Published in American Longwall Magazine
The new drive technology replaces direct current (DC) and AC/DC drives, effectively doing away with the high maintenance requirements of earlier motors.
The new OPTIDRIVE technology is the latest step in a gradual move to introduce VFD technology, dating back 11 years to when the first VFD was installed on a 17CM low-seam continuous miner.
“It went through its trials and tribulations but it proved to us the potential value of the VFD drive application for the AC drive on traction, but we never really realized that potential until we started putting it on shearing machines in 1996,” said Mike Adamczyk, Joy’s vice president global engineering.
With this first installation on a 7LS shearer, Joy introduced VFDs onto its longwall mining equipment. The ability to incorporate AC VFD traction was the starting point for the engineering design Adamczyk said, marking a major transition from the company’s 4LS and 6LS shearers which had DC traction.
By mid-2000 success with the shearer led to the idea that the technology could be applied to shuttle cars and continuous miners.
Across the various products, different factors have pushed the introduction of VFD technology. With the shearer the need was for more tractive effort and more power.
“Not only do the AC motors provide more power, they are also more reliable because you were getting away from the problems with brushes inherent with DC motors,” he said.
“On the continuous miner and shuttle car applications we were not necessarily looking for more power but for some of the control features this latest generation of drive gave us.”
In the case of the shuttle car, regenerative braking improves the ability of the machine to operate on gradients as well as reducing maintenance.
To date more than 30 newly delivered shuttle cars have been fitted with OPTIDRIVE. Joy’s third generation VFD is installed on over 35 operating shearers with the fourth version – the OPTIDRIVE - set to become the standard.
Joy’s move in this direction has been aided by several key technological developments. Advances in IGBT (insulated gate bipolar transistor) technology have allowed the technology to be compacted into a very small package which forms the basis of the multi-platform drive for all machines. IGBTs are a four-layer discrete power device usually found in high-voltage circuits.
“As the functionality of technology increases you shape your products to fit the technologies that exist,” said Fabian Dechant, director of control and automation systems.
Dechant pointed out that VFD is just one aspect of the OPTIDRIVE system: “VFD is an enabling technology while OPTIDRIVE is the integration of traction control with mechanics and motors. The software control is really the key to the success - how you integrate that drive into machines - whether a miner, a shearer, the FCT, or the controls for the shuttle car.”
Currently a few mines are using OPTIDRIVE technology on more than one piece of equipment. A Peabody mine has OPTIDRIVE on its 14CM27s continuous miners and 4FCTs.
Retrofits are an option but if equipment has DC or AC/DC motors these have to be changed, as well as the drive and control.
In the test case, according to Adamczyk, the OPTIDRIVE is successfully running in 10SC32 shuttle cars in what Joy has identified as difficult mining conditions.
“When we developed this drive for shuttle car applications we looked around the world at the most rigorous application in which our shuttle cars are used. We took power ratings in South Africa and in the US and identified what we felt was the best test case.”
Chosen to test the cars was Drummond Company’s Shoal Creek mine in Alabama, as its continuous miners cut the rock “middleman” between the Blue Creek and Mary Lee seams, and the mine floor could undulate severely. Shoal Creek has purchased the two new 10SC32 OPTIDRIVE trial shuttle cars and are working with Joy to retrofit their existing fleet.
OPTIDRIVE is now being applied across the broad spectrum of Joy’s product line of continuous miners, shuttle cars, shearers, and continuous 4FCT haulage.
