The Inventors of Aircraft Component Rewind
Simply put, rewinding means reproducing and replacing the coils of copper wire installed in the iron core of a stator, rotor, field, transformer or armature used in a motor or generator.
Before technicians remove the defective windings, they must understand exactly how the windings and insulation systems connect and interact, or they won’t be able to successfully complete a proper rewind. This is where AEM’s decades of experience and ability to reverse engineer come into play. In the 1950’s, AEM’s founders pioneered the aerospace standards that formed the foundation for the FAA Approved AEM1 Process Specification that we use today. This rewind process begins by gathering critical winding data. This data includes key specifications such as the number of slots, coils, and turns per coil as well as wire size, bracing, critical dimensions, and insulation parameters.
Rewinding motor sub-components isn’t as simple as you might think. It’s a fairly labor-intensive procedure — where everything is assembled and formed into shape using fixtures and special tooling.
Using rewound sub-components is the norm in the aerospace industry. Yet few companies are capable of offering this complex specialized service, now commonly known as aerospace generator or motor component rewind.
Once engineers confirm specification data, the general process of rewinding the electrical sub-component starts with an incoming inspection. Each part is subjected to a thorough evaluation of the component to determine if it is eligible for rewind. For example, if the core from the generator or motor is out of tolerance, it is rejected (bearing failures that damage the core ID are a common cause of rejection). Incoming AEM inspectors check the core to be certain that it is within specifications, which includes looking for core lamination damage or other defects. For rotating parts, inspectors look for shaft damage or spline wear that are beyond repair limits. Worn bearing journals that are out of tolerance can be plated to return them to their original manufacturer specifications.
A component rewind always involves carefully removing the old windings and cleaning the core. Once the core is prepared for rewind it is assigned to a rewind technician for replacement of the windings. This process includes re-insulating, winding and re-assembly, thus resetting the “service life clock” for the part. After rewind, components are vacuum impregnated with varnish, and then oven baked to cure the varnish. The main purpose behind the varnish process is to electrically insulate the windings/coils, protect the windings/coils from contaminants that could compromise their functionality, and to mechanically secure the coils so they become ruggedized and don’t move. Rotating parts (like armatures and rotors) require balancing in accordance with manufacturer or FAA approved specifications. In some cases, armatures and rotors require additional over-speed testing in order to set the windings in place, a service that’s not available at all rewind facilities.
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All parts are final inspected and electrically tested to ensure they meet the manufacturer’s identified requirements for return to service. Our experienced sales team stands ready to assist you for any component rewind or repair information that you may require.