Stall Protection
It is the function that cuts the drive and protects the motor from strain when the actuator cannot move although it has been commanded to. The GS740-3P declares this protection together with overcurrent protection and an independent watchdog. A stall typically arises from the cable coming up against its end, the joint seizing or the sheath being crushed.
The behaviour of a stalled DC motor is well known: since it does not turn it produces no back-EMF and the current rises far above the normal operating value. This current quickly heats both the winding and the driver stage. The protection monitors the current, interprets a condition exceeding the set threshold as strain, and cuts the drive.
If this protection trips in the field, the fault is almost always in the mechanics. Look at the following in order:
- Does the cable keep being pulled after the throttle lever has come to rest on its mechanical stop — that is, is the travel setting too much?
- Is there crushing or a sharp kink in the sheath?
- Does the throttle lever joint turn freely by hand?
This protection is not an overspeed protection; it monitors not the engine's speed but the strain on the actuator. The engine's own safety chain — the fuel shut-off solenoid, an air shut-off valve if required, and the engine protection switches — must be built separately.
Context in which this term is used: Electronic speed and throttle control on a diesel engine