Repairing motor equipment, such as through electric motor rewind in Singapore, is generally the most cost-effective option whenever these critical assets encounter failures. Of course, various factors dictate whether a repair is still the best course of action. Still, if that is the case, an electric motor can theoretically be repaired indefinitely. From a practical perspective, however, there is an upper limit, which is when the cost to repair becomes equivalent to 50%-80% of getting a newer model. Beyond that, there are also other technical limitations at play.
Read on as we look at the process to understand what these limits are.
Varnish dipping
A motor undergoes varnish dipping for three main reasons:
- Protect the coils/windings against contamination and ensure functionality
- Mechanically secure the coils to prevent unwanted movement
- Electrically insulate the coils/windings
This is an essential part of reconditioning motors and is often necessary with certain repair jobs. However, the issue with varnishing the same windings repeatedly without conducting a full strip and rewind is the risk of obstructions getting into the air vent openings in the stator or armature. This leads to the insulation on the windings choking off the airflow it needs to function properly, ultimately causing the motor to run hotter than usual and eventually overheating.
Once this happens, the operating temperature of the windings also increases to the point where they no longer function as expected. Over time, there will be a noticeable loss of overall motor performance due to underlying changes that may not be immediately obvious, such as faster degradation of the windings insulation. These factors combined all point towards inevitable motor failure.
By this time, a motor burnout and rewind will be required. The irony here is that this step should have been done in the first place to avoid this type of failure, provided the motor unit has never been rewound and comes with an extensive repair history. Knowing this history can be crucial to decision-making and starting new with a vacuum pressure impregnation (VPI) to ensure longevity.
Should a motor’s air vent openings get blocked over time, the best course of action would be to perform a burnout and rewind the coils, followed by VPI.
Electric motor burnout and rewind
The rewinding process begins with gathering winding data around key specifications such as the number of turns and slots per coil, bracing, wire size, insulation parameters, and critical dimensions. The repair shop verifies this data to ensure the windings are correct for the motor’s application and potentially offers redesign suggestions. Lastly, the core may suffer damage from the burnout process if no confirmation is done through a core-loss test, and if its insulation starts to fail, this factor could reduce the possibility of future repairs.
Once the data is verified, the motor will have its existing varnish burned in a temperature-controlled oven, followed by stripping or removing the windings from its stator core. Next, the newly fabricated coils get installed in the stator slots, with the utmost care taken for proper blocking and bracing, and completed by connecting the coils together. Finally, the new coils are tested according to EASA and IEEE standards and finished with the insulation process via VPI or a traditional varnish dip.
Electric motor redesign
Apart from the usual motor burnout and rewinding, some repair shops also offer redesigning services, which aim to increase the performance, reliability, life expectancy, and efficiency of a motor and its components. Redesigning involves a thorough analysis of its current design to provide suggestions on which aspects of the motor can be changed or fine-tuned, such as voltage, speed, and horsepower.
Other improvements may include better wiring insulation or laser-cut lamination designs to enhance the core. In some cases, it could be possible to implement improved induction rotor designs, machine a new shaft or end bells, or cast new fans. As an aside, they may also offer other products that are essential to the functioning of your critical assets, such as motor grease and transformer insulating oil, so consider getting all the resources you need for your equipment during this opportunity.
Conclusion
To summarise, as long as the shell remains, a motor can always be reconditioned and repaired. The only key thing to remember is that it will eventually need to undergo burnout and rewinding, addressing any disastrous winding issues, before it can be insulated again. And so, with proper maintenance and smart reconditioning, a motor can serve your business needs well for a very long time.
