Synchronous Motor: Constant Speed and Power Factor Correction Machine

International Journal of Emerging Trends in Engineering and Development Volume 15, No.5, 2025 Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 DOI: 10.5281/zenodo.17462452 Original Article ©2025 RS Publication, [email protected] 174 Synchronous Motor: Constant Speed and Power Factor Correction Machine Prof. Radharaman Arora 1 1 Department of Electrical Engineering, Sanjivani K. B. P. Polytechnic, Kopargaon Maharashtra State Board of Technical Education, Mumbai, Maharashtra, India [email protected] International Journal of Emerging Trends in Engineering and Development Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 ARTICLE INFO ABSTRACT ©2025 RS Publication Paper ID: IJETED68FF8DD8ED630 Received: 2025-09-22 Published: 2025-10-27 DOI: https://dx.doi.org /10.5281/zenodo.17 462452 Page No: 174-180 “In synchronous motors, the rotor runs exactly at the speed of the stator’s magnetic field, so there is no slip between them”. It operates on the principle of magnetic locking between the stator's rotating magnetic field, produced by a three-phase AC supply, and the rotor's magnetic field, created by a direct current (DC) excitation. Industries often employ synchronous motors in equipment such as pumps and compressors, particularly where steady speed and power factor adjustment are needed. Unlike induction motors, synchronous motors maintain a constant speed regardless of the load, making them suitable for precise and timingsensitive operations. However, they are not self-starting and require auxiliary starting mechanisms. The motor's performance can be analyzed using equations that define synchronous speed, torque, power, and efficiency. The ability of synchronous motors to operate at unity or leading power factor makes them valuable for improving system power quality. Keywords - synchronous motors , motor's performance , synchronous speed, torque, power, and efficiency, leading power factor. Cite This Paper: Prof. Radharaman Arora(2025). "Synchronous Motor: Constant Speed and Power Factor Correction Machine ". INTERNATIONAL JOURNAL OF EMERGING TRENDS IN ENGINEERING AND DEVELOPMENT (IJETED), vol. 15, no. 5, 2025, pp. 174-180. DOI: https://dx.doi.org/10.5281/zenodo.17462452 International Journal of Emerging Trends in Engineering and Development Volume 15, No.5, 2025 Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 DOI: 10.5281/zenodo.17462452 Original Article 175 INTRODUCTION Synchronous generators or alternators are used to convert mechanical power derived by steam, gas or hydraulic turbine to AC electric power. Synchronous generators are primary source of electric energy we consume today. Large AC power networks rely mostly on synchronous generators. Synchronous motors are built in large units as compared to induction motors. Used for constant speed industrial applications. A synchronous motor is a type of alternating current (AC) motor in which the rotation of the rotor is synchronized with the frequency of the supply current. That means the rotor turns at the same rate as the rotating magnetic field generated by the stator, maintaining a constant speed regardless of the load. This unique feature constant speed operation makes synchronous motors highly desirable in applications where precision and performance stability are essential. Synchronous Machines Construction 1. StatorArmature (Same as the stator of an Induction Machine) 2. RotorField Winding (DC Field) Generator  As a generator, this machine is widely used.  This is the machine which is used in all conventional power plants.  A synchronous generator is called as an Alternator. Motor  Since it runs only at synchronous speed, it is not widely used as a motor but for certain applications like electric clocks.  However, it is used to either produce or absorb reactive power. Construction Stator  It is a distributed winding.  The windings of each phase are distributed over several slots.  Three phase windings are wound 120 (electrical angle) apart in space International Journal of Emerging Trends in Engineering and Development Volume 15, No.5, 2025 Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 DOI: 10.5281/zenodo.17462452 Original Article 176 1. Rotor  It is excited by a DC current.  There are two types. 2.1 Cylindrical Rotorused where the turbine speed is high 2.2 Salient Pole Rotorused where the turbine speed is low Synchronous machine is a doubly excited machine. We can have field winding placed in stator and armature winding in rotor. This type is called an inverted synchronous machine International Journal of Emerging Trends in Engineering and Development Volume 15, No.5, 2025 Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 DOI: 10.5281/zenodo.17462452 Original Article 177 Pole machine, one revolution makes one cycle of alternating voltage. In a Ppole machine, 1 revolution/min – 1/60 * P/2 cycle/sec N rpm - N /60 * P/ 2 cycle/sec  =   Hz Vector Diagram of Synchronous Motor Neglected Losses International Journal of Emerging Trends in Engineering and Development Volume 15, No.5, 2025 Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 DOI: 10.5281/zenodo.17462452 Original Article 178 Working Principle 1. Three-phase AC supply to the stator: When a three-phase AC supply is given to the stator windings, it produces a rotating magnetic field (RMF) in the stator. This magnetic field rotates at a speed called the synchronous speed (Ns), given by:  = 120  - f = frequency of AC supply (Hz) - P = number of poles in the stator 2. DC supply to the rotor: The rotor of a synchronous motor is supplied with DC current, which creates a constant magnetic International Journal of Emerging Trends in Engineering and Development Volume 15, No.5, 2025 Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 DOI: 10.5281/zenodo.17462452 Original Article 179 field on the rotor. 3. Synchronization: When the rotor is brought up to near-synchronous speed (usually with the help of an external prime mover or damper winding), the rotor's magnetic field locks in with the rotating magnetic field of the stator. From this point on, the rotor rotates in perfect synchronism with the stator field — at exactly the synchronous speed. 4. Torque production: Once synchronized, the interaction between the magnetic fields of the stator and rotor produces torque. Unlike induction motors, a synchronous motor does not rely on slip to generate torque. Conclusion The synchronous motor is a crucial component in electrical engineering due to its ability to operate at a constant speed, regardless of load variations. Its working is based on the principle of magnetic locking between the rotor and the rotating magnetic field of the stator, which ensures synchronization at all times. This unique characteristic makes it ideal for applications requiring precision and steady operation. Although it is not self-starting and requires additional starting methods, the synchronous motor offers several advantages, including high efficiency, power factor correction capability, and stable performance under varying load conditions. Its contribution to industrial processes, particularly in heavy machinery and power systems, highlights its significance in modern electrical applications. In conclusion, the synchronous motor remains a reliable and efficient solution for fixed-speed applications and plays a key role in improving the overall performance and power quality of electrical systems. International Journal of Emerging Trends in Engineering and Development Volume 15, No.5, 2025 Available online on http://www.rspublication.com/ijeted/ijeted_index.htm ISSN 2249-6149 DOI: 10.5281/zenodo.17462452 Original Article 180 REFERENCES [1]. G. Neidhofer, “The evolution of the synchronous machine,” Engineering Science and Education Journal, pp. 239-248, October 1992. [2]. E. Boulter, “Historical development of rotor and stator winding insulation materials and systems,” IEEE Electrical Insulation Magazine, vol. 20, no. 3, pp. 25-39, May/June 2004. [3]. B. Gott, “Advances in turbogenerator technology,” IEEE Electrical Insulation Magazine, vol. 12, no. 4, pp. 28-38, July/August 1996. [4]. G. Miller, “Trends in insulation materials and processes for rotating machines,” IEEE Electrical Insulation Magazine, vol. 14, no. 5, pp. 7-11, September/October 1998. [5]. S. Kalsi, K. Weeber, H. Takesue, C. Lewis, “Development status of rotating machines employing superconducting field windings,” Proceeding of the IEEE, vol. 92, no. 10, pp. 1688-1704, October 2004 [6]. C. Chan, “The state of the art of electric and hybrid vehicles,” Proceedings of the IEEE, vol. 90, no. 2, pp. 247–275, Feb 2002. [7]. G. Pellegrino, A. Vagati, B. Boazzo, and P. Guglielmi, “Comparison of induction and PM synchronous motor drives for EV application including design examples,” IEEE Transactions on Industrial Applications, vol. 48, no. 6, pp. 2322–2332, Nov 2012. [8]. K. Chau, C. Chan, and C. Liu, “Overview of permanent-magnet brushless drives for electric and hybrid electric vehicles,” IEEE Transactions on Industrial Electronics, vol. 55, no. 6, pp. 2246– 2257, June 2008. [9]. A. Vagati, G. Pellegrino, and P. Guglielmi, “Comparison between SPM and IPM motor drives for EV application,” in 2010 International Conference on Electrical Machines (ICEM), Sept 2010, pp. 1–6. [10]. A. M. EL-Refaie and T. M. Jahns, “Optimal flux weakening in surface PM machines using fractional-slot concentrated windings,” IEEE Transactions on Industry Applications, vol. 41, no. 3, pp. 790–800, May 2005.