Inverter control principle of brushless motor

What is a brushless motor?

The biggest difference between DC brushless motor and DC brush motor is the difference of motor commutation mechanism, which is changed from brush commutation mechanism to semiconductor commutating component, and the brush and commutator are replaced by inverter circuit. Because the semiconductor commutating components have no mechanical wear and noise caused by mechanical wear, the flexibility of control is greatly increased, and the development and application of advanced motor control technologies are facilitated.

The brushless DC motor and the permanent magnet synchronous (PMSM) motor basically have the same structure. The brushless motor is a structure in which a permanent magnet is used as a rotor (rotation) and a coil is a stator (fixed), and the flow direction of the coil current and the motor are switched. The rotation of the combined motor. The motor is controlled by an external frequency converter and detects the position of the rotor in the position detection circuit and is used with the inverter.

The DC brushless motor control circuit needs to position the rotor of the motor to accurately control the motor to achieve high efficiency, low noise, and rapid response. There are mainly the following methods for position detection:

Hall sensor detection

The Hall element is used to detect the change of the magnetic field of the rotor made of a permanent magnet to detect the position of the rotor. This method is stable and reliable, but has low precision.

Inductive voltage detection

The position of the rotor is detected by the change of the induced voltage generated by the rotation of the rotor. This is one of the methods for detecting the position of the motor without the sensor. This method cannot detect the position of the rotor of the motor when the motor is stopped.

Current Detection

The current detection method belongs to the software algorithm class and requires a powerful computing power of the microprocessor.

The structural principle of brushless motor

The motor rotates by the same magnetic field and the opposite poles. By this action, changing the flow direction of the coil current on the stator changes the direction of the magnetic field of the stator, thereby driving the rotor (with a permanent magnet) to rotate. When a voltage is applied to the motor, it will be forward or reverse depending on the polarity of the voltage, and the speed will change in proportion to the voltage.

Suzhou Lianxinwei Electronics Co., Ltd. is located in Suzhou Industrial Park (Dushu Lake University District). Founded in 2011, Suzhou Lianxinwei Electronics Co., Ltd. is a high-tech enterprise focusing on the research and application of brushless motor control technology.

The company relies on the Key Laboratory of Integrated Circuits and Systems of Suzhou University of Southeast University, and has an experienced research team with unique technical advantages in the markets of drones, power tools, industrial fans and pumps, and has applied for many countries. A patented product with independent intellectual property rights.