Distributed generation: Short circuit current supplied for induction generators

Magnitude and duration of the short-circuit current supplied by induction generators is a matter of concern. Induction generators are mainly applied to produce electricity through wind turbines. Several papers showing analytical studies on short-circuit current have been published, but just a few with experimental results. Experimental results of 4 to 10 kW induction generator are presented. Four operating principles were investigated: remnant magnetism excitation, capacitor excitation, DC rotor excitation, and double feed. Short-circuit current supplied by remnant magnetism excited machine is presented, showing restart current after fault cleaning. Current first peak magnitude is ruled by the electromagnetic time constant, but current decaying part depends of electromagnetic and mechanical time constants, which can be estimated through simple tests. Good accuracy between analytical and experimental values is presented. Research shows that induction machine short-circuit contribution is closely related to excitation type and that the used initial and damped values represent an overestimation.