Large Synchronous Motor Failure Investigation: Measurements, Analysis, and Lessons Learned

In the oil and gas industry, large synchronous motors are used to drive water injection pumps to support the pressure of a reservoir and to maintain the production level of a reservoir over a longer period. Therefore, failures in such motors will have an adverse impact on operation and production. Even though synchronous motors are superior to induction motors in relation to system voltage regulation and power factor correction, their starting is more complicated. As a result, the application of synchronous motors requires careful engineering analysis in the design stage of a project to determine system requirements for a successful operation. This paper presents a failure analysis case study for three 11 000-hp synchronous motors at a gas-oil separation plant along with the starting issues faced prior to the occurrence of a permanent damage. The fundamentals of dynamic motor acceleration requirements to achieve a successful start will be reviewed. In addition, results of site measurements and subsequent computer simulation will be presented. The simulation results were substantiated by a failure root cause analysis report provided by the manufacturer. This paper also discusses the obstacles faced as a result of erroneous and limited data availability, and the approach to overcome such difficulties.