What is the primary purpose of the handbrake on an electric stacker?

The primary purpose of the handbrake on an electric stacker is to secure the stacker in place. This function is crucial because it ensures the stability of the equipment when it is not in motion, especially during loading or unloading operations. By engaging the handbrake, the operator prevents the stacker from rolling or moving unintentionally, which could lead to accidents or injuries.

While the other options may involve various functionalities of the stacker, they do not pertain to the handbrake's specific role. Increasing speed is not a function associated with the handbrake; instead, the handbrake is primarily about providing safety and stability. Lifting heavier loads is more related to the stacker's lifting capacity and design rather than the handbrake mechanism, which is not involved in load handling. Similarly, lowering the load safely engages different controls and mechanisms, not the handbrake, which solely serves as a safety feature when the stacker is stationary.