dynamoelectric

Dynamoelectric refers to electrical machines that convert energy between mechanical and electrical forms through electromagnetic action, typically using a commutator in early designs. The term historically encompassed devices that either generated electrical energy from mechanical energy (generators, or dynamos) or produced mechanical energy from electrical energy (motors). In modern terminology, these devices are generally called electrical machines and are classified into direct-current (DC) machines and alternating-current (AC) machines.

The basic operating principle involves electromagnetic induction: a magnetic field interacts with a rotating or moving conductor to induce voltage, while the device can be arranged to produce torque when supplied with current or to generate current when driven mechanically. In DC machines, a commutator and brushes convert the induced alternating voltage in the armature into direct current, enabling constant-direction torque or output. Early dynamoelectric generators used wound field coils or permanent magnets, and advances in magnetic materials and design increased efficiency, started widespread electrification, and enabled railway traction and industrial power systems.

Historically, dynamoelectric machines were central to the development of electric power systems in the 19th and early 20th centuries. As electrical engineering matured, terminology shifted toward broader categories such as electrical machines or electromechanical energy conversion devices, with DC and AC machines understood as distinct subtypes. Today, dynamoelectric is largely a historical or descriptive term, but it persists in some literature and in the names of certain older equipment.