POSTER 2015, PRAGUE MAY 14 1 Analysis of the Synchronous Machine in its Operational Modes: Motor, Generator and Compensator Prathamesh M. Dusane 1 , Minh-Quan Dang 2 , Famous O. Igbinovia 3 , Ghaeth Fandi 4 Dept. of Electrical Power Engineering, Czech Technical University, Technická 2, 166 27 Praha, Czech Republic dusanpra@fel.cvut.cz, dangminh@fel.cvut.cz, igbinfam@fel.cvut.cz, fandigha@fel.cvut.cz Abstract. This paper gives a brief evaluation of the Synchronous Machine. It describes the construction, operating principles and its applications in different operational modes: Motor, Generator and Compensator. It emphasizes the need for the use of synchronous machines for compensation purposes due to its numerous advantages in this regard in power system networks. Keywords Synchronous Machine, Synchronous Motor, Synchronous Compensator, Synchronous Generator, Power System Stability. 1. Introduction Synchronous is a Greek terminology which means operating at the same time [1]. Electric rotating machinery is an apparatus which consists of a rotating and stationery member that generates, converts, transforms or modifies electric power [2]. Faraday’s Law of Electromagnetic Induction, Ampere Biot-Savart’s Law of Electromagnetic Induced Forces and Lenz’s Law of Action and Reaction, with the law of energy conservation, all together constitute the basic theoretical bricks on which the operation of any electrical machine can be explained. The Synchronous Machine is an alternating current machine whose rotation under steady state condition is equal to the integral number of alternating current cycles in its stator. The rotor with permanent magnets or electromagnets rotates in synchronism with the Rotating Magnetic Field (RMF) created by the stator [1], [3]. Synchronous Machines can be classified as Generators, Motors and Compensators according to their uses. Generator action is observed when the rotor runs faster than the synchronous speed of the machine which is possible by means of a prime mover, motoring action is observed when the rotor is dragged behind the air-gap flux by retarding torque of a shaft-load [3]. A Synchronous Compensator is a Synchronous Motor whose shaft is allowed to rotate freely without any load [4]. Its field winding excitation is controlled by a voltage regulator to either generate or absorb reactive power as needed to adjust the grid's voltage, or to improve power factor [5]. This work discusses the basic principles of the Synchronous Machine and its uses as Motor, Generator and Compensator; it further explain in details the advantages and applications of the synchronous machine as a compensator in power system networks. 2. Construction of the Synchronous Machine The Synchronous Generator or Alternator was first conceptualized by Michael Faraday and Hippolyte Pixii, in accordance with the field winding of the rotor wound and the construction of the rotor frame. In its steady state the rotor rotates at a constant speed, and the rotating field also rotates with the same speed as the rotor. This speed is called synchronous speed, thus, the machine is called synchronous machine [6]. The machines construction is according to the shape of its rotors, they can be classified as Salient Pole and Cylindrical Rotor while the stator is similar for both cases, Figure 1. Shows a cross-section of both Salient Pole and Cylindrical Rotor synchronous machines. The Stator of the Machine is made up of a Sinusoidal distributed winding wound similar to the rotor, on sheets of steel laminations whose leads are taken out of the machine for power transfer. The air gap between the stator and rotor is made as small as possible to reduce the reluctance between the Salient Pole and Cylindrical Rotor synchronous machines and to decrease the magnetization current at no load, smaller air gap may cause mechanical issues [1], [7]. Figure 1 (a) Cylindrical Rotor Machine cross-sectional area. (b) Salient pole Rotor Machine cross-sectional area. [8]. The Cylindrical Rotor or Round Rotor is made up of cylindrical block of steel laminations with slots in its surface