Conveyor users and conveyor manufacturers have adapted the drum motor as the most efficient way to drive belt conveyors. With no external motor and gearbox, the drum motor saves space, eliminates the need for scheduled maintenance and enhances operator safety, according to Van der Graaf (VDG).
However, the challenge has been the ease and ability to adjust belt speed as plant processing requirements change. This is achieved via a frequency inverter (VFD), which often is located in a control room some distance away from the conveyor drive electric motor.
The long cable connecting the VFD to the electric motor can impede motor performance and substantially reduce its life and reliability. Voltage attenuation, due to the long cable length, contributes to inconsistent power being delivered to the motor. Resulting high-voltage electrical spikes amplification in the motor windings can cause complete motor failure.
The general approach to overcome these issues is to substantially increase the dielectric strength value of the magnet wire used in the electric motor windings. Sinusoidal filters also are installed to condition the power going to the motor and filter high-voltage spikes caused by the pulse-simulated sine wave of the VFD.
Recently, VDG has developed an advanced drum motor design, the IntelliDrive. The IntelliDrive design has the VFD integrated into the motor junction box, a new design electric motor that has an even higher efficiency, and additional capabilities.
On a standard electric motor, the rotor has to be magnetically induced by the stator. Using part of the magnetization produced by the stator windings to magnetically induce the rotor results in significant magnetic energy losses and reduces mechanical output. As a result, motor efficiency decreases.
With the IntelliDrive design drum motor, the rotor is magnetically self-induced by the use of permanent magnets installed on the rotor body. Lab test results show electrical savings of up to 72 percent vs. a conventional motor/gearbox conveyor drive.
The IntelliDrive drum motor is EtherNet/IP and MODBUS compatible, enables communication with other plant equipment, provides conveyor drive data feedback and control belt speed either remotely or directly at the drum motor. The IntelliDrive drum motor simplifies the selection of belt speed without loss of torque or belt-pull, substantially increasing the efficiency and the life of the electric motor, further minimizing downtime and decreasing overall operating costs.
VDG, www.vandergraaf.com