RUNNING INSTABILITY OF CAGE INDUCTION MOTORS CAUSED BY HARMONIC FIELDS DUE TO ECCENTRICITY - 2. SELF-EXCITED TRANSVERSEVIBRATIONS OF THE ROTOR/ EXZENTRIZITAETSFELDER ALS URSACHE VON LAUFINSTABILITAETEN BEI ASYNCHRONMASCHINEN TEIL 2: SELBSTERREGTE BIEGEEIGENSCHWINGUNGEN DES LAEUFERS.

THE UNBALANCED MAGNETIC PULL IN CAGE INDUCTION MOTORS POSSESSES A FORCE COMPONENT ACTING LIKE A SPEED DEPENDENT DAMPINGFORCE. DEPENDING ON ROTOR SPEED THIS FORCE COMPONENT WILL TAKE EITHER POSITIVE OR NEGATIVE VALUES. THE STABILITY-LIMIT PLOT THEREFORE MUST INCLUDE ELECTRO-MAGNETIC DAMPING OF THE ROTOR. SPEED DEPENDENT OR DEFLECTION DEPENDENT INTERIOR MECHANICAL DAMPING MAY, COMBINED WITH NEGATIVE ELECTROMAGNETIC DAMPING, GIVE A TOTAL NEGATIVE DAMPING OF THE SHAFT ABOVE OR BELOW SYNCHRONOUS SPEED. THE EXISTENCE OF ELECTROMAGNETICALLY CAUSED RUNNING INSTABILITY WAS PROVED BY EXPERIMENTS CARRIED OUT ON A 4-POLE MODEL MACHINE HAVING A MECHANICAL CRITICAL SPEED SIMILAR TO A LARGER HIGHLY RATED MACHINE. IN GERMAN.