Electronic Overcurrent Protection
Electronic protection that cuts the output when the current exceeds a set threshold. Unlike a fuse, it is not a consumable, and the system can run again once the cause is removed. Because its response time can go down to microseconds, it protects the power stage in a short circuit before the fuse does.
The current is usually measured with a shunt resistor or a Hall-type sensor, passed through a comparator, and the driver stage is switched off when the threshold is exceeded. To avoid nuisance trips on brief start-up surges, the measurement is usually filtered or a short delay is applied.
The logic of layered protection is as follows:
- Overcurrent protection: against short circuits and sudden overloads; the fastest layer.
- Current limit: instead of cutting off, it holds the current at the set value and the movement continues.
- Thermal protection: measures the effect, not the cause; the last line of defence against slowly accumulating heat.
- Fuse: protects the cable if the electronics fail.
The AntiSwitch function in the KS250 and PT500 modules serves a different purpose from protection: it interprets a rise in current not as a fault but as a sign that the movement has reached its mechanical end, and stops movement in that direction. On the PT500, independent thresholds are set for each direction with the A1 and A2 pots.
Context where this term is used: Locked Rotor and Thermal Protection