Experimental study on the short-circuit contribution of induction machines

Abstract

Induction machines are widely used in industrial facilities as motors and increasingly in distributed generation, particularly in wind turbines. The short-circuit current contributed by induction machines in the first cycle following a fault outside the machine can be significant, and common practices for calculating these currents are well established. However, experimental short-circuit tests described in this paper indicate that conventional steady-state tests used to determine the induction machine parameters do not accurately characterize the short-circuit behavior of the induction machine. Test results for both balanced and unbalanced short-circuit faults applied to a 6.8 kVA, 230 V wound-rotor induction machine are described in this paper, and compared with transient simulations run in PSCAD and short-circuit calculations using conventional techniques. The results indicate that for faults at the machine terminals, leakage flux saturation causes a significantly higher short-circuit current magnitude from the induction machine than would otherwise be expected using a linear model obtained from steady-state tests.