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Common faults and solutions of soft starters-Part 1

Sep 08, 2020

Common faults and solutions of soft starters-Part 1

Starter (also known as soft starter, motor soft starter), soft starter is a novel motor control device that integrates motor soft start, soft stop, light load energy saving and multiple protection functions. Its main composition is a three-phase parallel thyristor and its electronic control circuit connected in series between the power supply and the controlled motor. Using different methods to control the conduction angle of the three-phase parallel thyristor, the input voltage of the controlled motor can be changed according to different requirements, and different functions can be realized.



The following analysis soft starter in the daily application of the failure and corresponding countermeasures:

1. During the commissioning process, a start-up phase failure occurs, the soft starter fault light is on, and the motor does not respond. The reasons for the failure may be:

 ① When the starting method is electrified, the operation sequence is wrong. (The correct operation sequence should be the main power supply first, followed by the control power supply)

 ② The power supply lacks phase, the soft starter protection action. (Check power supply)

 ③ The output terminal of the soft starter is not connected to a load. (The soft starter can work normally after the output terminal is connected to the load)

2. When the user is in use, the start-up is complete and the bypass contactor does not close. The cause of the failure may be:

 ① During the start-up process, the protection device malfunctioned due to a small setting. (Just reset the protection device)

 ② During debugging, the parameter setting of the soft starter is unreasonable. (Mainly for soft starters below 55KW, reset the parameters of the soft starters)

 ③ The control circuit is in poor contact. (Check control circuit)

3. During the startup process, the user occasionally skips the air switch. The reasons for the failure are:

 ① The setting value of the air switch long delay time is too small or the air switch selection and the motor are not matched. (The parameters of the air switch are appropriately enlarged or the air switch is re-selected)

 ② The starting voltage parameter of the soft starter is set too high or the starting time is too long. (According to the load situation, the starting voltage is appropriately reduced or the starting time is appropriately shortened)

 ③ Due to the relatively large fluctuation of the grid voltage during the start-up process, it is easy to cause the soft starter to issue an incorrect command and cause an early bypass phenomenon. (It is recommended that users do not start high-power motors at the same time)

 ④ Start at full load when starting. (Try to reduce the load when starting)

4. When the user uses the soft starter, there is no display on the screen or garbled characters, and the soft starter does not work. The cause of the failure may be:

 ① The internal connection of the soft starter is loosened due to the vibration generated by external components during the use of the soft starter. (Open the cover of the soft starter and re-plug the display cable)  ② The soft starter control board is faulty. (Contact the manufacturer to replace the control board)

5. The soft starter reports a fault during startup, the soft starter does not work, and the motor does not respond. The cause of the failure may be:

 ① The motor is out of phase. (Check motor and peripheral circuit)

 ② The main element SCR in the soft starter is short-circuited. (Check whether the motor and grid voltage is abnormal. Contact the manufacturer to replace the SCR)

 ③ The filter board is short-circuited. (Replace the filter board)