Synchronous Motor Pull-in Process Analysis ¤ Zvi Vainer † , Boris Epshtein, Saad Tapuchi, Yoram Horen and Pavel Strajnikov Department of Electrical and Electronic Engineering, Shamoon College of Engineering, Beer-Sheva 80000, Israel † zvi.vainer@gmail.com Moshe Averbukh and Alon Kuperman ‡ Department of Electrical Engineering and Electronics, Ariel University, Ariel 40700, Israel ‡ alonku@ariel.ac.il Received 20 February 2014 Accepted 20 March 2015 Published 17 April 2015 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 a®ecting 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 di®erent scenarios, mentioned in the manuscript. Keywords: Synchronous motor; starting methods; pull-into-step process. 1. Introduction Synchronous motors (SMs) are used in a wide range of applications, particularly when the power output rating exceeds the corresponding speed rating. 1 Common applications are re¯ners, grinders, fans, metal rolling mills, marine propulsion, extruders, pumps and reciprocating compressors. SM are preferable in such appli- cations since they possess relatively higher e±ciencies compared to induction and dc *This paper was recommended by Regional Editor Piero Malcovati. ‡ Corresponding author. Journal of Circuits, Systems, and Computers Vol. 24, No. 6 (2015) 1550088 (13 pages) # . c World Scienti¯c Publishing Company DOI: 10.1142/S0218126615500887 1550088-1