Principles and Classification of Electrical Machines

Electromagnetic Classification of Electrical Machines

From an electromagnetic point of view, these machines can be considered a set consisting of a magnetic circuit and two electric circuits: one in the rotor and the other in the stator.

One of the windings or coils, run by an electric current, produces the magnetomotive force necessary to establish the flux in the overall magnetic machine; these are known as priming or excitation windings.

In the other winding, called the induced winding, an electromotive force is induced. This results in a torque (in the case of an electric motor acting as a motor) or a counter EMF, which produces a load torque (in the case of an electrical machine operating as a generator).

Electric Motor Operation

To understand the operation of an electric motor, it should be noted that there are conductors carrying an electric current that are located within magnetic fields.

Classification of Rotating Electric Machines

• DC machines
• AC machines

In turn, alternating current machines, depending on the nature of the inductor winding current, are divided into:

• Excited by direct current: Synchronous machines.
• Excited by alternating current: Asynchronous (or induction) and collector machines.

Power in Electrical Machines

Power is the energy an electrical machine develops per unit of time. The power supplied by an electric machine at a given time depends on a number of external conditions:

• The instantaneous electrical power supplied by a power generator will depend on the circuit that feeds them.
• The instantaneous mechanical power supplied by a motor will be conditioned by the resistance offered by the motor-driven mechanisms.

The Terminal Plate

The terminal plate is a plate of insulating material containing several threaded bolts, called terminals, which connect the beginning and end points of the motor windings.

The Nameplate

The nameplate is a metal plate usually located on the motor housing in a visible place. This plate is engraved with the major specifications of the motor, such as power output, engine speed, current drawn, and other technical data.

Changing the Direction of Rotation

In many cases, machines that use electric motors must change the direction of rotation of the motor to perform certain operations.