Gibela is a rail consortium tasked with building South Africa’s new fleet of 600 commuter trains.
Gibela was formed in 2013 as a black economic empowerment company. The Gibela Rail Transport Consortium is a venture between French rail company Alstom and South Africa’s Ubumbano Rail. Gibela has a R51 billion contract with the South African government to manufacture 600 trains for PRASA. The scope of the contract includes train maintenance, technical support and the manufacture and supply of spare parts.
Localisation is one of the four pillars of Gibela’s Economic Development Policy. Accordingly, Gibela aims to develop a robust and sustainable local supplier base through leveraging its majority shareholder’s expertise in an effort to contribute to the revitalisation of the local railway manufacturing industry through the implementation of a comprehensive localisation plan. This plan includes the purchase of local raw materials and components in order to ensure maximum South African content and equipping established and emerging local rail enterprises with the capability to be globally competitive. The success of the rolling stock project is underpinned by Gibela’s efforts and ability to find the best synergies, using historical references and experience as a system integrator, together with the skills and capability of suppliers in the conception of optimal solutions and manufacturing standards of the highest quality.
Passenger trains driven by traction motors provide a faster, smoother ride
Electric motors are a common means of powering a train, whether the energy required is carried on-board the train in the form of a diesel engine and its fuel or obtained from outside the train by connection with an external power supply carried by an overhead line or third rail. Electric traction is widely used around the world, particularly for routes with dense traffic, like urban and suburban railways or long distance, high speed lines that need electric traction to obtain the speeds required for inter-city travel.
The rotor induction brazing process. One size of traction motor is being used and 16 are needed per train making it a total of 9 600 motors that Gibela requires before taking into account spares. At this stage the company requires about 100 motors a month
It is important that commuter trains waste as little time as possible when leaving platforms, not only to save passengers time when travelling from station to station, but also to allow for trains to arrive at the station in quick succession, especially during peak periods.
In order to allow this, the motor that drives the train must be designed to provide high torque at low speed for fast acceleration from the platform, while displaying low torque once the train is running at high speed. Gibela uses traction motors – electric motors that do just this – in its passenger trains. These specially designed traction motors are now being locally produced by Gibela.
“Gibela’s trains use an electric multiple unit or EMU. This implies that each carriage or car is self-propelled and does not need a separate locomotive to pull the coaches. The four middle cars are propelled each with four separate traction motors. The 16 motors work in unison to ensure a fast, but smooth, departure for commuters,” says Dr Buyiswa Mncono-Liwani, corporate services and traction motors operation executive at Gibela. “The train is also made from lightweight stainless steel to further assist with this rapid acceleration, while being energy efficient.”
Once induction brazed the traction motor goes through a rotor quenching process
“Traction motors can be self-cooled, while exhibiting easy speed control with high motor efficiencies. Furthermore, the traction motor has low maintenance and running costs. The Gibela traction motors are manufactured to stringent tolerances in order to last 40 years,” adds Mncono-Liwani.
She explains that longevity is essential, because motors are the most expensive part of the train to replace. “To change a faulty motor, one needs to decouple the gangways and lift the chassis of the car in order to detach the bogie (the framework that carries a wheelset) to gain access to the motor. Most other subsystems can be removed with a forklift or crane from beneath or top of the train.”
Gibela’s passenger trains are designed specifically for South Africa’s gauge tracks. “From the mid-19th century, the 1.067m Cape gauge rail track became widespread in the British Empire. This was selected in South Africa to reduce the cost of building tracks across and through the mountains found in several parts of the country and is still the predominant gauge in South Africa,” explains Mncono-Liwani.
A lamination stack that has been lowered into the moulded stator frame. Cast in high grade SG iron the moulded stator frames have an inside diameter of 400mm and outside diameter of 550mm and each frame weighs 220 kilograms as cast and 193 kilograms when machined. The frames are supplied finished machined and painted to Alstom’s international specifications
To take advantage of high speed and axle load, most countries (55% of the lines in the world) have adopted the wider 1.435m standard gauge, and a universal traction motor can be used on such tracks. The width of the Cape gauge tracks do not allow for use of a universal traction motor. The Gibela traction motor had to be specifically designed to overcome the width constraints of South Africa’s tracks and still provide the same power characteristics as a universal traction motor.
“The same effective torque profile was achieved by designing a very narrow motor with a larger circumference,” says Mncono-Liwani.
Foundries awarded contract for supply of cast lightweight housings/casings and end shields
Traction motors are said to work as the engine of trains as it plays a role of supplying power to the wheels and giving it momentum to move. The management of Gibela were thrilled to announce that they will be using the latest technology when it comes to their new trains as the trains will travel at a 120km speed per hour.
The traction asynchronous motors use copper in the rotor design, which results in low losses due to the metal’s superior conductivity. Lower losses translate into higher energy efficiency and an increased power-to-weight ratio.
The traction motors being manufactured by Gibela have taken into account the company’s requirements for localisation. Brazing, winding and quenching are just some of the operations carried out at the Shosholoza Ave, Dunnottar, Nigel, Gauteng plant comprising a number of large scale workshops.
The purpose-built wound stator after the vacuum and pressure impregnation special process
The traction motor housings/casings, also known as moulded frames, were initially being imported while technology transfer and skills were being carried out with local suppliers. Two foundries – IPT Pefco and Naledi Foundry – have now won contracts to supply these moulded frames in which the traction motors are housed. The upskilling and business award to local suppliers is significant considering the demanding specifications that need to be adhered to in producing these parts.
Cast in high grade SG iron the moulded frames have an inside diameter of 400mm and outside diameter of 550mm and each frame weighs 220 kilograms as cast and 193 kilograms when machined. The frames are supplied finished machined and painted to Alstom’s international specifications.
One size of traction motor is being used and 16 are needed per train making it a total of 9 600 motors that Gibela requires before taking into account spares. At this stage the company requires about 100 motors a month.
Gibela will collaborate with global suppliers of rail components which are not currently manufactured in South Africa to establish a local base. The idea is to pair these international heavyweights with emerging local suppliers in joint venture partnerships to nurture the local supplier base and facilitate the all-important transfer of technology. The company has already recorded early success in expanding the capacity of local suppliers to enable them to deliver on the rolling stock contract.
