Yes. Bolani Ore Mines of SAIL has a system of downhill conveyors with VVVF and regenerating power. ■

Dear Ash:

I applied the first VFD to dowhill conveyors in 1977 at the La Caridad mine in Mexico. This was the first use of inverters on belt conveyors in the world. Conveyor Dynamics, Inc. has now installed many VFDs on downhills.

You can apply VFD to downhill conveyors in two ways:

1. 4 quadrant contol is required if you leave the VFD drive on-line.

This has been done on many installation around the world.

CDI has a number of VFD in Brazil for MBR and MRN mines,

Los Pelambres mine 25,000 kW in Chile, and many others.

2. 1 quadrant VFD control can be used if you transfer the drive

off-line once full speed is reached suing a line-synch transfer.

This was the way La Caridad was designed. Phelps Dodge

Morenci mine uses the same aproach on a 6000hp downhill

installed in 1990. This concepts requires two MCC's for each

motor controlled by the VFD. Furthermore, this allows the

VFD to be used on other conveyors. At La Caridad, I started

20 motors with 4 inverters configured with uphill and downhill,

fabric and steel cord belts, and with different motor drive

power ratios. This concept is more tricky in that you have to

know how motors load share to deveoped a proper design for

the transfer phase.

We are experts in this field and are happy to help

Lawrence Nordell

President

Conveyor Dynamics, Inc.

email: nordell@conveyor-dynamics.com ■