The continuous stream of rock to the processing plant determines the continuous rating of the motor needed to move the conveyor. But engineers also need to know how the conveyor is loaded, or overloaded. You need to know how much torque is required to ride through that temporary overloading caused by extra load or acceleration. But if we add a third requirement of 45 seconds of acceleration under load, and it is calculated that the torque requirement is 40 lb.-ft. Selection starts with knowing the load, or torque, requirements then choosing a drive with enough current to meet that need.
Drives supply current to the motor, motor current provides torque and torque moves loads.
Loads all have varying torque demands and, consequently, varying drives solutions. To help with this decision, information used to select a motor can be applied to size the drive. Almost all variable torque loads are either centrifugal fans or pumps. These make up nearly 70 percent of global motor applications. If the application is variable torque, then it almost always requires a normal-duty rated drive.