Impregnation is a crucial insulation process for motor windings. In most cases, the windings are impregnated without the frame, which maximizes space savings in the impregnation equipment, reduces contamination of the insulating varnish by machined parts, and doesn't affect the conformity of the frame end hole threads. However, sometimes impregnation with the frame is necessary. The biggest advantage of this is that the insulating varnish can fill the gap between the stator core and the frame, effectively improving heat dissipation during motor operation.
In actual production and processing, some machine bases may deform into ovals or other shapes after machining due to various factors, resulting in poor contact between the stator core and the machine base mating surfaces. This is a significant factor affecting motor heat dissipation. Impregnation of the machine base with varnish can effectively solve this problem. Furthermore, varnishing further enhances the strength of the motor stator, which has a certain effect on suppressing motor vibration and noise. Regardless of the process, each has its advantages and disadvantages; the manufacturing process should be practical and meet quality control requirements.
01 Purpose of impregnation and drying of motor windings
The purpose of impregnating and drying motor windings is to remove the moisture contained in the insulation material and fill all the air gaps with insulating varnish. This can improve the insulation strength and moisture resistance of the windings, as well as their heat resistance and heat dissipation. It can also improve the mechanical properties, chemical stability, thermal conductivity and heat dissipation effect of the winding insulation and delay aging. The quality of motor impregnation directly affects the temperature rise and service life of the motor.
The impregnation and drying processes must strictly adhere to the insulation treatment procedures to ensure good varnish penetration, a smooth varnish film surface, and high mechanical strength. This will ensure the stator windings are bonded together as a solid whole.
02 Vacuum Pressure Impregnation Insulation Process
Vacuum pressure impregnation involves pre-baking and dehumidifying the workpiece, then cooling it and placing it in a vacuum environment. This removes air and volatiles from the interior of the blank coil. The impregnation process relies on the gravity of the varnish in the vacuum, the capillary action of the coil, and the application of pressure from dry compressed air or inert gas to rapidly penetrate and fill the inner layer of the insulation structure. In China, vacuum pressure impregnation is currently still an intermittent insulation process. The drip-drying process takes place in the impregnation tank, while the drying process is generally carried out in a separate container or oven, using methods such as vacuum drying, atmospheric pressure static drying, or rotary drying.
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