The principle of conservation of energy is a basic principle of physics. The implication of this principle is: in a physical system with constant mass, energy is always conserved; that is, energy is neither produced out of thin air nor destroyed out of thin air, but can only change its form of existence.
In the traditional electromechanical system of rotating electrical machines, the mechanical system is the prime mover (for generators) or production machinery (for electric motors), the electrical system is the load or power source that uses electricity, and the rotating electrical machine connects the electrical system with the mechanical system. Together. In the process of energy conversion inside the rotating electric machine, there are mainly four forms of energy, namely electrical energy, mechanical energy, magnetic field energy storage and thermal energy. In the process of energy conversion, losses are generated, such as resistance loss, mechanical loss, core loss and additional loss.
For a rotating motor, the loss and consumption make it all converted into heat, causing the motor to generate heat, increase the temperature, affect the output of the motor, and reduce its efficiency: heating and cooling are the common problems of all motors. The problem of motor loss and temperature rise provides an idea for the research and development of a new type of rotating electromagnetic device, that is, electrical energy, mechanical energy, magnetic field energy storage and thermal energy constitute a new electromechanical system of rotating electrical machinery, so that the system does not output mechanical energy or electrical energy, but uses Electromagnetic theory and the concept of loss and temperature rise in rotating electrical machines completely, fully and effectively convert the input energy (electrical energy, wind energy, water energy, other mechanical energy, etc.) into heat energy, that is, all the input energy is converted into “loss” Effective heat output.
Based on the above ideas, the author proposes an electromechanical thermal transducer based on the theory of rotating electromagnetics. The generation of the rotating magnetic field is similar to that of a rotating electric machine. It can be generated by multi-phase energized symmetric windings or multi-pole rotating permanent magnets. , Using appropriate materials, structures and methods, using the combined effects of hysteresis, eddy current and the secondary induced current of the closed loop, to fully and fully convert the input energy into heat, that is, to convert the traditional “loss” of the rotating motor into effective Thermal energy. It organically combines electrical, magnetic, thermal systems and a heat exchange system using fluid as a medium. This new type of electromechanical thermal transducer not only has the research value of inverse problems, but also broadens the functions and applications of traditional rotating electrical machines.
First of all, time harmonics and space harmonics have a very rapid and significant effect on heat generation, which is rarely mentioned in the design of the motor structure. Because the application of chopper power supply voltage is less and less, to make the motor rotate faster, the frequency of the current active component must be increased, but this depends on a large increase in the current harmonic component. In low-speed motors, local changes in the magnetic field caused by tooth harmonics will cause heat. We must pay attention to this problem when choosing the thickness of the metal sheet and the cooling system. In the calculation, the use of binding straps should also be considered.
As we all know, superconducting materials work at low temperatures, and there are two situations:
The first is to predict the location of hot spots in the combined superconductors used in the coil windings of the motor.
The second is to design a cooling system that can cool any part of the superconducting coil.
The calculation of the temperature rise of the motor becomes very difficult because of the need to deal with many parameters. These parameters include the geometry of the motor, the rotation speed, the unevenness of the material, the composition of the material, and the surface roughness of each part. Due to the rapid development of computers and numerical calculation methods, the combination of experimental research and simulation analysis, the progress in motor temperature rise calculation has surpassed other fields.
The thermal model should be global and complex, without generality. Every new motor means a new model.
Post time: Apr-19-2021
