Effect of Thermal Corrosion on Performance of High Voltage Motors

Electrical reliability is a very important performance requirement for motor products, which is mainly achieved by controlling the temperature rise level of the motor. Therefore, the temperature rise of the motor winding is a key indicator for considering the quality of motor products, which is true for low-voltage motors and high-voltage motors. In order to ensure that the motor does not heat up, in addition to leaving enough margin during design, the processing technology during the motor manufacturing process and the specific operating conditions when it is put into use must be thoroughly and carefully investigated or simulated.

Poor welding during the production and processing of windings will cause the local temperature of the windings to rise and the winding resistance to increase; the anti-corona layer of the windings is damaged, which will cause corona discharge when the motor is running; excessive vibration of the motor will damage the winding insulation; conductive foreign matter enters the windings, and the environmental conditions are not good during actual use, which may cause damage to the motor windings. All these factors that may directly cause fatal damage to the conductive windings will threaten the normal operation of the motor. When the winding temperature exceeds the allowable insulation value, the bonding ability and mechanical strength of the insulation are reduced, causing the insulation to flow, age, delaminate, loosen, and peel, which accelerates the thermal corrosion of the insulation and shortens the service life of the coil.

In motor repair shops, we can find that the surfaces of many motor windings are seriously covered with dust, and a lot of it is charged dust. These are problems that many users tend to overlook.

Motor Temperature Rise

Temperature rise refers to the temperature of each component in an electronic and electrical device above the ambient temperature. When current flows through a conductor, it generates a thermal effect. As time goes by, the temperature of the conductor surface continues to rise until it stabilizes. The criterion for stability is that the temperature difference before and after all test points does not exceed 2K within a 1-hour test interval. At this time, the difference between the temperature of any test point and the average ambient temperature of the last 1/4 cycle of the test is called temperature rise, and the unit is K.

In order to verify the service life, stability and other characteristics of electronic products, the temperature rise of its important components (such as the windings of motor products) is usually tested. The device under test is placed at a specific temperature higher than its rated operating temperature. After stabilization, the temperature rise of the components above the ambient temperature is recorded to verify whether the design of this product is reasonable.

In electrical products, the rated temperature rise of the motor refers to the maximum allowable temperature rise of the motor winding under the specified ambient temperature, which depends on the insulation level of the winding. The temperature rise depends on the heating and heat dissipation of the motor during operation. The temperature rise is often used to judge whether the heat dissipation of the motor is normal.

The motor temperature refers to the actual heating temperature of each part of the motor, which has a great impact on the insulation material of the motor. Excessive temperature will cause insulation aging, shorten the life of the motor, and even cause insulation damage. In order to prevent insulation aging and damage, the temperature of various parts such as the motor winding is limited. This temperature limit is the allowable temperature of the motor.

The temperature rise of the motor will change under different environmental conditions. When the environmental conditions are poor, such as in plateau environments and sealed environments, the temperature rise of the motor will increase. Therefore, for motors under different working conditions, necessary adjustments should be made based on actual conditions.