Prof. Dr. Basil B. Saied
Power Electronics 7-3-2017
As a typical examples for applying SPWM,
Problem I
Single phase half-bridge SPWMVSI, the source voltage =120 V, the load is
resistive R= 20 Ω, the fundamental load current required to be = 2.25 A at
frequency = 50Hz, determine the value of modulation index ratio and draw to
scale the SPWM signal for the top IGBT device only. Assume frequency ratio
P=11.
Problem II
Single phase SPWMVSI, the source voltage =50 V, the load is resistive R= 10 Ω
and L =50 µH, the fundamental peak load voltage is required to be = 35V at
frequency = 20 kHz, determine the value of modulation index ratio and draw to
scale the SPWM signal for the top IGBT device only. Assume the switching
frequency of IGBT= 180 kHz.
Problem III
Three phase SPWMVSI, the source voltage = 600V, the load is star and resistive
where R= 20 Ω, the fundamental phase load voltage is VAn = 150 V, at
frequency = 50Hz, then:
1- Choose one of the suitable value of the following values for frequency ratio P
, the values are 11,15, 17. and state why you choose this value.
2-Calculate the value of modulation index.
3-Draw to scale the SPWM signal for the top IGBT device only.
4- Determine the switching frequency of the IGBT.
Prof. Dr. Basil B. Saied
Power Electronics 7-3-2017
As a typical examples for applying SHEPWM,
Problem 1:
In case of half-bridge single phase voltage source inverter, the dc link voltage
Vs=150 V, the output voltage is required to be = 50 V with lower significant
order is n = 13th harmonic order. Then answer the folloings:
1- Which type of PWM strategy you have to apply.
2- Draw roughly the PWM output voltage .
3- Show in clear step how you can achieve this.
Problem 2:
In case of three phase voltage source inverter, the dc link voltage Vs=550 V, the
output frequency is 1kHz and output voltage of 90% of its maximum value with
elimination of the most five significant harmonic components:. Then answer
the followings:
1- Which type of PWM strategy you have to apply.
2- describe how you obtain the switching angles.
3- Draw roughly the PWM output voltage .
4- Explain how to vary fundamental output voltage with variable frequency.
Problem 3:
For single phase voltage source inverter, the dc link voltage Vs=200 V, the
output frequency is 50 Hz and output voltage required to be 70% of its
maximum value with elimination of five most significant harmonic
components:. Then answer the followings:
1- Which type of PWM strategy you have to apply.
2- Derive the equations which can be applied to obtain variable fundamental
voltage.
3- Draw roughly the PWM output voltage .
4- Comment on the difference between SHEPWM or SPWM methods.