Patent ID: 8552757

Claim:
A method for detecting a fault in a rotating field machine having a motor connected to a frequency converter, in which current components are analysed at the frequency converter in a flux-based, particularly rotor-flux-based, coordinate system, a flux-forming current component (i vekd ) being subjected to a frequency analysis at the frequency converter in the flux-based, particularly rotor-flux-based, coordinate system, wherein a current operating point is detected at the frequency converter for at least one predetermined supply frequency (f sp ), said operating point being compared to a former operating point stored in a reference memory; wherein at least one critical frequency (f k ) is calculated and the frequency spectrum is analysed at this critical frequency (f k ); and wherein the critical frequency (f k ) of a stator fault is determined as f k =2 ·f sp and of a rotor winding fault as f k =2( f sp −n·p ) where: f sp is the supply frequency, n is the rotor speed, and p is the number of pole pairs.