Note:  Do not rely on this information. It is very old.

Hedgehog Transformer

Hedgehog Transformer, in electrical engineering, a special kind of transformer for the conversion of an alternating current of low potential and high current strength into one of high potential and low current strength, or vice versa. [Transformer.] The important characteristic of this transformer is that its soft iron core does not form a closed circuit; its ends are free, and the magnetic circuit is continued through air from the one pole to the other. It seems to be shown practically that such open circuit transformers are not so efficient in their conversion of electrical energy from one potential to another, as closed circuit instruments; the reason is as yet unknown.