Morgan Solution keeps Swiss Transport System Up and Running


Cobra trams, which have been operating in Zurich since 2001, are modern, low-floor trams with a maximum speed of 70 km/h and play a vital role in the transport infrastructure of Switzerland's largest city. However, over time, a proportion of the Cobra stock developed excessive bearing noise.

The damage was caused by variable frequency drive (VFD) induced voltages, which, once they exceed the resistance of the bearing lubricant, tend to discharge to the motor housing. This causes fusion craters in the bearings, which gradually increase in size and number. This in turn produces frosting, pitting and/or fluting, which ultimately leads to the bearings failing.

The existing methods of coping with this problem were costing Zurich's transport authorities a great deal in terms of maintenance and system reliability – meaning a better solution had to be found.

The retro-fit of the Cobra trams in Zurich with the new Aegis® SGR Conductive MicroFiber™ shaft grounding brush supplied by Morgan Advanced Materials is now in process and will be finished during the next three years. Using proprietary Electron Transport Technology™, the brush channels harmful currents to ground, thereby protecting the bearings from damage. The Aegis® SGR has the added benefit of extending motor life, and can be installed even in the field. It is the most effective grounding brush available, and offers the longest lasting protection, yet requires no maintenance.

As the Aegis® SGRs are now in increasing use in the Cobra fleet, the pitting and fluting of bearings has been eliminated. As a result, the transport system is fully operational for longer periods of time. Lifetime of 10 years is expected and will be proved by ongoing measurements and inspections, meaning maintenance costs should drop and reliability improve.

Martin Deiss of Morgan Advanced Materials’ Electrical Materials business is delighted by the outcome of this project: "The reputation of Zurich's public transport system is unsurpassed, and we are very pleased to have been able to maintain that. The maintenance-free nature of the Aegis® SGR makes it a convenient, elegant solution to what could easily have become a long-term and highly disruptive problem."

Established for more than a century, the Electrical Materials business of Morgan Advanced Materials, designs and manufactures a broad range of high performance solutions for rotary transfer systems, linear transfer systems and electrical carbon systems.

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