I want to use a winch to raise and lower a load, but now I'm unsure, if the winch can handle the lowering? Normally, winches are only used to pull a load, right? When I now reverse the motor direction, the winch unrolls the rope and gets pulled in addition by the load. Where goes now the energy? A big part should go into the gearbox i think. The motor cannot act as a generator, since it is powered when unrolling the winch, because of the stand still brake. So I think the load will accelerate until the friction in the gearbox is high enough to balance the system. Am I right with this assumption?
There are many types of winches with different mechanism to control the lifting and lowering of the load. A winch has to be able to Lift the load to a desired height and hold it there indefinitely and lower it safely with control.
Some winches are hydraulic, some use chain as the cable and the chain engages the moving wheel for safety. Most of light duty winches have friction controls for braking and lowering. These controls clutch onto the rope or cable and lower it in a controlled way and have release settings.
Some winches have levers that work like a Car jack and lift or lower the load in steps.
inexpensive, commercially-available 12VDC winches (as for mounting on front bumpers of 4x4 trucks) contain worm gear drives which exhibit a characteristic called SELF-LOCKING. this prevents the load from causing the electric motor to rotate backwards, unwind the cable spool, and lower the load when the motor is not energized. if you reverse the drive voltage on one of these, it will unspool and lower the load UNTIL you shut the motor off, at which point the winch will stop and the load will remain suspended at that point.