About soft starter and inverter, common faults and differences

- Jan 22, 2020-

What are soft starter and converter


Soft starter is a kind of motor control equipment integrating soft start, soft stop, light load energy saving and multi-function protection.In the whole process of starting the motor without impact and smooth, and according to the characteristics of the motor load to adjust the various parameters in the process of starting, such as current limit value, start time and so on. 

Variable-frequency Drive (VFD) is a power control device that controls ac motor by changing the mode of power supply frequency of the motor by using frequency conversion technology and microelectronic technology. 

The inverter is mainly composed of rectifier (ac to dc), filter, inverter (dc to ac), brake unit, drive unit, and detection unit micro-processing unit.The inverter can adjust the voltage and frequency of the output power supply by the internal IGBT, and provide the required power supply voltage according to the actual needs of the motor, so as to achieve the purpose of energy saving and speed regulation. In addition, the inverter also has many protective functions, such as overcurrent, overvoltage, overload protection and so on.With the continuous improvement of industrial automation, frequency converter has been widely used.

Common failures of soft starter


1. During the debugging process, the starting phase fault occurred. The fault light of the soft starter was on and the motor did not respond.

2. When the user finishes the starting process, the bypass contactor does not close. 

3. In the process of starting, the user occasionally has the phenomenon of jumping air switch. 

4. When the user USES the soft starter, the display screen does not display or the soft starter does not work. 

5. The soft starter in the starting times fault, the soft starter does not work, the motor does not respond.

Common inverter faults and solutions


1. Overcurrent fault

Overcurrent fault can be divided into acceleration, deceleration and constant speed overcurrent. 

The main reasons are that the acceleration time is too short, the load increases suddenly, the inverter output short circuit, the load distribution is uneven, the inverter and the motor capacity does not match, the internal rectifier side or inverter side components damage, power supply phase loss, the output is broken, the motor internal fault, the ground fault.And so on. 

The maintenance method is as follows: when the fault is checked, first disconnect the load and check the inverter.If there is still an overcurrent fault after disconnecting the load, it means that the internal components of the converter have failed and need further inspection and maintenance. 

Take corresponding measures: extend the acceleration time, design load distribution, check the line, prevent interference and mechanical vibration, reduce the sudden change of load.

2. Overpressure failure

Inverter overvoltage fault refers to the overvoltage tripping of the inverter when the dc bus voltage of the unit exceeds.