1. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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PERFORMANCE IMPROVEMENT 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
INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING
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ISSN 0976 – 6545(Print)
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Volume 4, Issue 3, May - June (2013), pp. 29-34
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2. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME
30
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.

3. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME
31
Figure1 Chording or short pitching of stator winding
III. TECHNICAL DATA
Table-1 THD at no load for 2/3 winding pitch
Kva 125
Slot 48
Winding pitch 2/3
Connection Series star
Phase 3
Volt 415
Harmonic no.5 Harmonic no.7
THD THD
V V
CH1 0.886 CH1 0.916
CH2 0.841 CH2 0.942
CH3 0.822 CH3 0.046
Table-2 THD at full load for 2/3 winding pitch
Harmonic no.5 Harmonic no.7
THD THD
V A V A
CH1 0.487 2.492 CH1 0.504 2.971
CH2 0.469 2.585 CH2 0.637 2.890
CH3 0.409 2.575 CH3 0.622 2.805

4. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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Table-3 THD at no load for 5/6 winding pitch
Kva 125
Slot 48
Winding pitch 5/6
Connection Series star
Phase 3
Volt 415
Harmonic no.5 Harmonic no.7
THD THD
V V
CH1 0.231 CH1 0.276
CH2 0.320 CH2 0.219
CH3 0.272 CH3 0.220
Figure-2 WDF (4.1%) at no load for 5/6 winding pitch
Table-4 THD at full load for 5/6 winding pitch
Harmonic no.5 Harmonic no.7
THD THD
V A V A
CH1 0.824 0.351 CH1 0.567 0.590
CH2 0.789 0.480 CH2 0.514 0.649
CH3 0.791 0.316 CH3 0.637 0.680

5. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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Figure-3 WDF (4.4%) at full load for 5/6 winding pitch
IV. 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.
V. ACKNOWLEDGEMENT
The authors wish to thank Mr, A.B, Chaudhuri,Former chief engineer of
CROMPTON GREAVES LTD.AHMEDNAGAR and Mr.N.Sraswati,Project Engineer in
CUMMINS GENERATOR TECHNOLOGY LIMITED AHMEDNAGAR for suggestion in
connection with this paper.
VI. REFRENCES
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6. International Journal of Electrical Engineering and Technology (IJEET), ISSN 0976 –
6545(Print), ISSN 0976 – 6553(Online) Volume 4, Issue 3, May - June (2013), © IAEME
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reducing stator iron losses in interior PM synchronous machines during flux-
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[6] Kai Zhang* and Liuchen Chang**Dept. of Electrical and Computer Engineering,
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