Compact interconnection enables low-floor technology in Vienna trams

Author : Mike Brooks, Market Manager – Transportation at HARTING

26 July 2017

One of the key requirements when designing modern light rail vehicles, or trams, is barrier-free accessibility. Low-floor technology makes boarding and exiting much easier, in particular for elderly people, passengers with baby carriages and wheelchair users.

This article originally appeared in the July 2017 issue of Electronic Product Design & Test; to view the digital editionclick here, and to register to receive your own printed copyclick here.

Low-floor technology has great advantages, but also presents significant design challenges. These include  the need for the platform’s top edges and entrance doors to be at the same height, as well as the requirement to completely avoid any steps in the passenger compartment, in order to provide maximum accessibility to all passengers.

Systems vendors have developed various solutions to implement rail vehicles with low floor technology. In addition to incorporating chassis using a ‘gantry’-based design (similar to a harbour crane, for instance), the vehicle also use bogies based on a modern axle-integrated design. Most importantly,  they all have one thing in common: extremely tight space conditions.

Connector solutions

In low-floor technology, tram builders are faced with increasingly smaller space between the chassis and the vehicle body floor to house a rising number of electrical components. As a result, design engineers are always searching for solutions that can offer the same power and/or current density in a smaller installation space, or a higher power and/or current density in the available space. 

In the Vienna tram system, the HARTING Technology Group, in close co-operation with their customer, has optimised the housing dimensions of the required connectors to ensure that the space requirement is reduced by some 40% compared to conventional solutions. The result fits optimally into a gap of just 8cm between tram car body and bogie.

Despite the small dimensions, the resulting interface delivers a real power package. The Han 22 HPR Slim connector is ultra-flat, yet still easily accommodates four 250 A high-current contacts. Equipped with a robust HPR housing made of die-cast aluminium, this connector satisfies the need for transmission of high power (for the motor connections, for example) in the underfloor area of rail vehicles.


For extreme space requirements, such as low-floor rail vehicles, ultra-flat interfaces are necessary. HARTING’s high-current connector portfolio provides a good solution when it comes to ensuring compact and efficient motor drives. Users can design their rail vehicles in a modular segmented manner, resulting in faster and more efficient maintenance and repair work.

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