Role of thyristors in controlled heating circuits In industrial heating controllers, thyristors most commonly function as which type of power-conversion element?

Introduction / Context:
Industrial electric heating often uses resistive elements powered from AC mains. Power is controlled either by phase-angle control within each half-cycle or by integral-cycle (burst) control. Thyristors are well suited for both modes due to their high current capability and simplicity.

Given Data / Assumptions:

• AC mains supply to a resistive heater.
• Target is to vary RMS voltage or duty on whole cycles.

Concept / Approach:
As AC regulators, antiparallel SCRs vary the portion of each half-cycle delivered (phase control) or gate entire blocks of cycles (integral-cycle). This directly modulates the effective RMS voltage across the heater, thus controlling power P = V_rms^2 / R without intermediate conversion stages.

Step-by-Step Solution:
Select topology: back-to-back SCRs on AC line.Choose control method: phase control (vary α) or integral-cycle (burst firing).Result: effective heater power adjusted smoothly from near 0% to ~100%.

Verification / Alternative check:
Commercial “thyristor power controllers” are marketed explicitly as AC regulators for heaters, ovens, and furnaces.

Why Other Options Are Wrong:

• Rectifier/inverter/chopper imply DC conversion stages not required for simple AC heaters.
• Cycloconverter is used for low-frequency AC drives, not basic heater control.

Common Pitfalls:

• Confusing DC heater supplies (where rectifiers or choppers may be used) with the far more common AC heater control.

Final Answer:
AC regulator (phase or integral-cycle control)