English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Zendy Plus

Presents the zaia usage as premium feature

ZAIA

Presents the pdf analysis as premium feature

PDF Analysis

Insights

Presents the summarisation as premium feature

Summarisation

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the access of premium content as premium feature

Premium Content

Zendy Tools

Zendy Open

The start-up of synchronous motor drive trains is usually associated with torsionally excited vibrations and low-cycle fatigue problems. Traditional calculation methods used for analysis of such a system involve computerized integrations with very small time steps and many degrees of freedom. A simple method is presented herein which uses the knowledge of system natural frequencies and mode shapes and a general dimensionless integration data plot. A sample prob lem is included to demonstrate the application of the method. The results are compared with the more rigorous, traditional method to illustrate the accuracy of the simplified method. A procedure is also included to relate the dynamic torque to the torsional low-cycle fatigue limit, thus establishing a safe num ber of starts. INTRODUCTION Large synchronous motors tend to have a decrease in acceleration just before they reach synchronous speed. At the same time, their vibratory exciting torque increases. This torque is at twice slip frequency, which coincides, for a mo ment, with the lowest torsional system natural frequency somewhere during the running up process. In other words, the 116 PROCEEDINGS OF THE TWELFTH TURBOMACHINERY SYI\IPOSIUM usually large inertia system is excited torsionally during every start-up (Figure 1). The level of vibratory shear stress that is reached depends on how fast the motor can pass the "critical speed," how much damping is available in the shafting, and, of course, the size of the shafting at the weakest link, such as at the bearing journal, shaft end, coupling, etc. It is not uncom mon to see shaft torsional low-cycle fatigue problems in these machinery trains, especially those associated with motors of "solid pole" structure [ l].

A Generalized And Simplified Transient Torque Analysis For Synchronous Motor Drive Trains.