| Abstract |
Resistive heaters are widely employed for various applications, and they often constitute
relatively large loads for the lines supplying them. Nevertheless, their regulation is still often
performed either by means of manual switches or thermostats, achieving a poor temperature
regulation and voltage flicker effects, or by means of Triac based voltage partializators, which
determine significant harmonic pollution levels and a low fundamental power factor. This paper
proposes unconventional solutions for the regulation of a.c. mono- and three- phase resistive
heaters, based on inexpensive regulation converters and a simple modulation technique. Such
regulators, while not involving relevant costs, permit to finely regulate the produced heating
power and to achieve low THD values, an almost unity power factor under sinusoidal supply, and
a pseudo-resistive equivalent behavior even in presence of voltage harmonics. Analytical results
are reported for ideal behavior conditions, and simulation results coming from purposely
developed semi-ideal models are presented and commented to confirm the theoretical conclusions.
The issues correlated to the design of a system controller are finally discussed, indicating a
possible configuration featuring a low-cost structure and a rule-based temperature control logic. |
