Page 51 – Numerical Problems (5-Level CHB Inverter)
Subject: Power Electronics
Level: GATE / PSU Advanced Numericals
🔹 Problem 1 – Number of Levels
A cascaded H-bridge inverter uses 3 identical H-bridge cells per phase. Find number of output voltage levels.
Formula: Levels = 2n + 1
n = 3 Levels = 2(3) + 1 = 7
Final Answer: 7 levels
🔹 Problem 2 – Maximum Output Voltage
A 5-level CHB inverter uses two DC sources of 200 V each. Find maximum output voltage.
Maximum output = +2Vdc = 200 + 200 = 400 V
Final Answer: 400 V
🔹 Problem 3 – Voltage Steps
For a 5-level inverter with Vdc = 250 V, list all output voltage levels.
+2Vdc = +500 V +Vdc = +250 V 0 −250 V −500 V
Answer: +500, +250, 0, −250, −500 V
🔹 Problem 4 – Total Number of Switches
Each H-bridge uses 4 switches. For a 5-level CHB inverter (2 H-bridges per phase), find total switches per phase.
Switches per H-bridge = 4 Total = 2 × 4 = 8 switches per phase
Final Answer: 8 switches per phase
🔹 Problem 5 – 3-Phase System Switch Count
For a 3-phase 5-level CHB inverter, find total number of switches.
Per phase = 8 switches 3 phases → 3 × 8 = 24 switches
Final Answer: 24 switches
🔹 Problem 6 – THD Concept
If number of levels increases from 5 to 7, what happens to THD?
More levels → waveform closer to sine → THD decreases.
🔹 Problem 7 – Required DC Sources
A 9-level CHB inverter is required. Find number of H-bridge cells per phase.
Levels = 2n + 1
9 = 2n + 1 2n = 8 n = 4
Final Answer: 4 H-bridges per phase
Exam Memory Section
✔ Levels = 2n + 1 ✔ Switches per phase = 4n ✔ More levels → Lower THD ✔ 5-level → 2 DC sources ✔ 7-level → 3 DC sources
Multilevel Inverter Numerical Series – Shaktimatha Learning
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