Mechanical braking of brushless DC motor

The brushless DC motor mechanical braking : disconnect the main electricity, and connect to a reverse voltage, when the rotor is about to stop, if there is a brake device at one end of the rotor, mechanical braking can be realized.


In fact, there is no free sliding state of brushless DC motor without driving voltage. One is that the motor has slot positioning torque, that is, the motor is in the open circuit state, and the shaft of the rotating motor can feel a ton of resistance. It is formed by the closure of permanent magnet and stator magnetic circuit of rotor, so even if the rotor is in a free state, it is still in a specific position.


In addition, because the brushless DC motor is in the power generation state at this time, although the switch tube is in the off state, the switch tube parallel has the reverse diode, which happens to be in the forward conduction state, it can feedback the energy generated by the power generation state back to the power supply, and it will inevitably be transformed into braking torque. If the rotor speed is high, the discharge capacity of the power supply should also be considered. Generally speaking, there is no need to consider the speed of rotation. Therefore, in the initial deceleration stage of the motor, the above braking force can be used to reduce the speed of the motor in the consideration of other rotation measures.


There are two simple ways to use brushless DC motor to brake quickly. One is energy consumption braking, the other is short connection braking, energy consumption braking is to consume the kinetic energy of motor on external braking resistance, and short connection braking is to consume the kinetic energy of motor on the stator winding of motor. Obviously, energy consumption braking is more beneficial to reduce motor heating. However, short-connection braking does not need to make any changes to the hardware, simpleness and convenience are its outstanding advantages, so it focuses on short-connection braking.