Fault Tolerant Operations in Adjustable-Speed Drives and Soft Starters for Induction Motors
Format of Original
Institute of Electrical and Electronics Engineers (IEEE)
IEEE Power Electronics Specialists Conference, 2007. PESC 2007
Fault tolerant operations of soft starters and adjustable-speed drives (ASDs) when experiencing power switch open-circuit or short-circuit faults are presented in this paper. The present low-cost fault mitigation solutions can be retrofitted into the existing off-the-shelf soft starters and ASDs with only minimum hardware modifications. The fault tolerant soft starters are capable of operating in a two-phase mode under the condition of thyristor/SCR open-circuit or short-circuit switch-fault in any one of the phases using a novel resilient closed-loop control scheme. The performance resulted from the present soft starter fault tolerant control has demonstrated reduced starting motor torque transient and inrush current magnitude. As for the ASDs, a low-cost fault mitigation strategy for low-speed applications such as "self-healing/limp-home" needs for vehicles and propulsion systems, with capabilities for mitigating transistor open-circuit and short-circuit switch-faults was developed. The present fault tolerant drive topology requires only minimum hardware modifications to the conventional off-the-shelf six-switch three-phase drive, with only the addition of electronic components such as triacs and fast-acting fuses. In addition, the present approach offers the potential of mitigating not only transistor switch-faults but also drive related faults such as rectifier diode short-circuit fault or dc link capacitor fault. Given in this paper is a complete set of simulation results that demonstrate the soundness and effectiveness of the present fault tolerant approaches.