Electric Motor Noise: How to Identify the Cause and Implement a Solution-EASA Document

EASA Document
Pdf Summary
The "Good Practice Guide to Maintain Motor Efficiency" by EASA, Inc. emphasizes repair and rewind techniques aimed at preserving or enhancing motor efficiency, reliability, and quality. The guide integrates findings from rewind studies conducted in 2019 and 2003, along with older studies and established industry practices. It covers the maintenance of three-phase, random-wound induction motors and also provides related information for form-wound stators.<br /><br />Key aspects include understanding motor energy losses (core, stator I²R, rotor I²R, friction and windage, and stray losses) and the effects of repair processes on these losses. It's crucial to minimize core and stator losses by ensuring proper burnout temperatures and careful coil removal to avoid damage to the stator core's interlaminar insulation.<br /><br />Motor repair involves several stages:<br />1. <strong>Preliminary Inspection</strong>: Recording motor nameplate data, external inspection, customer input, and internal inspection for contamination or mechanical damage.<br />2. <strong>Dismantling</strong>: Carefully disassembling the motor, noting the layout and orientation of components to ensure proper reassembly without damaging critical parts like the air gap surfaces or windings.<br />3. <strong>Removing and Cleaning the Old Winding</strong>: Accurate recording of winding details, core loss testing before and after stripping, removing coils without damaging the core, and cleaning the core to prevent increased losses.<br />4. <strong>Rewinding</strong>: Either copying the original winding or redesigning it for efficiency. This involves maintaining or increasing the copper cross-sectional area, keeping coil extensions short, and ensuring correct coil pitch and turns.<br /><br />The integrity of the repair is confirmed via core loss tests, resistance measurements, and phase balance tests before final reassembly. Additionally, mechanical repairs that can affect motor efficiency, like improper bearing fits or incorrect fan replacements, are highlighted.<br /><br />The guide underscores proper rotor and stator handling, and the importance of controlled varnishing processes to improve thermal conductivity and reduce I²R losses.<br /><br />Overall, adhering to these best practices ensures motors run efficiently, mitigating the risks of increased energy losses and guaranteeing reliable performance.
Keywords
motor efficiency
repair techniques
rewind techniques
three-phase motors
induction motors
core losses
stator losses
coil removal
rewinding
motor maintenance