Brushless DC Motor Working Principle
Brushless DC motor (BLDC) uses electronic phase-changing circuit to supply DC power to motor rotor winding. Since there is no mechanical brush, it is called brushless DC motor. Because of brushless DC motor with high efficiency and accurate control performance, and can use the electronic packaging to meet the needs of security specification features. Under the demands of global energy conservation and carbon reduction, it is widely applied in the field of air conditioning, such as common DC inverter, brushless DC technology; it also can be used in hybrid electric vehicle and some appliances of high economic value, such as electric fans and other products.
At present, the most common electronic driving mode is to use Hall Effect component or counter electromotive force to detect the mechanical angle and motor angle of motor rotor winding, and then accurately control the MOSFET switch to achieve continuous motor running.
Taking the way that uses hall component as an example, the Hall Effect should satisfy the following relationship:
Where VH is hall voltage, IH is hall current, KH/d is hall component electromagnetic coefficient, K is hall component unbalanced coefficient, and B is magnetic flux density. As seen from the equation, hall voltage is directly proportional to the magnetic flux density (i.e. the magnetic intensity of motor running) and hall current. Therefore, when the rotor's magnetic axis is not coaxial with hall components, the magnetic flux is small. In order to maintain the constant hall voltage, the hall current must be increased, so that the conduction sequence and time of motor rotor can be calculated accurately.
Because Hall component type brushless DC motor uses Hall components to induce the excitation sequence and time. When the phase of rotor isπ/2, the stator can be conducted, thus reducing the unnecessary energy waste. Also the necessary rotor rotating electromagnetic force can be provided timely, so as to greatly improve the motor output torque and efficiency, which is the biggest advantage provided by the brushless DC motor.
In the hardware of brushless DC motor, the mechanical phase converter and brush are replaced by the electronic circuit, so the problem of electric pollution will not appear. At the same time, for electrical signals captured by electronic circuits, other logic circuits can be used for signal amplification and comparison to improve motor operation efficiency.
And, more importantly, the problem that it is impossible to use external hardware protector to protect motor is resolved. In brushless DC motor, it is possible to use microprocessor and software to judge the electrical signal captured by electronic circuit, thus managing and protecting motor from stall, out of phase, overload, and other related security functions.