(In collocation with ECCE Tutorials)
Health Monitoring and Fault-Tolerant Operation of VFDs in On-the-Move Energy Technologies
Behrooz Mirafzal, Kansas State University
On-the-move industry comprises a variety of technologies including industrial, service and medical robotics, aircraft, electric and hybrid vehicles, trains, and drones, etc. Despite their differences, they have common specific characteristics and requirements. They generally apply electric motors and Variable Frequency Drives (VFDs). Therefore, VFDs must have resilient structures because of rapidly changing environmental conditions. They must have fault-tolerant structures to prevent catastrophic failures, such that, if some part of the structure is damaged and bypassed, the structure will not necessarily fail or collapse, as another part can replace the damaged part. Meanwhile, driven by the requirements of high power density, switching frequency of VFDs has become increasingly high over the past decade, leading to severe electric stress on the stator winding and bearings in motors. In this tutorial, the mechanism of electrical faults that could occur in VFDs and their associated fault diagnosis and fault-tolerant solutions will be presented. Specifically, the diagnosis and fault-tolerant solutions to switching faults in semiconductor devices such as short-circuit and open-circuit switching faults, as well as ground faults, in both low-voltage (LV) and medium-voltage (MV) VFD systems are presented. Furthermore, overvoltage on the stator windings and the diagnosis of winding short-circuit faults in the VFD-fed electric machines due to the short rise time of PWM voltage pulses and mismatch of the surge impedance will be elaborated. Finally, the mechanism of the bearing faults caused by the common-mode voltage induced by the fast-switching VFDs as well as the related fault detection and fault-tolerant solutions will be instructed.
Line-Ground Faults in Industrial Systems and Applications of Symmetrical Components for their Analysis and Protection
Rasheek Rifaat, Rifaat Engineering Inc.
A line-to-ground (L-G) faults is the most likely type of fault to occur in industrial power systems. Under L-G fault conditions, power systems are not symmetrical. Analysis, identification, and proper isolation of L-G faults prevents the progression of L-G faults into multiple phase faults with large fault currents and considerable damage to power systems and establishes a properly coordinated L-G protection system. It is necessary for industrial power system engineers to comprehend system asymmetrical behavior under L-G fault conditions and avoid false conclusions that could result from oversimplified system modeling. Misunderstanding of system under such conditions will also lead to incorrect inputs to protection coordination programs or inappropriate selection of protection functions and settings. One of the most effective tools in analyzing and verifying L-G fault conditions is the Symmetrical Components Method which was developed about a century ago, yet it still provides valuable analytical information. This tutorial provides an introduction to the symmetrical components method and discusses practical examples on its utilization as a tool for the verification of system parameters. It discusses tips, tricks, and tracks associated with such applications, especially for a system with diversified transformer connections and multiple sources with different neutral ground connections.
(1) Participation Fee is $125/tutorial and people can register to more than one tutorial.
(2) Conference administration reserves the right to cancel any of the tutorials if a minimum registration target is not achieved by early September, 2018. In case of cancellation, the registration fee will be refunded automatically.
(3) Registered persons, to any tutorial, will receive ALL operating tutorial materials.
(4) For participating in any of the IAS-AM tutorials, IEEE offers PDH credits for continuing education units, for renewal of professional engineering licensees.