It is not a problem, but it is the normal behavior of the soft starter. The soft starter is not a speed controller, it is only controlling the torque.
The ACC time and DEC time given in the ATS48 soft starter is for smooth ramp up and ramp down time of "motor torque" and it does not mention speed ramp up time. Hence the speed ramp up time will vary depending upon the load available on the motor. You may refer the screen shots attached below extracted from user manual, it indicates the time setting will ensure smooth increase and decrease of torque as shown in the graph.
When you start the motor with no-load, 2% to 20% torque may be sufficient to accelerate the motor to full speed, hence the motor will reach full speed faster. The initial torque "T90" parameter is set to 20% as default in factory setting, hence 20% torque will be given immediately after start command and the motor will reach to full speed faster(may be immediately like DOL starter) in no load.
For testing purpose at no load, you may reduce the T90 setting to 0% and increase the ACC and DEC setting to 60 sec(maximum), so that you may find possibly slow ramping of torque, which will help to ramp the speed comparatively slower at no-load.
As a normal commissioning procedure, this T90, ACC and DEC parameters should be set during load trail to get the proper ACC and DEC time duration of speed in normal operation.
The ACC time and DEC time given in the ATS48 soft starter is for smooth ramp up and ramp down time of "motor torque" and it does not mention speed ramp up time. Hence the speed ramp up time will vary depending upon the load available on the motor. You may refer the screen shots attached below extracted from user manual, it indicates the time setting will ensure smooth increase and decrease of torque as shown in the graph.
When you start the motor with no-load, 2% to 20% torque may be sufficient to accelerate the motor to full speed, hence the motor will reach full speed faster. The initial torque "T90" parameter is set to 20% as default in factory setting, hence 20% torque will be given immediately after start command and the motor will reach to full speed faster(may be immediately like DOL starter) in no load.
For testing purpose at no load, you may reduce the T90 setting to 0% and increase the ACC and DEC setting to 60 sec(maximum), so that you may find possibly slow ramping of torque, which will help to ramp the speed comparatively slower at no-load.
As a normal commissioning procedure, this T90, ACC and DEC parameters should be set during load trail to get the proper ACC and DEC time duration of speed in normal operation.
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