetic field from generating electromagnetic interference.

Toroidal transformers are more efficient than the cheaper laminated E-I types for a similar power level. Other advantages compared to E-I types, include smaller size (about half), lower weight (about half), less mechanical hum (making them superior in audio amplifiers), lower exterior magnetic field (about one tenth), low off-load losses (making them more efficient in standby circuits), single-bolt mounting, and greater choice of shapes. The main disadvantages are higher cost and limited power capacity (see Classification parameters below). Because of the lack of a residual gap in the magnetic path, toroidal transformers also tend to exhibit higher inrush current, compared to laminated E-I types.

Ferrite toroidal cores are used at higher frequencies, typically between a few tens of kilohertz to hundreds of megahertz, to reduce losses, physical size, and weight of inductive components. A drawback of toroidal transformer construction is the higher labor cost of winding. This is because it is necessary to pass the entire length of a coil winding through the core aperture each time a single turn is added to the coil. As a consequence, toroidal transformers rated more than a few kVA are uncommon. Small distribution transformers may achieve some of the benefits of a toroidal core by splitting it and forcing it open, then inserting a bobbin containing primary and secondary windings." End quote.

Regards,
tvtech