Brushless DC motor braking is usually using the motor itself for fast braking there are two simple ways, one is energy braking, and one is short-circuit braking. Energy braking is to consume the kinetic energy of the motor on the external braking resistor, and short-circuit braking is to consume the kinetic energy of the motor on the stator winding of the motor. Obviously, energy braking is more beneficial to reduce the heat of the motor. However, short-circuit braking does not require any hardware changes, so it is simple and convenient.
Short-circuit braking means that the upper (or lower) bridge arm of the motor's driver MOS tube is fully on and the lower (or upper) bridge arm is off when the brakes are applied, while the motor's three-phase stator windings are all shorted. The brushless dc motor in the power generation state is equivalent to the power supply being short-circuited. Because the resistance of the winding is relatively small, it can generate a large short-circuit current, and the kinetic energy of the motor is quickly released, which makes the motor instantaneously produce a great braking torque, and can achieve the effect of fast braking. The higher the motor speed, the higher the short-circuit current and the higher the braking force. However, it must be considered not to exceed the capacity of the MOS tube, so generally wait until the motor speed is reduced to a certain level before using short-circuit braking.
Usually, the forward and reverse rotation of the BLDC motor is realized by changing the logic relationship of the switch tube of the inverter to change the conduction sequence of each phase of the armature winding. In order to generate the maximum average electromagnetic torque in both forward and reverse rotation of the motor to ensure symmetrical operation, it is necessary to design the mutual positional relationship between the rotor position sensor, the main magnetic pole of the rotor and each phase winding of the stator, as well as the correct logical relationship.
The running direction of the motor can be controlled by controlling the on and off of the terminal "DIR" and the terminal "COM". The terminal "DIR" is internally pulled up to +12 with a resistor, which can be used with passive contact switches, or with control units such as PLCs with open collectors. When "DIR" and terminal "COM" are not connected, the motor runs clockwise (facing the motor shaft), otherwise, it runs counterclockwise. In order to avoid the damage of the brushless DC controller, when changing the direction of the motor, the motor should be stopped first before changing the direction.
The BLDC motor is a permanent magnet brushless synchronous motor. Its performance parameters, model, power supply voltage, output power, phase angle, presence or absence, photoelectric switch, or self-recognition function must be used in conjunction with the brushless DC motor controller. If you purchased a 48V BLDC motor, a matching 48V brushless motor controller is recommended.
And brushless DC motors do not have brushes and commutators, so to maintain the direction of rotation, an electronic commutator is required. The electronic commutator is controlled by the driver, and the brushless motor controller can also control the start and stop of the motor, forward and reverse rotation, speed, overvoltage, overcurrent, and under voltage protection. If there is no brushless DC motor controller, it will not work to directly power the DC brushless motor.
Proper pressure can increase the efficiency of the brushless motor so that it can function better during use.
Changing the resistance of the circuit for speed control
All kinds of brushless DC motors can be speed controlled by changing the resistance of the armature circuit. When the load is certain, the total resistance of the armature circuit increases with the increase of the external resistance in series, and the speed of the motor will be reduced. Changing the external resistance can be done with a contactor or a master switch.
Changing the voltage of the circuit for speed control
Continuously changing the operating voltage of the brushless motor power supply system can make the DC brushless motor in a wide range of infinitely variable speed. There are two ways to change the operating voltage of the brushless motor power supply system, one is the choice of generator set power supply system speed control system, the other is the choice of thyristor converter power supply speed control system.
Changing the current of the circuit for speed control
When the operating voltage of brushless motor is certain, even if the current of DC brushless motor is changed, the speed can be changed.
Lack of Power
Possible situations: For example, the power switch is not closed, the fuse of the front stage is blown, the fuse of the main circuit or control circuit of the motor is blown, the power control devices such as contactors are out of order, and the line wires are broken or loose. The solution is to start with the front-end fuse, and gradually check the wires and devices of the main circuit and control circuit of the motor, find out the cause and repair it.
Possible situations: bad contact between the brush and the commutator due to serious wear, jamming, insufficient spring pressure, etc.; the armature winding is disconnected; the excitation winding is disconnected and there is no residual magnetism, etc. The treatment method is to disconnect the power supply, and use the resistance gear of the multimeter to check the contact resistance between the brush and the commutator, and the resistance at both ends of each winding. If the resistance value is very large, it means that the fault exists, and then make further inspection to find the breakpoint and repair it.
The mechanical equipment or transmission mechanism of the brushless dc motor is stuck, and the starting load is too heavy. At this time, the power supply should be cut off quickly and the mechanical fault should be found.
When you are looking for a brushless DC motor, if you don't know how much power or torque to choose, on the one hand, you can communicate with our technicians and ask for help in your selection. On the other hand, it can also be calculated by the torque formula.
The brushless motor is mainly used to generate driving torque. As a power source for electrical appliances or various machinery, its main function is to convert mechanical energy into electrical energy. Under the action of the torque, the mechanical equipment installed with the brushless motor will change the position or angle of the object. Therefore, the torque can be calculated according to the definition formula. That is, T=P*9.8/N, or the mutual conversion factor can also be like this: T*N/9.8=P.
For example, when the power of the brushless DC motor we choose is 1000W, and the number of revolutions of the motor is 3000 rpm, there will be 1000W*9.8/3000rpm=3.27Nm. Or know the torque T of the brushless motor, when the power is required , then it can be like this: 3.27Nm *3000rpm/9.8≈1000W. This is the formula for calculating the torque of the DC brushless motor. Different types of motor torque have different calculation formulas, such as the torque calculation formula of ordinary asynchronous motor T=9550*P/N.
In the formula:
N—the rated speed of the motor, r/min;