Abstract: The iron core (2) and the windings (3, 4) of a transformer (1) are held together by a coil former (21) which is arranged in an injection mould in such a way that it comes into contact with said mould only with small parts at its surface, whereas the transformer (1) is a distance away from its walls. A plastic shell (22) is then moulded on to complete a small and light integral casing (7) enclosing the transformer all round and in an abutting manner. Joints between the coil former (21) and the shell (22) are essentially at the bottom of indentations which separate cooling fins (20).

Abstract: A transformer, typically a miniature transformer, to provide low-voltage power between, usually, 2 to 12 V from a power network has an auxiliary winding (6) inductively coupled to the core (9) of the transformer. A reference signal is provided from the power supply, and a monitoring circuit (32), which includes a difference-forming circuit (16) is coupled to receive (a) a signal from the auxiliary winding (6) and (b) the reference signal, the difference-forming signal providing an output in dependence on the state of magnetization of the core, by evaluating differences in magnetization (.DELTA.B) depending on whether power is being supplied by the transformer, or not. A circuit interruption element (10), typically a transistor, is serially connected between the power supply (1, 2) and the transformer.

Abstract: A mini-transformer features an iron or ferrite core (2) and primary and secondary windings (3, 4). Portions of the windings (3, 4) which extend beyond the iron or ferrite core (2) are covered on both sides with a thermoplastic material forming a lid (6, 7). The two lids or end bells (6, 7) are combined into one piece by means of first bars (12), which extend through the hollow spaces (9) between the windings (3, 4) and the iron or ferrite core (2) and fill them, and that the laminated iron or ferrite core (2) is fixed in itself by second bars (14) connecting the two lids (6, 7).