How does the driver protect itself under overload?
Under overload the motor current rises quickly; current-sensing drivers see that rise and cut or limit the motion. The AntiSwitch function on the KS250 and PT500 works exactly on this principle, and on the PT500 the threshold is set separately for each direction with the A1/A2 trimmers. The fact that the protection tripped should not be taken to mean the system is healthy.
Overload arrives in two forms: a sudden stall caused by mechanical jamming, or continuous high current caused by running above capacity. Current-threshold protection catches the first very quickly and the second as soon as the threshold is exceeded.
Two conditions must hold for this logic to work:
- The mechanics must withstand the stall force for the duration of the detection; otherwise damage occurs before the protection engages.
- There must be a distinguishable difference between the normal running current and the stall current. If the motor is already working at the edge of its capacity, the two values cannot be told apart.
For this reason the threshold is calibrated above the real running current but below the stall current. Set it too low and the motion is interrupted at normal load; set it too high and the protection does not do its job.
Commissioning advice: run the system with the heaviest real load, measure the current drawn, and place the threshold clearly above that value but below the stall value. Once the setting is made, mark the trimmer position with the label kit supplied with the product.
If the protection trips repeatedly, first check the mechanics (jamming, bearings, lubrication), then review the sizing.
The full topic: DC Motor Driver Selection Guide