Impregnation of electrcal machines with solventless resins

Abstract

In the past, solvents containing impregnation systems were in vogue, e.g. phenoloic‐alkyd, isophthalic polyester, silicone, etc. for electrical machines. The disadvantages of solvent borne impregnants are a higher dissipation factor (at elevated temperatures) and water absorption, etc., due to the presence of air voids formed during the curing process. The phenomenon has been controlled with the present day use of solvent/ess systems, e.g. polyester, polyesterimide, epoxy and silicone resins. Solvent/ess polyester resins are now indigenously available along with their additives such as: inhibitor, catalyst and reactive diluent, etc. Modern methods of impregnation for electrical machines in BHEL include: (a) Dip impregnation by rotational method (b) V P I process The methods include storing the catalysed resin in cool storage, warming for impregnation, and final impregnation under vacuum and pressure, and curing in an oven. A monitoring system has also been standardised for the impregnation resin to keep its viscosity and gelling time within the specified tolerances by the addition of an appropriate amount of inhibitor and reactive diluent. Proper monitoring keeps the tank life of the system indefinitely long and its properties within limits.

One Factor at a Time Analysis to Modify Potting Technique for Manufacturing of Bubble-Free High-Voltage Polyester Insulated Automotive Coils

“…The exponential relation (see Equation ( 17)) perfectly fits the data set with the fitting parameter as y o = 14.50 ± 0.70, A = 9.64 ± 1.90, and R o = −5.31 × 10 −4 , with the statistical relation error α = 0.1 (as exhibited in Table 1). Equation (17) almost confirms the exponential decrease in percent bubbled coils up to 55 ± 5 min. Intercept y o represents the minimum bubble proportion in the manufactured coils with preheating above 60 • C, i.e., 13.07 ± 1.70%.…”

“…Hence, an existing potting method was modified by changing several parameters during the insulation process to minimise the percentage of bubbles in the ignition coils. However, its non-economical maintenance entailed procedures and processes, i.e., vacuum impregnation (VI) and vacuum pressure impregnation (VPI), which were used to mitigate bubbles-related problems [17]. However, bubbles are formed in coils manufactured from these two processes due to the development of partial pressure in the vacuum chamber.…”

Polyester Usage in Manufacturing of Electrical and Mechanical Products and Assemblies

“…Impregnation with this process is done with highly viscous resin [11,13]. It needs high investment and is time-consuming process.…”