Contactor controls are the most simple and economical way to control motors common to overhead bridge cranes. A forward and reverse control signal is provided to reversing contactors allowing 3-phase power to be sent to the motor. However, contactor controls can be hard to control because they only have two functions: on and off.
The better way to control drive and hoist motors is with a Variable Frequency Drive (VFD), also known as Adjustable Frequency Drives (AFD). The primary advantage of VFD’s is the ability to program different parameters (or settings) into the device. These parameters are able to change the minimum & maximum speed, acceleration time, and maximum allowable motor amperage just to list a few.