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You must know several starting methods of motors. The most basic ones are △-type starting method, Y-type starting method, auto-transformer soft-starting method, reactor current-limiting soft-starting method, variable frequency speed regulation starting method, etc. Wait.
     The reason why there are so many starting methods is inseparable from the needs in practical applications. Direct starting sometimes cannot meet the needs of production and life. The obvious defect is that excessive starting torque will impact the equipment and shorten the service life. The most important thing is It affects the control accuracy, so some occasions must use soft start, and the most ideal way for soft start is frequency conversion speed regulation start, which can maintain a high starting torque in a slow start state, but it is used in some control requirements that are not too high The cost performance of the equipment is not high, and the cost is relatively high. Today I will talk about a cost-effective soft-start control method that I have come into contact with. It is a thyristor soft-start control circuit.
The composition of the thyristor-controlled soft-start circuit is very simple. The core component is a soft starter, and the core component of the soft starter is six thyristors, so it is commonly known as the thyristor soft-start control circuit. The starter is connected in series in the three-phase circuit of the motor. When starting, by controlling the conduction of the thyristor, the voltage on the motor increases slowly. If you use a multimeter to measure the starting voltage of the motor when starting, you can intuitively see that the voltage indication of the multimeter rises from zero to 380 volts. In the high process, when the voltage applied to the motor rises smoothly to full voltage, that is, after the motor runs normally, the starter will automatically cut off the power supply to the motor, and then another contactor (KM2) will cut into the grid voltage to continue to maintain the motor. This is similar to the process of starting a fluorescent lamp.The soft start method can effectively reduce the instantaneous starting current of the motor. When the motor starts directly, the instantaneous current can rise to 5-7 times of the rated current. After the thyristor voltage regulation and soft start, it will hardly cause voltage fluctuations, which is also effective on the other hand. Harmful harmonics are avoided!