Phase-Controlled Multibank Resistive Heating With Optimized Current Harmonics

Abstract

This paper proposes an SCR phase controlled 3-phase 3-wire industrial heating system using multiple Delta Banks of resistors. In the proposed scheme, out of two similar groups denoted as ‘Set’, each has two resistance banks with a finite ratio of maximum power dissipation between them and operating with same controlled firing angle. Each bank of resistance is ‘Delta’ connected, one with SCRs in phase while the other with SCRs in line. This proposed configuration eliminates triplen besides some major characteristic harmonics in the line current. ‘Delta’ connection permits use of same voltage rating of all resistors. In the proposed scheme, two such Sets are operated with a fixed firing angle difference to substantially reduce residual harmonics without any additional filters. An offline-optimization process determines the operating conditions of the sets. The proposed scheme with simple construction & operation, wide power range, low THD makes it a practical and cost-effective solution. The modeling, analysis and performance of the proposed scheme are presented, with supporting simulation and experimental results.