A train controlled by ABB variable-speed drives is helping visitors to Oman experience the wonders of a two-million year-old natural cave system, deep in the desert.

ABB Drives Alliance member Sentridge Control supplied four ABB ACS 800 industrial drives, each of 30 kW and four ABB high-efficiency 37 kW motors to power the train at the Al Hoota cave.
Al Hoota cave is a major tourist attraction in Oman, receiving thousands of visitors a year. The operators of the cave needed a transport system that would take visitors a distance of over half a kilometre from the visitor centre to the cave in comfort and safety.

Severn-Lamb, a manufacturer of specialised vehicles and people moving solutions based in Warwickshire, was asked to provide a suitable transport method for the application. The operators needed the transport method to be energy efficient and also quiet to run so it didn’t spoil the visitor experience or disturb the 100 plus species of wildlife that live in the cave system.

Electric propulsion was the only practical solution to meet these requirements. Patrick Lamb, Managing Director of Severn-Lamb, says: “We were looking for a propulsion supplier that was both reputable and had an international presence with regards to warranty and support.”

Together with Sentridge Control, Severn-Lamb designed a propulsion system for an electric train that would run along a 700 metres track, with 100 metres being within the cave itself. Capable of carrying 48 passengers, the train takes three-phase, 415 V power from an electrified third rail and can travel at up to 20 kilometres per hour.

Glen Hickman of Sentridge Control says: “The drive solution was designed to be redundant so that if we lose one motor, the train can still keep driving. Another feature of the solution is the communication capabilities of the drives. A built-in drive-to-drive link allows the drives to talk to each other, via a master-follower arrangement, enabling them to run at the same speed and share the load.”

The drives allow the train to be driven from either end by transferring the master drive function to the rear most drive. Another feature that could be used in the future is the ability for the drives to receive a signal from an external pick up mounted on the train, allowing them to detect points and reduce speed accordingly.

The drives need to operate in an ambient temperature that can reach 50 degrees Celsius. Severn-Lamb worked with Sentridge Control to devise an innovative cooling system that feeds air to the drives from the main cab air conditioning system.

Greg Squires, Engineering Director for Severn-Lamb says: “We were very impressed with the on-site support provided by ABB, which we needed to call on a couple of times. Flying engineers out to the area is expensive, so the ability to use ABB’s local engineers was a real benefit for us when commissioning the system.”