Page 40 – Three Phase Voltage Source Inverter (VSI)
Subject: Power Electronics
Topic: Three Phase Bridge Inverter
Level: GATE / PSU Core Concept
.png "Power electronics")
🔹 Introduction
A three-phase VSI converts DC voltage into three-phase AC output. It is widely used in motor drives, EVs, UPS and industrial applications.
🔹 Circuit Configuration
- Six switches (S1–S6)
- Three legs (Phase A, B, C)
- Each leg has two switches
- Upper & lower switches are complementary
Important: Never turn ON both switches of same leg (shoot-through fault).
🔹 180° Conduction Mode
Each switch conducts for 180°. At any instant, three switches are ON.
- Produces quasi-square output
- Lower harmonic performance than PWM
🔹 120° Conduction Mode
Each switch conducts for 120°. Only two switches conduct at a time.
- Reduced switching overlap
- Different line voltage waveform
🔹 Line Voltage Expression
VLL = √3 × Vph
For square wave inverter:Fundamental Line Voltage: VLL1 = (√6 / Ï€) × Vdc
🔹 Advantages
- High efficiency
- Suitable for high power applications
- Used in induction motor drives
- Basis for PWM inverters
🔹 GATE Important Points
- Difference between 120° & 180° conduction
- Line vs phase voltage relation
- Switching sequence table
- Fundamental RMS calculation
Quick Revision
Three Phase VSI → 6 switches
180° mode → 3 ON
120° mode → 2 ON
VLL1 = (√6 / Ï€) Vdc
Power Electronics Series – Shaktimatha Learning
.png)
No comments:
Post a Comment