6545(Print), ISSN (Online) Volume 4, Issue 3, May - June (2013), IAEME & TECHNOLOGY (IJEET)

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1 INTERNATIONAL International Journal of JOURNAL Electrical Engineering OF ELECTRICAL and Technology (IJEET), ENGINEERING ISSN 0976 & TECHNOLOGY (IJEET) ISSN (Print) ISSN (Online) olume 4, Issue 3, May - June (2013), pp IAEME: Journal Impact Factor (2013): (Calculated by GISI) IJEET I A E M E PERFORMANCE IMPROEMENT OF SYNCHRONOUS GENERATOR BY STATOR WINDING DESIGN Mr. Sumit Kumar & Prof.Dr. A.A Godbole Bharti vidyapeeth Deemed University College of Engineering Pune ABSTRACT The development of an alternate approach for modeling of steady-state performance of synchronous machines including the effects of harmonics. This approaches should preserve the important property of finite element analysis that each model parameter is related to a physical section of the machine its shape, and its material properties.in this report winding design is compared with an existing design for the same specification; objective behind this winding design is to reduce harmonics, temperature rise and to improve efficiency of the machine. I. INTRODUCTION Power systems consist of elements for generation, transmission, distribution and loads. The synchronous machines are the main generating units of power systems. From the load side, synchronous motors are also used. This makes the synchronous machine one of the most important components of electric power systems. The main overall objectives of power systems are security and reliability. Security of power systems means that the power systems are within their steady-state power flow constraints. Reliable operation of power systems refers to their ability to continuously supply the required electrical energy without interruption under abnormal operating conditions such as faults, switching, and load changes. In both modes of operation the power system behavior is dependent on the electrical and Electro mechanical processes of synchronous machines.quality of electrical performance is a measure of how close the electrical output of the generator is to a true sine wave. The actual voltage waveform from rotating machinery is never perfect. Internal generator and external load characteristics cause distortions in the wave. These factors impair the consistency of the 29

2 generator output, and can result in voltage regulator sensing errors and incorrect instrument reading. In brief; harmonics are energy levels existing at multiples of the fundamental wave s frequency. The main source of harmonic is non-sinusoidal field form, which can be made sinusoidal and the total harmonics can be eliminated. But it is not an easy job because air gap offers maximum reluctance to the flux path due to which air gap cannot be made to vary sinusoidally, if air gap is made to vary sinusoidally around the machine, then field form would be sinusoidal and total harmonics would be eliminated. But field form cannot be sinusoidal due to saturation in iron parts and hence we cannot totally eliminate all harmonics but can decrease them. Field form is nothing but distribution of flux in machine. This flux distribution determines the wave shape of generated voltage in armature winding. In case of alternators, the voltage and currents induced are having sinusoidal waveforms. But practically we cannot get sinusoidal waveforms when such alternators are loaded. Due to the loading conditions, the generated waveform deviates from ideal waveforms. Such a non-sinusoidal waveform is called complex wave. By Fourier transform this complex waveform can be shown to be built of a series of sinusoidal waves whose frequencies are integral multiples of the frequency of fundamental wave. Sinusoidal components or harmonic functions are called harmonics of the complex waves. The fundamental wave is defined as that component which is having same frequency as that of complex wave. The component which is having doubled the frequency of that of fundamental wave called is called second harmonic. While the component which is having the frequency three times that of fundamental is called third harmonic and so on. The complex wave contains both the even as well as odd harmonics. Out of the even and odd harmonics a wave containing fundamental component and even harmonics only is always unsymmetrical about X-axis whereas a complex wave containing fundamental component and odd harmonics only is always symmetrical about X-axis. In case of alternators the voltage generated is mostly symmetrical as the field system and coils are all symmetrical. So the generated voltage or current will not have any even harmonics in most of the cases. The waveform distortion can cause problems in voltage regulation, generator and load overheating, and inaccurate instrument readings. Both voltage and current may have harmonic components. The current components produce heat and are therefore derating factors for the generator as well as system motors. II. HARMONIC REDUCTION BY CHORDING With the coil span less than the pole pitch the emf generated is proportional to cos(n*α/2). Where, αis angle of chording n is order of harmonic. The harmonic emf can therefore, be considerably reduced or entirely eliminated by choosing a proper value of α. 30

3 Figure1 Chording or short pitching of stator winding III. TECHNICAL DATA Table-1 at no load for 2/3 winding pitch Kva 125 Slot 48 Winding pitch 2/3 Connection Series star Phase 3 olt 415 CH CH CH CH CH CH Table-2 at full load for 2/3 winding pitch A A CH CH CH CH CH CH

4 Table-3 at no load for 5/6 winding pitch Kva 125 Slot 48 Winding pitch 5/6 Connection Series star Phase 3 olt 415 CH CH CH CH CH CH Figure-2 WDF (4.1%) at no load for 5/6 winding pitch Table-4 at full load for 5/6 winding pitch A A CH CH CH CH CH CH

5 Figure-3 WDF (4.4%) at full load for 5/6 winding pitch I. CONCLUSION This paper is comparing the result obtained from chording the stator winding by 2/3 and 5/6. Harmonic no.5 and harmonic no.7 Is reduced by chording the winding by 5/6. we have designed, manufactured and tested a synchronous generator whose harmonic has been reduced.since harmonic is reduced at design stage cost of power generation is also not affected.our work has improved performance of the generator consequently the power quality.. ACKNOWLEDGEMENT The authors wish to thank Mr, A.B, Chaudhuri,Former chief engineer of CROMPTON GREAES LTD.AHMEDNAGAR and Mr.N.Sraswati,Project Engineer in CUMMINS GENERATOR TECHNOLOGY LIMITED AHMEDNAGAR for suggestion in connection with this paper. I. REFRENCES [1] Paolo mattavelli, member, IEEE Synchronous frame harmonic control for high performance ac power supplies IEEE transactions on industry applications vol.37, no. 3, may/june [2] Zhu,xi xiao andyongdong li,department of electrical engineering,tsinghua university, Beijing, , China Permanent magnet synchronous motor current ripple reduction withharmonic back-emf compensation National high technology research and development program of China (Project no.2007aa04z216). [3] T. Yoshida, T. Kamejima, H. Ishikawa and H. Naitoh Gifu University, 1-1 yanagido, Gifu, , JAPAN Higher harmonic currents reduction for interior permanent magnet synchronous motors The 2010 International power electronics conference. [4] Katsumi. Yamazaki, and Yu Fukushima Dept. of E. E. C. E., Chiba Institute of Technology, , Tsudanuma, Narashino, Chiba, , Japan, Effect of Eddy- Current Loss Reduction by Magnet Segmentation in Synchronous Motors with Concentrated Windings. [5] Seok-Hee Han* Wen L. Soong+ Thomas M. Jahns**University of Wisconsin Madison, WI, USA +University of Adelaide, Adelaide, Australia. An analytical design approach for 33

6 reducing stator iron losses in interior PM synchronous machines during fluxweakeningoperation. [6] Kai Zhang* and Liuchen Chang**Dept. of Electrical and Computer Engineering, University of New Brunswick, CANADA. Harmonic current reduction for a PWM rectifier with very low carrier ratio in a microturbine system /05/$ IEEE CCECE/CCGEI, Saskatoon, May [7] T. Onuki, T. Iwamoto, W.1. leon, H.Watanabe, S. Katoh, and A. Nakamoto Electrical, Electronics and Computer Engineering,Waseda University34-1 Ohkubo Shinjuku-ku,Tokyo , JAPAN A novel rotor construction for reducing higher space harmonics in the permanent magnets synchronous motor /98/$10.00 Q 1998 IEEE. [8] Pradipta K. Das and Amulya K. Das Gupta, Member, IEEE. Inductance Coefficients of Three-Phase Inductor Alternators: Part I Analytical Study. IEEE TRANSACTIONS ON POWER APPARATUS AND SYSTEMS, OL. PAS-88, NO. 11, NOEMBER [9]A.K.Sawhney,Design of electrical machine Dhanpat Rai and Publishing Company Ltd. [10] Technical manual UC27- CUMMINS GENERATOR TECHNOLOGY. [11] Pooja Agrawal and Ritesh Diwan, Sensorless Control of Surface-Mount Permanent- Magnet Synchronous Motors, International Journal of Electrical Engineering & Technology (IJEET), olume 4, Issue 2, 2013, pp , ISSN Print : , ISSN Online: [12] ishal Rathore and Dr. Manisha Dubey, Speed Control of Asynchronous Motor using Space ector Pwm Technique, International Journal of Electrical Engineering & Technology (IJEET), olume 3, Issue 3, 2012, pp , ISSN Print : , ISSN Online: