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Low temperature constant resistance moment and improvement of permanent magnet micromotor
- Nov 10, 2017 -

Micro-motor in the increasingly wide range of applications, has infiltrated all aspects of life, of which the largest amount of micro-permanent magnet DC motor. Miniature permanent magnet DC motor with simple structure, small size, with less copper, high efficiency, popular in the automotive industry.

Motor vehicle application environment is generally harsh, the actual degree of use is not at room temperature, but in high / low temperature; such as motor stalls caused by high temperature rise, the motor is wrapped in poor thermal conductivity caused by the accumulation of plastic parts, In temperature or cold weather conditions such as the use of cars. Therefore, the automotive motor must withstand high and low temperature test, usually -40 ° C in practical applications, customers are more concerned about the performance of high and low temperature motor, such as low temperature start, low temperature noise, high and low temperature performance changes, thermal shock resistance, high resistance Low temperature storage, temperature control protection.

This article focuses on the motor starting torque at low temperature increases the phenomenon of starting voltage (V) starting current (A) starting voltage (V) starting current (A) forward reversal forward reversal forward reversal reversal forward reversal 3 Cause of increase of low-temperature start-up torque The analysis of the motor structure shows that the static load torque T consists of two parts: mechanical static friction torque Tm and cogging torque TfTVtT ......

From the previous knowledge, low temperature static load torque changes have taken place. In a model of the motor were tested on the size of this change, the data in Table 2. The friction torque test method is not magnetizing the permanent magnet, and then measured.

Table 2 low temperature and room temperature friction torque / total resistance moment comparison From the data in Table 2 we can see: 1) the total static resistance torque at low temperature is much larger than at room temperature; 2) the total static resistance torque, cogging torque than friction torque Much larger, that is, the total static resistance torque is mainly caused by the cogging torque: 3) The increase in the low temperature is mainly the cogging torque.

Cogging torque is an inherent phenomenon in cogging permanent magnet motors and is an important parameter in PMDC performance. In such motors, the cogging torque is determined by the fact that the rotor has a mechanism that allows its teeth and stator along a particular direction Magnet) alignment trend, the trend will produce an oscillating torque. Cogging torque arises from the tangential force between the rotor teeth and the permanent magnets of the stator as a result of the interaction of the rotor slots with the permanent magnet stator.

3.1 The effect of temperature on magnetic force The influence of temperature on magnetic force is mainly related to the thermal stability of permanent magnet I. "Thermal stability refers to the degree of change of magnetic property due to the change of the ambient temperature of the permanent magnet, also known as temperature stability. When the ambient temperature of the permanent magnet rises from t to tl, the flux density drops from B0 to B1: when the temperature returns from to, the flux density rises to B 'instead of B0. When the temperature changes between , The magnetic density in the claw and clam change of 3.2 degrees on the polar arc coefficient of the polar arc coefficient also has an impact on Tj. Many studies have shown that 121, the arc coefficient of Tc has an optimal value exists, at this optimal value Tq minimum, greater than or less than the value of T will become larger. According to the data, T of PMDC increases with the increase of the pole arc in 130 to 180 pole arcs. Our actual use of the arc is in this range.

Many of our magnetizers, for some specific reason, sometimes deliberately demagnetize a specific area of the permanent magnet (mostly the perimeter area of the permanent magnet) during magnetization. For example, S1 magnetization method, the typical distribution of the magnetic flux density, as can be seen from the figure: the highest saturation of the permanent magnet, to the boundary of the saturation is getting smaller and smaller. That is to say there is an area of unsaturation. At low temperature, the Br in the unsaturated region will increase, which relatively increases the arc width of eight magnetic flux density distribution of eight S1 magnetization 3.3 Low temperature on the cogging torque Cogging torque and permanent magnet residual magnetic induction Intensity or thickness Lm. IEEE Du Hongjun and so on. Torsional Positioning Torque Analysis of Permanent Magnet Motor. Micro motor,



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