The Influence of Main Pump with High-Voltage Variable Frequency Drives on Electric Motors Periodic Repair

摘要

The main objective of the research is to investigate the effect of periodic switching on/off in cyclical pumping on resistance to wear of high voltage electric motors of main pump units. Frequent motors starts in a cyclic pumping lead to accelerated wear of the mechanical motor parts owing to the impact of dynamic loads at startup, as well as winding insulation due to high inrush currents flow. As a result accelerated depreciation may decrease residual life, overhaul period and service life of electric motors. The main factors affecting the service life of insulation motors are winding temperature, and as a consequence, the thermal aging of the insulation. The use of variable frequency drive can significantly reduce the cyclic transfer modes, or even eliminate them. The authors obtained analytical expressions for the evaluation of insulation deterioration at the start of the motor, which allow us to study the impact of the following factors: insulation class, the start time, break time at work, initial and nominal temperature, the temperature rise of the windings over the ambient temperature. Cold starts and hot operating conditions, as well as the percentage of the hottest startups in the total number of starts have a drastic impact on insulation deterioration. The obtained expressions for the isolation depreciation are used to determine the change timing of overhauls of high voltage electric main pump units. The developed method was tested and approved by the use of a variable frequency drive at the oil pumping stations, the construction section of Leninsk-Nurlino-Nizhnevartovsk-Kurgan-Kuibyshev trunk pipeline. The analysis showed that the installation of variable frequency drive motors on three main pump units at technological area resulted in the decline of the starts number up to 14%. The results can be used for pipeline transport by oil companies when planning the timing and costs of the current and capital repairs of high voltage electric motors main pump units.