| 摘要 |
PROBLEM TO BE SOLVED: To identify the phase to which a heater that is disconnected or of which the lifetime or the like expires belongs.SOLUTION: Line currents Ir, Is and It and inter-line voltages Ers, Est and Etr of delta connection three-phase heaters 21-23 are detected, an estimated value (a) of a phase current Irs of one of three phases is set and based on the estimated value and the line currents Ir and It of two phases among the detected line currents, a line current Is' of remaining one phase is calculated. If a difference between the calculated line current Is' and the detected line current Is is greater than an allowable error (e), the phase current estimated value (a) is corrected as a correction phase current estimated value a' and the calculation of the line current is repeated until the difference between the calculated line current Is and the detected line current Is' is settled within the allowable error (e). On the basis of the correction phase current estimated value a' at the time when the difference between the line current Is' and the detected line current Is is settled within the allowable error (e), calculated phase currents (b) and (c) of the other phases and the detected inter-line voltages Ers, Est and Etr, resistance values Rrs, Rst and Rtr of the phases are calculated.SELECTED DRAWING: Figure 1 |
