The varnishing process for capacitor motor stators is a critical step in improving insulation strength during motor manufacturing. Its core role is to delay insulation aging and reduce the risk of electrical failure by filling gaps in the insulation material, enhancing structural integrity, optimizing thermal conductivity, and improving environmental adaptability.
During motor operation, capacitor motor stator windings are subjected to repeated effects of electromagnetic forces, vibration, and thermal expansion and contraction. This can cause tiny gaps between the winding and the core, and between turns. If these gaps are not filled through the varnishing process, moisture, dust, and corrosive substances in the air can gradually penetrate the insulation structure, causing partial discharge or electrochemical corrosion, ultimately leading to insulation breakdown. After varnishing, the insulating varnish penetrates the contact surface between the winding and the core, the gaps between turns, and the pores of the insulating paper, forming a dense, bubble-free insulation layer. This transforms the gaps previously filled with air into a solid dielectric with high dielectric strength, significantly improving voltage withstand capability.
Another important role of the varnishing process is to enhance the mechanical integrity of the capacitor motor stator structure. During motor operation, electromagnetic forces induce winding vibration. Long-term vibration can cause the insulation layer to wear or loosen. After varnishing, the insulating varnish bonds the windings to the core into a rigid, integrated unit, reducing damage to the insulation structure caused by electromagnetic vibration while enabling the windings to withstand greater mechanical stress. For example, under conditions of frequent starts and stops or shock loads, varnishing effectively prevents insulation peeling and conductor displacement caused by vibration, thereby maintaining long-term insulation stability.
Optimizing thermal conductivity is also a key way the varnishing process improves insulation strength. Unvarnished winding gaps are filled with air, which has a much lower thermal conductivity than insulating varnish. During motor operation, if heat generated by the windings cannot be dissipated promptly, it can lead to excessive localized temperature rises and accelerate insulation aging. After varnishing, the insulating varnish replaces the air in the gaps, and its improved thermal conductivity helps transfer heat more evenly to the core and casing, reducing hotspot temperatures. For example, in motors operating in high-temperature environments, varnishing can reduce winding temperature rise, thereby delaying insulation degradation caused by thermal aging.
This improved environmental adaptability further reinforces the varnishing process's effectiveness in enhancing insulation strength. Capacitor motor stators may be exposed to humidity, salt spray, and chemical corrosion, all of which can accelerate the degradation of insulation materials. The dense paint film formed after varnishing effectively blocks the intrusion of moisture, salt spray, and corrosive gases, while also preventing mold growth within the insulation structure. For example, for motors used in coastal areas or chemical plants, varnishing can significantly reduce the risk of insulation failure due to environmental corrosion, extending the motor's service life.
Varnishing also improves insulation strength by reducing the effect of partial discharge. In unvarnished winding gaps, air, acting as the insulating medium, is susceptible to partial discharge under high voltage, generating corrosive gases such as ozone and nitrogen oxides, which further damage the insulation structure. After varnishing, the insulating varnish fills the gaps and improves dielectric uniformity, suppressing partial discharge and thus protecting the insulation layer from electrical corrosion. This characteristic is particularly important in high-voltage or variable-frequency motors, where operating voltage fluctuations are significant and require a higher degree of partial discharge suppression capability from the insulation system.
