Unbalanced Magnetic Pull in Three-phase Electric Motors-EASA Document

EASA Document
Pdf Summary
The "Good Practice Guide to Maintain Motor Efficiency" provides detailed instructions for service technicians on repairing and rewinding premium efficiency motors while maintaining their performance. The guide draws on research from the 2019 and 2003 rewind studies and offers best practices established in the industry.<br /><br />Key Points include:<br /><br />1. <strong>Terminology and Energy Losses:</strong> Understanding the types of energy losses which include core, stator I2R, rotor I2R, friction, windage, and stray load losses is essential in effectively addressing them in motor repairs.<br /><br />2. <strong>Motor Repair Processes:</strong><br />   - <strong>Preliminary Inspection:</strong> Record detailed motor nameplate data and results of external inspections alongside customer input.<br />   - <strong>Dismantling the Motor:</strong> Document terminal box layouts, orientations of components, and carefully remove the rotor to avoid damage.<br />   - <strong>Internal Core Inspection:</strong> Assess for water ingress, severe overheating, or mechanical damage to the stator or rotor cores.<br />   - <strong>Removing and Cleaning:</strong> Safe burnout of old windings, followed by careful cleaning and testing of core losses to avoid reducing efficiency.<br /><br />3. <strong>Rewinding the Motor:</strong><br />   - Recreate the original winding configuration, minimizing coil extensions and ensuring proper mean length of turn (MLT) to maintain low resistance and efficiency.<br />   - Consider changing to a two-layer lap winding where appropriate, ensuring all turns are well-fitted and exposed to airflow for better cooling.<br />   - Test winding resistance and phase balance before impregnation, and ensure proper varnish application for dielectric strength and heat transfer.<br /><br />4. <strong>Mechanical Repairs:</strong> Attention to detail in repairing core damage, precision in reassembly, correctly sizing bearings and seals, and maintaining original fan setups are crucial.<br /><br />5. <strong>Reassembling the Motor:</strong> Careful reassembly following original configurations, proper grease application, ensuring fan placements, and careful handling to prevent core damage.<br /><br />The guide emphasizes that missteps in any part of the process can lead to decreased efficiency. Proper documentation, testing, and adherence to standards at each stage are critical for maintaining motor efficiency post-repair. The appendix includes a thorough bibliography for further details and study, ensuring that users have access to comprehensive, technically sound information.
Keywords
Motor Efficiency
Service Technicians
Repairing Motors
Rewinding Motors
Energy Losses
Motor Repair Processes
Internal Core Inspection
Rewinding Configuration
Mechanical Repairs
Motor Reassembly