VTU Module-2 | Phase Controlled Converter

18EC36 | POWER ELECTRONICS & INSTRUMENTATION | Module-2 VTU Notes

Summary:

The concept of a Phase Controlled Converter is a fundamental topic in power electronics and plays a crucial role in controlling the flow of electrical power in various applications. This concept encompasses control techniques for single-phase half-wave and full-wave controlled rectifiers, both with resistive and inductive loads, while also considering the effect of the freewheeling diode.

1. Control Techniques:

Phase-controlled converters are designed to regulate the output voltage or current by controlling the conduction angle of the semiconductor devices (usually thyristors or silicon-controlled rectifiers, SCRs). By adjusting the firing angle of these devices, the converter can control the power delivered to the load.

2. Single-Phase Half-Wave Controlled Rectifier:

In a single-phase half-wave controlled rectifier, only one half of the input AC voltage is converted to DC. By varying the firing angle of the SCR, the output voltage can be controlled and adjusted as needed. This configuration is often used in applications where partial wave rectification is sufficient.

3. Single-Phase Full-Wave Controlled Rectifier:

A single-phase full-wave controlled rectifier rectifies both halves of the AC input waveform, resulting in a smoother DC output. Similar to the half-wave rectifier, the firing angle of the SCRs determines the output voltage level. This configuration is preferred in applications requiring smoother DC output voltage.

4. Resistive and Inductive Loads:

Phase-controlled converters can be applied to both resistive and inductive loads. When driving a resistive load, the converter controls the average output voltage to regulate the power delivered. In contrast, when driving an inductive load, additional considerations are necessary, such as reactive power control and commutation techniques to manage the inductive nature of the load.

5. Effect of Freewheeling Diode:

In phase-controlled converters, the freewheeling diode (also known as the commutating diode) plays a crucial role. It provides a path for the inductive load current to circulate when the SCRs are turned off, preventing voltage spikes and ensuring smooth operation. Understanding the behavior and importance of this diode is essential for proper converter design.

In conclusion, a Phase Controlled Converter is a versatile tool in power electronics, allowing precise control of electrical power for various applications. Mastery of control techniques, understanding of different load types, and awareness of the freewheeling diode's role are essential for designing efficient and reliable power conversion systems.