Below is a critical speed map of an 800-hp DC motor sitting on a 6- ft-high concrete pedestal. The motor usually operates at 1,000 rpm. The vibration levels, which were excessive, occurred with the motor horizontal ends in phase. Rigid-body modes considered, what can we say based on the results of where the equivalent support stiffness resides? (Remember, the first rigid-body mode is the lowest of the modes in frequency.)

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1000000 160000 Frequency (CPM) 10.000 1000 10 3 104 Enter 'F' to end 105 1006 Equivalent Support Stiffness (lb/in) -Running Speed 197