The hydraulic grab does not have an own drive unit. The hydraulic drive from the excavator provides the power. It is directly connected to the suspension of the excavator and the hydraulic supply lines.
Similar to the Motor grab, the closing force is transferred to the material through a convenient lever ratio in conjunction with the proper deadweight. The only difference is that the hydraulic drive is not included in the grab. An additional way to transfer the force is the relatively rigid connection to the excavator.