What are the electrical properties of insulating materials?


Release time:

2023-10-24

The electrical characteristics of insulating materials include dielectric coefficient, dielectric loss, breakdown field strength and insulation resistivity, which are very important for the reliability and service life of motor winding operation. The basic requirements for the performance of insulating materials include electrical characteristics, heat resistance and mechanical properties. The following is a brief introduction to the electrical characteristics of insulating materials by Longkou Tengda Company.

The electrical characteristics of insulating materials include dielectric coefficient, dielectric loss, breakdown field strength and insulation resistivity, which are very important for the reliability and service life of motor winding operation. The basic requirements for the performance of insulating materials include electrical characteristics, heat resistance and mechanical properties. The following is a brief introduction to the electrical characteristics of insulating materials by Longkou Tengda Company.

1. Dielectric coefficient of insulating material

The overall dielectric coefficient of the insulating material indicates the movement of charges in the internal structure of the insulating material under the influence of the electric field, I .e. the degree of electric polarization. It usually decreases gradually with the increase of electric field frequency and increases with the moisture absorption of the material. Because the temperature affects the electric polarization, there will be a peak at a certain ambient temperature.

2, the dielectric loss of insulation materials.

Insulating materials under the influence of electric field, because of leakage and electrical polarization and other causes of energy loss. The size of the dielectric loss is usually indicated by the loss power or loss angle tangent. Under the influence of DC voltage, instantaneous charging current, absorption current and leakage current will be taken. When an AC voltage is applied, the instantaneous charging current is a reactive current; the leakage current is in phase with the voltage and is an active current; the absorption current has both a reactive current component and an active current component.

3. Breakdown field strength of insulating material

3.1 thermal breakdown. Under the influence of the alternating electric field, the internal structure of the insulating material generates heat due to dielectric loss. If it cannot be dissipated in time, the temperature of the internal structure of the material will rise, causing molecular damage and breakdown, called thermal breakdown. The thermal breakdown voltage decreases with the increase of the ambient temperature of the surrounding medium, the material thickness increases, the heat dissipation standard becomes worse, and the breakdown field strength decreases; when the number of times is frequent, the dielectric loss increases and the breakdown field strength decreases.

3.2 electrical breakdown. Under the influence of strong electric field, the internal structure of the insulation charged particles move excessively, collide and free, destroy the molecular formula, so that the next breakdown, called electric breakdown. The electrical breakdown voltage increases linearly with the thickness of the material. In a uniform electric field, unless the time of the impulse voltage is shorter than 10 seconds, the electrical breakdown field strength is usually irrelevant to the voltage action time.

3.3 discharge breakdown. Under the influence of strong electric field, the bubbles involved in the internal structure of the insulating material are discharged due to ionization; impurities are also heated and vaporized by the electric field to produce bubbles, so that the continuous development of bubble discharge directly leads to the breakdown of the material, which is called discharge breakdown.

The breakdown of insulating materials, often the above three forms exist at the same time, there is no way to separate. Impregnating insulating materials with insulating paint or glue can not only improve the electric field distribution and increase the electric breakdown field strength, but also improve the heat dissipation standard to increase the thermal breakdown field strength.

4. Insulation resistivity

Insulating materials under the action of voltage, there will always be a small leakage of conductive flow. This current flows partly through the internal structure of the material and partly through the surface of the material. Therefore, insulation resistivity can be divided into volume resistivity and surface resistivity.

In addition to the electrical characteristics of the insulating material described above, there are electrical characteristics such as corona resistance, arc resistance, and leakage resistance. Electrical characteristics of the electrical insulation material requirements, to the breakdown of the electric field strength and insulation resistance is important.