A New Electric Drive for City Buses

ZF developed and implemented a new central electric drive for city buses in record-breaking time. A test vehicle which has this central drive integrated into its system was pulled up to the specialist trade fair Busworld 2017.

We are currently experiencing a huge population influx into cities worldwide. Given this backdrop, public transport systems are becoming an important weapon in the fight against the constant threat of gridlock. Buses are of utmost importance in ensuring hassle-free transportation of the citizens of big cities. Meanwhile, legislators are passing increasingly strict exhaust emission standards for private vehicles and buses alike worldwide. With an average consumption of 30 liters of diesel over 100 kilometers for the latter, this is not an easy challenge to overcome.

Boosting environmental protection: The transfer to electric drives

Electromobility is the solution to the question of how to reduce noise and exhaust gas emissions in cities. ZF is a systems supplier and has several electric drives for various types of vehicle in its portfolio. For example, the AVE 130 electric portal axle has already proven itself and has gone into volume production for application in low-floor buses. "In many regions, and particularly in China, which constitutes a growth market, high-floor platforms are standard", says Dr. Jochen Witzig. He is responsible for the development of transmission systems for buses at ZF. The engineers have thus developed the CeTrax central electric drive especially for high-floor buses, although it is also suitable for use in low-floor buses. With a maximum power output of up to 300 kilowatts and a maximum torque of 4,400 newton meters, CeTrax is second to none in terms of performance when compared with a classic drive. Thanks to its ability to climb 25-percent gradients, the new drive from ZF can also take on the challenges of the urban landscape.

Test vehicle: The CeTrax central electric drive can be integrated into both high-floor and low-floor buses.

CeTrax: Easy to integrate into existing bus platforms

A compact powerhouse: This central electric drive is unbelievably quiet when it runs, but delivers a maximum torque of 4,400 newton meters.

CeTrax premiered at Busworld 2017, the most important trade fair of the industry, held in Kortrijk in Belgium. ZF presented a test vehicle which contains the new central electric drive there. Professional visitors and media representatives from all over the world were able to experience the new drive's road capability for themselves at a press tour.

"The key feature of CeTrax is its plug-and-drive approach", explains Witzig. He means that CeTrax can easily be installed in existing bus platforms without any changes needing to be made to:

  • the chassis,
  • the axles,
  • the statics or
  • the differential.

"We can therefore start taking a targeted approach for manufacturers that want to integrate an electric drive into their existing classic bus models. Our CeTrax solution saves on costs and reduces the workload involved in technical integration as well as in service," Witzig explains. Even ZF's test vehicle is already based on a volume production vehicle.

Clean air, almost silent, more comfort

CeTrax is a real win for passengers, pedestrians, bus operators, communities and cities alike: Driving the bus produces locally zero emissions. This means that passengers waiting at bus stops are no longer breathing in exhaust gases. City centers are also no longer polluted with environmentally hazardous CO₂ and noxious nitrogen oxide. In addition, an electric drive like CeTrax is simply much quieter when it is running than an internal combustion engine. This benefits passengers and residents alike. With CeTrax, the rolling noise produced by the tires is louder than the noise produced by the engine.

From concept to product, quick as a flash

ZF presented the CeTrax central electric drive to the public for the first time ever at the IAA Commercial Vehicles trade fair in 2016. Further development, installation in a ZF test vehicle and adjustment of the electric drive took just under a year – this makes CeTrax a prime example of ZF's sleek, dynamic development process. With the CeTrax central electric drive, the company not only reacted quickly to changing market requirements but also drove the electromobility revolution forward.

In a nutshell

ZF makes city buses locally emission-free by implementing electric drives. With the electric AVE 130 axle already being used in low-floor buses, ZF is now taking the opportunity to present a central electric drive for high-floor buses at the leading trade fair for buses, Busworld 2017. The central drive can also be used for low-floor buses, though. This drive, called CeTrax, is already integrated into an innovation prototype. CeTrax targets markets like China, markets where high-floor buses are ubiquitous in cities' transport systems. One special feature of CeTrax is that, as a central drive, it can be integrated into existing vehicle platforms without any issues.

Further related articles