来源：http://www.jnmcd.com 发布时间：2019-04-08 浏览：次
Brushless DC motor is a kind of synchronous motor, that is to say, the speed of motor rotor is affected by the speed of stator rotating magnetic field and the number of rotor poles (p): n = 60.f/p. When the pole number of the rotor is fixed, the rotor speed can be changed by changing the frequency of the stator rotating magnetic field. Brushless DC motor is a synchronous motor plus electronic control (driver), which controls the frequency of stator rotating magnetic field and feeds the speed of motor rotor back to the control center for repetitive correction, in order to reach the way close to the characteristics of DC motor. That is to say, the brushless DC motor can control the motor rotor to maintain a certain speed when the load changes in the rated load range.
The DC brushless driver includes power supply and control unit: the power supply provides three-phase power supply to the motor, and the control unit converts the input power frequency according to the demand. The power supply can be directly input by direct current (usually 24v) or by alternating current (110v/220v). If the input is alternating current, it must be converted to direct current by converter. Whether DC or AC input is to be converted into motor coil, the DC voltage must be converted from a converter to a three-phase voltage to drive the motor.
Converter (Inverter) is generally divided into six power transistors (q1-q6) which are connected by upper arm (q1, q3, q5)/lower arm (q2, q4, q6) motor as a switch to control the flow through the motor coil. The control unit provides the opportunity for PWM (pulse width modulation) to determine the switching frequency of power transistors and commutation of converters.
DC brushless motor usually hopes to use speed control which can be stabilized at the set value without too much change when the load changes. So Hall-sensor is installed inside the brushless DC motor, which can induce magnetic field, as the closed-loop control of speed, and as the basis of phase sequence control. But this is only used as speed control and not as positioning control.
Characteristics of DC Brushless Motor
1. DC brushless motor can replace DC motor speed regulation, frequency converter + frequency converter motor speed regulation, asynchronous motor + reducer speed regulation;
2. The brushless DC motor has the advantages of traditional DC motor, while the structure of carbon brush and sliding ring is cancelled.
3. The brushless DC motor can operate at low speed and high power, which can save the heavy load directly driven by the reducer.
4. DC brushless motor has small volume, light weight and large output.
5. DC brushless motor has excellent torque characteristics, good middle and low speed torque performance, large starting torque and small starting current.
6. DC brushless motor stepless speed regulation, wide range of speed regulation, overload can be strong;
7. The brushless DC motor has good soft start, soft stop and braking characteristics, which can eliminate the original mechanical braking or electromagnetic braking installation.
8. DC brushless motor has high efficiency, no excitation loss and carbon brush loss, eliminating multi-stage deceleration loss, and the comprehensive power saving rate can reach 20%~60%.
9. DC brushless motor has high reliability, good stability, strong adaptability and simple maintenance.
10. DC brushless motor can withstand stable vibration, low noise, small vibration, smooth operation and long service life.
11. DC brushless motor does not produce sparks, especially suitable for explosive places, with explosion-proof type;
12. DC brushless motor can choose trapezoidal wave magnetic field motor and sinusoidal wave magnetic field motor according to demand.
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