How to determine whether a soft start is faulty

- Aug 01, 2019-

The multimeter measures the resistance value between the three input ends of the main circuit and the shell and the phases, which is normally infinite. It measures the resistance value between the input end and the output end of each phase, which is more than 100M ohm. Then, power on, and the display screen is free from fault alarm.

1. In the process of debugging, the starting alarm phase failure occurs, the soft starter fault light is on, and the motor does not respond.The cause of the failure may be:

(1) start the way to use a live way, the operation order is wrong.(the correct operation order should be to send the main power supply first, then the control power supply)

(2) power phase loss, soft starter protection action.(check power supply)

(3) the output end of the soft starter is not connected with the load.(soft starter can work normally only when the output end is connected with load)

2. After the user starts, the bypass contactor does not close.The fault may be caused by:

(1) in the process of starting, the protection device due to small setting error action.(just reset the protection device)

(2) during debugging, the parameters of the soft starter are not reasonable.(mainly for the soft starter below 55KW, reset the parameters of the soft starter)The control line contact is bad.(check the control circuit)

3. During the starting process, the user occasionally appears the phenomenon of air switching.Reasons for failure:

(1) air switch long delay setting value is too small or air switch selection and motor does not match.(appropriate amplification of air switch parameters or re-selection of air switch)

(2) the starting voltage parameter of the soft starter is set too high or the starting time is too long.(reduce the starting voltage or shorten the starting time appropriately according to the load)

(3) during the starting process, due to large voltage fluctuation of the power grid, it is easy to cause the soft starter to issue wrong instructions, and the phenomenon of early bypass occurs.(users are advised not to start high-power motors at the same time)

(4) Start with full load.(minimize load when starting)

4. When the user USES the soft starter, the display screen does not show or there is a garbled code, and the soft starter does not work.The fault may be caused by:

(1) soft starter in the use of the process of external components generated by the vibration of the soft starter internal line vibration loose.(open the cover of the soft starter and re-plug the display screen)

(2) soft starter control board fault.(contact the manufacturer to replace the control board)

5. The soft starter fails in the starting time. The soft starter does not work and the motor does not respond.The fault may be caused by:

(1) motor lack of phase.(check motor and peripheral circuit

(2) the main element of the soft starter thyristor short circuit.Check whether the motor and network voltage are abnormal.Contact the manufacturer to replace the thyristor)

(3) filter plate breakdown short circuit.(replace the filter plate)

6. Starting timeout occurs when the soft starter is under starting load.The soft starter stops working and the motor stops freely.Reasons for failure:

(1) unreasonable parameter setting.(reset the parameters, increase the starting voltage and lengthen the time appropriately)

(2) Start with full load.(minimize load when starting)

7. During the starting process, the current is unstable and excessive.Reasons may include:

(1) the ammeter indication is not accurate or does not match with the transformer.(replace with a new ammeter)

(2) the power grid voltage is not stable, fluctuation is relatively large, causing the soft starter error operation.(contact the manufacturer to replace the control board)

(3) the soft starter parameter setting is unreasonable.(reset parameters)

8. The soft starter starts repeatedly.Reasons for failure:

(1) in the process of starting the peripheral protection element action, the contactor can not be closed, leading to the soft starter repeated start.(check peripheral components and wiring)

9. When starting, the overheat fault lamp lights up, and the soft starter stops working:

(1) start frequently, resulting in high temperature, cause the soft starter overheating protection action.(the starting times of soft starter should be controlled at no more than 6 times per hour, especially the heavy load must be paid attention to)

(2) in the process of starting, the protection element action, so that the contactor can not bypass, soft starter for a long time, cause the protection action.(check peripheral circuit)

(3) overload start time too long cause overheating protection.(when starting, reduce the load as much as possible)

(4) the parameter setting of the soft starter is unreasonable.Too long, too low starting voltage.(increase the starting voltage)

(5) the cooling fan of the soft starter is damaged and cannot work normally.(replace fan)

10. Thyristor damage:

(1) when the motor starts, the overcurrent will break down the soft starter.Check whether the soft starter power matches the motor power and whether the motor is loadedMove)

(2) the cooling fan of the soft starter is damaged.(replace fan)

(3) start frequently, high temperature will be damaged thyristor.(control the number of starts)

(4) filter plate damage (replacement of damaged components) input phase, the fault causes a lot of factors:

- check whether the incoming power supply and the motor incoming wire are loose;

- whether the output is connected with load and whether the load matches the motor;

- use a multimeter to detect the breakdown of the modules or thyristors of the soft starter and whether their trigger gate resistance meets the requirements of normal conditions (general)Around 20-30);

- whether the internal wiring socket is loose.