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VPI (Vacuum Pressure Impregnation) System

AEM is proud to announce the installation and commissioning of a new VPI (Vacuum Pressure Impregnation) system. This new addition does not only enhance AEM’s capability but also improves our services to the customers by ensuring increased reliability and maximized performance of the windings systems of high and low voltage motors, generators, and other electrical equipment.

What is Vacuum Pressure Impregnation?

Vacuum Pressure Impregnation (VPI) is basically an impregnating process for the rewound components (e.g. stator, rotor, armature windings). As its name suggests, it entails vacuum and pressure cycles during the impregnation stage.

The VPI process removes moisture and air voids from the winding insulation by first applying a vacuum, then introducing resin under vacuum, and finally applying high pressures to push the resin into the pockets and crevices of the winding insulation materials.

For a successful VPI process, it is imperative to have a strong control of timing, vacuum/pressures, and the temperatures along with the use of high-quality insulation materials/resin.

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Benefits of VPI

A winding that is properly VPI processed and baked will have superior characteristics, which will support a longer insulation life, greater heat dissipation and hence, reduced probability of motor failure. Some of the key benefits are:

  • Enhanced dielectric (insulation) strength
  • Excellent heat transfer
  • Better performance in harsh environment and superior protection against the contaminants
  • Enhanced mechanical strength
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Typical VPI process

The item (stator, rotor, armature etc.) is preheated and placed in the VPI chamber. Temperature and capacitance probes are connected to ensure quality is maintained during the cycle.
Vacuum introduced into the chamber and once reached the set vacuum level, the item dwells in the vacuum for the set amount of time. The vacuum level and timing is crucial and depends upon the size and type of winding.
While still under vacuum, the resin is introduced from the reservoir into the VPI chamber manually and soaks into the winding. It is ensured leads or other components are not soaked.
Pressure is then introduced in to the chamber at the required level to penetrate the resin deep into the windings. The pressure level and timing is crucial to ensure maximum penetration.
The resin is automatically transferred back to the reservoir and the cycle is completed. The item is left hanging to drain excess resin and removed from the chamber.
The item placed in the curing oven at the required temperature for set amount of time. Baking temperature and duration is critical to achieve best results.