Ensuring the longevity and robustness of an insulation system is integral to the maintenance of motors and generators. With age, the insulation used for the coils and windings begins to deteriorate quite considerably, causing gaps and voids that could affect the temperature and efficiency of the material. These voids occur between the wires, leaving the motor or generator susceptible to moisture and other outside influences. The deterioration is often due to the aging process of the insulation system and the nature of the materials utilized in its construction.
What is Vacuum Pressure Impregnation?
Used on high voltage motors and generators, Vacuum Pressure Impregnation (VPI) is a system that significantly reduces the rejection rates and maintains the longevity of an electric apparatus. As its name implies, vacuum pressure impregnation (VPI) is a procedure that involves the use of vacuum and pressures to remove air, gas, and moisture from an electric apparatus, and with the use of a resin, penetrates the turns, coils, slots, and insulation. The operation involves the submersion of the material into the resin, which fills up all gaps and voids. Through the process of preheating, dry-vacuuming, heating, wet-vacuuming, pressure, draining, and curing, the resin binds with the components of the insulation system to form into a solid, homogenous structure.
Benefits of VPI Over Traditional Bake and Dip Method
Varnishes can lose approximately 50% of their initial volume during the baking process with conventional impregnation, which could result in the formation of air pockets and gaps, subsequently degrading the material. This, in addition to the “Heat Jacket” caused by frequent varnish dips, reduces heat dissipation in traditional dip and bake methods.
VPI, in contrast, creates through the resin application a 100% solid structure that is significantly more effective at conducting heat. In addition, Sloan uses a 100% solids epoxy resin, widely recognized as the “gold standard” of VPI resins.The removal of air pockets from the windings also makes it is less susceptible to cracking and corona, guarantying the leak-proof and corrosion-proof of the critical parts in operation, and thus ensuring the sustenance and longevity of the material.
The solid structure created through the VPI process provides the motor with longer insulation life, ensures that the motor is less susceptible to chemicals and moisture, reduces the motor’s coil movement and friction, and overall, ensures remarkable improvement in the quality of the motor.
Also, as a result of dead-air spaces that could potentially result from the traditional dip and bake methods, hot-spots can occur within the motor coils. VPI’s solid structure, on the other hand, means that the material is well equipped with lower thermal resistance path, which in turn results to lower hot-spot temperatures and lower temperature rises.
This additionally reduces mechanical vibrations making for a less noisy motor. Furthermore, the VPI process and the use of a resin strengthen the motor significantly, enabling it to endure increase voltage stress levels without risk of damage or failure.
The VPI method also saves you a lot of money in the long run considering that it is more cost efficient than conventional bake and dip methods. Likewise, it is a greener alternative to maintaining the insulation system on your high voltage motor or generator.
All things considered, maintaining your motor or generator through the VPI method guarantees the efficacy and robustness of its insulation system by ensuring the following: it is an effective heat conductor; it is less susceptible to cracks, leaks, corrosion, chemicals, and moisture; it is equipped with lower thermal resistance path; it strengthens the motor and increases its endurance against high voltage levels without risking damage or failure. Motor failure often occurs as a result of a faulty or degraded insulation system. Thus, it is important to ensure that your insulation system undergoes thorough care.