Working principle of the brushless dc motor and the frequency of the phase noise formula
1. The basic structure of brushless dc motor brushless dc motor using electronic switch circuit and a sensor instead of a brush and a phase change, make the motor has the characteristics of dc motor, but also has ac motor has simple structure, reliable operation and convenient maintenance.
dc power supply power to motor stator winding through the switch circuit, the motor rotor position provided by the position sensor detection and signal to trigger electronic switch circuit of power switch device conduction or deadline, to control the rotation of the motor, the structure is shown in figure 1.
2. The working principle of brushless dc motor to LN65 - in this paperZL motor as an example, the working principle of the machine. The motor for 8 12 slot, at one moment, the location of the relationship between the stator and rotor is shown in figure 2. Remove the motor of a unit (Figure 2 1/4 part is rotor each a pair of very)To simplify the analysis, a rotor each roll Angle, the position sensor sensing the position of rotor, the control circuit to control signal logic transformation after the position signal, control signal control electronic switch after driving circuit isolating amplifier in the circuit of power switch device, make the motor work of each phase winding in a certain order.
3. Phase noise of frequency calculation formula deduced figure 3 said the six working state of the machine. Among them, said three 1 s and 0 s to the direction of the current in the winding, 1 as positive, zero for negative. From the head end winding in three-phase winding into, was right in the end, from the end of the winding into, first set out to be negative. you can see from figure 3, brushless dc motor of a unit (The stator or rotor of the motor to)Within a cycle is 6 kinds of working condition, the status of the adjacent two transformations, the stator and the rotor will produce torque ripple, the commutation torque ripple. Since the motor with 4, corresponding to a cycle, there will be 4 x6 = 24 kinds of working condition. From what has been discussed above, it can be derived brushless dc motor commutation torque ripple frequency, referred to as 'commutation frequency for: f = i× k×p×n/60(1) with i— The frequency of order; One by one in phase noise frequency, Hz; k—Stator rotor in each pair of extremely in the working state of the corresponding number of one cycle; P—Motor logarithmic; n—Motor speed, RPM. because most of the motor is the 6 kinds of condition, so the formula can be simplified as F = 0. 1×p×没有(2) when a first order of brushless dc motor commutation frequency is close to or equal to any one part of the motor system's inherent frequency, can produce obvious vibration and phase noise, frequency and phase frequency f.
