LAUSR

The vibrational responses with a relatively high amplitude are due to the interference with the resonant operational range of the rotating machinery. The average operating speeds for engine cold testing pass through several critical regions while ramping from idle to the maximum testing speed. The resonant severity differs from one critical speed to another depending on the sequence of interference and the cyclic triggering of the machine harmonic distortion. A better understanding of the harmonic distortions can be built by creating a detailed Campbell diagram including the excitations generated by the engine and the electrical drive. This paper defines a comprehensive Campbell diagram including the excitations generated by the variable frequency drive and the engine and locates all the possible critical speeds. The critical speeds are used to create an inverted excitations diagram to graphically locate the most destructive resonance region in the range of the operating speed. A novel graphical methodology is described in the current paper inspired by the linear programming simplex representation.