Transient
Analysis of Synchronous Motor Trains F. R. Szenasi,
7th Turbomachinery Symposium, Texas A&M University,
December 1978 .
This paper discusses
the philosophy of optimum location of torsional critical speeds
which will be excited by the transient startup, as well as methods
of adjusting the resonant frequencies. Pulsating torque, average
torque, and acceleration rate during startup are considered in choosing
the best frequency range for the resonances. Both steady-state and
transient torsional excitation are discussed along with the applicable
stress criterion. A method to determine the allowable number of
startups is presented involving cumulative fatigue considerations
which apply to the transient torsional stresses. The severity of
the backlash in gears and geared couplings is discussed and methods
for calculating the response of the system to instantaneous negative
torque are presented. The proper choice of couplings can change
mode shapes, reduce backlash severity, and add damping which can
reduce the detrimental effects to the torsional system. The proper
specifications of couplings and gears in the design stage and the
proper definition of service conditions greatly aid the gear and
coupling manufacturers and can result in a system which will operate
reliably, even under backlash conditions.
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