Abstract

The present technical disclosure relates to a control system for an electrically heated process apparatus as well as to a corresponding method of operating, in particular of controlling, an electrically heated process apparatus comprising a plurality of FeCrAl heating elements supplied and/or driven by at least one three-phase thyristor power supply unit, in particular configured in delta, open delta or star with or without neutral, the method comprising:

(a)   measuring per-leg voltage and current;

(b)   calculating instantaneous resistance R;

(c)   comparing the calculated resistance R to a reference resistance R₀;

(d)   computing a ratio R₀/R;

(e)   automatically reducing a process temperature setpoint as a function of R₀/R, in particular by applying a lookup table or polynomial function that correlates R₀/R with a safe temperature setpoint to maintain per-element electrical loading below rated limits; and

(f)    adjusting thyristor control to reflect the adjusted setpoint.

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Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

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