Trident SA (Pty) Ltd, the OEM of the Goodman brand of underground locomotives tells IM it is looking to cement its position in the global underground mining rail market by looking at AC-driven locomotives. Designed at the Trident SA Motor Division, a prototype 75AC motor is in testing and initial results are very favourable, as such the company anticipates the 75AC being available within the coming months.In terms of what this brings to the mining industry Trident SA had this to say: “Mining is a very competitive industry. Cost control is an important part of management operation. Another important aspect is safety. Locomotives often operate in poorly lit environments and braking and speed control are vital aspects of their operation. Trident SA have developed a low voltage AC drive for mine locomotives to suit mines with existing drives, but who want to retain their present battery and charger sets. Trident SA have a simple conversion to AC drives for just this market.”The traditional motor in underground mining rail has been a DC motor, usually series wound. This motor is well known and has been in use for over a century in mining the world over. Problems associated with this type of motor are its tendency to overspeed, and electric braking has its complications in terms of control and life of the motor. Repair costs are also high with DC motors. AC motors are becoming more common in surface traction, and other applications such as electric automobiles. However, the usual control technology has been at relatively higher voltages than battery operated mine locomotives utilise. This has restricted the entry into this market.“This has now changed with the recent test work currently being finalised at Trident SA near Johannesburg. Trident have developed a specially designed low speed AC motor to enable the use of low voltage batteries, as are common in underground mine transport. This now means AC drives will be soon available for both new and conversions of existing locomotives. The benefit of this low speed high torque AC motor is that simple conversions of existing locomotives is now opening up possibilities for cost conscience mine operators.”“The benefits of AC are close control of speed, and braking now can return energy back into the battery thus extending the range between battery changes, as well as saving wear on mechanical braking systems. Further, AC motors, as is well known, are low in maintenance and are very robust in tough conditions, and repair costs are much lower than DC motors. The modern electrical inverter has developed into a reliable low maintenance device with ease of operation by the driver. The electronic control allows many possibilities for remote control, automation and naturally has ease of operation by the driver.”In addition to the AC-drive project, Trident in conjunction with its Mendi-Trident joint venture partners has now opened a Commutator Division where they manufacture commutators for all types of electric motors including their own motors and also commutators for main-line surface locomotives. Surface rail is an area where Trident will be focusing much more effort in the future as it brings its rail and electrical motor experience out of the mines and into the infrastructure arena.Trident has in recent years also opened and is now successfully running a Hydraulic Braking Division that manufactures and re-manufactures hydraulic braking systems for its range of locomotives. These systems have long been the standard in South African mines as they deliver a safer and more efficient means of braking than traditional mechanical systems. These systems are designed to “fail to safe” and thus enhance the safety of the Trident locomotive product.