Question

A thyristor controlled reactor is used to get :

• A. Variable resistance
• B. Variable capacitance
• C. Variable inductance
• D. Improved reactor power factor

Hint:

TCR: \[ \text{Thyristor Controlled Reactor} \] works as: \[ \text{Controllable Inductive Reactance} \]

Answer 1

The Correct Option is C

Concept: A Thyristor Controlled Reactor (TCR) is a power electronic device used in:
• FACTS devices,
• reactive power compensation,
• voltage control systems. It consists of: \[ \text{Inductor + Anti-parallel thyristors} \] By controlling firing angle, effective inductive reactance is varied.

Step 1: Understanding TCR operation. In a TCR:
• thyristors control conduction angle,
• current through reactor changes,
• reactive power absorbed changes. Hence effective inductive reactance becomes controllable.

Step 2: Effect of firing angle. When firing angle changes: \[ \alpha \uparrow \Rightarrow I_L \downarrow \] Thus effective inductance behavior varies dynamically.

Step 3: Understanding why it is called variable inductance. Since current through reactor can be controlled continuously: \[ X_L = \omega L \] appears variable to the system. Therefore TCR acts as: \[ \text{Variable Inductance} \]

Step 4: Analyzing options.
• Variable resistance \(\rightarrow\) incorrect
• Variable capacitance \(\rightarrow\) incorrect
• Variable inductance \(\rightarrow\) correct
• Improved reactor power factor \(\rightarrow\) not primary function

Step 5: Selecting the correct answer. Hence correct option is: \[ \boxed{(3)} \]