Asynchronous Machine Sets for Electrical Laboratories Part 2: Power Characteristics

Asynchronous generators belong to popular rotating machines used in small hydroelectric power plants and in small petrol generators with a simple regulation of the output voltage. In the published texts available, the use of three-phase asynchronous generators is nearly always applied with a symmetric excitation of the generator connected into a star and loaded with a symmetric load. The paper presents the results of measuring of excitation and load characteristics of asynchronous generators in frequently neglected operating modes. The research task focused on monitoring the operation of three-phase asynchronous generators with symmetric and asymmetric excitation and mainly with non-symmetric load. The extreme case was the situation in which the three-phase generator was loaded merely in single phase, and a single-phase or multi-phase asymmetric excitation was applied. Simultaneously, the operation of the generator was monitored in its sub-synchronous, synchronous and over-synchronous revolutions. The basic results are presented; the machine set can operate in 686 ways of the generatoŕs excitation, three load modes can be applied. The key finding was made - asynchronous generators can operate in a very reliable and stabile way when the island mode and subsynchronous revolutions are applied.