Brushless DC motors consist of a motor body and a driver and are a typical mechatronics product. Since brushless DC motors operate in an automatic manner, they do not require additional starting windings on the rotor like synchronous motors that start under heavy load under variable frequency speed regulation, nor do they produce oscillations and step-outs when the load changes suddenly. The permanent magnets of small and medium-capacity brushless DC motors now mostly use rare earth neodymium iron boron (Nd-Fe-B) materials with high magnetic energy levels. Therefore, the volume of rare earth permanent magnet brushless motors is one frame size smaller than that of three-phase asynchronous motors of the same capacity.
Brushless motors are high-efficiency, low-noise, and stable motors. Unlike traditional brushed motors, brushless motors do not have carbon brushes on their rotors, so they do not require lubrication and run more stably. Because of these advantages, brushless motors are widely used in various fields, such as automobiles, industry, medical care, and home appliances. More information about brushless motors or custom brushless DC motors can be found at Brushless.
Three-wire connection
Three-wire connection is the most common connection method. This connection method requires three cables, that is, the three output lines of the motor (U, V, W) are connected to the three output lines of the driver respectively, and the phase lines are usually marked with different colors for easy distinction. It should be noted that the phase sequence must be correctly matched, otherwise the motor will reverse or fail to operate normally. It is suitable for scenarios that are sensitive to cost and space requirements, but attention should be paid to low-speed performance limitations and phase sequence matching issues, such as fans, water pumps, etc.
Two-wire connection
The two-wire connection usually refers to a simplified version of the connection method, which is easy to understand and implement. This connection method is common in low-power brushless motors, especially those applications that do not require precise position control, such as model aircraft, fans, etc. A capacitor is required to be connected in the middle of one coil of the motor and then connected to the two output lines of the driver. This connection method is suitable for situations where the direction of the motor needs to be changed periodically. When connecting, it is necessary to ensure that the output lines of the motor correspond to the output lines of the driver one by one, otherwise, the motor may not operate normally or abnormalities may occur.
Four-wire connection
Four-wire connection is a variant of a three-wire connection. It requires an external controller to control the direction of the motor. In addition to the power lines (positive and negative), the Hall sensor lines for position feedback are also included. This connection method can provide more precise motor control because it allows the driver to know the exact position of the motor, resulting in smoother operation and more efficient communication. This connection method is suitable for situations where customized motor steering is required and for applications that require high precision and stable performance, such as robots, electric vehicles, etc.
In addition to the connection method, it is also very important to choose the appropriate motor driver. In general, the selection of motor drivers is determined by the model, voltage, power and load characteristics of the motor. If the driver is not selected well, it will reduce the efficiency and life of the motor and may even cause damage to the motor.
It should be noted that although brushless motors must have a driver to rotate, the driver is not required for every brushless motor. Some small motors, such as mobile phone vibration motors, can be rotated through the internal drive circuit without the need for an external driver.
