What does it mean? Why use either one instead of the old Dip and Bake method?
VPI stands for Vacuum Pressure Impregnation an insulating method whereby a new winding is preheated, placed in a vessel and put under vacuum to remove air and moisture. Resin is then allowed to cover the windings, (still under a vacuum) forcing trapped air bubbles to expand and pop. Finally, pressure is placed over the resin to reduce the size of any bubbles that escaped the first two steps. Ideally, this method will wet every bit of the winding surface with insulating varnish, eliminating voids to insure corona free motor operation. This method is commonly used on form-wound coils and very large random windings.Trickle Impregnation utilizes controlled AC electrical current to produce heat and vibration in a new winding while impregnating resin is poured over and through the winding from both ends. This method uses less varnish than the Dip and Bake method, and saves cleanup time, since no resin is applied to machined fits and threaded holes.
