DEPARTMENT OF ELECTRICAL POWER ENGINEERING

COLLEGE OF ENGINEERING

POWER ELECTRONICS

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Fourier Series and THD for a Square-Wave Inverter Example:

The full bridge inverter shown has a switching frequency sequence that produces a square wave voltage across a series RL load. .

Determine:

  • a. Amplitudes of the Fourier series terms for the square wave load voltage
  • b.Amplitudes of the Fourier series terms for load current
  • c.Power absorbed by the load
  • d. Total harmonic distortion (THD) of the load voltage and the load current

Please enter the input value:

Input voltage (positive value only): V

Resistance:

ohm
Inductor: mH
Switching Frequency: Hz

The amplitude of load voltage is determined from

Vn = (4 Vdc) / n

The amplitude of each current is determined from

In = Vn /Zn

Power at each frequency is determined from

Pn = I2rms R

See Fourier Series Analysis

a)and b) Fourier series quantities

n
fn(Hz)
Vn(V)
Zn()
In(A)

Pn(W)

1

3

5

7

9

c)

Power absorbed by the load P = Pn = W

d)

THDv = = %

THDI = = %

Click for explanation of Fourier series quantities.

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