Dielectric heating power stage using thyristors In industrial dielectric heating systems requiring high-frequency AC for heating, the thyristor-based power stage typically consists of:

Introduction / Context:
Dielectric heating (also called radio-frequency heating) requires high-frequency alternating electric fields to heat insulating materials. Mains frequency (50/60 Hz) is too low, so power-electronic conversion is used to produce the required high-frequency AC.

Given Data / Assumptions:

• Supply is standard AC mains.
• Load needs high-frequency AC (tens of kHz commonly).
• Thyristor-based conversion stages are considered.

Concept / Approach:

The most common approach is AC → DC → high-frequency AC. A controlled rectifier (or diode bridge with DC link) first produces DC. An inverter then synthesizes high-frequency AC to drive the dielectric heating electrodes. This two-stage 'rectifier–inverter' chain allows control of output frequency and power level independently from the grid frequency.

Step-by-Step Solution:

Verification / Alternative check:

Industrial RF heaters and induction heaters commonly use rectifier–inverter chains; an AC regulator alone cannot change frequency, and a chopper works on DC only (no HF AC generation).

Why Other Options Are Wrong:

(a) Chopper does not create AC. (b) Controlled rectifier alone gives DC output. (c) AC regulator only varies RMS at line frequency. (e) Cycloconverters are typically used for low-frequency outputs, not high-frequency dielectric heating.

Common Pitfalls:

Confusing dielectric heating (needs high frequency) with resistance heating (mains frequency is acceptable).

Final Answer:

Rectifier–inverter combination