Influence of eddy current heat and parameter selection of motor magnetic drive pump
When the eddy current of the magnetic drive pump is in the coupling rotation, the thickness of the metal wall of the isolation sleeve placed between the inner and outer magnetic rotors is cut and the alternating magnetic field lines are generated in the casing section. The thermal effect of the magnetic field eddy current is called eddy heat.
The process by which eddy currents affect eddy currents is called the supersonic effect process. On the one hand, the working magnetic field is weakened, the transmitted force or torque is reduced, on the other hand, the eddy current loss is generated, the energy is released in the form of heat, the power (energy) of the prime mover is consumed, the working efficiency is lowered, and the metal isolation sleeve seals the magnetic transmission device. During normal operation, due to the generation of eddy currents, the heat is continuously released, and the ambient temperature of the magnetic material is continuously increased. When the temperature rises to a rated temperature value, the magnetic properties of the magnet decrease with the temperature, and the magnetic properties can be lowered. The transmitted force or torque drops, affecting the normal operation of the magnetic device. When the temperature rises to the Curie temperature point of the magnetic material, the magnetic properties of the magnetic material completely disappear, that is, the working action of the magnetic transmission device completely fails to generate eddy current loss. Factor analysis and selection of relevant parameters 1 Theoretical and experimental measurements show that the magnitude of the magnetic eddy current loss is related to the thickness t of the isolation sleeve. Under the condition of meeting the strength requirements of the isolation sleeve, the smaller the wall thickness of the isolation sleeve is, the better.
The magnitude of the magnetic eddy current loss is proportional to the electrical conductivity у of the spacer material. The conductivity is large and the eddy current loss is large. Therefore, it is preferable to select the electrical conductivity of the isolation sleeve.
The magnitude of the magnetic eddy current loss is proportional to the magnitude of the magnetic field and the cube of the radius of curvature r, and is proportional to the square of the length of the magnetic path. When designing the structure, the r value should be reduced as much as possible, and the L value should be appropriately increased to help control or reduce the eddy current loss. This is because the r-value large magnetic rotor rotates at a high speed first, which causes the alternating magnetic field to have a great influence in the isolation sleeve. Therefore, the active machine speed should not be selected high on the premise of meeting the design requirements.
The above discussion and analysis show that the metal isolation sleeve in the magnetic actuator generates eddy currents and causes power loss. As long as the parameters and permanent magnetic materials are properly selected, the eddy current size can be effectively controlled or the eddy current loss can be reduced to a minimum.
