Vector diagram and phasor diagram of synchronous motor
- 1. Vector diagram and Phasor diagram of Synchronous Motor Contents: Vector diagram Phasor diagram Synchronous condenser Applications of Synchronous motor References Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram
- 2. Vector Diagram and Phasor diagram of Synchronous Motor • The equivalent circuit of a synchronous motor is exactly same as the equivalent circuit of a synchronous generator, except that the reference direction of IA is reversed. • The basic difference between motor and generator operation in synchronous machines can be seen either in the magnetic field diagram or in the phasor diagram. • In a generator, EA lies ahead of Vf, and BR lies ahead of Bnet. In a motor, EA lies behind Vf, and BR lies behind Bnet. • In a motor the induced torque is in the direction of motion, and in a generator the induced torque is a countertorque opposing the direction of motion. Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram
- 3. Vector Diagram d IA Vf EA jIA Xs d IA Vf EA jIA Xs d Bs Bnet BR wsync Fig. The phasor diagram (leading PF: overexcited and |Vt|<|EA|) and the corresponding magnetic field diagram of a synchronous motor. Fig. The phasor diagram of an underexcited synchronous motor (lagging PF and |Vt|>|EA|). Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram
- 4. Phasor Diagram • (a) Unity power factor • In this unity power factor, the excitation of the synchronous motor is 100% or in normal excitation. • (b) Lagging power factor • In this unity power factor, the excitation of the synchronous motor is less than 100%. • (c) Leading power factor • In this unity power factor, the excitation of the synchronous motor is greater than 100%. Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram
- 5. Phasor Diagram Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram
- 6. Synchronous motor can be used as synchronous condenser • An over excited synchronous motor running on no load is known as synchronous capacitor or synchronous condenser. • A synchronous motor takes a leading current when over excited and therefore, behaves as a capacitor. • As compared with a synchronous motor with equal armature voltage and current rating a synchronous capacitor requires more copper in the field winding to carry large field current. • The synchronous capacitor does not require so large shaft and bearings as the synchronous motor because no shaft torque is required. Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram
- 7. Applications of Synchronous Motor Synchronous motors are usually used in large sizes because in small sizes they are costlier as compared with induction machines. The principal advantages of using synchronous machine are as follows: – Power factor of synchronous machine can be controlled very easily by controlling the field current. – It has very high operating efficiency and constant speed. – For operating speed less than about 500 rpm and for high-power requirements (above 600KW) synchronous motor is cheaper than induction motor. In view of these advantages, synchronous motors are preferred for driving the loads requiring high power at low speed; e.g; reciprocating pumps and compressor, crushers, rolling mills, pulp grinders etc. Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram
- 8. References : Kongunadu College of Engineering & Technology Synchronous Motor vector and phasor diagram S.No Book s / Web Sources 1 A.E. Fitzgerald, Charles Kingsley, Stephen. D. Umans, ‘Electric Machinery’, Tata Mc Graw Hill publishing Company Ltd, 2003. 2 D.P. Kothari and I.J. Nagrath, ‘Electric Machines’, Tata McGraw Hill Publishing Company Ltd, 2002. 3 P.S. Bhimbhra, ‘Electrical Machinery’, Khanna Publishers, 2003. 4 M.N.Bandyopadhyay, Electrical Machines Theory and Practice, PHI Learning PVT LTD., New Delhi, 2009. 5 K. Murugesh Kumar, ‘Electric Machines’, Vikas Publishing House Pvt. Ltd, 2002. 6 Syed A. Nasar, Electric Machines and Power Systems: Volume I, Mcgraw -Hill College; International ed Edition, January 1995. 7 J. Ganavadivel, ‘Electrical Machines II’, Anuradha publications, Fourth edition, 2015. 8 U.A.Bakshi &M.V.Bakshi, ”Electrical Machines II,” Technical Publications, Second revised edition, 2016. 9 Google and Wikipedia