What is the smallest size motor a ATS48 will run when the SST parameter is "ON"? (Unloaded).

Issue:
What is the smallest size motor a ATS48 will run when the SST parameter is "ON"? (Unloaded).

Product Line:

ATS48

Environment:
SSt

Cause:
n/a

Resolution:
When SST is "on" the torque control and the control of the minimum current (Icl/20) is disabled. But this function has also its limit.
With SST, the minimum current to not trip in PhF fault is difficult to evaluate because it depends on the "I Hold" of the thyristors (the minimum current a thyristor needs to conduct without gate activated), this value is fluctuating regarding the batch and the thyristor range.

If the motor current is under of the "I hold" of one of the thyristor the starter will trip in PHF because there is a bad conduction on a phase.
So if the starter trips in PHF with SST "on" it means it can't control the motor because the current is so low that the thyristor can't work (physical limit).
The only solution is to increase the motor current by increasing the range, the load or the coupling of the motor.
For instance in our lab for AT48D17Q we have a non loaded motor of 0.37kW 380V and it works with SST.