Zhejiang Shuyi Electric Co. Ltd

1. Startup Curve – Set the time for voltage boost at startup

Description: Ramp boost soft start. This starting method is the simplest, it does not have current closed-loop control, and only adjusts the conduction angle of the thyristor to increase it as a function of time. The disadvantage is that, due to the unrestricted current, when the motor is started, sometimes a large inrush current is generated to damage the thyristor, which has a great impact on the power grid and is rarely used in practice. Start-up time can be adjusted within 1-30 seconds.

2. Stop curve – set the speed of voltage drop at stop time

Description: When the motor stops, the traditional control method is completed by instantaneous power failure. But there are many applications where momentary shutdown of the motor is not allowed. For example, if the pump system of high-rise buildings and buildings is stopped instantaneously, it will produce a huge “water hammer” effect, which will damage the pipes and even the pumps. In order to reduce and prevent the “water hammer” effect, the motor needs to be stopped gradually, that is, soft stop. The use of a soft starter can meet this requirement. The soft stop function in the soft starter is that after the thyristor receives the stop command, the conduction angle is gradually reduced from full conduction, and the process transitions to full shutdown after a certain period of time. The parking time can be adjusted from 0 to 30s according to actual needs.

3. Description of current limiting function: In this starting method, the starting current is gradually increased in the initial stage of motor starting, and when the current reaches the preset value, it remains constant until the start is completed. During the starting process, the rate of current rise and change can be adjusted and set according to the motor load. If the current rising rate is large, the starting torque will be large and the starting time will be short. This starting method is the most widely used starting method, especially suitable for starting fans and pumps.

4. Choice of connection method

Note: The main circuit of the soft starter can have different connection methods, that is, “external connection” with the motor or “internal connection” with the motor, and switch S1 is in the corresponding position.

“External” is to connect the power components of the soft starter to the outside of the delta-connected motor to control the line current of the motor. “Internal connection” is to connect the power components of the soft start to the inside of the delta-connected motor, and control the phase current of the delta-connected motor. Since the line current is 1.73 times the phase current, the same soft starter can increase the control current (power) by 1.73 times when “inline”.


Tel/Fax: 0086-577-62840011

WhatsApp: 008613355775769

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