Current Protection — On a Levelling Jack
Current protection is a hardware protection that cuts the movement when the current drawn by the jack motor exceeds a set threshold. It protects the motor and the screw mechanism in cases of hitting the end of the mechanical stroke, striking an obstacle or overloading. On the KTS200 the current protection works at hardware level on the GRV485 control unit.
In a DC motor the current is proportional to the torque demanded at the shaft. When the jack reaches the end of its stroke or the footplate catches on an obstacle, the torque demand grows rapidly; as the motor approaches standstill the current rises to the order of the starting current. The driver measures this value and cuts the output when the threshold is exceeded.
- The protection guards both the motor against winding heating and the screw mechanism against excessive axial load.
- The same measurement is also used for ground contact detection; the two functions read the same signal with different thresholds.
- If the voltage sags because of a weak battery or thin cable, the motor cannot produce torque, the current rises and the protection may trip early.
If you get frequent protection faults, look at the electrical side first: measure the battery voltage under load, look for heating and oxidation at the connection terminals. If the electrical side is sound, move to the mechanical side: check whether there is a foreign object, corrosion or a bent shaft in the path of the jack. Trying to disable the protection turns a fault into permanent damage.
The context in which this term is used: RV automatic levelling guide
For the general definition of the concept and its difference from a fuse, see the entry Current Protection (Overcurrent Protection).