In a single-phase cycloconverter built with a center-tapped transformer and controlled rectifiers, do all thyristors necessarily conduct for equal durations over a modulation cycle?

Introduction / Context:
Cycloconverters synthesize a low-frequency output by selecting segments of the input waveform using controlled rectifiers. In center-tapped configurations, multiple thyristors are used per half-cycle and their conduction windows are determined by the modulation pattern and load current continuity.

Given Data / Assumptions:

• Single-phase cycloconverter with center-tapped transformer.
• Thyristor conduction depends on firing angles and load current.

Concept / Approach:
Because the output frequency is a fraction of the input frequency, conduction intervals are apportioned to shape the output. Depending on the required output waveform, load power factor, and current continuity, individual thyristors may conduct for different durations within the same output cycle.

Step-by-Step Solution:
1) The controller selects which rectifier group conducts to form positive or negative output segments.2) Firing angles shift dynamically across input cycles to approximate the desired low-frequency output.3) Consequently, each device’s conduction time can vary; equalization is not an inherent requirement.
Verification / Alternative check:
Waveform plots in cycloconverter texts show unequal conduction periods when constructing non-sinusoidal segments at low output frequencies.
Why Other Options Are Wrong:

• Always equal or must be equal: not generally true; depends on modulation.
• Cannot be equal: they can coincidentally be equal for special cases.
• Unity power factor condition: not a guarantee of equality.

Common Pitfalls:

• Assuming symmetry mandates identical conduction intervals.
• Overlooking dependence on load and target waveform.

Final Answer:
Durations may or may not be equal.