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Why does another dip bake improve the temperature rise motor performance?

Date:2022-06-21   Author:XINDA MOTOR

The temperature rise is a very critical performance index of the motor. If the temperature rise performance is not good, the service life and operation reliability of the motor will be greatly reduced. Factors affecting the temperature rise of the motor, in addition to the selection of the design parameters of the motor itself, many factors in the manufacturing process will cause the temperature rise of the motor to not meet the requirements of safe operation of the motor.

To test the temperature rise of the motor, it is necessary to carry out the thermal stability temperature rise test of the motor, and it is impossible to find the problem of the temperature rise of the motor by a simple factory test. A large number of actual thermal stable temperature rise tests of motors show that: improper selection of fans and unsuitable thermal components have a great impact on temperature rise, but the problem of temperature rise caused by dipping paint is often encountered, and the usual remedy is to re-dip Paint once.

In order to improve production efficiency, most of the small and medium-sized motors do not have a base dipping paint. In addition to the dipping and drying quality of the winding itself, the tightness of the iron core and the frame also directly affects the final temperature rise of the motor. Theoretically, the mating surfaces of the machine base and the iron core should be closely matched, but due to the deformation of the machine base, not only the iron core, etc., it will artificially cause an air gap between the two mating surfaces, which is not conducive to the motor. Thermal insulation for heat dissipation. The use of dipping paint with a frame not only fills the air gap between the mating surfaces, but also avoids the possible factors that may damage the motor winding during the manufacturing process because of the protection of the casing. The lift control has a certain improvement effect.

Knowledge Expansion - Heat Transfer

Heat conduction is referred to as heat conduction. The heat transfer process between two objects in contact with each other and with different temperatures, or between different temperature parts of the same object without relative macroscopic displacement, is called heat conduction. The property of a substance to conduct heat is called the thermal conductivity of an object. Heat transfer in dense solids and in still fluids is purely thermal conduction. The thermally conductive part is involved in the heat transfer in the moving fluid.

Thermal conduction relies on the thermal movement of electrons, atoms, molecules and lattices in materials to transfer heat. However, the properties of the materials are different, the main thermal conduction mechanisms are different, and the effects are also different. Generally speaking, the thermal conductivity of metals is greater than that of non-metals, and the thermal conductivity of pure metals is greater than that of alloys. Among the three states of matter, the thermal conductivity of the solid state is the largest, followed by the liquid state and the smallest in the gaseous state.

The thermal conductivity of metals mainly depends on the thermal motion of free electrons, and the thermal conductivity of metal materials with good electrical conductivity is also large. The heat conduction of non-metallic materials mainly relies on the way of elastic waves generated by the vibration of the lattice structure to transfer energy. In physics, it is called phonon transfer energy. During the transfer process, if there are phonon scattering factors, such as crystal gaps and cracks, the thermal conductivity will drop significantly. The thermal conductivity of liquid is in the range of 0.07-0.7W/(m·K), and the heat conduction mechanism of liquid is more complicated. The heat conduction of the gas depends on the thermal motion of the molecules. The speed of the molecules in the high temperature region is higher than that in the low temperature region, and energy is transferred to the molecules in the low temperature region through molecular collisions. Gas thermal conductivity is in the range of 0.006-0.7W/(m·K). Gas molecules have a greater impact on thermal conductivity. The smaller the molecular weight, the lighter the weight, and the faster the movement speed, the greater the thermal conductivity. The power plant generator adopts hydrogen cooling instead of air cooling, and the cooling effect is better.

When the temperature increases, the thermal motions of electrons and lattices in pure metals intensify at the same time. As a result, the directional shuttle motion of free electrons, which play a major role in the heat conduction process of pure metals, is hindered. Therefore, as the temperature increases, the thermal conductivity of pure metals decreases. The heat conduction of non-metals mainly depends on the vibration of atoms, molecules and lattices. As the temperature increases, the vibration increases, and the thermal conductivity increases. The heat conduction of gas mainly depends on the thermal motion of molecules, the temperature increases, the thermal motion accelerates, and the thermal conductivity increases accordingly.

Thermal insulation or thermal insulation materials are often used in construction, thermal energy, cryogenic technology. Most of them are porous materials, and air with poor thermal conductivity is stored in the pores, so they can play the role of heat insulation and heat preservation. And they are all discontinuities, and the heat transfer has both the heat conduction of the solid skeleton and the air, as well as the air convection and even the radiation. In engineering, the thermal conductivity converted by this composite heat transfer is called apparent thermal conductivity. Apparent thermal conductivity is not only affected by material composition, pressure and temperature, but also by material density and moisture content. The lower the density, the more small voids in the material and the lower the apparent thermal conductivity. However, when the density is small to a certain extent, it means that the internal voids have increased or have been connected to each other, causing internal air convection, heat transfer enhancement, and apparent thermal conductivity increase. On the other hand, the pores in the thermal insulation material are easy to absorb water, and the evaporation and migration of water under the action of the temperature gradient greatly increase the apparent thermal conductivity.