AC traction systems replace conventional DC traction motors in a locomotive. They provide higher levels of wheel to rail adhesion and enable less powerful locomotives, or a smaller number of locomotives, to be used for a specific task.

Application relevance

Australian operators have demonstrated benefits on certain routes that were originally operated by conventional DC locomotives. The available benefits will be dependent on grade severity and other specific factors.

Case studies indicate that technology adoption is likely to require a long procurement process. Part of the reason for this is that specific design adaptations for Australia must account for a smaller kinematic envelope compared to some overseas applications and requirements.

Potential benefits

Although AC traction can reduce fuel consumption, the potential benefits may depend on the mixture of performance of other locomotives on the same track (i.e. may be reduced to slowest track running time).

Other benefits for the operator include reduced maintenance requirements due to the fewer number of locomotives performing the same tasks, and quicker servicing turnaround times. Supporting this argument, a Halcrow study (on behalf of SCT Logistics) indicated that 20% of maintenance issues related solely to the specific technology associated with DC traction.

Key implementation considerations

Available US data suggests that the premium over a DC locomotive has reduced from 40% when AC traction was first introduced in the mid-1990s, to about 10% in recent years

The primary drawback of AC traction systems is the cost. However, other considerations that have required resolution include size, weight and noise.

Examples of implementation

Introducing the next generation locomotive to the Australian rail network

This detailed case study discusses Australia’s first AC traction locomotive certified to operate across the Interstate Rail Network (specifically Melbourne to Perth). Detailed planning and modelling is illustrated using cost benefit analysis to explain the decision for choosing AC traction. SCT Logistics achieved up to 30% more loading with AC traction and this enabled two or three locomotives to replace four DC traction locomotives (Ramsey et al 2008).

Advantages and benefits of modern AC traction technology

This Queensland Rail case study describes the advantages of AC Traction Technology, notably the ability to substitute five DC locomotives with three AC locomotives (Latour et al. 2008).

For the full report on fuel saving opportunities in the road and rail sectors, see Fuel for Thought – Identifying potential energy efficiency opportunities in the Australian road and rail sectors (opens in a new window) PDF 1.5 MB.