Synchronous motor pull-in process analysis

Zvi Vainer, Boris Epshtein, Saad Tapuchi, Yoram Horen, Pavel Strajnikov, Moshe Averbukh, Alon Kuperman

Research output: Contribution to journalArticlepeer-review


In this paper, simple approach to analyzing the starting procedure of synchronous motors (SMs) is presented with an emphasis on the pull-in process. Instead of the classical, mostly intuitive pulling-repelling torque approach, an analytical method based on the motor mechanical part swing equation is employed. Factors affecting starting and pull-in processes are clearly indicated and torque impulse balance leading to a pull into step is revealed. It is shown that if the motor fails to pull into step within a single oscillation, it can still be synchronized during one of the succeeding acceleration periods. The crucial role of the excitation winding energizing instant is demonstrated as well. Moreover, the revealed similarity between the SM and phase locked loop (PLL) operations, leads to the conclusion that the algorithms use for analyzing the operation of one may be employed for investigating the other. Experimental results are given to demonstrate the different scenarios, mentioned in the manuscript.

Original languageEnglish
Article number1550088
JournalJournal of Circuits, Systems and Computers
Issue number6
StatePublished - 27 Jul 2015


  • Synchronous motor
  • pull-into-step process
  • starting methods


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