The transformer used for electric welding. (See Welding, Electric.) It is a transformer with very long primary and exceedingly short and thick secondary. It is used with the alternating current in the primary, and produces in the secondary circuit which includes the bars to be welded a very low potential difference. Owing to the very [...]

A transformer with its iron core entirely outside of and enclosing the primary and secondary winding. It may be made by the use of outer iron wire windings as core.

Transformers connected in series upon the primary circuits. The term, like “multiple transformers,” only applies to the connection, not to the transformer. Series transformers are but little used.

A transformer with oil insulation. The advantage of this insulation is that if pierced it at once closes, so that no permanent injury ensues. It is a self-healing form of insulation.

A transformer connected in parallel with others between the two leads of the primary circuit. The term refers to the connection only and not to any peculiarity of the transformer itself.

An induction coil transformer whose iron core is composed of a bundle of iron wires, which after the wire windings are in place have their ends spread out to reduce to some extent the reluctance of the circuit, which at the best is high, as the air acts as the return circuit. This transformer has [...]

A transformer wound upon an enclosed core, such as the hedgehog transformer (see Transformer, Hedgehog), or common induction coil.

A machine of the dynamo type for changing the potential of a circuit. In one form two armatures are mounted on one shaft in a single field or in separate fields; one is a motor armature driven by the original current; the other generates the new current. This is a motor dynamo. In 1874 Gramme [...]

An apparatus for transforming a continuous into an alternating current or the reverse. The combination of a continuous current dynamo with an alternating current one is sometimes employed. It is a form of motor dynamo. Another type is a regular dynamo with ordinary commutator and with, in addition thereto, two, three or four contact rings, [...]

A type of continuous current transformer, resembling a dynamo with armature and field both stationary, but with revolving commutator, by which the magnetic polarity of a double wound armature is made to rotate. This secures the desired action, of a change or lowering of potential.