When a brushless motor requires soft start, soft start is the process of starting by changing the gate angle from voltage 0 to full voltage.
The brushless motor adopts soft start, and the starting time and initial torque can be set to achieve soft start and soft stop of the equipment. The starting current is limited, and the price is moderate.
Compared with traditional starting methods, the advantages of brushless motor soft starting method are:
This is a motor based on the principle of thyristor phase-shifting voltage regulation, which is mainly used for starting control of brushless motors. It has good starting effect but high cost. Due to the use of thyristor components, the harmonic interference generated by thyristors during operation is significant, which has a certain impact on the power grid.
In addition, fluctuations in the power grid can also affect the connection of thyristors, especially when there are multiple thyristors in the same power grid. Therefore, due to the development of power electronics technology, the failure rate of thyristors is very high, so the maintenance of technicians is also very high.

(1) No surge current. When the soft starter starts the motor, the starting current of the brushless motor increases linearly from zero to the set value by gradually increasing the conduction angle of the thyristor. Not affected by the motor, the reliability of power supply is improved, the power supply starts smoothly, the impact torque on the load machine is reduced, and the service life of the machine is extended.
(2) The soft stop function, which refers to smooth deceleration and gradual stopping, can overcome the drawbacks of instantaneous power outages, reduce the impact on heavy machinery, avoid water hammer effects in the elevation water supply system, and reduce equipment damage.
(3) The starting parameters are adjustable, and can be freely and continuously adjusted to a good starting current according to the load situation of the power grid and the characteristics of relay protection.
The brushless motor soft starter is actually a voltage regulator. When the motor starts, the output only changes the voltage, not the frequency. In the following situations, the motor needs to use soft start:

(1) Motors are usually difficult to start under load control;
(2) When the power grid is unstable or the voltage drop is large, the motor is difficult to start;
(3) When the capacity of the factory transformer is limited, the starting current of the brushless motor is too high, which affects the normal operation of other equipment and may even endanger the use of the transformer;
(4) When it is necessary to start and adjust the device position multiple times at the same time;
(5) During the process of clicking to start, there have been cases where the motor burned out due to excessive starting current;
(6) The launcher needs to be updated;
(7) Build, expand, or renovate production lines.
The principle of the high-voltage brushless motor soft start cabinet is to automatically adjust the resistance value infinitely by tapping the liquid resistance in the rotor circuit, so that the series resistance value always meets the requirements of the motor's mechanical characteristics. This enables the brushless motor to start smoothly without generating impact while obtaining the starting torque and current, achieving the goal of automatically short circuiting the rotor circuit after starting.
2024.7.18  ZG