### Effect of Harmonic Components on an Induced EMF in Alternators:

Before knowing how harmonic components effect the induced EMF let us know**what are harmonics**and

**harmonic components in alternators**.In synchronous machines, voltages and currents are induced, which are in sinusoidal waveforms.But in practical these sinusoidal waveforms will deviate to form non-sinusoidal waveforms.These non-sinusoidal waveforms are expressed in terms of Fourier transforms which are the sum of series of sinusoidal waveforms.Now let us understand the

**effect of harmonic components on the synchronous generator.**

**Must Read:**

- Principle and working of Synchronous generator or alternator
- Harmonics in Synchronous Machines(Alternators) | Slot Harmonics

The flux density distribution around the air gap in all well designed alternators symmetrical with respect to the abscissa and also to polar axes.Thus it can be expressed with the help of a Fourier series which do not contain any even harmonics.

So flux density at any angle θ from the interpolar axis is given by,

B = Bm1 sin θ + Bm3 sin 3θ +........... + Bmx sin xθ

where x = Order of the

**harmonic component**which is odd

Bm1 = Amplitude of fundamental component of flux density

Bm3 = Amplitude of 3rd harmonic component of flux density

Bmx = Amplitude of Xth (odd)

**harmonic component**of flux density

The e.m.f. generated in a conductor on the armature of a rotating machine is given by

ec = B.l.v

Substituting value of B,

ec = [Bm1 sin θ + Bm3 sin 3θ +........... + Bmx sin xθ].l.v

l = Active length of conductor in metre

d = Diameter of the armature at the air gap

v = Linear velocity = π d ns

where ns = Synchronous speed in r.p.s.

Now NS = 120f/P

ns = 120f/60P = 2f/P

v = π d 2f/P

ec = [Bm1 sin θ + Bm3 sin 3θ +........... + Bmx sin xθ].l.v

l = Active length of conductor in metre

d = Diameter of the armature at the air gap

v = Linear velocity = π d ns

where ns = Synchronous speed in r.p.s.

Now NS = 120f/P

ns = 120f/60P = 2f/P

v = π d 2f/P

Area of each fundamental pole,

A1 = πdl/P

ec = [Bm1 A1 2f sin θ + Bm3 A1 2f sin 3θ +........... + Bmx A1 2f sin xθ]

A1 = πdl/P

ec = [Bm1 A1 2f sin θ + Bm3 A1 2f sin 3θ +........... + Bmx A1 2f sin xθ]

Area of xth harmonic pole, Ax = πdl/xP = A1/x

This is because there are xP poles for the xth order harmonic.

ec = 2f [Bm1 A1 sin θ + Bm3 3A3 sin 3θ +........... + Bmx xAx sin xθ]

Bm1 A1 = Φ1m = Maximum value of fundamental flux per pole

Similarly, the average value of xth harmonic flux per pole can be obtained as,

Φx = (2/π)Ax Bmx

Substituting the values of flux in ec we get the expression for e.m.f. induced per conductor as,

This is because there are xP poles for the xth order harmonic.

ec = 2f [Bm1 A1 sin θ + Bm3 3A3 sin 3θ +........... + Bmx xAx sin xθ]

Bm1 A1 = Φ1m = Maximum value of fundamental flux per pole

Φ1= (2/π)Φ1m = Average value of fundamental flux per pole

Similarly, the average value of xth harmonic flux per pole can be obtained as,

Φx = (2/π)Ax Bmx

Substituting the values of flux in ec we get the expression for e.m.f. induced per conductor as,

ec = πf (Φ1 sin θ + 3Φ3 sin 3θ +........... + xΦx sin xθ)

Instantaneous value of fundamental frequency e.m.f. generated in a conductor is,

ec1 = πfΦ1 sin θ V

Instantaneous value of fundamental frequency e.m.f. generated in a conductor is,

ec1 = πfΦ1 sin θ V

Hence the R.M.S. value of fundamental frequency e.m.f. generated in a conductor is,

### Effect of Harmonic Components on Pitch Factor in Synchronous Generator:

We know that,

α = Angle of the short pitch for fundamental flux wave then it changes for the various

3α = For 3rd harmonic component

5α = For 5th harmonic component

**harmonic component**of flux as,3α = For 3rd harmonic component

5α = For 5th harmonic component

x = Order of the

**harmonic component**### Effect of Harmonic Components on Distribution Factor in Alternators:

Similar to the pitch factor, the distribution factor is also different for various halt components.The general expression to obtain distribution factor is,

### Total E.M.F. Generated due to Harmonics in synchronous Generator:

Consider the windings to short pitch and distributed, the e.m.f. of a fundamental frequency is given by,

E1ph = 4.44 Kc1 Kd1 Φ1 f Tph V

where Tph = Turns per phase in series

Φ1 = Fundamental flux component

While the phase e.m.f. of Xth order

E1ph = 4.44 Kc1 Kd1 Φ1 f Tph V

where Tph = Turns per phase in series

Φ1 = Fundamental flux component

While the phase e.m.f. of Xth order

**harmonic component**of frequency is given by,**Line EMF**: For star connected, the line or terminal induced e.m.f. is √3 times the total phase e.m.f.But it should be noted that with star connection, the 3rd

**harmonic voltages**do not appear across line terminals though present in phase voltage.

Key Point:

*In delta connection also, 3rd,9th,15th..... harmonic voltages do not appear at the line terminals.*

**Also Read:**
Φ3 = 1/3*(10% of Φ1) = 0.0333Φ1

Now today we have learnt about

**Conclusion:**Now today we have learnt about

**Effect of Harmonic Components on Synchronous Generator or Alternator**and also emf generated due to harmonic components in Synchronous Generator or Alternator.You can download this article as pdf, ppt.If any queries, you can mail @ palakalaamarnath@gmail.com
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