The merits of VFD

BUCYRUS says underground mines still running equipment with DC motors should consider swapping to variable frequency drives to increase productivity.

Angie Tomlinson

The original equipment manufacturer said mines could make maintenance and service life gains by replacing DC motors with AC motors.

Bucyrus has applied VFD controls to many of its room and pillar products, including battery-powered haulers, shield movers, continuous miners and feeder breakers.

The VFD controls used on the Un-A-Hauler and Vers-A-Trac are manufactured exclusively for Bucyrus and boast advanced flux vector control, autocheck system diagnostics, advanced I/O protection, self-characterisation, and a network of data-sharing system modules.

“Adding a VFD control to Bucyrus rubber-tired battery-powered equipment increases speed, maneuverability and responsiveness while allowing the operator to monitor machine performance with the onboard machine management system,” Bucyrus said.

“This means faster discharge times for the Un-A-Hauler and quicker shield-loading times for the Vers-A-Trac. Regenerative braking saves power and reduces brake system wear and maintenance.”

Bucyrus feeder breaker performance can also benefit from VFD conveyor control by monitoring the feeder load to prevent jams.

If the breaker load exceeds the motor rating, the control reduces chain speed.

If the excessive load continues, a jam-clearing cycle is started. This minimises equipment damage such as broken or bent chain flights, premature wear on the chain and sprockets, and shock loading of the gear boxes. It also allows haulage operators to unload their cars more quickly.

Bucyrus says addition of a VFD to a continuous miner increases speed, motor torque and motor torque control, allowing faster repositioning and improved sump and cutting performance.

The continuous miner VFDs control the AC motors which power the left and right tracks. The VFD control is backward compatible with existing continuous miners. The AC drives feature motor overload protection, the CAN communication interface, enhanced diagnostics and closed loop control.

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