In our last article, we’ve introduced the magnetic materials in permanent magnet motors. And in today’s article, let’s take a look at the relationship between motor performance and permanent magnet material function. In short, the performance of a motor is directly related to the performance parameters of the permanent magnet materials used. Here are some performance parameters of the permanent magnet materials:
For DC motors, under the same winding parameters and test conditions, the higher the remanence, the lower the no-load speed, and the lower the no-load current; the greater the maximum torque, the higher the efficiency at the highest efficiency point. In the actual test, the no-load speed and the maximum torque are generally used to determine the remanence standard of the permanent magnet material.
For the same winding parameters and electrical parameters, the reason why the higher the remanence, the lower the no-load speed and the lower the no-load current, is that the motor in operation produces enough reverse induced voltage at a relatively low speed so that the algebraic sum of the electromotive force applied to the winding is reduced.
In the process of motor operation, there is always the influence of temperature and reverse demagnetization. From the perspective of motor design, the higher the coercive force, the smaller the thickness direction of the permanent magnet material, and the smaller the coercive force, the greater the thickness direction of the permanent magnet material.
Squareness only affects the flatness of the efficiency curve of the motor performance test. Although the straightness of the motor efficiency curve has not yet been listed as an important index standard, this is very important for the continuous travel distance of the in-wheel motor under natural road conditions. Because of the different road conditions, the motor cannot always work at the maximum efficiency point. This is one of the reasons why some motors have low maximum efficiency but a long-running distance. A good in-wheel motor should not only have a high maximum efficiency but also the efficiency curve should be as level as possible. The lower the slope of efficiency reduction, the better. As the market, technology, and standards of in-wheel motors mature, this will gradually become an important standard.
Inconsistent remanence: Even some individual ones with particularly high performance are not good, because the magnetic flux of each unidirectional magnetic field section is inconsistent, resulting in asymmetry of torque and vibration.
Inconsistent coercivity: In particular, the coercivity of individual products is too low, which is prone to reverse demagnetization, resulting in inconsistent magnetic fluxes of the magnets and vibration of the motor. This effect is more significant for brushless motors.
Thank you for reading our article and we hope it can help you to have a better understanding of the relationship between motor performance and permanent magnet material function. If you want to know more about magnets, we would like to advise you to visit Stanford Magnets for more information.
Stanford Magnets is a leading magnet supplier across the world. It has been involved in R&D, manufacturing, and sales of magnets since the 1990s and provides customers with high-quality permanent magnets like neodymium magnets, SmCo magnets, AlNiCo magnets, and ferrite magnets (ceramic magnets) at a very competitive price.