Every rotating electrical machine requires an exciter field. The exciter field of the direct current machine, generated by the main poles, is a permanent magnetic field of constant value. We differentiate between various exciter categories.
An exciter field is realised by means of permanent magnets. This exciter category is mainly used for lower-power machines.
The necessary voltage to generate an exciter field is attained from a voltage source (e.g. accumulators) outside the machine. Natural excitation is a particular excitation category.
In this case the necessary excitation voltage is provided by a generator (exciter machine) which is coupled directly to the main machine.
Because of remanance (residual magnetism), the main poles evidence a weak exciter field. In accordance with U0 = c • Φ • n the rotation of the rotor winding induces only a small rotor voltage in the exciter field. Rotor winding rotation however enables a weak current to pass through the exciter winding. This current increases the exciter field whereby a greater rotor voltage is induced. This is, moreover, a continuous process leading to a fully fledged exciter field. This alternating effect is termed “dynamoelectric principle”. One differentiates between the following self-excitation categories:
[Ukrainian] [English] [Russian]