8inch 10inch 11inch 12inch 36V 48V Hub Motors
Generally, the current required by the motor at startup is much larger than the rated current, which is about 6 times of the rated current. Under such a current, the motor will suffer a greater impact than when it works normally. Such impact will increase the loss of the motor, reduce the life of the motor, and even cause damage to other parts inside the machine when the current is too large. Under such circumstances, people begin to pay attention to the research of motor soft start, hoping to make the motor start smoothly and smoothly through related technologies.
1, the motor soft start principle
In the prior art, the research on motor soft start is mainly to control the start of three-phase AC asynchronous motor, and the soft start of the motor is realized by using the three-phase AC asynchronous motor, which provides protection for the start and stop of the motor. This technology has been widely used in the industrial field. In industry, this technology has been used to replace the traditional Y/△ startup, and good results have been achieved.
Three-reverse parallel thyristor (SCR) can adjust the voltage of soft starter, and it is the voltage regulator of soft starter. When the three-reverse parallel thyristor is connected to the circuit, it plays a connecting role between the power supply and the stator of the motor. When it is clicked to start, the voltage inside the thyristor will gradually rise, and the motor will slowly accelerate under the action of voltage. When the running speed reaches the required speed, the thyristor will be fully turned on. At this time, the clicked voltage is the same as the rated voltage, which can not only realize Under such circumstances, the motor runs normally under the protection of thyristor, which makes the motor suffer less impact and loss, thus significantly prolonging the service life of the motor and keeping the motor in good working condition.

2. Soft start technology of asynchronous motor
2.1, thyristor AC voltage regulating soft start
The AC voltage regulating soft start of thyristor mainly changes the connection mode of thyristor, changing the traditional connection mode into connecting to three windings, thus realizing the power supply to thyristor in parallel. Thyristor soft starter has strong adjustability, so users can make appropriate adjustments to the motor according to their different needs, and make the starting mode of the motor more suitable for their own needs through corresponding changes.

2.2. Adjustment principle of three-phase AC voltage regulating soft starter
Three-phase AC voltage regulating soft starter makes full use of the characteristic curve of AC voltage to start the motor. The idea of using the characteristic curve of AC voltage to realize the soft start of the motor like this is the main idea of the motor soft starter. It mainly uses three pairs of thyristors inside the motor to connect the motor in series, and changes the opening time by controlling the trigger pulse and trigger angle. In this case, the input terminal of the motor can keep enough voltage to control the starting of the motor. When the motor is started, the voltage will become the rated voltage, then the three bypass contactors will be combined, and the motor can be connected to the grid.
3. Advantages of soft start over traditional start
“Soft start” can not only greatly reduce the starting impact of the transmission system itself and prolong the service life of key components, but also greatly shorten the impact time of the motor starting current, reduce the thermal impact load on the motor and the influence on the power grid, thus saving electric energy and prolonging the service life of the motor. In addition, by using the “soft start” technology, the motor with smaller capacity can be selected in the selection of motor, thus reducing unnecessary equipment investment. Star start-up depends on changing the wiring of motor winding, thus changing the voltage at start-up. The voltage at start-up is reduced, making the start-up current smaller, and the impact on bus at start-up is reduced, so that the voltage drop of bus at start-up is within the allowable range (it is required that the voltage drop of bus should not exceed 10% of rated voltage). Auto-decompression start-up can also reduce the current at start-up, which is achieved by changing the voltage tap of auto-transformer.
For example, the requirements for the power grid in the start-up of 4 groups of 36 kilowatts. The normal working current of a 36 kW motor is about 70A, and the direct starting current is about 5 times of the normal current, that is, the current required for four groups of 36 kW motors to start at the same time is 1400A；; The requirement of star start-up for power grid is 2-3 times of normal current and 560-840A of power grid current, but it will have a great impact on voltage at the start-up, which is equivalent to about 3 times of normal voltage. The requirement of soft start for power grid is also 2-3 times of normal current, that is, 560-840A. However, the impact of soft start on voltage is about 10%, which basically won’t have a big impact.