Bubbles Have Severe Negative Effects on Motor Windings

Insulation treatment is a critical electrical process in motor winding manufacturing. Its primary purpose is to fill all gaps within the winding with insulating varnish and cure it into a solid, integrated structure. This ensures effective heat dissipation during operation while reliably maintaining the winding's vibration resistance.

Preheating during the winding insulation treatment process is to drive away any possible water vapor in the windings; Impregnation, especially the VPI impregnation process, aims to eliminate any possible air bubbles in the windings and completely fill all the gaps within the windings with insulating varnish to prevent subsequent re-entry of air.

During the operation of a motor, electrical aging is a form of winding insulation aging. Its essence is the cumulative effect of insulation performance deterioration on the insulation surface or in certain areas due to discharge, and this deterioration process is irreversible.

There are two causes of partial discharge in windings: high inter-turn voltage and inter-turn air gaps or bubbles. Compared with power frequency motors, variable frequency motors are more prone to generating higher inter-turn voltages. If the insulation treatment of the windings is not effective, the windings of variable frequency motors should be more likely to experience partial discharge problems. Compared with other dielectrics, the dielectric constant of gas is relatively small. Under the action of a strong electric field, the electric field strength in the air gaps and bubbles in the windings will be much higher than that in other media. Naturally, partial discharge problems are prone to occur, and the local temperature of partial discharge can reach thousands of degrees. Repeated discharge effects will cause the insulation here to deteriorate in performance, and in severe cases, the winding will be directly broken down. Therefore, to prevent the electrical aging of insulation or to slow down the electrical aging process as much as possible, one of the most effective ways is to pay attention to or even eliminate the bubbles during the winding processing.

For variable-frequency motors, insulation electrical aging is more likely to occur, and the insulation treatment process should be more stringent, including the use of dedicated electromagnetic wires with higher resistance to impulse voltage and corona in the motor windings. In practical applications, due to the particularity of the operation of variable-frequency motors, anti-corona electromagnetic wires have become the top choice for motor manufacturers, and high-end insulating materials integrating nanotechnology have also emerged as The Times require.